Patterns Of Water Use Efficiency Research Articles

Diurnal and Seasonal Variations of Water Use Efficiency of Rice–Wheat Rotation Cropland in the Jianghuai River Basin of China

ABSTRACTRice–wheat rotation cropland is one of the most important agroecosystems in South China, the escalation of conflict between food demand augment and water supply shortage increased with climate change. Water use efficiency plays a more significant role in optimising water and carbon management. Thus, the diurnal and seasonal variations of water use efficiency were assessed by the 3‐year eddy covariance observations in the Shouxian National Observatory, a typical rice–wheat rotation station. The results revealed a ‘U’‐shaped diurnal pattern of water use efficiency for winter wheat (Triticum aestivum L.) and rice (Oryza sativa L.). Seasonal water use efficiency had two peaks with the highest in the winter wheat‐growing season. The average water use efficiency for the rice–wheat rotation cropland was 2.85 g C kg−1 H2O over the whole year with 2.62 and 3.11 g C kg−1 H2O for winter wheat and rice, respectively. However, gross primary productivity and evapotranspiration of rice were higher than those of winter wheat. Temperature, photosynthetically active radiation were the principal impact factors of water use efficiency in the rice‐growing season. Comparatively, soil water and vapour pressure deficit dominated the water use efficiency changes in the winter wheat‐growing season. Our analyses can help understand the water use requirements for carbon assimilation on rice–wheat rotation cropland on the field scale.

Contrasting patterns of water use efficiency and annual radial growth among European beech forests along the Italian peninsula

Tree mortality and forest dieback episodes are increasing due to drought and heat stress. Nevertheless, a comprehensive understanding of mechanisms enabling trees to withstand and survive droughts remains lacking. Our study investigated basal area increment (BAI), and δ13C-derived intrinsic water-use-efficiency (iWUE), to elucidate beech resilience across four healthy stands in Italy with varying climates and soil water availability. Additionally, fist-order autocorrelation (AR1) analysis was performed to detect early warning signals for potential tree dieback risks during extreme drought events. Results reveal a negative link between BAI and vapour pressure deficit (VPD), especially in southern latitudes. After the 2003 drought, BAI decreased at the northern site, with an increase in δ13C and iWUE, indicating conservative water-use. Conversely, the southern sites showed increased BAI and iWUE, likely influenced by rising CO2 and improved water availability. In contrast, the central site sustained higher transpiration rates due to higher soil water holding capacity (SWHC). Despite varied responses, most sites exhibited reduced resilience to future extreme events, indicated by increased AR1. Temperature significantly affected beech iWUE and BAI in northern Italy, while VPD strongly influenced the southern latitudes. The observed increase in BAI and iWUE in southern regions might be attributed to an acclimation response.

The influence of nitrogen fertilization on crop production and ecohydrology in an endorheic river basin

Nitrogen fertilization is extensively applied in agricultural activities to boost food production, which changes the local hydrologic and carbon cycles. Quantitative evaluation of nitrogen fertilization on carbon and hydrologic dynamics remains challenging due to the complex linkage between hydrologic and biogeochemical processes during irrigation. To address the challenge, we utilized the Community Land Model 5 (CLM5) with activated crop module (CLM5-Crop) to investigate the response of crop yield, gross primary production (GPP), evapotranspiration (ET), and water use efficiency (WUE) to nitrogen fertilization in the cropland area of the Heihe River Basin (HRB) in northwestern China. Two batches of numerical experiments (irrigation and non-irrigation) with different nitrogen fertilization rates (0, 5, 10, 15, and 20 gN m−2, respectively) during 2000–2012 were designed to gain insights into the feedback of agricultural production and ecohydrological response to fertilization. As a result, the crop yield is significantly promoted by ∼ 120% with the nitrogen fertilization rate increasing from 0 to 20 gN m−2 under irrigation conditions. Unlike the crop yield, a clear peak of GPP is observed at the nitrogen fertilization rate of 5 gN m−2 under irrigation conditions, while higher nitrogen fertilization rates have no further promotion on GPP. ET shows a weak response to the nitrogen fertilization but a good correlation with irrigation. Different crops show different patterns of WUE under different nitrogen fertilization rates. Overall, our study demonstrates that the different influence of nitrogen fertilization on crop yield and hydrologic dynamics in a large endorheic river basin and such a finding should be taken into consideration in the future agricultural activities for the balance between food production and carbon neutrality.

Exploring the spatial structure and impact factors of water use efficiency in China

Improving water use efficiency is an essential strategy in the response to the global water crisis. The assessment of water use efficiency serves as the foundation for improving water use efficiency and water governance. Based on the mixed methods including Super-SBM model, GML index, spatial analysis, and Tobit model, this study assesses the water use efficiency from the scales of regional and provinces in China from 2011 to 2020, explores the evolution characteristics and spatial pattern of water use efficiency, and identifies the impact factors of water use efficiency. The results indicate that regional water use efficiency in China varies significantly by space, the highest in the eastern region with an average value of 0.8052, and the lowest in the central region with an average value of 0.5709. From 2011 to 2020, the average water use efficiency in China is 0.7042, which is in a low efficiency state, and roughly two thirds of the country's provinces use water inefficiently or ineffectively. In addition, regional differences of water use efficiency in China have a tendency of divergence and polarization. The technological progress change is the major factor for promoting water use efficiency. Economic development, water endowment, water use structure, scientific and technological development, and urban development have significant effects on water use efficiency in different regions respectively, while industrial structure and water governance have insignificant effects. This study supports researchers and practitioners in comprehending the characteristics and spatial patterns of water use in China, and also enriches the research system of water governance and integrated water resources management.

Regional Differences and Convergence of Urban Water Use Efficiency in the Yangtze River Economic Belt

This study used a two-stage network data envelopment analysis model to measure the water use efficiency of 108 cities in the Yangtze River Economic Belt in the initial water use and wastewater treatment phases from 2009 to 2019. We divided the urban water use efficiency of six significant urban clusters in the Yangtze River Economic Belt using the Dagum Gini coefficient. We also tested the convergence characteristics of urban water use efficiency in six significant urban clusters in the Yangtze River Economic Belt using convergence and convergence kinds. According to this report, the Yangtze River Economic Zone’s cities often have low levels of water use efficiency, which is primarily due to ineffective wastewater treatment. The 108 cities in the Yangtze River Economic Zone are divided into four types based on the average values of water use efficiency in the initial use and wastewater treatment phases; the highest number of cities are in the double-low category, with low average values of water use efficiency in the initial use and wastewater treatment phases. During the study period, spatial differences in urban water use efficiency in the Yangtze River Economic Zone narrowed, with the differences stemming mainly from hyperdensity, followed by intra- and inter-regional differences. Meanwhile, there is convergence in urban water use efficiency in the Yangtze River Economic Belt, significant β convergence in the urban agglomerations of the Yangtze River Delta, Jianghuai, middle reaches of the Yangtze River, Chengdu–Chongqing, and Central Yunnan, and insignificant β convergence in the Central Qian urban agglomeration. After considering control factors, such as industrial structure, financial development level, environmental regulation, economic development level, and science and education development level, the water use efficiency of the six major urban clusters in the Yangtze River Economic Belt converges faster, but the influence of these control factors on the water use efficiency of each urban cluster is heterogeneous. Research results have reference value for the development of improvement strategies on differentiated urban water use efficiency in the Yangtze River Economic Belt. By measuring the regional differences in water use efficiency of urban agglomerations in the Yangtze River Economic Belt and clarifying their convergence mechanism, it provides a basis for analyzing the spatial pattern of water use efficiency in urban agglomerations and has reference value for formulating differentiated urban water use efficiency improvement strategies in the Yangtze River Economic Belt.

Spatio-temporal patterns and drivers of carbon–water coupling in frozen soil zones across the gradients of freezing over the Qinghai-Tibet Plateau

The carbon and water cycle patterns of frozen soil ecosystems in regions, such as the Qinghai-Tibet Plateau (QTP), which have fragile and sensitive ecologies, are possibly affected by climate change. However, these patterns along the gradients of varying degrees of freezing remain poorly understood. In this study, we examine the spatio-temporal patterns of water use efficiency (WUE), gross primary productivity (GPP), and evapotranspiration (ET) in six frozen soil zones of the Qinghai-Tibet Plateau (QTP) with varying degrees of frozen soil. The analysis is based on the frozen soil classification criteria and remote sensing data from 2001 to 2020. The influences of six climatic, nine edaphic, and two botanic parameters on these patterns is also investigated. The results indicate that 48.05%, 24.07%, and 20% of the regions in QTP exhibit significantly upward trends of GPP, ET, and WUE, respectively. The highest increase trends were observed in GPP in the middle-thick seasonally frozen ground zone (2.36 g C m−2 yr−1), ET in the mountain permafrost zone (2.35 mm yr−1), and WUE in the predominantly continuous permafrost zone (0.003 g C kg−1 H2O yr−1). Meanwhile, GPP and WUE decrease progressively with the increase of freezing degrees, from the short-time frozen ground zone (GPP: 604.99 ± 51.99 g C m−2; WUE: 2.34 ± 0.15 g C kg−1 H2O) to the predominantly continuous permafrost zone (GPP: 114.07 ± 11.77 g C m−2; WUE: 0.33 ± 0.04 g C kg−1 H2O), while ET does not show significant differences across the three permafrost zones. The enhanced vegetation index is the primary factor affecting GPP and WUE in most frozen soil zones, whereas climate variables mainly impact ET. Our findings emphasize the importance of considering the effects of different freezing degrees of frozen soil when analyzing the response of the carbon and water cycles in the QTP in the context of climate change.

Assessment of JSBACHv4.30 as a land component of ICON-ESM-V1 in comparison to its predecessor JSBACHv3.2 of MPI-ESM1.2

Abstract. We assess the land surface model JSBACHv4 (Jena Scheme for Biosphere Atmosphere Coupling in Hamburg version 4), which was recently developed at the Max Planck Institute for Meteorology as part of the effort to build the new Icosahedral Nonhydrostatic (ICON) Earth system model (ESM), ICON-ESM. We assess JSBACHv4 in simulations coupled with ICON-A, the atmosphere model of ICON-ESM, hosting JSBACHv4 as land component to provide the surface boundary conditions. The assessment is based on a comparison of simulated albedo, land surface temperature (LST), leaf area index (LAI), terrestrial water storage (TWS), fraction of absorbed photosynthetic active radiation (FAPAR), net primary production (NPP), and water use efficiency (WUE) with corresponding observational data. JSBACHv4 is the successor of JSBACHv3; therefore, another purpose of this study is to document how this step in model development has changed model biases. This is achieved by also assessing, in parallel, the results of coupled land–atmosphere simulations with the preceding model ECHAM6 hosting JSBACHv3. Large albedo biases appear in both models over ice sheets and in central Asia. The temperate to boreal warm bias observed in simulations with JSBACHv3 largely remained in JSBACHv4, despite the very good agreement with observed LST in the global mean. For the assessment of changes in land water storage, a novel procedure is suggested to compare the gravitational data from the Gravity Recovery And Climate Experiment (GRACE) satellites to simulated TWS. It turns out that the agreement of the changes in the seasonal cycle of TWS is sensitive to the representation of precipitation in the atmosphere model. The LAI is generally too high, which is partly caused by too high soil moisture and also by the parameterization of the phenology itself. The pattern of WUE is, for both models, largely as observed. In India, WUE is too high, probably because JSBACH does not incorporate irrigation in our simulations. WUE differences between the two models can be traced back to differences in precipitation patterns in the two coupled land–atmosphere simulations. For both models, most NPP biases can be associated with biases in water stress, LAI, and FAPAR. In particular, the NPP bias of the Eurasian steppes has switched from positive in JSBACHv3 to negative in JSBACHv4. This difference is mainly caused by weaker precipitation and lower FAPAR of ICON-A–JSBACHv4 in July, which is most probably caused by a feedback loop between too little soil moisture, evaporation, and clouds. While the size and patterns of biases in albedo and LST are largely similar between the two model versions, they are less well correlated for precipitation- and vegetation-related variables like FAPAR. Overall, the biases found in the different assessment variables are either already known from the previous implementation in the Max Planck Institute Earth System Model (MPI-ESM) or have changed because of the coupling with the new atmospheric component ICON-A. Accordingly, this study demonstrates the technically successful completion of the re-implementation of JSBACH into ICON-ESM-V1. As discussed, there is a good perspective on mitigating the biases by an improved representation of the processes.

Patterns and driving factors of water and nitrogen use efficiency in Robinia pseudoacacia L. on the Loess Plateau in China

Water use efficiency (WUE) and nitrogen use efficiency (NUE) demonstrates the competitive strategies of plants with limited resources, which is important in mediating survival productivity and fitness of plants. Previous studies have found that there is a trade-off relationship between WUE and NUE and that they are affected by many factors, such as climate variables, geographical variables and soil properties. However, the patterns of WUE and NUE in Robinia pseudoacacia on the Loess Plateau are unclear and their driving factors need to be investigated to advance our knowledge of these key parameters to understand the coupling of carbon, nitrogen and water cycle. In this study, we calculated the WUE and NUE in Robinia pseudoacacia along a precipitation transect on the Loess Plateau and examined the effects of influencing factors on WUE and NUE. Our results showed that WUE varied from 64.03 to 103.08 μmol mmol−1, and NUE varied from 11.26 to 18.19 gC g−1N. Latitude played a substantial role in WUE, and soil nitrogen (ammonium nitrogen and total nitrogen) played a substantial role in NUE. In addition, NUE in Robinia pseudoacacia was lower than the average value of whole plants on the Loess Plateau, and the growth of Robinia pseudoacacia was mainly restricted by phosphorus. By dividing into three zones, zone 3 had higher WUE in where with higher latitude and lower precipitation, and NUE was not significant among the three zones. These results highlight the importance of location variables and soil chemical properties to WUE and NUE and provide useful information for understanding the coupling of carbon, nitrogen and water cycle of plants in ecosystems.

Spatiotemporal patterns of water use efficiency in China and responses to multi-scale drought

Drought is a natural disaster that profoundly affects the carbon and water cycles in terrestrial ecosystems. Quantifying the responses of terrestrial carbon and water cycles to drought is crucial for assessing the impacts of climate variability on these ecosystems. Using Moderate Resolution Imaging Spectroradiometer gross primary productivity (GPP) and evapotranspiration (ET) products, this study evaluated the spatiotemporal patterns and trends of water use efficiency (WUE) for China’s terrestrial ecosystems from 2000 to 2014 and analyzed their responses to multi-scale drought across different river basins, vegetation types, and climatic zones. The key findings are as follows: (1) The annual WUE in China’s vegetated areas has significantly increased at a linear rate of 0.01/gC kg−1 H2O a−1 (P < 0.05). (2) The spatial patterns of average annual WUE in China’s vegetated areas had large spatial variability. Higher average annual WUE values were found in the basins with high forest or cropland coverage and within humid climatic zones. Lower average annual WUE values were found in the basins with high grassland coverage and within arid and semi-arid climate zones. In total, 40.59% of the WUE in China’s vegetated areas significantly increased (P < 0.05). They were mainly distributed in Northern China. (3) From 2000 to 2014, WUE values in 32.79%, 7.21%, 23.33%, and 8.57% of the China’s vegetated areas were highly sensitive to drought in the growing season, spring, summer, and autumn, respectively. (4) The growing season, summer, and autumn had significantly higher correlations (P < 0.05) over the Standardized Precipitation and Evapotranspiration Index-24 time scale than those over the other time scales. (5) During the growing season, WUE values in river basins with a humid climate and forest coverage were more sensitive to drought than to other river basins.

Coupling Water and Carbon Fluxes to Constrain Estimates of Transpiration: The TEA Algorithm

AbstractPlant transpiration (T), biologically controlled movement of water from soil to atmosphere, currently lacks sufficient estimates in space and time to characterize global ecohydrology. Here we describe the Transpiration Estimation Algorithm (TEA), which uses both the signals of gross primary productivity and evapotranspiration (ET) to estimate temporal patterns of water use efficiency (WUE, i.e., the ratio between gross primary productivity and T) from which T is calculated. The method first isolates periods when T is most likely to dominate ET. Then, a Random Forest Regressor is trained on WUE within the filtered periods and can thus estimate WUE and T at every time step. Performance of the method is validated using terrestrial biosphere model output as synthetic flux data sets, that is, flux data where WUE dynamics are encoded in the model structure and T is known. TEA reproduced temporal patterns of T with modeling efficiencies above 0.8 for all three models: JSBACH, MuSICA, and CASTANEA. Algorithm output is robust to data set noise but shows some sensitivity to sites and model structures with relatively constant evaporation levels, overestimating values of T while still capturing temporal patterns. The ability to capture between‐site variability in the fraction of T to total ET varied by model, with root‐mean‐square error values between algorithm predicted and modeled T/ET ranging from 3% to 15% depending on the model. TEA provides a widely applicable method for estimating WUE while requiring minimal data and/or knowledge on physiology which can complement and inform the current understanding of underlying processes.

Water Use Efficiency and Its Influencing Factors in China: Based on the Data Envelopment Analysis (DEA)—Tobit Model

Water resources are important and irreplaceable natural and economic resources. Achieving a balance between economic prosperity and protection of water resource environments is a major issue in China. This article develops a data envelopment analysis (DEA) approach with undesirable outputs by using Seiford’s linear converting method to estimate water use efficiencies for 30 provinces in China, from 2008–2016,and then analyzes the influencing factors while using a DEA-Tobit model. The findings show that the overall water use efficiency of the measured Chinese provinces, when considering sewage emissions as the undesirable output, is 0.582. Thus, most regions still need improvement. Provinces with the highest water efficiency are located in economically developed Eastern China. The spatial pattern of water use efficiency in China is consistent with the general pattern of regional economic development. This study implies that factors like export dependence, technical progress, and educational value have a positive influence on water use efficiency. Further, while industrial structure has had a negative impact, government intervention has had little impact on water use efficiency. These research results will provide a scientific basis for the government to make plans for water resource development, and it may be helpful in improving regional sustainable development.

Sexual dimorphism in water and nitrogen use strategies inHonckenya peploides: timing matters

Aims Sexes of dimorphic species often differ in ecophysiological traits and display spatial segregation. These differences have been interpreted as an evolved response of the sexes to meet the specific resource demands associated with reproduction. Sexes may differ not only in the amount of resources allocated to reproduction but also in the timing of allocation to reproduction. In this study, we hypothesize that as a consequence of their specific resource demands for reproduction, the sexes of the dune plant Honckenya peploides differ in terms of temporal patterns of water use efficiency and nitrogen use and acquisition. Methods Water use efficiency, as inferred from leaf carbon isotope discrimination (Δ13C), nitrogen use, estimated by leaf nitrogen isotope composition (δ15N), and the foliar carbon and nitrogen contents were measured in males and females at three different points in time. Important Findings Females had greater water use efficiency than males, regardless of time. The ratio of N15 to N14 did not change with time in males, but significantly decreased in August for females. The total N content in the leaf tissues of females decreased as the season progressed, while in males a decrease was only found from April to June and then it remained constant from June to August. A similar pattern, but reversed, was followed by the foliar C/N ratio. Additionally, negative relationships between leaf Δ13C and N content were found at all times for males and only at the end of the season for females. Thus, our hypothesis that sex-specific patterns of nitrogen and water use efficiency will depend on time was supported. Overall, our results highlight the importance of including time in studies of sexual dimorphism, and also the role that physiological specialization plays in meeting the specific demands associated with reproduction.

Spatial–temporal patterns of water use efficiency and climate controls in China's Loess Plateau during 2000–2010

Accurate assessments of spatial–temporal variations in water use efficiency (WUE) are important for evaluation of carbon and water balances. In this study, the spatial and temporal patterns of WUE and associated climate controls in China's Loess Plateau are investigated over 2000–2010 by utilizing remote sensing data and multiple statistical methods; which provides a greater understanding about how WUE changed after the Grain to Green Program (GTGP) launched. Carbon sequestration (i.e., net primary productivity, NPP) is estimated with the CASA model and water consumption (i.e., evapotranspiration, ET) is obtained from the MODIS product (i.e., MOD16). Our results identify an increasing trend in the regional mean NPP that amounted to 7.593gC/m2·yr with an average value of 310.035gC/m2·yr. Changes in ET are segmented into three stages, the growth (2000−2003), decline (2004–2006) and stable (2007–2010) stages. Regional WUE is measured at 0.915gC/mm·m2 and shows an upward trend at a rate of 0.027gC/mm·m2·yr. Spatially, significant regional heterogeneity is found in both NPP and WUE with gradients decreasing from the southeast to the northwest, but sharp rises detected in northern Shaanxi. At the biome level, the annual average WUE of the four groups decrease in the order of grasslands>woodlands>shrublands>croplands. Moreover, all biomes in the grassland ecosystems exhibit a growth in WUE as does the arid desert zone in the northwestern region, suggesting that vegetation in moderately water-deficient areas may have a higher tolerance to drought. Among different meteorological factors, precipitation and drought severity index (DSI) in the Loess Plateau show a latitudinal zonality and influences the WUE, which indicated that the moisture rather than temperature would be the major control factor of the regional WUE. Finally, significant variation in vegetation WUE sensitivity in response to meteorological factors is noted. Temperature is found to be the dominant driving factor of shrublands WUE, whereas precipitation primarily influenced the WUE of grasslands, croplands, and woodlands.

Effect of the replacement of a native savanna by an African Brachiaria decumbens pasture on the CO&lt;sub&gt;2&lt;/sub&gt; exchange in the Orinoco lowlands, Venezuela

In the Orinoco lowlands, savannas have been often replaced by pastures composed of the C4 grass, Brachiaria decumbens Stapf. We addressed following questions: (1) How does the replacement of the native vegetation affect CO2 exchange on seasonal and annual scales? (2) How do biophysical constraints change when the landscape is transformed? To assess how these changes affect carbon exchange, we determined simultaneously the CO2 fluxes by eddy covariance, and the soil CO2 efflux by a chamber-based system in B. decumbens and herbaceous savanna stands. Measurements covered a one-year period from the beginning of the dry season (November 2008) to the end of the wet season (November 2009). During the wet season, the net ecosystem CO2 exchange reached maximum values of 23 and 10 μmol(CO2) m−2 s−1 in the B. decumbens field and in the herbaceous savanna stand, respectively. The soil CO2 efflux for both stands followed a temperature variation during the dry and wet seasons, when the soil water content (SWC) increased above 0.087 m3 m−3 in the latter case. Bursts of CO2 emissions were evident when the dry soil experienced rehydration. The carbon source/sink dynamics over the two canopies differed markedly. Annual measurements of the net ecosystem production indicated that the B. decumbens field constituted a strong carbon sink of 216 g(C) m−2 y−1. By contrast, the herbaceous savanna stand was found to be only a weak sink [36 g(C) m−2 y−1]. About 53% of the gross primary production was lost as the ecosystem respiration. Carbon uptake was limited by SWC in the herbaceous savanna stand as evident from the pattern of water-use efficiency (WUE). At the B. decumbens stand, WUE was relatively insensitive to SWC. Although these results were specific to the studied site, the effect of land use changes and the physiological response of the studied stands might be applicable to other savannas.

Measurement and simulation of diurnal variations in water use efficiency and radiation use efficiency in an irrigated wheat-maize field in the North China Plain

Quantifying diurnal patterns of water use efficiency (WUE) and radiation use efficiency (RUE) for wheat and maize is important for assessing water use by plants and crop productivity. Water and carbon dioxide fluxes from an irrigated wheat-maize double-crop field from November 2002 to October 2003 were measured using the Eddy Covariance method. Evident differences were observed between the diurnal patterns of WUE for wheat and maize. The WUE values of wheat peaked near 9, 15 and 12 mg CO2 g H2O in the morning, and then decreased linearly with time and recovered in the late afternoon (4:00pm) before sunset in March, April and May, respectively. The WUE of maize increased after sunrise and retained stable values of 6, 14 and 12 mg CO2 g H2O from mid-morning to mid-afternoon (10:00am –2:00pm) and then decreased slowly with time until sunset in July, August and September, respectively. Similar patterns were observed in the RUE of wheat and maize. Over the three months of the study, averaged RUE was 1.76 g C MJ−1 for the wheat crop and 1.87 g C MJ−1 for the maize crop. A coupled photosynthesis and transpiration model was used to simulate the diurnal variations in WUE under variable climate conditions. Measurement results and sensitivity analysis show that the difference in the diurnal variation pattern in WUE between wheat and maize resulted from the different carbon fixing mechanisms of wheat and maize.

PRESERVATION OF CHESTNUT (CASTANEA SATIVA MILL.) GENETIC RESOURCES AND ADAPTIVE POTENTIAL IN RELATION TO ENVIRONMENTAL CHANGES

A brief review of a series of studies, dealing with adaptedness of Castanea sativa Mill. to environmental water availability, is provided. The ecophysiological knowledge of the mechanisms underlying the species capability to cope with contrasting environments is crucial to assess the evolutionary potential of C. sativa under a scenario of global change. Carbon and oxygen stable isotope methodologies offer powerful ecophysiological strategies of investigation on patterns of water-use efficiency and of exploitation of water sources. Water-use efficiency and the capability to explore shallow or deep soil water pools are plant characters which are strictly linked and affected by both environmental and genetic features. The adaptive significance of these complex quantitative traits is shown and briefly discussed along the review. Finally, a summary of the present knowledge on chestnut adaptedness is presented together with relevant perspectives for future ecophysiological studies.

Sweet corn response to combined nitrogen and salinity environmental stresses

To define the nature of the combined response curve of sweet corn (Zea mays L.) plants to nitrogen and salinity, a lysimeter study was designed to follow water and solute budgets with combinations of the two variables over wide ranges of 0.5–7.5 dS m−1 and 0–150% of local N-fertilization recommendations. Patterns of water-use efficiency, N content, N uptake, and shoot dry-matter yield indicated the predominance of environmental interactions over Cl-nitrate physiological antagonism. At low salinities, the leaf N content, N uptake, and yield increased with increased N fertilization up to 45% of local N-fertilization recommendations, nitrogen was efficiently stripped from the percolating water and practically no nitrate was leached. At higher N fertilization the amount of leached N increased linearly with increased N input, and N uptake and yield were independent of N rates, levelling off at increased values for decreased salinities. The Liebig–Sprengel and Mitscherlich–Baule models were evaluated against measured data; both achieved similar values for the system's inherent N, the salinity level corresponding with zero-yield, and the predicted yields, which were highly correlated with the experimental data (R2 > 0.9). It is suggested that both models can be used successfully in mechanistic-based plant–soil solution models to predict yield, water and nutrient needs, and the resulted N leaching.