Environmental Science › Global and Planetary Change

Plant Water Relations and Carbon Dynamics

Works Count: 74005

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Description

This cluster of papers explores the impact of drought and heat-induced tree mortality on global forests, highlighting emerging climate change risks. It delves into mechanisms of plant survival and mortality during drought, ecosystem dynamics, carbon cycling, and the role of stomata in driving environmental change. The research also evaluates the vulnerability of forests to drought, the global distribution of terrestrial carbon dioxide uptake, and the implications of widespread tree mortality triggered by climate stress.

Keywords

Drought; Tree Mortality; Climate Change; Ecosystem Resilience; Evapotranspiration; Carbon Balance; Hydraulic Conductance; Stomatal Response; Global Vegetation Models; Eddy Covariance

Evaporation and environment.

1965-01-01

Monteith Jl

A turgid leaf exposed to bright sunshine can transpire an amount of water several times its own weight during a summer day. Rapid evaporation is sustained by a supply of … A turgid leaf exposed to bright sunshine can transpire an amount of water several times its own weight during a summer day. Rapid evaporation is sustained by a supply of heat from the atmosphere and by a movement of water within the plant preventing the desiccation of leaf tissue. In analysis, the need for energy and the need for water have often been disassociated. Meteorologists investigating the energetics of transpiration have assumed that leaves behave like pieces of wet, green blotting paper, and plant physiologists have demonstrated mechanisms for the conduction of water at arbitrary rates unrelated to the physics of the environment. This paper describes progress towards a reconciliation of parallel concepts in meteorology and physiology. The path for the diffusion of water vapour from leaf cells to the free atmosphere is divided into two parts, one determined primarily by the size and distribution of stomata, and the other by wind speed and the aerodynamic properties of the plant surface. Diffusive resistances for single leaves and for plant communities are established from measurements in the laboratory and in the field and are then used: (i) to predict relative rates of evaporation from leaves with wet and dry surfaces; (ii) to investigate the dependence of transpiration rate on wind speed and surface roughness; (iii) to demonstrate that the relation between transpiration rate and lead area is governed by stomatal closure in leaves well shaded from sunlight; (iv) to calculate maximum rates of transpiration for different crops and climates. A final section on the convection of dry air stresses the importance of physiological restraint on the rate of transpiration from an irrigated field surrounded by dry land.

A Model Predicting Stomatal Conductance and its Contribution to the Control of Photosynthesis under Different Environmental Conditions

1987-01-01

J. Timothy Ball , Ian E. Woodrow , Joseph A. Berry

Physicochemical and Environmental Plant Physiology

1991-01-01

Park S. Nobel

Natural evaporation from open water, bare soil and grass

1948-04-22

H. L. Penman

Two theoretical approaches to evaporation from saturated surfaces are outlined, the first being on an aerodynamic basis in which evaporation is regarded as due to turbulent transport of vapour by … Two theoretical approaches to evaporation from saturated surfaces are outlined, the first being on an aerodynamic basis in which evaporation is regarded as due to turbulent transport of vapour by a process of eddy diffusion, and the second being on an energy basis in which evaporation is regarded as one of the ways of degrading incoming radiation. Neither approach is new, but a combination is suggested that eliminates the parameter measured with most difficulty—surface temperature—and provides for the first time an opportunity to make theoretical estimates of evaporation rates from standard meteorological data, estimates that can be retrospective. Experimental work to test these theories shows that the aerodynamic approach is not adequate and an empirical expression, previously obtained in America, is a better description of evaporation from open water. The energy balance is found to be quite successful. Evaporation rates from wet bare soil and from turf with an adequate supply of water are obtained as fractions of that from open water, the fraction for turf showing a seasonal change attributed to the annual cycle of length of daylight. Finally, the experimental results are applied to data published elsewhere and it is shown that a satisfactory account can be given of open water evaporation at four widely spaced sites in America and Europe, the results for bare soil receive a reasonable check in India, and application of the results for turf shows good agreement with estimates of evaporation from catchment areas in the British Isles.

Principles of Environmental Physics

1974-03-01

J. L. Monteith , William E. Reifsnyder

PREFACE TO THE SECOND EDITION LIST OF SYMBOLS 1. SCOPE OF ENVIRONMENTAL PHYSICS 2. GAS LAWS Pressure, volume and temperature Specific heats Lapse rate Water and water vapour Other gases … PREFACE TO THE SECOND EDITION LIST OF SYMBOLS 1. SCOPE OF ENVIRONMENTAL PHYSICS 2. GAS LAWS Pressure, volume and temperature Specific heats Lapse rate Water and water vapour Other gases 3. TRANSPORT LAWS General transfer equation Molecular transfer processes Diffusion coefficients Radiation laws 4. RADIATION ENVIRONMENT Solar radiation Terrestrial radiation Net radiation 5. MICROCLIMATOLOGY OF RADIATION (i) Interception Direct solar radiation Diffuse radiation Radiation in crop canopies 6. MICROCLIMATOLOGY OF RADIATION (ii) Absorption and reflection Radiative properties of natural materials Net radiation 7. MOMENTUM TRANSFER Boundary layers Wind profiles and drag on uniform surfaces Lodging and windthrow 8. HEAT TRANSFER Convection Non-dimensional groups Measurements of convection Conduction Insulation of animals 9. MASS TRANSFER (i) Gases and water vapour Non-dimensional groups Measurement of mass transfer Ventilation Mass transfer through pores Coats and clothing 10.MASS TRANSFER (ii) Particles Steady motion 11.STEADY STATE HEAT BALANCE (i) Water surfaces and vegetation Heat balance equation Heat balance of thermometers Heat balance of surfaces Developments from the Penman Equation 12.STEADY STATE HEAT BALANCE (ii) Animals Heat balance components The thermo-neutral diagram Specification of the environment Case studies 13.TRANSIENT HEAT BALANCE Time constant General cases Heat flow in soil 14.CROP MICROMETEOROLOGY (i) Profiles and fluxes Profiles Profile equations and stability Measurement of flux above the canopy 15.CROP MICROMETEOROLOGY (ii) Interpretation of measurements Resistance analogues Case studies: Water vapour and transpiration Carbon dioxide and growth Sulphur dioxide and pollutant fluxes to crops Transport within canopies APPENDIX BIBLIOGRAPHY REFERENCES INDEX

Improvements to a MODIS global terrestrial evapotranspiration algorithm

2011-04-15

Qiaozhen Mu , Maosheng Zhao , Steven W. Running

Response of mean annual evapotranspiration to vegetation changes at catchment scale

2001-03-01

Lu Zhang , Warrick Dawes , Glen Walker

It is now well established that forested catchments have higher evapotranspiration than grassed catchments. Thus land use management and rehabilitation strategies will have an impact on catchment water balance and … It is now well established that forested catchments have higher evapotranspiration than grassed catchments. Thus land use management and rehabilitation strategies will have an impact on catchment water balance and hence water yield and groundwater recharge. The key controls on evapotranspiration are rainfall interception, net radiation, advection, turbulent transport, leaf area, and plant‐available water capacity. The relative importance of these factors depends on climate, soil, and vegetation conditions. Results from over 250 catchments worldwide show that for a given forest cover, there is a good relationship between long‐term average evapotranspiration and rainfall. From these observations and on the basis of previous theoretical work a simple two‐parameter model was developed that relates mean annual evapotranspiration to rainfall, potential evapotranspiration, and plant‐available water capacity. The mean absolute error between modeled and measured evapotranspiration was 42 mm or 6.0%; the least squares line through the origin had as lope of 1.00 and a correlation coefficient of 0.96. The model showed potential for a variety of applications including water yield modeling and recharge estimation. The model is a practical tool that can be readily used for assessing the long‐term average effect of vegetation changes on catchment evapotranspiration and is scientifically justifiable.

Recent decline in the global land evapotranspiration trend due to limited moisture supply

2010-10-01

Martin Jung , Markus Reichstein , Philippe Ciais +7 more

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A remote sensing surface energy balance algorithm for land (SEBAL). 1. Formulation

1998-12-01

W.G.M. Bastiaanssen , Massimo Menenti , R.A. Feddes +1 more

Model for predicting evaporation from a row crop with incomplete cover

1972-10-01

J. T. Ritchie

A model is presented for calculating the daily evaporation rate from a crop surface. It applies to a row crop canopy situation in which the soil water supply to the … A model is presented for calculating the daily evaporation rate from a crop surface. It applies to a row crop canopy situation in which the soil water supply to the plant roots is not limited and the crop has not come into an advanced stage of maturation or senescence. The crop evaporation rate is calculated by adding the soil surface and plant surface components (each of these requiring daily numbers for the leaf area index), the potential evaporation, the rainfall, and the net radiation above the canopy. The evaporation from the soil surface E s is calculated in two stages: (1) the constant rate stage in which E s is limited only by the supply of energy to the surface and (2) the falling rate stage in which water movement to the evaporating sites near the surface is controlled by the hydraulic properties of the soil. The evaporation from the plant surfaces E p is predicted by using an empirical relation based on local data, which shows how E p is related to E o through the leaf area index. The model was used to obtain the total evaporation rate E = E s + E p of a developing grain sorghum ( Sorghum bicolor L.) canopy in central Texas. The results agreed well with values for E measured directly with a weighing lysimeter.

Isotopic Composition of Plant Carbon Correlates With Water-Use Efficiency of Wheat Genotypes

1984-01-01

Graham D. Farquhar , R. A. Richards

Variation in carbon-isotope composition among and between wheat genotypes was correlated with variation in water-use efficiency in separate pot experiments conducted in spring-summer and in winter. In the main, winter … Variation in carbon-isotope composition among and between wheat genotypes was correlated with variation in water-use efficiency in separate pot experiments conducted in spring-summer and in winter. In the main, winter experiment, the water-use efficiencies ranged from 2.0 to 3.7 mmolC/mol H2O (means of four replicates) while the corresponding isotope effects for leaf material ranged from 1.0225 to 1.0194. 13C was more abundant in grain than in leaves and stems. It is suggested that carbon-isotope analysis may be a useful tool in selection for improved water-use efficiency in breeding programmes for C3 species.

Reference Crop Evapotranspiration from Temperature

1985-01-01

George H. Hargreaves , Zohrab Samani

MEASURED lysimeter evapotranspiration of Alta fescue grass (a cool season grass) is taken as an index of reference crop evapotranspiration (ETo). An equation is presented that estimates ETo from measured … MEASURED lysimeter evapotranspiration of Alta fescue grass (a cool season grass) is taken as an index of reference crop evapotranspiration (ETo). An equation is presented that estimates ETo from measured values of daily or mean values of maximum and minimum temperature. This equation is compared with various other methods for estimating ETo. The equation was developed using eight years of daily lysimeter data from Davis, California and used to estimate values of ETo for other locations. Comparisons with other methods with measured cool season grass evapotranspiration at Aspendale, Australia; Lompoc, California; and Seabrook, New Jersey; with lysimeter data from Damin, Haiti; and with the modified Penman for various locations in Bangladesh indicated that the method usually does not require local calibration and that the estimated values are probably as reliable and useable as those from the other estimating methods used for comparison. Considering the scarcity of complete and reliable climatic data for estimating crop water requirements in developing countries, this proposed method can do much to improve irrigation planning design and scheduling in the developing countries.

Forests and Climate Change: Forcings, Feedbacks, and the Climate Benefits of Forests

2008-06-12

Gordon B. Bonan

The world's forests influence climate through physical, chemical, and biological processes that affect planetary energetics, the hydrologic cycle, and atmospheric composition. These complex and nonlinear forest-atmosphere interactions can dampen or … The world's forests influence climate through physical, chemical, and biological processes that affect planetary energetics, the hydrologic cycle, and atmospheric composition. These complex and nonlinear forest-atmosphere interactions can dampen or amplify anthropogenic climate change. Tropical, temperate, and boreal reforestation and afforestation attenuate global warming through carbon sequestration. Biogeophysical feedbacks can enhance or diminish this negative climate forcing. Tropical forests mitigate warming through evaporative cooling, but the low albedo of boreal forests is a positive climate forcing. The evaporative effect of temperate forests is unclear. The net climate forcing from these and other processes is not known. Forests are under tremendous pressure from global change. Interdisciplinary science that integrates knowledge of the many interacting climate services of forests with the impacts of global change is necessary to identify and understand as yet unexplored feedbacks in the Earth system and the potential of forests to mitigate climate change.

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How Plants Cope with Water Stress in the Field? Photosynthesis and Growth

2002-06-15

M. M. Chaves , J. S. Pereira , João Marôco +6 more

Plants are often subjected to periods of soil and atmospheric water deficit during their life cycle. The frequency of such phenomena is likely to increase in the future even outside … Plants are often subjected to periods of soil and atmospheric water deficit during their life cycle. The frequency of such phenomena is likely to increase in the future even outside today’s arid/semi‐arid regions. Plant responses to water scarcity are complex, involving deleterious and/or adaptive changes, and under field conditions these responses can be synergistically or antagonistically modified by the superimposition of other stresses. This complexity is illustrated using examples of woody and herbaceous species mostly from Mediterranean‐type ecosystems, with strategies ranging from drought‐avoidance, as in winter/spring annuals or in deep‐rooted perennials, to the stress resistance of sclerophylls. Differences among species that can be traced to different capacities for water acquisition, rather than to differences in metabolism at a given water status, are described. Changes in the root : shoot ratio or the temporary accumulation of reserves in the stem are accompanied by alterations in nitrogen and carbon metabolism, the fine regulation of which is still largely unknown. At the leaf level, the dissipation of excitation energy through processes other than photosynthetic C‐metabolism is an important defence mechanism under conditions of water stress and is accompanied by down‐regulation of photochemistry and, in the longer term, of carbon metabolism.

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Physiological and environmental regulation of stomatal conductance, photosynthesis and transpiration: a model that includes a laminar boundary layer

1991-04-01

G. J. Collatz , J. Timothy Ball , Cyril Grivet +1 more

From tropics to tundra: Global convergence in plant functioning

1997-12-09

Peter B. Reich , Michael B. Walters , David S. Ellsworth

Despite striking differences in climate, soils, and evolutionary history among diverse biomes ranging from tropical and temperate forests to alpine tundra and desert, we found similar interspecific relationships among leaf … Despite striking differences in climate, soils, and evolutionary history among diverse biomes ranging from tropical and temperate forests to alpine tundra and desert, we found similar interspecific relationships among leaf structure and function and plant growth in all biomes. Our results thus demonstrate convergent evolution and global generality in plant functioning, despite the enormous diversity of plant species and biomes. For 280 plant species from two global data sets, we found that potential carbon gain (photosynthesis) and carbon loss (respiration) increase in similar proportion with decreasing leaf life-span, increasing leaf nitrogen concentration, and increasing leaf surface area-to-mass ratio. Productivity of individual plants and of leaves in vegetation canopies also changes in constant proportion to leaf life-span and surface area-to-mass ratio. These global plant functional relationships have significant implications for global scale modeling of vegetation–atmosphere CO 2 exchange.

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Climate-Driven Increases in Global Terrestrial Net Primary Production from 1982 to 1999

2003-06-06

Ramakrishna Nemani , Charles D. Keeling , Hirofumi Hashimoto +5 more

Recent climatic changes have enhanced plant growth in northern mid-latitudes and high latitudes. However, a comprehensive analysis of the impact of global climatic changes on vegetation productivity has not before … Recent climatic changes have enhanced plant growth in northern mid-latitudes and high latitudes. However, a comprehensive analysis of the impact of global climatic changes on vegetation productivity has not before been expressed in the context of variable limiting factors to plant growth. We present a global investigation of vegetation responses to climatic changes by analyzing 18 years (1982 to 1999) of both climatic data and satellite observations of vegetation activity. Our results indicate that global changes in climate have eased several critical climatic constraints to plant growth, such that net primary production increased 6% (3.4 petagrams of carbon over 18 years) globally. The largest increase was in tropical ecosystems. Amazon rain forests accounted for 42% of the global increase in net primary production, owing mainly to decreased cloud cover and the resulting increase in solar radiation.

Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009

2010-08-19

Maosheng Zhao , Steven W. Running

Terrestrial net primary production (NPP) quantifies the amount of atmospheric carbon fixed by plants and accumulated as biomass. Previous studies have shown that climate constraints were relaxing with increasing temperature … Terrestrial net primary production (NPP) quantifies the amount of atmospheric carbon fixed by plants and accumulated as biomass. Previous studies have shown that climate constraints were relaxing with increasing temperature and solar radiation, allowing an upward trend in NPP from 1982 through 1999. The past decade (2000 to 2009) has been the warmest since instrumental measurements began, which could imply continued increases in NPP; however, our estimates suggest a reduction in the global NPP of 0.55 petagrams of carbon. Large-scale droughts have reduced regional NPP, and a drying trend in the Southern Hemisphere has decreased NPP in that area, counteracting the increased NPP over the Northern Hemisphere. A continued decline in NPP would not only weaken the terrestrial carbon sink, but it would also intensify future competition between food demand and proposed biofuel production.

A Simple Parameterization of Land Surface Processes for Meteorological Models

1989-03-01

J. Noilhan , Serge Planton

A parameterization of land surface processes to be included in mesoscale and large-scale meteorological models is presented. The number of parameters has been reduced as much as possible, while attempting … A parameterization of land surface processes to be included in mesoscale and large-scale meteorological models is presented. The number of parameters has been reduced as much as possible, while attempting to preserve the representation of the physics which controls the energy and water budgets. We distinguish two main classes of parameters. The spatial distribution of primary parameters, i.e., the dominant types of soil and vegetation within each grid cell, can be specified from existing global datasets. The secondary parameters, describing the physical properties of each type of soil and vegetation, can be inferred from measurements or derived from numerical experiments. A single surface temperature is used to represent the surface energy balance of the land/cover system. The soil heat flux is linearly interpolated between its value over bare ground and a value of zero for complete shielding by the vegetation. The ground surface moisture equation includes the effect of gravity and the thermo-hydric coefficients of the equations have been either calculated or calibrated using textural dependent formulations. The calibration has been made using the results of a detailed soil model forced by prescribed atmospheric mean conditions. The results show that the coefficients of the surface soil moisture equation are greatly dependent upon the textural class of the soil, as well as upon its moisture content. The new scheme has been included in a one-dimensional model which allows a complete interaction between the surface and the atmosphere. Several simulations have been performed using data collected during HAPEX-MOBILHY. These first results show the ability of the parameterization to reproduce the components of the surface energy balance over a wide variety of surface conditions.

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Climate and the efficiency of crop production in Britain

1977-11-25

J. L. Monteith

The efficiency of crop production is defined in thermodynamic terms as the ratio of energy output (carbohydrate) to energy input (solar radiation). Temperature and water supply are the main climatic … The efficiency of crop production is defined in thermodynamic terms as the ratio of energy output (carbohydrate) to energy input (solar radiation). Temperature and water supply are the main climatic constraints on efficiency. Over most of Britain, the radiation and thermal climates are uniform and rainfall is the main discriminant of yield between regions. Total production of dry matter by barley, potatoes, sugar beet, and apples is strongly correlated with intercepted radiation and these crops form carbohydrate at about 1.4 g per MJ solar energy, equivalent to 2.4% efficiency. Crop growth in Britain may therefore be analysed in terms of ( a ) the amount of light intercepted during the growing season and ( b ) the efficiency with which intercepted light is used. The amount intercepted depends on the seasonal distribution of leaf area which, in turn, depends on temperature and soil water supply. These variables are discussed in terms of the rate and duration of development phases. A factorial analysis of efficiency shows that the major arable crops in Britain intercept only about 40 % of annual solar radiation and their efficiency for supplying energy through economic yield is only about 0.3%. Some of the factors responsible for this figure are well understood and some are immutable. More work is needed to identify the factors responsible for the large differences between average commercial and record yields.

A General Model for the Origin of Allometric Scaling Laws in Biology

1997-04-04

Geoffrey B. West , James H. Brown , Brian J. Enquist

Allometric scaling relations, including the 3/4 power law for metabolic rates, are characteristic of all organisms and are here derived from a general model that describes how essential materials are … Allometric scaling relations, including the 3/4 power law for metabolic rates, are characteristic of all organisms and are here derived from a general model that describes how essential materials are transported through space-filling fractal networks of branching tubes. The model assumes that the energy dissipated is minimized and that the terminal tubes do not vary with body size. It provides a complete analysis of scaling relations for mammalian circulatory systems that are in agreement with data. More generally, the model predicts structural and functional properties of vertebrate cardiovascular and respiratory systems, plant vascular systems, insect tracheal tubes, and other distribution networks.

Large-scale forest girdling shows that current photosynthesis drives soil respiration

2001-06-01

Peter Högberg , Anders Nordgren , Nina Buchmann +6 more

On the Relationship Between Carbon Isotope Discrimination and the Intercellular Carbon Dioxide Concentration in Leaves

1982-01-01

Graham D. Farquhar , M. H. O'leary , Joseph A. Berry

Theory is developed to explain the carbon isotopic composition of plants. It is shown how diffusion of gaseous CO2 can significantly affect carbon isotopic discrimination. The effects on discrimination by … Theory is developed to explain the carbon isotopic composition of plants. It is shown how diffusion of gaseous CO2 can significantly affect carbon isotopic discrimination. The effects on discrimination by diffusion and carboxylation are integrated, yielding a simple relationship between discrimination and the ratio of the intercellular and atmospheric partial pressures of CO2. The effects of dark respiration and photorespiration are also considered, and it is suggested that they have relatively little effect on discrimination other than via their effects on intercellular p(CO2). It is also suggested that various environmental factors such as light, temperature, salinity and drought will also have effects via changes in intercellular p(CO2). A simple method is suggested for assessing water use efficiencies in the field.

On the Temperature Dependence of Soil Respiration

1994-06-01

Jon Lloyd , John Taylor

From previously published measurements of soil respiration rate (R) and temperature (T) the goodness of fit of various R vs T relationships was evaluated. Exponential (Q 10 ) and conventional … From previously published measurements of soil respiration rate (R) and temperature (T) the goodness of fit of various R vs T relationships was evaluated. Exponential (Q 10 ) and conventional Arrhenius relationships between T and R cannot provide an unbiased estimate of respiration rate. Nor is a simple linear relationship appropriate. The relationship between R and T can, however, be accurately represented by an Arrhenius type equation where the effective activation energy for respiration varies inversely with temperature. An empirical equation is presented which yields an unbiased estimator of respiration rates over a wide range of temperatures. When combined with seasonal estimates of Gross Primary Productivity (GPP) the empirical relationship derived provides representative estimates of the seasonal cycle of net ecosystem productivity and its effects on atmospheric CO 2 (...)

Assessing the eddy covariance technique for evaluating carbon dioxide exchange rates of ecosystems: past, present and future

2003-04-01

Dennis Baldocchi

Abstract The eddy covariance technique ascertains the exchange rate of CO 2 across the interface between the atmosphere and a plant canopy by measuring the covariance between fluctuations in vertical … Abstract The eddy covariance technique ascertains the exchange rate of CO 2 across the interface between the atmosphere and a plant canopy by measuring the covariance between fluctuations in vertical wind velocity and CO 2 mixing ratio. Two decades ago, the method was employed to study CO 2 exchange of agricultural crops under ideal conditions during short field campaigns. During the past decade the eddy covariance method has emerged as an important tool for evaluating fluxes of carbon dioxide between terrestrial ecosystems and the atmosphere over the course of a year, and more. At present, the method is being applied in a nearly continuous mode to study carbon dioxide and water vapor exchange at over a hundred and eighty field sites, worldwide. The objective of this review is to assess the eddy covariance method as it is being applied by the global change community on increasingly longer time scales and over less than ideal surfaces. The eddy covariance method is most accurate when the atmospheric conditions (wind, temperature, humidity, CO 2 ) are steady, the underlying vegetation is homogeneous and it is situated on flat terrain for an extended distance upwind. When the eddy covariance method is applied over natural and complex landscapes or during atmospheric conditions that vary with time, the quantification of CO 2 exchange between the biosphere and atmosphere must include measurements of atmospheric storage, flux divergence and advection. Averaging CO 2 flux measurements over long periods (days to year) reduces random sampling error to relatively small values. Unfortunately, data gaps are inevitable when constructing long data records. Data gaps are generally filled with values produced from statistical and empirical models to produce daily and annual sums of CO 2 exchange. Filling data gaps with empirical estimates do not introduce significant bias errors because the empirical algorithms are derived from large statistical populations. On the other hand, flux measurement errors can be biased at night when winds are light and intermittent. Nighttime bias errors tend to produce an underestimate in the measurement of ecosystem respiration. Despite the sources of errors associated with long‐term eddy flux measurements, many investigators are producing defensible estimates of annual carbon exchange. When measurements come from nearly ideal sites the error bound on the net annual exchange of CO 2 is less than ±50 g C m −2 yr −1 . Additional confidence in long‐term measurements is growing because investigators are producing values of net ecosystem productivity that are converging with independent values produced by measuring changes in biomass and soil carbon, as long as the biomass inventory studies are conducted over multiple years.

Climate change, phenology, and phenological control of vegetation feedbacks to the climate system

2012-11-29

Andrew D. Richardson , Trevor F. Keenan , Mirco Migliavacca +3 more

A review of catchment experiments to determine the effect of vegetation changes on water yield and evapotranspiration

1982-02-01

Jan Bosch , John D. Hewlett

Estimates of the Annual Net Carbon and Water Exchange of Forests: The EUROFLUX Methodology

1999-01-01

Marc Aubinet , Achim Grelle , Andreas Ibrom +7 more

Causes and consequences of variation in leaf mass per area (LMA): a meta‐analysis

2009-04-16

Hendrik Poorter , Ülo Niinemets , Lourens Poorter +2 more

Summary Here, we analysed a wide range of literature data on the leaf dry mass per unit area (LMA). In nature, LMA varies more than 100‐fold among species. Part of … Summary Here, we analysed a wide range of literature data on the leaf dry mass per unit area (LMA). In nature, LMA varies more than 100‐fold among species. Part of this variation ( c . 35%) can be ascribed to differences between functional groups, with evergreen species having the highest LMA, but most of the variation is within groups or biomes. When grown in the same controlled environment, leaf succulents and woody evergreen, perennial or slow‐growing species have inherently high LMA. Within most of the functional groups studied, high‐LMA species show higher leaf tissue densities. However, differences between evergreen and deciduous species result from larger volumes per area (thickness). Response curves constructed from experiments under controlled conditions showed that LMA varied strongly with light, temperature and submergence, moderately with CO 2 concentration and nutrient and water stress, and marginally under most other conditions. Functional groups differed in the plasticity of LMA to these gradients. The physiological regulation is still unclear, but the consequences of variation in LMA and the suite of traits interconnected with it are strong. This trait complex is an important factor determining the fitness of species in their environment and affects various ecosystem processes. Contents Summary 565 I. LMA in perspective 566 II. LMA in the field 567 III. Inherent differences 568 IV. Relation with anatomy and chemical composition 570 V. Environmental effects 572 VI. Differences in space and time 577 VII. Molecular regulation and physiology 579 VIII. Ecological consequences 580 IX. Conclusions and perspectives 582 Acknowledgements 582 References 582 Appendices 587

The worldwide leaf economics spectrum

2004-04-01

Ian J. Wright , Peter B. Reich , Mark Westoby +7 more

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Global convergence in the vulnerability of forests to drought

2012-11-01

Brendan Choat , Steven Jansen , Timothy J. Brodribb +7 more

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Coupling an Advanced Land Surface–Hydrology Model with the Penn State–NCAR MM5 Modeling System. Part I: Model Implementation and Sensitivity

2001-04-01

Fei Chen , Jimy Dudhia

This paper addresses and documents a number of issues related to the implementation of an advanced land surface–hydrology model in the Penn State–NCAR fifth-generation Mesoscale Model (MM5). The concept adopted … This paper addresses and documents a number of issues related to the implementation of an advanced land surface–hydrology model in the Penn State–NCAR fifth-generation Mesoscale Model (MM5). The concept adopted here is that the land surface model should be able to provide not only reasonable diurnal variations of surface heat fluxes as surface boundary conditions for coupled models, but also correct seasonal evolutions of soil moisture in the context of a long-term data assimilation system. In a similar way to that in which the modified Oregon State University land surface model (LSM) has been used in the NCEP global and regional forecast models, it is implemented in MM5 to facilitate the initialization of soil moisture. Also, 1-km resolution vegetation and soil texture maps are introduced in the coupled MM5–LSM system to help identify vegetation/water/soil characteristics at fine scales and capture the feedback of these land surface forcings. A monthly varying climatological 0.15° × 0.15° green vegetation fraction is utilized to represent the annual control of vegetation on the surface evaporation. Specification of various vegetation and soil parameters is discussed, and the available water capacity in the LSM is extended to account for subgrid-scale heterogeneity. The coupling of the LSM to MM5 is also sensitive to the treatment of the surface layer, especially the calculation of the roughness length for heat/moisture. Including the effect of the molecular sublayer can improve the simulation of surface heat flux. It is shown that the soil thermal and hydraulic conductivities and the surface energy balance are very sensitive to soil moisture changes. Hence, it is necessary to establish an appropriate soil moisture data assimilation system to improve the soil moisture initialization at fine scales.

A simple hydrologically based model of land surface water and energy fluxes for general circulation models

1994-07-20

Xu Liang , Dennis P. Lettenmaier , Eric F. Wood +1 more

A generalization of the single soil layer variable infiltration capacity (VIC) land surface hydrological model previously implemented in the Geophysical Fluid Dynamics Laboratory general circulation model (GCM) is described. The … A generalization of the single soil layer variable infiltration capacity (VIC) land surface hydrological model previously implemented in the Geophysical Fluid Dynamics Laboratory general circulation model (GCM) is described. The new model is comprised of a two‐layer characterization of the soil column, and uses an aerodynamic representation of the latent and sensible heat fluxes at the land surface. The infiltration algorithm for the upper layer is essentially the same as for the single layer VIC model, while the lower layer drainage formulation is of the form previously implemented in the Max‐Planck‐Institut GCM. The model partitions the area of interest (e.g., grid cell) into multiple land surface cover types; for each land cover type the fraction of roots in the upper and lower zone is specified. Evapotranspiration consists of three components: canopy evaporation, evaporation from bare soils, and transpiration, which is represented using a canopy and architectural resistance formulation. Once the latent heat flux has been computed, the surface energy balance is iterated to solve for the land surface temperature at each time step. The model was tested using long‐term hydrologic and climatological data for Kings Creek, Kansas to estimate and validate the hydrological parameters, and surface flux data from three First International Satellite Land Surface Climatology Project Field Experiment intensive field campaigns in the summer‐fall of 1987 to validate the surface energy fluxes.

Regional vegetation die-off in response to global-change-type drought

2005-10-10

David D. Breshears , Neil S. Cobb , Paul M. Rich +7 more

Future drought is projected to occur under warmer temperature conditions as climate change progresses, referred to here as global-change-type drought, yet quantitative assessments of the triggers and potential extent of … Future drought is projected to occur under warmer temperature conditions as climate change progresses, referred to here as global-change-type drought, yet quantitative assessments of the triggers and potential extent of drought-induced vegetation die-off remain pivotal uncertainties in assessing climate-change impacts. Of particular concern is regional-scale mortality of overstory trees, which rapidly alters ecosystem type, associated ecosystem properties, and land surface conditions for decades. Here, we quantify regional-scale vegetation die-off across southwestern North American woodlands in 2002-2003 in response to drought and associated bark beetle infestations. At an intensively studied site within the region, we quantified that after 15 months of depleted soil water content, >90% of the dominant, overstory tree species ( Pinus edulis , a piñon) died. The die-off was reflected in changes in a remotely sensed index of vegetation greenness (Normalized Difference Vegetation Index), not only at the intensively studied site but also across the region, extending over 12,000 km 2 or more; aerial and field surveys confirmed the general extent of the die-off. Notably, the recent drought was warmer than the previous subcontinental drought of the 1950s. The limited, available observations suggest that die-off from the recent drought was more extensive than that from the previous drought, extending into wetter sites within the tree species' distribution. Our results quantify a trigger leading to rapid, drought-induced die-off of overstory woody plants at subcontinental scale and highlight the potential for such die-off to be more severe and extensive for future global-change-type drought under warmer conditions.

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A dynamic global vegetation model for studies of the coupled atmosphere‐biosphere system

2005-02-26

Gerhard Krinner , Nicolas Viovy , Nathalie de Noblet‐Ducoudré +6 more

This work presents a new dynamic global vegetation model designed as an extension of an existing surface‐vegetation‐atmosphere transfer scheme which is included in a coupled ocean‐atmosphere general circulation model. The … This work presents a new dynamic global vegetation model designed as an extension of an existing surface‐vegetation‐atmosphere transfer scheme which is included in a coupled ocean‐atmosphere general circulation model. The new dynamic global vegetation model simulates the principal processes of the continental biosphere influencing the global carbon cycle (photosynthesis, autotrophic and heterotrophic respiration of plants and in soils, fire, etc.) as well as latent, sensible, and kinetic energy exchanges at the surface of soils and plants. As a dynamic vegetation model, it explicitly represents competitive processes such as light competition, sapling establishment, etc. It can thus be used in simulations for the study of feedbacks between transient climate and vegetation cover changes, but it can also be used with a prescribed vegetation distribution. The whole seasonal phenological cycle is prognostically calculated without any prescribed dates or use of satellite data. The model is coupled to the IPSL‐CM4 coupled atmosphere‐ocean‐vegetation model. Carbon and surface energy fluxes from the coupled hydrology‐vegetation model compare well with observations at FluxNet sites. Simulated vegetation distribution and leaf density in a global simulation are evaluated against observations, and carbon stocks and fluxes are compared to available estimates, with satisfying results.

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On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm

2005-07-25

Markus Reichstein , Eva Falge , Dennis Baldocchi +7 more

Abstract This paper discusses the advantages and disadvantages of the different methods that separate net ecosystem exchange (NEE) into its major components, gross ecosystem carbon uptake (GEP) and ecosystem respiration … Abstract This paper discusses the advantages and disadvantages of the different methods that separate net ecosystem exchange (NEE) into its major components, gross ecosystem carbon uptake (GEP) and ecosystem respiration ( R eco ). In particular, we analyse the effect of the extrapolation of night‐time values of ecosystem respiration into the daytime; this is usually done with a temperature response function that is derived from long‐term data sets. For this analysis, we used 16 one‐year‐long data sets of carbon dioxide exchange measurements from European and US‐American eddy covariance networks. These sites span from the boreal to Mediterranean climates, and include deciduous and evergreen forest, scrubland and crop ecosystems. We show that the temperature sensitivity of R eco , derived from long‐term (annual) data sets, does not reflect the short‐term temperature sensitivity that is effective when extrapolating from night‐ to daytime. Specifically, in summer active ecosystems the long‐term temperature sensitivity exceeds the short‐term sensitivity. Thus, in those ecosystems, the application of a long‐term temperature sensitivity to the extrapolation of respiration from night to day leads to a systematic overestimation of ecosystem respiration from half‐hourly to annual time‐scales, which can reach >25% for an annual budget and which consequently affects estimates of GEP. Conversely, in summer passive (Mediterranean) ecosystems, the long‐term temperature sensitivity is lower than the short‐term temperature sensitivity resulting in underestimation of annual sums of respiration. We introduce a new generic algorithm that derives a short‐term temperature sensitivity of R eco from eddy covariance data that applies this to the extrapolation from night‐ to daytime, and that further performs a filling of data gaps that exploits both, the covariance between fluxes and meteorological drivers and the temporal structure of the fluxes. While this algorithm should give less biased estimates of GEP and R eco , we discuss the remaining biases and recommend that eddy covariance measurements are still backed by ancillary flux measurements that can reduce the uncertainties inherent in the eddy covariance data.

Soil water content and temperature as independent or confounded factors controlling soil respiration in a temperate mixed hardwood forest

1998-02-01

Eric A. Davidson , E.L. Belk , Richard D. Boone

Abstract Variation in soil temperature can account for most of the seasonal and diel variation in soil CO 2 efflux, but the temperature effect is not always consistent, and other … Abstract Variation in soil temperature can account for most of the seasonal and diel variation in soil CO 2 efflux, but the temperature effect is not always consistent, and other factors such as soil water content are known to influence soil respiration. The objectives of this research were to study the spatial and temporal variation in soil respiration in a temperate forested landscape and to evaluate temperature and soil water functions as predictors of soil respiration. Soil CO 2 fluxes were measured with chambers throughout an annual cycle in six study areas at the Harvard Forest in central Massachusetts that include soil drainage classes from well drained to very poorly drained. The mean annual estimate of soil CO 2 efflux was 7.2 Mg ha –1 , but ranged from 5.3 in the swamp site to 8.5 in a well‐drained site, indicating that landscape heterogeneity is related to soil drainage class. An exponential function relating CO 2 fluxes to soil temperature accounted for 80% of the seasonal variation in fluxes across all sites ( Q 10 = 3.9), but the Q 10 ranged from 3.4 to 5.6 for the individual study sites. A significant drought in 1995 caused rapid declines in soil respiration rates in August and September in five of the six sites (a swamp site was the exception). This decline in CO 2 fluxes correlated exponentially with decreasing soil matric potential, indicating a mechanistic effect of drought stress. At moderate to high water contents, however, soil water content was negatively correlated with soil temperature, which precluded distinguishing between the effects of these two confounded factors on CO 2 flux. Occurrence of high Q 10 values and variation in Q 10 values among sites may be related to: (i) confounding effects of high soil water content; (ii) seasonal and diel patterns in root respiration and turnover of fine roots that are linked to above ground phenology and metabolism; and (iii) variation in the depth where CO 2 is produced. The Q 10 function can yield reasonably good predictions of annual fluxes of CO 2 , but it is a simplification that masks responses of root and microbial processes to variation in temperature and water content throughout the soil.

Evaluation of ecosystem dynamics, plant geography and terrestrial carbon cycling in the LPJ dynamic global vegetation model

2003-02-01

S. Sitch , Benjamin Smith , I. Colin Prentice +7 more

The Lund–Potsdam–Jena Dynamic Global Vegetation Model (LPJ) combines process-based, large-scale representations of terrestrial vegetation dynamics and land-atmosphere carbon and water exchanges in a modular framework. Features include feedback through canopy … The Lund–Potsdam–Jena Dynamic Global Vegetation Model (LPJ) combines process-based, large-scale representations of terrestrial vegetation dynamics and land-atmosphere carbon and water exchanges in a modular framework. Features include feedback through canopy conductance between photosynthesis and transpiration and interactive coupling between these 'fast' processes and other ecosystem processes including resource competition, tissue turnover, population dynamics, soil organic matter and litter dynamics and fire disturbance. Ten plants functional types (PFTs) are differentiated by physiological, morphological, phenological, bioclimatic and fire-response attributes. Resource competition and differential responses to fire between PFTs influence their relative fractional cover from year to year. Photosynthesis, evapotranspiration and soil water dynamics are modelled on a daily time step, while vegetation structure and PFT population densities are updated annually. Simulations have been made over the industrial period both for specific sites where field measurements were available for model evaluation, and globally on a 0.5°° × 0.5°° grid. Modelled vegetation patterns are consistent with observations, including remotely sensed vegetation structure and phenology. Seasonal cycles of net ecosystem exchange and soil moisture compare well with local measurements. Global carbon exchange fields used as input to an atmospheric tracer transport model (TM2) provided a good fit to observed seasonal cycles of CO2 concentration at all latitudes. Simulated inter-annual variability of the global terrestrial carbon balance is in phase with and comparable in amplitude to observed variability in the growth rate of atmospheric CO2. Global terrestrial carbon and water cycle parameters (pool sizes and fluxes) lie within their accepted ranges. The model is being used to study past, present and future terrestrial ecosystem dynamics, biochemical and biophysical interactions between ecosystems and the atmosphere, and as a component of coupled Earth system models.

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Energy balance closure at FLUXNET sites

2002-10-28

Kell Wilson , A. H. Goldstein , Eva Falge +7 more

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A global analysis of root distributions for terrestrial biomes

1996-11-01

Robert B. Jackson , Josep G. Canadell , James R. Ehleringer +3 more

The interpretation of the variations in leaf water potential and stomatal conductance found in canopies in the field

1976-02-26

P. G. Jarvis

Attempts to correlate values of stomatal conductance and leaf water potential with particular environmental variables in the field are generally of only limited success because they are simultaneously affected by … Attempts to correlate values of stomatal conductance and leaf water potential with particular environmental variables in the field are generally of only limited success because they are simultaneously affected by a number of environmental variables. For example, correlations between leaf water potential and either flux of radiant energy or vapour pressure deficit show a diurnal hysteresis which leads to a scatter diagram if many values are plotted. However, a simple model may be adequate to relate leaf water potential to the flow of water through the plant. The stomatal conductance of illuminated leaves is a function of current levels of temperature, vapour pressure deficit, leaf water potential (really turgor pressure) and ambient CO 2 concentration. Consequently, when plotted against any one of these variables a scatter diagram results. Physiological knowledge of stomatal functioning is not adequate to provide a mechanistic model linking stomatal conductance to all these variables. None the less, the parameters describing the relationships with the variables can be conveniently estimated from field data by a technique of non-linear least squares, for predictive purposes and to describe variations in response from season to season and plant to plant.

Gap filling strategies for defensible annual sums of net ecosystem exchange

2001-03-01

Eva Falge , Dennis Baldocchi , Randall J. Olson +7 more

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Stomatal Control of Transpiration: Scaling Up from Leaf to Region

1986-01-01

P. G. Jarvis , K. G. McNaughton

Europe-wide reduction in primary productivity caused by the heat and drought in 2003

2005-09-01

P. Ciais , Markus Reichstein , Nicolas Viovy +7 more

Terrestrial ecosystem production: A process model based on global satellite and surface data

1993-12-01

Christopher Potter , James T. Randerson , Christopher B. Field +4 more

This paper presents a modeling approach aimed at seasonal resolution of global climatic and edaphic controls on patterns of terrestrial ecosystem production and soil microbial respiration. We use satellite imagery … This paper presents a modeling approach aimed at seasonal resolution of global climatic and edaphic controls on patterns of terrestrial ecosystem production and soil microbial respiration. We use satellite imagery (Advanced Very High Resolution Radiometer and International Satellite Cloud Climatology Project solar radiation), along with historical climate (monthly temperature and precipitation) and soil attributes (texture, C and N contents) from global (1°) data sets as model inputs. The Carnegie‐Ames‐Stanford approach (CASA) Biosphere model runs on a monthly time interval to simulate seasonal patterns in net plant carbon fixation, biomass and nutrient allocation, litterfall, soil nitrogen mineralization, and microbial CO 2 production. The model estimate of global terrestrial net primary production is 48 Pg C yr −1 with a maximum light use efficiency of 0.39 g C MJ −1 PAR. Over 70% of terrestrial net production takes place between 30°N and 30°S latitude. Steady state pools of standing litter represent global storage of around 174 Pg C (94 and 80 Pg C in nonwoody and woody pools, respectively), whereas the pool of soil C in the top 0.3 m that is turning over on decadal time scales comprises 300 Pg C. Seasonal variations in atmospheric CO 2 concentrations from three stations in the Geophysical Monitoring for Climate Change Flask Sampling Network correlate significantly with estimated net ecosystem production values averaged over 50°–80° N, 10°–30° N, and 0°–10° N.

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Mechanisms of plant survival and mortality during drought: why do some plants survive while others succumb to drought?

2008-04-14

Nate G. McDowell , William T. Pockman , Craig D. Allen +7 more

Summary Severe droughts have been associated with regional‐scale forest mortality worldwide. Climate change is expected to exacerbate regional mortality events; however, prediction remains difficult because the physiological mechanisms underlying drought … Summary Severe droughts have been associated with regional‐scale forest mortality worldwide. Climate change is expected to exacerbate regional mortality events; however, prediction remains difficult because the physiological mechanisms underlying drought survival and mortality are poorly understood. We developed a hydraulically based theory considering carbon balance and insect resistance that allowed development and examination of hypotheses regarding survival and mortality. Multiple mechanisms may cause mortality during drought. A common mechanism for plants with isohydric regulation of water status results from avoidance of drought‐induced hydraulic failure via stomatal closure, resulting in carbon starvation and a cascade of downstream effects such as reduced resistance to biotic agents. Mortality by hydraulic failure per se may occur for isohydric seedlings or trees near their maximum height. Although anisohydric plants are relatively drought‐tolerant, they are predisposed to hydraulic failure because they operate with narrower hydraulic safety margins during drought. Elevated temperatures should exacerbate carbon starvation and hydraulic failure. Biotic agents may amplify and be amplified by drought‐induced plant stress. Wet multidecadal climate oscillations may increase plant susceptibility to drought‐induced mortality by stimulating shifts in hydraulic architecture, effectively predisposing plants to water stress. Climate warming and increased frequency of extreme events will probably cause increased regional mortality episodes. Isohydric and anisohydric water potential regulation may partition species between survival and mortality, and, as such, incorporating this hydraulic framework may be effective for modeling plant survival and mortality under future climate conditions. Contents Summary 1 I. Introduction 2 II. Consequences of vegetation mortality 3 III. Global patterns of mortality 3 IV. Hypotheses on mechanisms of drought‐related mortality 4 V. Evidence for hypothesized mechanisms 5 VI. Implications of future climate on hypothesized mortality mechanisms 13 VII. Conclusions 15 Acknowledgements 15 References 15

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On the Assessment of Surface Heat Flux and Evaporation Using Large-Scale Parameters

1972-02-01

C. H. B. Priestley , R. J. Taylor

In an introductory review it is reemphasized that the large-scale parameterization of the surface fluxes of sensible and latent heat is properly expressed in terms of energetic considerations over land … In an introductory review it is reemphasized that the large-scale parameterization of the surface fluxes of sensible and latent heat is properly expressed in terms of energetic considerations over land while formulas of the bulk aerodynamic type are most suitahle over the sea. A general framework is suggested. Data from a number of saturated land sites and open water sites in the absence of advection suggest a widely applicable formula for the relationship between sensible and latent heat fluxes. For drying land surfaces, we assume that the evaporation rate is given by the same formula for evaporation multiplied by a factor. This factor is found to remain at unity while an amount of water, varying from one site to another, is evaporated. Following this a linear decrease sets in, reducing the evaporation rate to zero after a further 5 cm of evaporation, the same at several sites examined.

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Special Paper: A Global Biome Model Based on Plant Physiology and Dominance, Soil Properties and Climate

1992-03-01

I. Colin Prentice , Wolfgang Crämer , Sandy P. Harrison +3 more

A model to predict global patterns in vegetation physiognomy was developed from physiological considera tions influencing the distributions of different functional types of plant.Primary driving variables are mean coldest month … A model to predict global patterns in vegetation physiognomy was developed from physiological considera tions influencing the distributions of different functional types of plant.Primary driving variables are mean coldest month temperature, annual accumulated temeprature over 5°C, and a drought index incorporating the seasonality of precipitation and the available water capacity of the soil.The model predicts which plant types can occur in a given environment, and selects the potentially dominant types from among them.Biomes arise as combinations of domi nant types.Global environmental data were supplied as monthly means of temperature, precipitation and sunshine (interpolated to a global 0.5° grid, with a lapse-rate correc-

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Greening of the Earth and its drivers

2016-04-22

Zaichun Zhu , Shilong Piao , Ranga B. Myneni +7 more

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Properties of Gases and Liquids

2013-01-01

J. L. Monteith , Mike H. Unsworth

Linking growth dynamics and intra-annual density fluctuations to late-summer precipitation in humid subtropical China

2025-06-25

Chunsong Wang , Zhuangpeng Zheng , Jiani Gao +3 more | Frontiers in Plant Science

Global warming has intensified extreme rainfall events and prolonged droughts, significantly impacting tree growth and wood formation. This study investigates the effects of late-summer precipitation variability on the intra-annual growth … Global warming has intensified extreme rainfall events and prolonged droughts, significantly impacting tree growth and wood formation. This study investigates the effects of late-summer precipitation variability on the intra-annual growth dynamics of Cunninghamia lanceolata and Cryptomeria fortunei in humid subtropical China. Microcores were collected from 12 trees at 7–10 days intervals between March and December from 2021 to 2023 in the Gushan Mountains. Typically, high temperatures and rainfall deficits in July induce cambial dormancy, while subsequent rainfall in August and September reactivates growth, resulting in a bimodal growth pattern. However, in 2022, an unprecedented drought (August–October rainfall 77% below average) shortened the growing season, causing an early cessation of growth and a rare unimodal growth pattern. In contrast, persistent rainfall in 2023 accelerated cell enlargement to 7 μm d - ¹ and significantly increased latewood intra-annual density fluctuations (L-IADFs). Notably, despite abundant late-summer rainfall in 2021, L-IADFs did not form, indicating a nonlinear and inconsistent relationship between rainfall and L-IADFs. These findings highlight the critical role of late-summer precipitation variability in shaping tree growth patterns and wood density in southeastern China. Given the expected increase in precipitation variability under climate change, regional forest ecosystems may become more vulnerable. This study provides valuable insights for forest management strategies to enhance resilience and mitigate climate-related risks.

DNDC modelling of greenhouse gas exchange from a boreal legume grassland under organic and mineral nitrogen management

2025-06-25

Tulasi Lakshmi Thentu , Daniel Forster , Yuan Li +6 more | Journal of Environmental Management

While grasslands are the cornerstone of Finnish livestock industries, practices for mitigating greenhouse gas (GHG) emissions are not well elucidated. Here, we used eddy covariance flux data measured on clover … While grasslands are the cornerstone of Finnish livestock industries, practices for mitigating greenhouse gas (GHG) emissions are not well elucidated. Here, we used eddy covariance flux data measured on clover grassland in eastern Finland to calibrate and validate the Heat Exchange DNDC (HE-DNDC) model in response to synthetic mineral (Nmin) and organic manure (Norg) fertilizer. The study covered an entire grass/crop rotational cycle, and the study years were represented as R1 (May 20, 2017-May 19, 2018), R2 (May 20, 2018-May 19, 2019), and R3 (May 20, 2019-May 19, 2020). Simulated carbon flux was good/fair, evidenced by relatively high Mean Absolute Error (MAE) (11.1-20.9 kg C ha-1) for both the treatments. For over 60 % of the observations, simulated biomass yield values were within one standard deviation of the measured values, indicating reasonable simulation accuracy. Cumulative measured N2O emissions were 7.5 kg N ha-1 (Nmin) and 10.9 kg N ha-1 (Norg), with simulations closely matching Nmin (6.9 kg N ha-1), but underestimating Norg (7.3 kg N ha-1). Simulated net GHG balance (NGB) indicated that grasslands were a carbon sink for Norg in R1. During R2 and R3 (crop re-establishment) grasslands became a carbon source regardless of fertilizer treatment. We conclude that DNDC provides a reasonable estimation of the magnitude and timing of GHG fluxes associated with organic and mineral fertilizer application in boreal grasslands, although significant improvements are needed in simulating processes governing N2O emissions.

Balance hídrico en regiones cafeteras mediante el déficit de evaporación

2025-06-25

Fernando Reyes-González , Arturo Galvis-Spínola , T. M. Hernández-Mendoza +2 more | Tecnología y Ciencias del Agua

La zonificación del área cafetera mexicana se realiza geográficamente, pero dada la diversidad climática de esta, dicha clasificación difícilmente capta la homogeneidad ambiental y no representa las condiciones adaptativas del … La zonificación del área cafetera mexicana se realiza geográficamente, pero dada la diversidad climática de esta, dicha clasificación difícilmente capta la homogeneidad ambiental y no representa las condiciones adaptativas del cultivo. Con la evapotranspiración se pretende identificar la salida de humedad regional y, aunque es aceptada por la academia, esta es estimada y la calidad de la información generada depende de la capacidad predictiva del algoritmo o de la eficiencia del modelo empleados. Por ello, se propuso un indicador evaluativo del balance hídrico (BH) del área cafetera de Oaxaca, Puebla y Veracruz con los periodos húmedos y secos definidos por su pluviosidad. Se colectaron datos mensuales de precipitación y evaporación del área estudiada (1921-2018), cuyo cociente se denominó “déficit de evaporación (DE)” (DE > 1.0: exceso, DE < 1.0: déficit). La estación húmeda (PH=junio: septiembre) y seca (PS=noviembre: abril) fueron delimitadas, con PH y el mes más lluvioso anual se delimitaron zonas con pluviosidad homogénea (PP6 = junio, PP7 = julio, PP8 = agosto, PP9 = septiembre), con el cálculo del DE y su modificación, el DEP1 (cociente del DE en PS vs. DE anual y su relación con el DE en enero) se delimitaron zonas con humedad homogénea y se validó DEPH con la tendencia en PS y el cálculo del DE por mes y sitio específicos. DEP1 es un índice climático que detecta variaciones temporales y espaciales del BH de áreas cafeteras (R2 = 0.92), y contribuirá a gestionar los recursos hídricos y evaluar la adaptación ambiental del cultivo.

Paired eddy covariance site reveals consistent net C sinks over three growing seasons in an African arid and grassy shrubland

2025-06-24

Amukelani Maluleke , Gregor Feig , Christian Brümmer +3 more | Agricultural and Forest Meteorology

Impact of the 2022/2023 extreme heatwave-drought on forests in North China: assessing canopy dieback and its driving factors

2025-06-24

Kuo‐Shen Chen , J. Wang , Xiang Xiang +4 more | Agricultural and Forest Meteorology

Evaluating evapotranspiration models for simulation of soil water dynamics in data-scarce paddy growing areas of Eastern India

2025-06-24

Partha Pratim Adhikary , Sheelabhadra Mohanty , S.K. Rautaray +1 more | Environmental Earth Sciences

Evapotranspiration estimation in Jeddah using FAO and Hargreaves methods

2025-06-24

Shokry Abdelaziz | World Journal of Advanced Engineering Technology and Sciences

The purpose of this study was to compare two well-known techniques for calculating evapotranspiration (ET₀), which is an important component of the hydrological cycle, particularly in arid and semi-arid areas … The purpose of this study was to compare two well-known techniques for calculating evapotranspiration (ET₀), which is an important component of the hydrological cycle, particularly in arid and semi-arid areas such as Jeddah, Saudi Arabia. The simplified, temperature-dependent Hargreaves equation and the physically based FAO Penman-Monteith equation (PME) were the main subjects of the study. Reference ET₀ was calculated using daily meteorological data from station 41024 (1997-2011), which included temperature, humidity, and wind speed. PME produced more detailed and typically higher ET₀ values since it took into account a wide range of climatic factors, according to the analysis that compared the estimates from the two methodologies. The Hargreaves approach, which just used temperature, on the other hand, generated estimates that were lower and less variable. This study provides these results in context by contrasting them with earlier studies, such the work done by Al-Subhi (2012) utilizing Dalton's equation. The results illustrate the necessity for reliable ET₀ estimation techniques in water-scarce ecosystems subject to climatic extremes, underscoring the crucial balance between data availability and estimation accuracy.

The Variations in Leaf‐Level Photosynthesis and Intrinsic Water Use Efficiency of Different Spike Types Winter Wheat in North China

2025-06-24

Xiaowen Xu , Yi Lv , Jingyi Shao +6 more | Journal of Agronomy and Crop Science

ABSTRACT In the context of water scarcity, enhancing water use efficiency (WUE) of winter wheat has become a crucial objective in the advancement of water‐saving agriculture. This study aimed at … ABSTRACT In the context of water scarcity, enhancing water use efficiency (WUE) of winter wheat has become a crucial objective in the advancement of water‐saving agriculture. This study aimed at comparing the changes in WUE in winter wheat of different spike types, and to elucidate the factors influencing intrinsic water use efficiency (WUEi) of leaf characteristics and photosynthetic traits. Field experiments involved two winter wheat spike types: large‐spike (SN30, TN18) and multi‐spike (JM22, QH001). We assessed genotypic variations in photosynthetic parameters, WUEi, instantaneous water use efficiency (WUEn), and leaf stable carbon isotope discrimination (Δ 13 C) across major growth stages. The results demonstrate that the average yield of the large‐spike (10.81 × 10 3 kg ha −1 ) was 18.04% higher than that of the multi‐spike. The photosynthetic rate of winter wheat was highest at anthesis stage (between 16.68 and 24.88 μmol m −2 s −1 depending on genotypes); the Δ 13 C values exhibited a range of 20.59‰–21.68‰ in the large‐spike. Significant inter‐annual differences emerged in transpiration rates (Tr), WUEi, and WUEn. Overall, large‐spike wheat demonstrated superior photosynthetic capacity and water use efficiency. The results indicated a negative correlation between WUEi and Δ 13 C and stomatal conductance (Gs), which suggests that the decline in WUEi is primarily limited by stomatal conductance. These findings emphasise the interaction between leaf photosynthetic characteristics and WUEi acclimation strategies.

A framework of crop water productivity estimation from UAV observations: A case study of summer maize

2025-06-23

Minghan Cheng , Ni Song , Josep Peñuelas +5 more | Agricultural Water Management

Spatial and temporal characteristics of vegetation resilience to drought in China

2025-06-23

Mengyuan Wei , Liang Jiao , Peng Zhang +4 more | Science China Earth Sciences

Implementing deep soil and dynamic root uptake in Noah-MP (v4.5): impact on Amazon dry-season transpiration

2025-06-23

Carolina A. Bieri , Francina Domínguez , Gonzalo Míguez-Macho +1 more | Geoscientific model development

Abstract. Plant roots act as critical pathways of moisture from the subsurface to the atmosphere. Deep moisture uptake by plant roots can provide a seasonal buffer mechanism in regions with … Abstract. Plant roots act as critical pathways of moisture from the subsurface to the atmosphere. Deep moisture uptake by plant roots can provide a seasonal buffer mechanism in regions with a well-defined dry season, such as the southern Amazon. Here, mature forests maintain transpiration (a critical source of atmospheric moisture in this part of the world) during drier months. Most existing state-of-the-art Earth system models do not have the necessary features to simulate subsurface-to-atmosphere moisture variations during dry-downs. These features include groundwater dynamics, a sufficiently deep soil column, dynamic root water uptake (RWU), and a fine model spatial resolution (<5 km). To address this, we present DynaRoot, a dynamic root water uptake scheme implemented in the Noah-Multiparameterization (Noah-MP) land surface model, a widely used model for studying kilometer-scale regional land surface processes. Our modifications include the implementation of DynaRoot, eight additional resolved soil layers reaching a depth of 20 mm, and soil properties that vary with depth. DynaRoot is computationally efficient and ideal for regional- or continental-scale climate simulations. We perform four 20-year uncoupled Noah-MP experiments for a region in the southern Amazon basin. Each experiment incrementally adds physical complexity. The experiments include the default Noah-MP with free drainage (FD), a case with an activated groundwater scheme that resolves water table variations (GW), a case with eight added soil layers and soil properties that vary with depth (SOIL), and a case with DynaRoot activated (ROOT). Our results show that DynaRoot allows mature forests in upland regions to avoid water stress during dry periods by taking up moisture from the deep vadose zone (where antecedent precipitation still drains downward). Conversely, RWU in valleys can access moisture from groundwater (while remaining constrained by the water table). Temporally, we capture a seasonal shift in RWU from shallower layers in wetter months to deeper soil layers in drier months, particularly over regions with dominant evergreen broadleaf (forest) vegetation. Compared to the control case, there is a domain-averaged increase in transpiration of about 29 % during dry months in the ROOT experiment. Critically, the ROOT experiment performs best in simulating the temporal evolution of dry-season transpiration using an observation-based ET (evapotranspiration) product as the reference. Future work will explore the effect of the DynaRoot uptake scheme on atmospheric variables in a coupled modeling framework.

Water-use efficiency – indications from carbon and oxygen stable isotope composition of crop plants

2025-06-23

Leah Eitelberg , Yajie Sun , Wulf Amelung +1 more | Plant and Soil

Abstract Background & Aims Enhancing water use efficiency (WUE) is critical in the regulation of water stress in plants. Since both WUE and 13 C discrimination depend on stomatal conductance … Abstract Background & Aims Enhancing water use efficiency (WUE) is critical in the regulation of water stress in plants. Since both WUE and 13 C discrimination depend on stomatal conductance ( gₛ ) and CO 2 assimilation rate ( A ), Δ 13 C values have been widely utilized as a proxy for WUE. However, to distinguish whether changes in WUE are attributable to variations in A or gₛ , δ 1 ⁸O values are increasingly incorporated into the analysis. In this review, we aim to analyze the advantages and limitations of this dual isotopic model for identifying the drivers of changes in plant WUE. Methods We conducted a literature review to examine the factors governing the correlation between WUE and isotopic values. Additionally, we collate existing studies to discuss where the dual isotope model offers valuable insights into changes in WUE and where it reaches its limits. Results While previous studies on trees revealed that the dual-isotope model effectively identified the relationship of WUE to climatic factors, WUE in crops is additionally controlled by plant group characteristics and fertilization effects. These determining factors can also be identified through the application of the dual isotope model, however, under conditions of low vapor pressure deficit, the applicability of the dual isotope model appears to be limited. Conclusion The dual isotope model holds significant potential for elucidating the mechanisms controlling WUE. This is particularly relevant for crops, as it facilitates the identification of cultivars and soil management practices that ensure high biomass production, even under conditions where gₛ is reduced due to water stress.

Addressing Weather Data Gaps in Reference Crop Evapotranspiration Estimation: A Case Study in Guinea-Bissau, West Africa

2025-06-22

Gabriel Garbanzo , Jesus Céspedes , Marina Padrão Temudo +4 more | Hydrology

Crop water use (ETc) is typically estimated as the product of crop evapotranspiration (ETo) and a crop coefficient (Kc). However, the estimation of ETo requires various meteorological data, which are … Crop water use (ETc) is typically estimated as the product of crop evapotranspiration (ETo) and a crop coefficient (Kc). However, the estimation of ETo requires various meteorological data, which are often unavailable or of poor quality, particularly in countries such as Guinea-Bissau, where the maintenance of weather stations is frequently inadequate. The present study aimed to assess alternative approaches, as outlined in the revised FAO56 guidelines, for estimating ETo when only temperature data is available. These included the use of various predictors for the missing climatic variables, referred to as the Penman–Monteith temperature (PMT) approach. New approaches were developed, with a particular focus on optimizing the predictors at the cluster level. Furthermore, different gridded weather datasets (AgERA5 and MERRA-2 reanalysis) were evaluated for ETo estimation to overcome the lack of ground-truth data and upscale ETo estimates from point to regional and national levels, thereby supporting water management decision-making. The results demonstrate that the PMT is generally accurate, with RMSE not exceeding 26% of the average daily ETo. With regard to shortwave radiation, using the temperature difference as a predictor in combination with cluster-focused multiple linear regression equations for estimating the radiation adjustment coefficient (kRs) yielded accurate results. ETo estimates derived using raw (uncorrected) reanalysis data exhibit considerable bias and high RMSE (1.07–1.57 mm d−1), indicating the need for bias correction. Various correction methods were tested, with the simple bias correction delivering the best overall performance, reducing RMSE to 0.99 mm d−1 and 1.05 mm d−1 for AgERA5 and MERRA-2, respectively, and achieving a normalized RMSE of about 22%. After implementing bias correction, the AgERA5 was found to be superior to the MERRA-2 for all the studied sites. Furthermore, the PMT outperformed the bias-corrected reanalysis in estimating ETo. It was concluded that PMT-ETo can be recommended for further application in countries with limited access to ground-truth meteorological data, as it requires only basic technical skills. It can also be used alongside reanalysis data, which demands more advanced expertise, particularly for data retrieval and processing.

Contribution of drought-avoidant strategy to gross primary productivity of three forest ecosystems in China

2025-06-21

Caiyi Zhang , Xingfei Jiang , Minyue Si +1 more | Agricultural and Forest Meteorology

Effect of snow cover and soil temperature on tree and forest floor processes: a case study in mature boreal forest

2025-06-21

Lauri Lindfors , Vilma Ylilauri , Jie Xu +7 more | Journal of Forestry Research

Abstract The duration of snow cover has shortened in the boreal region, and the amount of seasonal snow decreased. This affects the coupling between soil and air temperatures and may … Abstract The duration of snow cover has shortened in the boreal region, and the amount of seasonal snow decreased. This affects the coupling between soil and air temperatures and may thus lead to colder soil and deeper soil frost. We prevented snow reaching the forest floor for two winters in mature boreal forest and studied how that affects tree and forest floor processes. The studied species were Scots pine, Norway spruce, silver birch, and a dwarf shrub bilberry. Decreased soil temperature, due to the lack of snow cover, decreased forest floor respiration in winter and spring. Simultaneously, response of respiration to temperature seemed to increase, perhaps due to the exposure of forest floor vegetation to cold air temperature. Indeed, lack of snow cover induced mortality of bilberry, but the remaining ramets grew more in height and their average leaf size was larger likely to compensate for the lost plant biomass. Lack of snow cover also affected tree hydraulics as tree water uptake was decreased in spring, and the start of the sap season delayed in birch. Pine and birch tended to grow less in the snow exclusion treatment (differences not statistically significant), whereas spruce grew more. Coarse root traits, e.g. water content and cellular frost damages, were not affected by the snow exclusion treatment. The results of this case study increase our understanding on the effects of changing snow cover on spring-time tree and forest floor processes in mature boreal forest, but also reveal the need for further studies on mature trees.

Effects of Soil Moisture Heterogeneity on Temperature‐Humidity Dissimilarity in the Convective Boundary Layer

2025-06-21

Cheng Liu , Heping Liu , Jianping Huang +4 more | Journal of Geophysical Research Atmospheres

Abstract Surface moisture heterogeneity degrades temperature‐humidity (‐) similarity in the atmospheric surface layer, yet the underlying physical mechanisms driving this dissimilarity remain underexplored. This study employs large‐eddy simulations coupled with … Abstract Surface moisture heterogeneity degrades temperature‐humidity (‐) similarity in the atmospheric surface layer, yet the underlying physical mechanisms driving this dissimilarity remain underexplored. This study employs large‐eddy simulations coupled with a land‐surface model to investigate ‐ similarity in the convective boundary layer (CBL) over surfaces with varying scales of surface moisture heterogeneity. Results reveal that as the heterogeneity scale increases, patch‐scale thermally induced circulations develop and interact with cellular turbulent organized structures, significantly altering scalar transport and turbulence dynamics. The patch‐scale thermally induced circulations enhance horizontal advection, modify the production and transport of scalar variances, and lead to a disproportionate increase in the standard deviations of temperature () and humidity (), accompanied by a reduction in ‐ covariance (). As a result, ‐ similarity is substantially reduced throughout the CBL. Spectral analysis reveals that ‐ dissimilarity is most strongly influenced by turbulent motions at scales corresponding to patch lengths. The findings offer insights into the role of surface heterogeneity in shaping scalar similarity in the CBL, with implications for land‐atmosphere interactions and parameterization in numerical models.

Spatio-temporal variation of evapotranspiration partitioning and its response to environmental factors in a semi-arid region of northern China

2025-06-21

Jiping Yao , Xiaoman Jiang , Ruihong Yu +7 more | Ecological Indicators

The nonlinear drought response and its critical threshold of Stipa krylovii roshev. typical steppe phenology

2025-06-20

Erhua Liu , Guangsheng Zhou , Huailin Zhou | International Journal of Biometeorology

Non‐stationary forest responses to hotter droughts: a temporal perspective considering the role of past legacies

2025-06-20

Xavier Serra‐Maluquer , Julen Astigarraga , César Morales‐Molino +1 more | Ecography

Global change is altering forests worldwide, with multiple consequences for ecosystem functioning. Temporal changes in climate, and extreme, compounded weather events like hotter droughts are affecting the demography, composition and … Global change is altering forests worldwide, with multiple consequences for ecosystem functioning. Temporal changes in climate, and extreme, compounded weather events like hotter droughts are affecting the demography, composition and function of forests, leading to a highly uncertain future. To accurately predict future forest responses to hotter droughts, we highlight the need for considering a broad temporal perspective. So far, most ecological studies do not integrate different timespans and temporal resolutions, making it difficult to assess two critical time‐related aspects of forest responses to hotter droughts: the legacies of past disturbances (i.e. the effect of past events on current responses) and their role in non‐stationary responses (i.e. changing effects over time). To incorporate the effect of past hotter droughts on today's forest distribution, structure, composition and function, we identify and define key forcings and forest responses operating across three key timescales, ranging from hours to millennia. First, the shortest timescale considered (i.e. from hours to a decade) usually addresses physiological processes as well as individual tree and population performance. Second, the intermediate timescale (i.e. from decades to centuries) encompasses changes in community composition, stand structure and forest dynamics. Last, the longest timescale (i.e. from centuries to millennia) is crucial for understanding biogeographical processes that shape current species and trait pools. Then, we assess how the contrasting timespans and temporal resolutions used by different ecological subfields and approaches provide critical insights into characterising and understanding the influence of past events on ongoing responses to hotter droughts. We conclude that the holistic view gained from integrating disciplines with complementary temporal perspectives will result in a more comprehensive understanding of forest functioning and we provide a roadmap for achieving this, thereby improving our ability to predict forest responses to climate change.

Carbon and water fluxes characteristics and differential regulation mechanisms in dryland ecosystems

2025-06-20

Simin Zhang , Limin Duan , Lina Hao +4 more | Journal of Hydrology

Trapped-ion laser cooling in structured light fields

2025-06-20

NULL AUTHOR_ID | Physical Review Applied

Climate science and the case of the missing moisture

2025-06-20

Erica Gies | Nature Water

Quantifying the Independent and Interactive Effects of Environmental Drivers on Dry-Day Evapotranspiration Between Two Slope Positions in a Larch Forest

2025-06-20

Zebin Liu , Mengfei Wang , Shan Liu +4 more | Forests

Differences in environmental conditions due to slope topography result in differences in evapotranspiration along slopes, but it is unclear how changes in environmental conditions affect the variations in evapotranspiration along … Differences in environmental conditions due to slope topography result in differences in evapotranspiration along slopes, but it is unclear how changes in environmental conditions affect the variations in evapotranspiration along slopes. Therefore, we monitored dry-day evapotranspiration (ETd), solar radiation, vapor pressure deficit (VPD), and soil moisture downslope and upslope on a larch plantation hillslope from July to September 2023 to reveal the mechanisms driving ETd variations. The results revealed that the difference in ETd values between the downslope and upslope positions varied by month, with comparable ETd values at both positions in July and higher ETd values at the downslope position than at the upslope position in August and September. An ETd model combining the effects of solar radiation, VPD, and soil water content was developed, which explained 68% of the variation in ETd. The contributions of solar radiation, VPD, soil moisture, and their interactions to ETd varied across slope positions, and ETd was limited mainly by solar radiation downslope and by soil moisture upslope. Our study improves the understanding of the mechanisms governing the variations in evapotranspiration along slopes, and provides a new methodology for quantifying the effects of environmental differences between slope positions on evapotranspiration.

Global variation in vegetation carbon use efficiency inferred from eddy covariance observations

2025-06-19

Xiangzhong Luo , Ruiying Zhao , Housen Chu +7 more | Nature Ecology & Evolution

Terrestrial ecosystems have been serving as a strong carbon sink that offsets one-quarter of anthropogenic CO2 emissions. Carbon use efficiency (CUE), the percentage of photosynthesized carbon that is available for … Terrestrial ecosystems have been serving as a strong carbon sink that offsets one-quarter of anthropogenic CO2 emissions. Carbon use efficiency (CUE), the percentage of photosynthesized carbon that is available for biomass production and other secondary carbon products, is one factor determining the carbon sink size. The global variation in CUE remains unclear, however, as recent reports disagree over the responses of CUE to temperature, dryness, forest types and stand age, and there are limited direct observations to constrain the related uncertainty. Here, we propose to infer CUE from spatially distributed observations of land-atmosphere CO2 exchange from global eddy covariance sites based on the degree of ecosystem respiration-photosynthesis coupling. Across 2,737 site-years, CUE derived from eddy covariance observations is 0.43 ± 0.12, consistent with previous inventory-based estimates (0.47 ± 0.12, n = 301) but with a better representation of spatial-temporal variation in CUE. We find that CUE consistently decreases with temperature, precipitation, light availability and stand age, with a substantial difference in the baseline CUE among biomes. Importantly, CUE of deciduous forests is typically 15% higher than that of evergreen forests, suggesting that over the long-term deciduous forests are more efficient in using photosynthate. Our study advances the understanding of the global variation in CUE and provides insights to guide best practices of forest conservation, management and restoration for carbon sequestration.

Drought Amplifies the Suppressive Effect of Afforestation on Net Primary Productivity in Semi-Arid Ecosystems: A Case Study of the Yellow River Basin

2025-06-19

F Wang , Ziqi Zhang , Mingxuan Du +2 more | Remote Sensing

As a critical ecologicalbarrier in the semi-arid to semi-humid transition zone of northern China, the interaction between afforestation and climatic stressors in the Yellow River Basin constitutes a pivotal scientific … As a critical ecologicalbarrier in the semi-arid to semi-humid transition zone of northern China, the interaction between afforestation and climatic stressors in the Yellow River Basin constitutes a pivotal scientific challenge for regional sustainable development. However, the synthesis effects of afforestation and climate on primary productivity require further investigation. Integrating multi-source remote sensing data (2000–2020), meteorological observations with the Standardized Precipitation Evapotranspiration Index (SPEI) and an improved CASA model, this study systematically investigates spatiotemporal patterns of vegetation net primary productivity (NPP) responses to extreme drought events while quantifying vegetation coverage’s regulatory effects on ecosystem drought sensitivity. Among drought events identified using a three-dimensional clustering algorithm, high-intensity droughts caused an average NPP loss of 23.2 gC·m−2 across the basin. Notably, artificial irrigation practices in the Hetao irrigation district significantly mitigated NPP reduction to −9.03 gC·m−2. Large-scale afforestation projects increased the NDVI at a rate of 3.45 × 10−4 month−1, with a contribution rate of 78%, but soil moisture competition from high-density vegetation reduced carbon-sink benefits. However, mixed forest structural optimization in the Three-North Shelterbelt Forest Program core area achieved local carbon-sink gains, demonstrating that vegetation configuration alleviates water competition pressure. Drought amplified the suppressive effect of afforestation through stomatal conductance-photosynthesis coupling mechanisms, causing additional NPP losses of 7.45–31.00 gC·m−2, yet the April–July 2008 event exhibited reversed suppression effects due to immature artificial communities during the 2000–2004 baseline period. Our work elucidates nonlinear vegetation-climate interactions affecting carbon sequestration in semi-arid ecosystems, providing critical insights for optimizing ecological restoration strategies and climate-adaptive management in the Yellow River Basin.

Xylem Hydraulic Properties of Five Pinus Species Grown in Common Environment Vary From Needles to Roots With Needle Length and Native‐Range Climate

2025-06-19

Na Wang , Jean‐Christophe Domec , Sari Palmroth +5 more | Plant Cell & Environment

ABSTRACT Plant hydraulics govern water transport linking root to mesophyll surfaces, affecting gas‐exchange, survival and growth. Xylem and leaf structural and functional characteristics vary widely among Pinus species, even when … ABSTRACT Plant hydraulics govern water transport linking root to mesophyll surfaces, affecting gas‐exchange, survival and growth. Xylem and leaf structural and functional characteristics vary widely among Pinus species, even when growing under similar conditions. We quantified the variation of xylem anatomy, hydraulic function, and within‐tree hydraulic resistivity distribution, among five widely ranging southern US species: Pinus echinata , Pinus elliottii , Pinus palustris , Pinus taeda and Pinus virginiana . We found that, across species, needle length (NL) explained most of the variation in needle hydraulic properties. Resistivity to water flow in needles through tracheids' bordered‐pits decreased linearly from ~99% to 8% with increasing NL; total tracheid resistivity in branches and roots was partitioned between bordered‐pits and lumens similarly regardless of NL. Mean annual precipitation typical of the species' climatic range (CR) accounted for the variation in root hydraulic properties. Despite strong root‐to‐branch correlations of several attributes, neither NL nor CR explained the variation of any branch attribute. The results suggest that NL dominates needle xylem anatomy and function in a manner consistent with increasing hydraulic efficiency with NL, but CR produces genetic differences resulting in increased resistance to more negative xylem pressures with decreasing precipitation, at a cost of reduced hydraulic efficiency.

LAI-Derived Atmospheric Moisture Condensation Potential for Forest Health and Land Use Management

2025-06-19

Jung-Jun Lin , Ali Nadir Arslan | Remote Sensing

The interaction between atmospheric moisture condensation (AMC) on leaf surfaces and vegetation health is an emerging area of research, particularly relevant for advancing our understanding of water–vegetation dynamics in the … The interaction between atmospheric moisture condensation (AMC) on leaf surfaces and vegetation health is an emerging area of research, particularly relevant for advancing our understanding of water–vegetation dynamics in the contexts of remote sensing and hydrology. AMC, particularly in the form of dew, plays a vital role in both hydrological and ecological processes. The presence of AMC on leaf surfaces serves as an indicator of leaf water potential and overall ecosystem health. However, the large-scale assessment of AMC on leaf surfaces remains limited. To address this gap, we propose a leaf area index (LAI)-derived condensation potential (LCP) index to estimate potential dew yield, thereby supporting more effective land management and resource allocation. Based on psychrometric principles, we apply the nocturnal condensation potential index (NCPI), using dew point depression (ΔT = Ta − Td) and vapor pressure deficit derived from field meteorological data. Kriging interpolation is used to estimate the spatial and temporal variations in the AMC. For management applications, we develop a management suitability score (MSS) and prioritization (MSP) framework by integrating the NCPI and the LAI. The MSS values are classified into four MSP levels—High, Moderate–High, Moderate, and Low—using the Jenks natural breaks method, with thresholds of 0.15, 0.27, and 0.37. This classification reveals cases where favorable weather conditions coincide with low ecological potential (i.e., low MSS but high MSP), indicating areas that may require active management. Additionally, a pairwise correlation analysis shows that the MSS varies significantly across different LULC types but remains relatively stable across groundwater potential zones. This suggests that the MSS is more responsive to the vegetation and micrometeorological variability inherent in LULC, underscoring its unique value for informed land use management. Overall, this study demonstrates the added value of the LAI-derived AMC modeling for monitoring spatiotemporal micrometeorological and vegetation dynamics. The MSS and MSP framework provides a scalable, data-driven approach to adaptive land use prioritization, offering valuable insights into forest health improvement and ecological water management in the face of climate change.

Impacts of Extreme Drought and Heatwave Events on Evergreen Forests in Warm and Humid Climate Regions

2025-06-19

Ge Yu , Mijun Zou , Yali Ding +4 more | Environmental Research Letters

Abstract Afforestation and reforestation are widely recognized as key ecological approaches for addressing global warming. However, the increasing frequency, duration, and intensity of extreme climate events, especially in warm and … Abstract Afforestation and reforestation are widely recognized as key ecological approaches for addressing global warming. However, the increasing frequency, duration, and intensity of extreme climate events, especially in warm and humid regions, pose great challenges to the carbon sequestration efficiency and ecological stability of forest ecosystems. Consequently, understanding the different performances of planted versus natural forests under extreme conditions in such vulnerable regions is urgently needed. This study investigated the impacts of drought and heatwave events on the gross primary productivity (GPP) and water use efficiency (WUE) of natural and planted evergreen forests. The response of ecological stability to event intensity and duration was assessed by anomalies, and resistance and resilience were calculated using the GPP and WUE, respectively. Our findings revealed that (1) GPP anomaly was more sensitive to heatwaves, whereas WUE anomaly was more sensitive to drought in both forest types; notably, natural forests presented smaller GPP and WUE anomalies during extreme events; (2) natural forests presented superior resistance across varying intensities and durations, whereas planted forests generally presented greater resilience; and (3) threshold comparisons indicated that natural forests could withstand more intense drought and heatwaves. In terms of duration, natural forests presented greater resistance to drought events lasting up to three months, whereas planted forests presented greater resilience to heatwave events lasting more than two months. These findings provide valuable insights and guidance for forest management under climate extremes and contribute to a more reliable foundation for strategies to mitigate global warming.

Applicability of a closed-path analyser for simultaneous eddy covariance measurement of carbon dioxide, water vapor, nitrous oxide, methane, ozone and ammonia fluxes in a horticultural crop

2025-06-19

Gianfranco Rana , Domenico Vitale , Alessandro Azzolini +6 more | The Science of The Total Environment

Combined effects of tree canopy and root systems on soil hydraulic properties: A field monitoring of a Populus alba

2025-06-19

Xu-Guang Gao , Jipeng Wang , Xianwei Li +3 more | Rhizosphere

Water deficit is increasingly limiting vegetation productivity in China

2025-06-19

Hanshi Sun , Yongming Cheng , Liu Liu +2 more | Ecological Indicators

Does aridity modulate species mixing effects on growth response to drought in pine-oak forests in Mediterranean mountains?

2025-06-19

Carmen Ureña-Lara , M. Esther Pérez Corona , Verónica Cruz‐Alonso +2 more | Forest Ecology and Management

Estimating Leaf CO2 Assimilation in C3 Plants Using a Handheld Porometer With Chlorophyll Fluorometer in Field Conditions

2025-06-18

Kensuke Kimura , Erina Fushimi , Etsushi Kumagai +4 more | Plant Cell & Environment

ABSTRACT Gas exchange measurement is the gold standard method for determining leaf CO 2 assimilation rate ( A n ). However, conventional systems for measuring A n often require time … ABSTRACT Gas exchange measurement is the gold standard method for determining leaf CO 2 assimilation rate ( A n ). However, conventional systems for measuring A n often require time and/or effort to collect numerous samples in the field owing to their high weight and large size. Here, we present an efficient and convenient method for estimating A n using a handheld porometer with a chlorophyll fluorometer, facilitating on‐the‐go assessment of A n in the field. This porometer‐fluorometer method integrates the measured stomatal conductance and quantum yield of photochemistry in PSII into a biochemical photosynthesis model, incorporating model uncertainties into a single calibrated parameter. Using this method, we successfully estimated A n variations in 12 species under field conditions, with a root mean square error of 2.0 μmol m −2 s −1 , despite using the common parameter set. In contrast, without calibration (i.e., with the often‐assumed parameter value), this method greatly overestimated A n . These results highlight the importance of appropriate calibration depending on prevailing conditions, particularly the light source. In summary, this method demonstrates the potential for accessible, high‐throughput, and accurate estimation of A n in diverse plants, thereby addressing a key bottleneck in field‐based phenotyping of photosynthesis. However, further studies are required to reduce the uncertainties imposed on the calibrated parameter.

Net Ecosystem Exchanges of Spruce Forest Carbon Dioxide Fluxes in Two Consecutive Years in Qilian Mountains

2025-06-18

B. Qiao , Lili Sheng , Kelong Chen +1 more | Applied Sciences

The net ecosystem CO2 exchange (NEE) of spruce forest ecosystems is poorly understood by the lack of measurements of CO2 in the Qilian Mountain of Western China. Thus, we conducted … The net ecosystem CO2 exchange (NEE) of spruce forest ecosystems is poorly understood by the lack of measurements of CO2 in the Qilian Mountain of Western China. Thus, we conducted consecutive measurements of CO2 fluxes using tower-based the eddy covariance method from 2021 to 2022. These results indicated that daily NEE of spruce forest indicated a robust temporal pattern ranging from −28.43 to 29.62 g C m−2 from 2021 to 2022. Remarkable carbon sink characteristics were presented from late May to late September. Month accumulative NEE fluxes ranged from −336.57 to 142.22 g C m−2 in two years. Additionally, average carbon sink was 591.51 ± 37.41 g C m−2 in Qilian Mountain. NEE was negatively driven by vapor pressure deficit (VPD) and average air temperature (p < 0.05), as determined using the structural equation model. However, the direct effect coefficient of precipitation on NEE was weak. VPD was positively driven by air temperature and negatively determined by precipitation. In conclusion, a future warming scenario would significantly decrease the carbon sink of the spruce forest in Qilian Mountain.

Multiple global change factors alter the scaling of nitrogen to phosphorus in alpine plants

2025-06-18

Jiapu Li , Xuebin Yan , Pinwei Zhang +7 more | Functional Ecology

Abstract The stoichiometry and allometry of nitrogen (N) and phosphorus (P) reflect nutrient absorption and dynamic allocation by plants, and can be regulated by global change factors (e.g. nitrogen enrichment, … Abstract The stoichiometry and allometry of nitrogen (N) and phosphorus (P) reflect nutrient absorption and dynamic allocation by plants, and can be regulated by global change factors (e.g. nitrogen enrichment, climate warming and altered precipitation). Yet, how multiple global change factors act interactively to influence the stoichiometric characteristics of N and P and their scaling relationships in different plant organs remains poorly understood. In a field experiment with treatments of nitrogen addition (N add ), warming (W) and reduced precipitation (Pr) in an alpine meadow, we examined how global change factors interact to alter N and P stoichiometric characteristics of leaves and seeds. An allometry model (i.e. N = β P α ) was employed to detect changes in the scaling of plant N to P under different treatments. Our results showed that nitrogen addition significantly increased leaf N concentration (+44.0%), seed N concentration (+16.9%) and leaf N:P ratios (+27.8%) under ambient temperatures and significantly increased leaf N concentration (+53.7%) and leaf N:P ratios (+46.4%) under ambient precipitation. Importantly, nitrogen addition and warming (or reduced precipitation) had synergistic effects on P concentration of leaves and seeds, and antagonistic effects on N:P ratios of leaves. Moreover, although none of the three global change factors individually altered the scaling of N to P, nitrogen addition interacted with warming or with reduced precipitation to decrease the scaling exponents in leaves and increase them in seeds. Our results suggest that multiple global change factors can alter the N and P allocation patterns and result in decoupling of N and P in different plant organs. These findings highlight the importance of considering interactions of multiple factors when predicting dynamic changes in plant stoichiometric characteristics and nutrient utilization strategies under global change scenarios. Read the free Plain Language Summary for this article on the Journal blog.

Large-scale responses to induced organization gradients in a cloud model

2025-06-18

Wei-Ming Tsai , Brian Mapes | Journal of the Atmospheric Sciences

Abstract To illuminate the nature of convective organization, a competition for uniformly supplied destabilization is staged in a nonrotating cyclic cloud model. Scattered convection in a control-run equilibrium is driven … Abstract To illuminate the nature of convective organization, a competition for uniformly supplied destabilization is staged in a nonrotating cyclic cloud model. Scattered convection in a control-run equilibrium is driven to aggregate in a belt covering half the domain, by prescribing vertically sheared wind or warm-rain process denial. The equilibrium response is a belt-scale ascent which transports moisture toward the perturbed area. Larger and longer-lived rainstorms occur, whose competitive success earns the title of “organized”. Such success is revealed by the resulting domain-wise circulations and suppressed rainfall over the unperturbed areas. Although shear is adverse to columnar updrafts, it has beneficial effects later, fostering wider (less-entraining) updrafts and perhaps another kinetic energy source besides buoyancy. Warm-rain process denial (more purely adverse to columnar precipitation processes) reveals similar responses in equilibrant circulations and precipitation as the shear experiments, overall suggesting a “hardship breeds hardiness” interpretation. Sudden denial in a belt illustrates the multi-timescale succession: cloud water builds up (few hours), a pulse of rain (hours 5-10) initiates the belt-scale circulation, and some continuing refinement (up to 20 hours) warms the upper levels everywhere, reducing all updrafts’ buoyancy. Parameterization of organization in terms of such controlling factors is discussed.

Seasonal variation and key factors influencing evapotranspiration partitioning in alpine ecosystems of the Qinghai Lake Basin

2025-06-18

Wenyang Cao , Yao Wu , Jiayin Liu +4 more | Ecological Indicators

Carbon–water coupling in California almond orchards: a multi-scale assessment of ecosystem water use efficiency using eddy covariance and remote sensing

2025-06-18

Srinivasa Rao Peddinti , Isaya Kisekka | The Science of The Total Environment

Water use efficiency (WUE) at the ecosystem level is a critical ecophysiological indicator that integrates carbon-water coupling processes and provides essential insights for sustainable agriculture in water-limited environments. This study … Water use efficiency (WUE) at the ecosystem level is a critical ecophysiological indicator that integrates carbon-water coupling processes and provides essential insights for sustainable agriculture in water-limited environments. This study investigated the dynamics of WUE in California almond orchards, a high-value and water-intensive crop system of global economic significance, by combining eddy covariance (EC) measurements with satellite remote sensing to analyze seasonal and interannual patterns from 2020 to 2022. Gross primary productivity (GPP) was estimated using the Vegetation Photosynthesis Model (VPM), while evapotranspiration (ET) was derived using the pySEBAL surface energy balance model applied to Landsat imagery. The ratio of these fluxes provided spatially distributed WUE estimates. Daily GPP ranged from ~0.5 to 11.5 g C m-2 d-1, while ET ranged from ~0.5 to 7.5 mm d-1, with both fluxes peaking during mid-summer. WUE values exhibited distinct seasonal patterns (ranging from ~0.5 to 5.9 g C kg-1 H2O), with higher efficiency during dormancy and lower values during fruit development stages, averaging 2.14 g C kg-1 H2O over the study period. GPP and ET showed similar seasonal patterns and responded in tandem to key climatic variables (solar radiation, air temperature, and humidity), suggesting common environmental drivers govern these processes. WUE exhibited more complex behavior: it increased slightly with greater precipitation and humidity and declined under high solar radiation, high vapor pressure deficit (VPD), and extreme temperatures. The remote sensing-derived GPP and ET agreed well with EC tower measurements (R2 ≈ 0.87-0.88), affirming the reliability of the integrated approach. This study advances our understanding of carbon-water coupling in perennial almond orchard systems. It provides valuable ecological indicators for precision irrigation management in the face of increasing water scarcity and climate variability.

A Flexible Snow Model (FSM 2.1.1) including a forest canopy

2025-06-18

Richard Essery , Giulia Mazzotti , Sarah Barr +3 more | Geoscientific model development

Abstract. Multiple options for representing physical processes in forest canopies are added to FSM, which is a model with multiple options for representing physical processes in snow on the ground. … Abstract. Multiple options for representing physical processes in forest canopies are added to FSM, which is a model with multiple options for representing physical processes in snow on the ground. The canopy processes represented are shortwave and longwave radiative transfer; turbulent transfers of heat and moisture; and interception, sublimation, unloading, and melt of snow in the canopy. There are options for Beer's law or two-stream approximation canopy radiative transfer, linear or non-linear canopy snow interception efficiency, and time- and melt-dependent or temperature- and wind-dependent canopy snow unloading. Canopy mass and energy balance equations can be solved with one or two model layers. Model behaviour on stand scales is compared with observations of above- and below-canopy shortwave and longwave radiation, below-canopy wind speed, snow mass on the ground, and subjective estimates of canopy snow load. Large-scale simulations of snow cover extent, snow mass, and albedo for the Northern Hemisphere are compared with observations and land-only simulations by state-of-the-art Earth system models. Without accounting for uncertainty in forest structure metrics and parameter values, the ranges of multi-physics ensemble simulations are not as wide as seen in intercomparisons of existing models. FSM2 provides a platform for rapid investigation of sensitivity to model structure and parameter values or ensemble-based data assimilation for snow in open and forested environments.

High-resolution spatially interpolated FAO Penman-Monteith crop reference evapotranspiration maps of Sicily Island (Italy) and Jucar River system (Spain) using AgERA5 and ERA5-Land reanalysis datasets

2025-06-17

Alberto Garcia‐Prats , Juan Manuel Carricondo-Antón , Matteo Ippolito +4 more | Journal of Hydrology Regional Studies

Tree ring isotopes reveal an intensification of the hydrological cycle in the Amazon

2025-06-17

Bruno Barçante Ladvocat Cintra , Emanuel Gloor , Jessica C. A. Baker +5 more | Communications Earth & Environment

Abstract Over recent decades the Amazon region has been exposed to large-scale land-use changes and global warming. How these changes affect Amazonia’s hydrological cycle remains unclear as meteorological data are … Abstract Over recent decades the Amazon region has been exposed to large-scale land-use changes and global warming. How these changes affect Amazonia’s hydrological cycle remains unclear as meteorological data are scarce. We use tree ring oxygen isotope records to confirm that the Amazon hydrological cycle has intensified since 1980. Diverging isotopic trends from terra firme and floodplain trees from distinct sites (approximately 1000 km apart) in Western Amazon indicate rainfall amounts increased during the wet season and decreased during the dry season at large-scale. Using the Rayleigh distillation model, we estimate that wet season rainfall increased by 15–22%, and dry season rainfall decreased by 8–13%. These diverging trends provide evidence, independent from existing climate records, that the seasonality of the hydrological cycle in the Amazon is increasing. Continuation of the observed trends will have a pervasive impact on Amazon forests and floodplain ecosystems, and strongly affect the livelihoods of the regional riverine communities.

Long-term variations in the ratio of transpiration to evapotranspiration and their drivers in a humid subalpine forest

2025-06-17

Yuhao Xiang , Genxu Wang , Arthur Geßler +5 more | Agricultural and Forest Meteorology

Evaluation of a novel approach to partitioning respiration and photosynthesis using eddy covariance, wavelets and conditional sampling

2025-06-17

Pedro Henrique Herig Coimbra , Benjamin Loubet , Olivier Laurent +7 more | Agricultural and Forest Meteorology

Magnetic Resonance Imaging as a tool for investigating frost heave dynamics: a new experimental setup and application

2025-06-17

Christelle Tabbiche , J. Roca , Rahima Sidi‐Boulenouar +6 more | Canadian Geotechnical Journal

Frost heave in frozen soils is a critical geotechnical phenomenon driven by thermal gradients, moisture migration, and ice formation. Understanding this process is essential for ensuring infrastructure stability in cold … Frost heave in frozen soils is a critical geotechnical phenomenon driven by thermal gradients, moisture migration, and ice formation. Understanding this process is essential for ensuring infrastructure stability in cold regions. While previous studies have contributed to understanding frost heave mechanisms, they provide limited insight into local changes within the sample during freezing, particularly regarding the distribution of unfrozen water content. To address this gap, this study introduces the development of a new experimental setup, specifically designed for Magnetic Resonance Imaging (MRI) to investigate the frost heave behavior of sandy soils. MRI was used to track the distribution of the local amount of unfrozen water content during freezing. Frost heave tests were conducted on saturated sandy soils. The testing program and the experimental results are presented and discussed, focusing on the freezing point, temperature evolution at different elevations within the specimens, water uptake monitoring, local water content distribution, and frost heave progression. This new apparatus offers a realistic laboratory approach to studying the effect of freezing and thawing on soils.

Hydraulic Traits Constrain Salinity-Dependent Niche Segregation in Mangroves

2025-06-16

Haijing Cheng , Y. E. Chen , Yunhui Peng +2 more | Plants

To understand the mechanisms underlying species assemblage along salt gradients in intertidal zones, we measured the xylem hydraulic vulnerability curves (HVCs), leaf water potential (ψ), stomatal conductance (gs), specific leaf … To understand the mechanisms underlying species assemblage along salt gradients in intertidal zones, we measured the xylem hydraulic vulnerability curves (HVCs), leaf water potential (ψ), stomatal conductance (gs), specific leaf area (SLA), and wood density (WD) for six mangrove species of Avicennia marina, Bruguiera gymnorrhiza, Aegiceras corniculatum, Kandelia obovata, Sonneratia apetala, and Sonneratia caseolaris. We found the following: (1) A. marina and B. gymnorhiza had the most negative P50 (water potential at which 50% of hydraulic conductivity was lost), while S. caseolaris and S. apetala had the least negative P50, indicating different resistance to embolism in xylem; (2) P50 and P88 (water potential at which 88% of hydraulic conductivity was lost) declined with increasing salinity from the onshore to offshore species, as their water regulation strategy meanwhile transitioned from isohydry to anisohydry; (3) B. gymnorhiza had smaller SLA but larger hydraulic safety margin (HSM), implying potentially higher capacity of water retention in leaves and lower risk of hydraulic failure in xylem. These results suggest that hydraulic traits play an important role in shaping the salt-driven niche segregation of mangroves along intertidal zones. Our research contributes to a more comprehensive understanding of the hydraulic physiology of mangroves in salt adaption and may facilitate a general modeling framework for examining and predicting mangrove resilience to a changing climate.

Contribution of Different Forest Strata on Energy and Carbon Fluxes over an Araucaria Forest in Southern Brazil

2025-06-16

Marcelo Bortoluzzi Diaz , Pablo E. S. Oliveira , Vanessa de Arruda Souza +7 more | Forests

Forest–atmosphere interactions through mass and energy fluxes significantly influence climate processes. However, due to anthropogenic actions, native Araucaria forests in southern Brazil, part of the Atlantic Forest biome, have been … Forest–atmosphere interactions through mass and energy fluxes significantly influence climate processes. However, due to anthropogenic actions, native Araucaria forests in southern Brazil, part of the Atlantic Forest biome, have been drastically reduced. This study quantifies CO2 and energy flux contributions from each forest stratum to improve understanding of surface–atmosphere interactions. Eddy covariance data from November 2009 to April 2012 were used to assess fluxes in an Araucaria forest in Paraná, Brazil, across the ecosystem, understory, and overstory strata. On average, the ecosystem acts as a carbon sink of −298.96 g C m−2 yr−1, with absorption doubling in spring–summer compared to autumn–winter. The understory primarily acts as a source, while the overstory functions as a CO2 sink, driving carbon absorption. The overstory contributes 63% of the gross primary production (GPP) and 75% of the latent heat flux, while the understory accounts for 94% of the ecosystem respiration (RE). The energy fluxes exhibited marked seasonality, with higher latent and sensible heat fluxes in summer, with sensible heat predominantly originating from the overstory. Annual ecosystem evapotranspiration reaches 1010 mm yr−1: 60% of annual precipitation. Water-use efficiency is 2.85 g C kgH2O−1, with higher values in autumn–winter and in the understory. The influence of meteorological variables on the fluxes was analyzed across different scales and forest strata, showing that solar radiation is the main driver of daily fluxes, while air temperature and vapor pressure deficit are more relevant at monthly scales. This study highlights the overstory’s dominant role in carbon absorption and energy fluxes, reinforcing the need to preserve these ecosystems for their crucial contributions to climate regulation and water-use efficiency.