Seasonal Water Deficit Research Articles

Agro-Physiological Traits and Fatty Acids Composition of Camelina: Effects of Late Season Water Deficit and Iron and Zinc Biofortification

Agro-Physiological Traits and Fatty Acids Composition of Camelina: Effects of Late Season Water Deficit and Iron and Zinc Biofortification

Comparative metabolome profiling of two contrasting wheat cultivars in late-season water deficit

Abiotic stresses, including water deficit, cause myriad changes in plant metabolism. Metabolomics is a powerful tool for understanding plant resistance to such stresses. Therefore, this research was conducted to evaluate the effects of after anthesis water deficit (WD: from anthesis to maturity), i.e., maintaining moisture at field capacity (well-watered: WW) and 50% field capacity, on metabolome profiling (amino acids, hormones, nucleotides, soluble and insoluble sugars, sugar alcohols, and enzymes) in grains of two contrasting wheat cultivars grown in a greenhouse at Razi University as a factorial experiment. Based on the results, WD decreased grain yield (57%), 1000 grain weight (50%), and grain plant-1 (9%) in the sensitive cultivar (SC), while it had no significant effect on the tolerant cultivar (TC). In WW, the concentration of IAA, glucose, and fructose, as well as the activity of three invertase isoforms (vacuolic, cytosolic, and cell wall bound), were significantly higher at 10 days after anthesis compared to 17 and 31 days. In WD, these traits were significantly reduced in SC. ABA and sucrose concentration and sucrose synthase activity were significantly higher 17 days after anthesis than 10 days after anthesis. WD. In contrast to ABA, sucrose concentration decreased significantly in growing grains of SC in WD. The ATP/ADP ratio, inositol, glycerol and erythritol contents of TC were significantly higher in WD than in SC. Among the different amino acids, asparagine, glutamine and lysine were the highest, while ACC and methionine were the lowest. Contrary to SC, WD significantly increased the sum of the amino acid concentrations determined in the grains of TC, i.e. asparagine (22%), aspartic acid (48%), glycine (48%), ACC (79%) and valine (133%). These findings could help us to understand the resistance mechanisms to late season water deficit, which can increase sink strength (sink size and sink activity) and achieve higher yield quantity and quality in wheat.

Analyses on Characteristics of Spatial Distribution and Matching of the Human–Land–Water–Heat System on the Yunnan Plateau

Water, soil, and heat are strategic supporting elements for human survival and social development. The degree of matching between human-land-water-heat elements directly influences the sustainable development of a region. However, the current evaluation of the matching of human-land-water-heat elements overlooks the influence of elevation factors on the matching results, especially evident in mountainous areas. Taking the Yunnan Plateau with distinctive mountainous features as the research subject, divided into 11 elevation ranges, the Lorenz Gini coefficient, asymmetry coefficient, matching distance, and imbalance index are used to assess the spatial matching and balance of human-land-water-heat elements. A projection tracing model is employed to analyze its water resource carrying capacity. Analyses revealed that the Gini coefficient of monthly precipitation from the 1950s to 2022 on the Yunnan Plateau increases with increasing latitude, whereas the correlation with elevation is notably lower. The asymmetry coefficient increases gradually from west to east with change in longitude. The mismatch of the human–land–water–heat system in regions at different elevations is in the order 1800–2000 m > 2000–2200 m > 1400–1600 m > 800 m > other areas. The matching of the human–land–water–heat system in different wet–dry years and seasons also fluctuates with elevation, resulting in serious seasonal drought and water shortage problems in mountainous areas with elevations of 1200–1600, 1800–2000 m, and >2600 m. The spatial equilibrium of temperature and precipitation in regions of different elevations is best, followed by that of cultivated land, while that of the population is the worst. The Gini coefficients for different water cycle processes of precipitation, surface runoff, and regulating storage capacity for water supply continue to increase. Specifically, the Gini coefficient of industrial water supply is the highest, reaching 0.576, and that of agricultural irrigation is the lowest (0.424). Through artificial regulation of lake and reservoir water, seasonal changes in the demand for agricultural irrigation water are offset to achieve a demand–supply balance and matching of land and water resources. The water resource capacity of different elevation ranges is evenly underloaded. However, the potential of the water resource capacity varies obviously with elevation in the order 2000–2200 m < 1800–2000 m < 1600–8000 m < 1400–1600 m < other areas. It appears that the greater the human–land–water–heat system mismatch, the smaller the regional potential of the water resource capacity.

Genotypic responses to phosphorus and water management in winter wheat: Strategies to increase resource use efficiency and productivity

The phosphorus (P) addition can be helpful in the mitigation of the adverse effects of water deficit stress. However, the efficiency of wheat in utilizing both components has not been assessed in field conditions. This research aims to assess the effects of P and water addition on phosphorus use efficiency (PUE) and water productivity (WP) in field conditions for select wheat cultivars co-adapted to climate-induced agronomic challenges. Three wheat cultivars were selected based on their PUE and water WP from a previous experiment. The trials were conducted in field conditions over two consecutive years, from 2020 to 2021 (Season 1) and 2021–2022 (Season 2). The plants were grown on an andisol with a soil P concentration of 10 mg P kg−1 and 30 mg P kg−1. Two irrigation treatments were imposed: Well-watered (+W) and dryland (-W). The plants were sampled at three stages: tillering (Z25), anthesis (Z65), and ripening (Z95). At the end of the phenological cycle, grain yield components, grain yield, grain quality, PUE, and WP were evaluated. Phosphorus addition promotes plant growth, especially in the early vegetative stages, by enhancing tiller development and nutrient and water uptake. These effects were critical during the anthesis and ripening stages, enhancing yield components and higher grain production. Differential responses were observed across cultivars, underscoring the genotype-specificity in PUE and WP. Seasonal water deficit stress modulated these effects, highlighting a more complex genotype-environment-nutrient interaction. The water addition promoted PUE and WP, suggesting a synergy between the two components. Among the cultivars, Chevignon outperformed in grain yield, PUE, and WP. However, while phosphorus, water, and environmental factors influenced grain quality, the genetic background of the cultivar was the primary determinant of these components. This study advocates for implementing individual nutrient management strategies tailored to the specific cultivar and adaptable to environmental conditions under climate change.

Sweet potato yield and quality characteristics affected by different late-season irrigation levels.

Seasonal late-season water deficits negatively affect the yield and quality of sweet potatoes in northern China. However, the amount of late-season irrigation to achieve high yield and consistent quality storage root remains undetermined. We assessed the yield and some qualitative traits of sweet potatoes such as size, shape, skin/flesh colour and nutritional content, as influenced by five irrigation levels (T0: unirrigated control; T1: 33% ETc; T2: 75% ETc; T3: 100% ETc; and T4: 125% ETc). Late-season irrigation significantly increased yield and marketable yield. Yields for T2 and T3 were significantly higher than other treatments, whereas T2 had the highest Grade A rating in a 2-year test. The vertical length of storage roots gradually increased with an increase in irrigation level, whereas the maximum width remained unchanged. The proportion of long elliptic and elliptic storage roots also increased, whereas the proportion of ovate, obovate and round storage roots gradually decreased. The skin and flesh colours became more vivid as the level of irrigation increased, with the skin colour becoming redder and the flesh colour becoming more orange-yellow. The levels of carotenoids, vitamin C and soluble sugar were significantly higher in irrigated crops, with the highest vitamin C and soluble sugar levels in T2 and the highest carotenoid levels in T3 treatment. Taken together, these results demonstrate the potential of moderate irrigation in the late-season to improve both yield production and quality potential. The results are of great importance for improving the market value of sweet potatoes and increasing grower profits. © 2024 Society of Chemical Industry.

ASSESSMENT OF IRRIGATION WATER REQUIREMENTS FOR APPLES, PEARS, AND PLUMS IN THE KOLUBARA AND MORAVA DISTRICTS UNDER CHANGING CLIMATE CONDITIONS

Climate change, which manifests through shifts in temperature, rainfall patterns, and the frequency of extreme events like droughts and floods, has a substantial impact on agricultural production and food security. This study investigates the influence of climate change on the irrigation needs of apple, pear, and plum crops in two fruit-growing districts in western Serbia, specifically in the Kolubara and Morava districts. This research aims to provide valuable insights for farmers to plan and adapt their production strategies in response to evolving climate conditions. To estimate the water requirements, crop evapotranspiration (ETc), effective rainfall (Pe), and water deficit (In) were determined using historical climate data from meteorological stations in Valjevo (Kolubara district) and Požega (Morava district) for the observed period (1961 - 2021). For projecting future water requirements (2021 - 2040), we employed data from eight regional climate models within the EURO – CORDEX project. The analysis of water requirements for apple, pear, and plum was conducted for both grassed and non-grassed orchards.
 In the Kolubara district, the average seasonal water deficit during the observed period was 356 mm in grassed orchards and 191 mm in non-grassed orchards, with the most significant irrigation requirements occurring in July and August, representing 60 - 70% of the seasonal water requirement. Looking ahead to the future period (2021 - 2040), the average water deficit increases to 401 mm in grassed orchards and 202 mm in non-grassed orchards, marking a 13% and 6% rise, respectively, compared to the observed period. This signifies a need for 1 to 2 additional irrigation sessions. In the Morava district, the average seasonal water deficit during the observed period was 403 mm in grassed orchards and 236 mm in non-grassed orchards, with the highest irrigation requirements in June, July, and August, accounting for 80 - 90% of the seasonal water requirement. Due to an anticipated increase in total precipitation in the future period (2021 - 2040) in the Morava district, there is a decrease in the seasonal water deficit by 3% in grassed orchards and 16% in non-grassed orchards. However, even with reduced water requirements in the future, there remains a significant requirement for irrigation in May, June, July, and August when rainfall is limited.

Assessing Water Security and Coupling Coordination in the Lancang–Mekong River Basin for Sustainable Development

Water security is crucial for the sustainable development of regional water resources. Here, we utilize the Driver-Pressure-State-Impact-Response (DPSIR) framework to construct an indicator system for assessing water security in the Lancang–Mekong River Basin (LMRB). This study also delves into the level of development in the coupling coordination between the economic and social systems and the water resources systems in the basin. The findings reveal that the overall water security situation in the LMRB is satisfactory, with three countries (China, Laos, and Vietnam) surpassing the “safe” threshold and three countries (Thailand, Cambodia, and Myanmar) “Basically safe”. However, water security issues persist, particularly in relation to water pollution and scarcity. Seasonal water shortages and water-related disasters arise due to uneven rainfall distribution throughout the year and inadequate regulating facilities such as wetlands and reservoirs. In addition, the overall coupling coordination level in the LMRB is low, ranging between 0.3 and 0.4, corresponding to a moderate imbalance level in the assessment criteria system. Specifically, Laos and China exhibit the highest coupling coordination level, with a degree of 0.36, whereas Thailand and Myanmar demonstrate the lowest level, with degrees of 0.33 and 0.31, respectively. Overall, our results offer a scientific foundation for the sustainable development of countries within the LMRB.

Climate change impacts on hydrometeorological and river hydrological extremes in Quito, Ecuador

Study regionQuito, Ecuador Study focusThe study region faces two water-related challenges, which, to date, have only been studied to a minimal extent: extreme precipitation events and water shortage in the dry season. This study investigates the current conditions and future changes in short-duration events, low river discharges and associated uncertainties. Daily precipitation and temperature projections from 19 state-of-the-art global climate models (CMIP6) and four future scenarios (SSP1–2.6, SSP2–4.5, SSP3–7.0 and SSP5–8.5) are downscaled with delta change and more advanced quantile perturbation methodologies. Temporal disaggregation is applied to obtain sub-daily precipitation with five extreme value distributions (EVDs). Three conceptual hydrological models are implemented to quantify the impacts on river flows. Variance decomposition is applied to estimate the uncertainty share of climate models, hydrological models, and EVDs in the results. New hydrological insightsThe results indicate an intensification of extreme precipitation events, with short-duration events expected to be more intense by up to 30% in the near future (2021–2050) and up to 60% in the far future (2070–2099). The river peak discharges are projected to increase by 5–20% and 10–50% in the near and far future, respectively. On the contrary, the low river flows are projected to decrease by 0–13% and 0–30% for the respective time horizons. Overall, climate models are the dominant source of uncertainty.

Groundwater mapping and locally engaged water governance in a small island terrain: Case study of Karainagar island, Northern Sri Lanka

AbstractGroundwater is a vital resource under threat in island communities. Karainagar, a 22 km2island, is one of seven islands off the coast of Jaffna in Northern Sri Lanka, with its population of just about 11,000 persons, experiences seasonal water shortage, and salinity in groundwater as twin threats impacting on their lives. This paper reports on a 3‐year study (October 2019 to September 2022) to map groundwater dynamics of Karainagar island spatially and seasonally and discusses the patterns revealed in terms of community needs, policy implications, and governance ideas that could already be considered by relevant authorities and citizens jointly. Thirty‐six dug wells used for drinking, domestic, agricultural, and public purposes were selected, and water level, salinity, and pH changes recorded along with daily rainfall. This paper offers a thorough description of the geography, land use, distribution of wells, and water bodies, followed by discussion of the current status of the groundwater in Karainagar island. Year‐to‐year differences in rainfall pattern resulted in different rates of change and range in water level with a corresponding reverse pattern seen in salinity with some exceptions across the island. Cumulative rainfall required to reach full capacity of wells ranged from 652 to 892 mm over the 3 years with an average figure of 739 mm of rain. This implies that any further rainfall during early phase of the main rainy season is potential surface water for storage and runoff. Practices such as unregulated pumping and construction of tube wells are argued to be contributing to increase in salinity levels with health implications for residents. A participatory governance approach that overcomes limitations of the existing institutional approach is proposed. Its success based on broad stakeholder engagement, improved equity, and transparency when supported by adequate policies and village level aquifer monitoring will enable sustainability of groundwater resources in Karainagar.

Effects of drought stress memory on the accumulation of stress-protective compounds in naturally grown pine and spruce

Forest trees are subjected to multiple stressors during their long lifetime and therefore require effective and finely regulated stress-protective systems. Stressors can induce protective systems either directly or with the involvement of stress memory mechanisms. Stress memory has only begun to be uncovered in model plants and is unexplored in coniferous species. Therefore, we studied the possible role of stress memory in the regulation of the accumulation of stress-protective compounds (heat shock proteins, dehydrins, proline) in the needles of naturally grown Scots pine and Norway spruce trees subjected to the subsequent action of long-term (multiyear) and short-term (seasonal) water shortages. Although the water deficit was relatively mild, it significantly influenced the pattern of expression of stress memory-related heat shock factor (HSF) and SWI/SNF genes, indicating the formation of stress memory in both species. In spruce, dehydrin accumulation was increased by water shortage in a manner compatible with Type II stress memory. The accumulation of HSP40 in spruce needles was positively influenced by long-term water shortage, but this increase was unlikely to be of biological importance due to the concomitant decrease in HSP70, HSP90 and HSP101 accumulation. Finally, proline accumulation was negatively influenced by short-term water deficit in spruce. In pine, no one protective compound accumulated in response to water stress. Taken together, the results indicate that the accumulation of stress-protective compounds was generally independent of stress memory effects both in pine and in spruce.

Influence of seasonal climatic water deficit and crop prices on rainfed crop grain harvest, repurposing, and abandonment in the western U.S.A.

Increasing climate aridity and drought, exacerbated by global warming, are increasing risks for western United States of America (U.S.A.) rainfed farming, and challenging producers’ capacity to maintain production and profitability. With agricultural water demand in the region exceeding limited supplies and fewer opportunities to develop new water sources, rainfed agriculture is under increasing pressure to meet the nation’s growing food demands. This study examines three major western U.S.A. rainfed crops: barley, spring wheat, and winter wheat. We analyzed the relationship between crop repurposing (the ratio of acres harvested for grain to the total planted acres) to seasonal climatic water deficit (CWD). To isolate the climate signal from economic factors, our analysis accounted for the influence of crop prices on grain harvest. We used historical climate and agricultural data between 1958 and 2020 to model crop repurposing (e.g. forage) across the observed CWD record using a fixed effect model. Our methodology is applicable for any region and incorporates regional differences in farming and economic drivers. Our results indicate that farmers are less likely to harvest barley and spring wheat for grain when the spring CWD is above average. Of the major winter wheat growing regions, only the Northern High Plains in Texas showed a trend of decreasing grain harvest during high CWD. For the majority of major crop growing regions, grain prices increased with lower levels of grain harvest. Interestingly, winter wheat repurposing is significantly higher in the southern Great Plains (∼50% harvested for grain) compared to the rest of the West (∼90%). Our results highlight that the major barley and spring wheat regions’ grain harvests are vulnerable to high spring CWD and low summer CWD, while winter wheat grain harvest is unaffected by variable CWD in most of the West.

Deficit irrigation effects on adjunct and all‐malt barley yield and quality

AbstractSemiarid regions are reliant on irrigation to produce large‐yielding and high‐quality malt barley (Hordeum vulgare L.). Drought in the western United States is of concern as surface and ground water reductions are occurring that affect irrigation water availability. Implementing a seasonal water deficit compared to evapotranspiration (ET) is a potential strategy to reduce water usage if yield and quality can be maintained. Research was conducted in Aberdeen, ID, on the effects of deficit irrigation on yield, grain quality, and malt characteristics. Five genotypes were selected to represent those used for large‐scale adjunct brewing and those targeted at the all‐malt craft industry. Irrigation was managed at three rates (100%, 75%, and 50%) of estimated crop evapotranspiration (ETc) using sprinkler irrigation. Total aboveground dry matter was not affected by irrigation until soft dough (Feekes 11.2). Yield was similar within a genotype with irrigation reduction from 100% ETc to 75% ETc. Averaged across genotypes, yields were 6936 kg ha−1 at 100% ETc and 6297 kg ha−1 at 75% ETc. At 75% ETc, protein remained just below the adjunct target (130 g kg−1) for four of five genotypes while all five exceeded the all‐malt target (120 g kg−1). Reduced irrigation decreased malt extract and increased diastatic power, where β‐glucan either did not differ or increased. Deficit irrigation is promising, particularly for adjunct brewing; however, expected changes to malting quality must be understood and genotype selection, altered fertilizer management, and/or changes to malting criteria may be needed for implementation.

Optimal water allocation integrated with water supply, replenishment, and spill in the in-series reservoir based on an improved decomposition and dynamic programming aggregation method

Abstract In humid regions with the monsoon climate, seasonal water shortages and water spills occur alternately because of uneven temporal and spatial distributions of water resources. An optimization model for the in-series reservoir (ISR) with replenishment pumping stations was developed to obtain the minimum annual sum of water shortage and systematically considered the reservoir operation rule of water spill and replenishment. This model features multiple dimensions; dynamic programming (DP) may cause a ‘curse of dimensions’, while the decomposition-coordination method has difficulty in judging logic conditions in the reservoir operation rules. So, an improved decomposition and DP aggregation (DDPA) method was proposed. The proposed model and the method were applied to a real case in the humid region of southern China. Compared to a conventional scheduling method, the water supply was increased by 0.8% and replenishment was reduced by 2.5%. Moreover, a comparison between DDPA and six heuristic algorithms was discussed. All heuristic algorithms' objective function values only obtained local optimal solutions, and the water shortage of the system was 0.12–20.5%. The obtained results demonstrated that DDPA was the better choice for highly complex multi-reservoir systems. The proposed optimization algorithm enriched the optimization theory of multi-dimensional and multi-variable complex systems.

The climate change effects on agricultural drought in the Be River Basin

Drought is one of the extreme weather events that has been occurring with increasing frequency and complexity as well as having negative effects on water resources and agricultural production. The focus of the present study is to investigate the climate change effects on agricultural drought in the Be River Basin. The SWAT model was applied to simulate the soil moisture content and Standardized Soil Water Index (SSWI) was utilized to estimate the characteristics of agricultural drought. In addition, the future climate conditions for the three periods (2022–2040, 2042–2060, and 2062–2080) were generated by the delta change method based on the outputs of five global climate models. The results show that agricultural drought is anticipated to increase in the frequency, intensity, and duration (up to 168.82%, depending on time and emission scenarios). Moreover, drought events and water shortage in the dry season tend to be more likely to happen soon in the Be River Basin. These results are consistent with the changing trends of related soil moisture. Besides, the results contribute reliable scientific evidence to help managers and policy makers having appropriate plans in the future.

Sewage Water Treatment Using Chlorella Vulgaris Microalgae for Simultaneous Nutrient Separation and Biomass Production

Recovery of wastewater is essential for better management of water resources and can aid in reducing regional or seasonal water shortages. When algae were used to clean wastewater, amazing benefits were guaranteed, such as a decrease in the formation of dangerous solid sludge and the creation of valuable algal biomass through recycling of the nutrients in the wastewater. The trace elements nitrogen, phosphorus, and others that microalgae need for cell development are frequently present in contaminated wastewater. Hence, microalgal bioremediation is used in this study as an effective technique for the simultaneous treatment of COD, NH3-N, and orthophosphate from domestic wastewater and biomass production. Different concentrations of wastewaters were used. The maximum removals attained were: 84% of COD on the fifth day using the lowest mixing ratio of 50%, 95% of ammoniacal nitrogen, and 97% of phosphorus. The highest biomass production was achieved at day 12, except for the mixing ratio of 80% where the growth rate increased until day 14 at 400 mg/L.

Inoculation with Azospirillum argentinense Az19 improves the yield of maize subjected to water deficit at key stages of plant development

Water deficit constitutes a severe limitation to agricultural productivity. In the context of sustainable crop production, the potential of microbial biotechnology to increase plant drought tolerance and improve crop yields under adverse conditions is gaining relevance. This work aimed to compare the performance of Azospirillumargentinense strain Az19 to that of strain Az39, the most widely used for commercial inoculants, when inoculated in maize plants exposed to water deficit. For this purpose, greenhouse and field assays were conducted. In the greenhouse experiment, strain Az19 prevented the adverse effect of water deficit at V2 stage on maize growth. Moreover, the percentage of fertile plants and the ear weight decreased significantly under water deficits imposed at V2 and flowering in Az39-inoculated plants but not in Az19-inoculated plants. In the first field trial with the commercial maize hybrid DOW DS 515 PW, Az19-inoculated plants were those which better tolerated the water deficit imposed. In the second field trial, two maize genotypes with differential drought sensitivity (LP 29×LP 2542, sensitive; LP 882 (923)×LP 4703, tolerant) were tested. Higher tolerance to water deficit was detected in plants inoculated with A. argentinense Az19, with a noticeable effect on grain yield components in the sensitive genotype. Based on these results, we propose the use of A. argentinense Az19 for the formulation of more targeted Azospirillum-based inoculants, suitable for agroecological areas subjected to seasonal water deficits.

Study on Water Regulation of Yong’an River Basin Based on Ecological Flow Guarantee

Water resources are the necessary guarantee to support the development of human society and one of the most important resources to maintain the health and stability of the ecological environment. With the gradual increase of China’s population and the gradual increase of water consumption for industry, life and agriculture, the water consumption for ecological environment can not be met. As a result, some rivers have dried up, biological habitat has been lost and species diversity has been reduced. Therefore, how to ensure the river ecological flow is a very urgent problem to be solved. This paper selects Yong’an River Basin as the research object. Yong’an river is a mountainous river with the characteristics of uneven distribution of natural runoff throughout the year and seasonal water shortage. At present, the ecological flow demand of the river has not been considered in the reservoir operation. In this paper, four different scheduling schemes are set up according to the two constraints of ecological base flow and target ecological flow. Finally, the reservoir group operation scheme with better water supply assurance rate and ecological flow assurance rate is determined.

Tree growth periodicity in the ever‐wet tropical forest of the Americas

Abstract The occurrence of annual growth rings in tropical trees—the result of the seasonal activity of vascular cambium—has been explained by seasonal water deficit or flooding periods. However, little is known about the drivers of annual tree‐ring formation under tropical hyper‐humid conditions without clear seasonal dry periods or flooding (ever‐wet conditions). Shelford's law states that the deficit or the excess of environmental resources limits plant growth. Accordingly, we hypothesize that excess soil moisture, a slight seasonal reduction of precipitation and a reduction in light availability determine rhythmic growth in ever‐wet tropical forests. We first assessed the occurrence of rhythmic growth in 14 tree species from the Biogeographic Chocó Region (annual rainfall 7200 mm) using three methods: Radiocarbon (14C) dating (all studied species), tree‐ring synchronization (4 species that have replicates) and automatic dendrometers (two species). Then, we assessed the effect of environmental drivers (rainfall, short‐wave radiation, temperature and soil moisture) on tree growth based on tree ring and dendrometer observations. We present evidence of annual tree‐ring formation in all 14 studied tree species. Depending on the tree species, we observed positive and negative correlations between growth, water availability and light availability. These relationships suggest that both excess or deficit of environmental resources may explain the seasonal pattern of tree growth. Although we cannot differentiate between excess soil water and low light availability by high cloudiness, we suggest that cloudiness frequency could affect tree growth in these forests. Synthesis. We reveal the annual formation of growth rings in the unexplored wetter‐end tropical forests, where seasonal growth depends on either high soil moisture and hypoxia or light limitations by cloudiness and photosynthesis constraints.

Downscaling global land-use/cover change scenarios for regional analysis of food, energy, and water subsystems

Integrated assessment models (IAMs) capture synergies between human development and natural ecosystems that have important implications for the food-energy-water (FEW) nexus. However, their lack of fine-scale representation of water regulatory structure and landscape heterogeneity impedes their application to FEW impact studies in water-limited basins. To address this limitation, we developed a framework for studying effects of global change on regional outcomes for food crops, bioenergy, hydropower, and instream flows. We applied the new methodology to the Columbia River Basin (CRB) as a case study. The framework uses the Demeter land-use and land-cover change (LULCC) downscaling tool, which we updated so that water rights are spatially integrated in the land allocation process. We downscaled two LULCC scenarios (SSP2-RCP 4.5 and SSP5-RCP 8.5) under three levels of irrigation expansion: no expansion (historical extent), moderate expansion (all land presently authorized by a water right is irrigated), and maximum expansion (new water rights are granted to cover all irrigable land). The downscaled scenarios were evaluated using a hydrology-cropping systems model and a reservoir model coupled in a linear fashion to quantify changes in food and bioenergy crop production, hydropower generation, and availability of instream flows for fish. The net changes in each sector were partitioned among climate, land use, and irrigation-expansion effects. We found that climate change alone resulted in approximately 50% greater production of switchgrass for bioenergy and 20% greater instream flow deficits. In the irrigation-expansion scenarios, the combination of climate change and greater irrigated extent increased switchgrass production by 76% to 256% at the cost of 42% to 165% greater instream flow deficits and 0% to 8% less hydropower generation. Therefore, while irrigation expansion increased bioenergy crop productivity, it also exacerbated seasonal water shortages, especially for instream use. This paper provides a general framework for assessing benchmark scenarios of global LULCC in terms of their regional FEW subsystem outcomes.

Evaluating the spatial and temporal variability of groundwater uptake by riparian vegetation in a humid southeastern US catchment

AbstractIn environments with shallow water tables, vegetation may use groundwater to support transpiration (TG). This process has been carefully studied in some arid climates but rarely in humid climates—even those with severe droughts and seasonal water deficits. As such, the role of TG in humid‐catchment hydrology is poorly constrained. We analysed water table fluctuations from nine monitoring wells along three transects in a second‐order forested catchment to estimate TG at plot and whole‐riparian zone scales. Average TG estimated around all well locations ranged from 1.06 to 4.95 mm d−1 and did not change systematically as a function of distance from stream channel or with plot‐scale tree basal area. Counter to some previous studies, we found that TG was greater when the water table depth was deeper. Furthermore, the pattern of TG with water table depth was not monotonic at all locations. The ratio of TG to potential evapotranspiration tended to increase over the growing season, reflecting the progressive decrease in soil moisture storage and a greater reliance by vegetation on groundwater. Due to the lack of consistent spatial patterns in TG, we explored the number of monitoring wells needed to consistently estimate average TG within the 95% confidence bounds of the true mean. Based on this analysis, six or more wells were needed to consistently fall within the 95% confidence interval of the true mean. While this is based on the observed variability at a single site, it provides information for others considering this approach in similar upland forested catchments in humid regions.