Variation In Water Availability Research Articles

Mycorrhizal symbiosis alleviates plant water deficit within and across generations via phenotypic plasticity

Abstract Phenotypic plasticity is essential for organisms to adapt to local ecological conditions. It is expected that mutualistic interactions, such as arbuscular mycorrhizal (AM) symbiosis, mediate plant phenotypic plasticity, although it is not clear to what extent this plasticity may be heritable (i.e. transgenerational plasticity). We tested for plant plasticity within‐ and across‐generations in response to AM symbiosis and varying water availability in a full factorial experiment over two generations, using a genetically uniform line of a perennial apomictic herb, Taraxacum brevicorniculatum. We examined changes in phenotype, performance and AM fungal colonization of the offspring throughout plant development. AM symbiosis and water availability triggered phenotypic changes during the life cycle of plants. Additionally, both factors triggered adaptive transgenerational effects especially detectable during the juvenile stage of the offspring. Water deficit and absence of AM fungi caused concordant plant phenotypic modifications towards a ‘stress‐coping phenotype’, both within and across generations. Parental environment also affected AM fungal colonization of the offspring. Juvenile offspring of amply watered parents and adut offspring of mycorrhizal parents had increasing length of root colonized by AM fungi when they were under water stress. Synthesis. We show that, in addition to providing beneficial transgenerational effects in offspring traits proxies of fitness (such as increased biomass, survival or nutritional status), AM symbiosis can trigger transgenerational plasticity in anatomical and physiological traits related to resource‐use acquisition, and further influence offspring AM fungal colonization. Our results show that AM symbiosis could improve plants' ability to cope with environmental stress, not only within, but also across generations.

FACTORS AFFECTING THE NUMBER OF ARMS ON A SAGUARO (CARNEGIEA GIGANTEA)

The average number of arms on a saguaro (Carnegiea gigantea) increases with saguaro height, but there is considerable variation among saguaros for any given height. This variation has been largely attributed to variation in water availability among individual plants. To test this hypothesis, I recorded the height and number of arms of a sample of 425 saguaros within Organ Pipe Cactus National Monument along with values of three variables that should affect arm production through their effect on water availability: (1) the number of neighboring saguaros under the same nurse tree canopy, (2) the presence of a wash within 5 m, and (3) the presence and identity of any living or dead plant associate. Deviation from the number of arms expected for a given saguaro height was negatively related to the number of saguaro neighbors and positively related to the presence of a nearby wash. Saguaros growing with live associates also had fewer arms than those growing alone, and saguaros growing with dead associates had more arms than those growing alone. Each of these results is consistent with the idea that arm production is affected by water availability.

Analysis of South American climate and teleconnection indices

Oceanic heat anomalies affect climate in remote regions through the atmospheric cycle. South America (SA) was the first region found associated with EI Niño, which affects the fishery, agriculture, forestry, and livestock industry of SA. As approximately 60% of the total water is used for agriculture, climate changes in SA caused by ocean anomalies have led to the variability of available water, especially for irrigation water. Where the precipitation is low and/or the temperature is high, the availability and quality of water resources are under pressure. For instance, droughts associated with La Niña severely limited water supply and irrigation requirements between 25°S - 40°S in west-central Argentina and central Chile. In order to study the relationship between ocean variability and the climate of SA, 19 teleconnection indices (TI) related to Ocean abnormity are considered. The 19 indices are: the sea surface temperature (SST) and their anomaly in 4 Niño regions (SST1 + 2, SST3, SST3.4, SST4, ANOM1 + 2, ANOM3, ANOM3.4, ANOM4), Southern Oscillation Index (SOI), Oceanic Niño Index (ONI), Outgoing Longwave Radiation (OLR), Arctic Oscillation (AO), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), Pacific-North America (PNA), Atlantic Multi-decadal Oscillation (AMO), West and East of Indian Ocean Dipole (IODW, IODE), and the difference between IODW and IODE (IODd). High-resolution gridded climate data (1982–2016) from the Global Precipitation Climatology Centre (GPCC), the Climate Prediction Center (CPC), and the National Centers for Environmental Prediction (NCEP) are applied for correlation analyses. The results show that the 89.4% area of South American climate has a significant correlation with the SST in Niño region 1 + 2, the mean correlation coefficient is 0.55 for NCEP precipitation and 0.54 for CPC temperature. The lag duration for the remote correlation is around 2–3 months. It is the first attempt to analyze the correlation relationship based on 19 TIs, which can provide comprehensive insight into the climate of SA at a high-resolution scale. These findings are helpful for identifying the sensitive factors that affect climate in SA, for projecting the climate variables of SA, and for managing the irrigation water resources of SA.

Effects of deforestation and afforestation on water availability for dry bean production in Haiti

Haitian watersheds suffer from a lack of environmental management and the absence of conservation practices, which impairs natural resources and agricultural productivity. This is aggravated by harvesting trees to compensate for reduced crop production and income. Deforestation can further deteriorate the natural and agricultural systems by increasing the temporal variability of water availability, often realized in the forms of floods and droughts. The goal of this study was to determine the effects of both deforestation and afforestation on water resources and agricultural productivity. We selected the Courjolle River watershed and its downstream irrigation districts because they represent the linkage between the upstream forest and downstream agricultural areas. Watershed hydrology and dry bean growth were simulated with the Soil and Water Assessment Tool (SWAT) model and the CSM-CROPGRO–Dry bean model of the Decision Support System for Agrotechnology Transfer (DSSAT). The parameters for both models were calibrated to streamflow and dry bean growth measurements that were made in the study areas. Deforestation and afforestation scenarios were developed based on an understanding of the local landscape. The modeling experiment showed that deforestation could decrease water availability and stability, causing a decrease in dry bean production, while afforestation had the opposite effect. An increase of the afforested areas from 25% to 100% of the watershed increased the streamflow by 2–7%, compared to the current land cover, during dry periods. On the other hand, an increase in deforested areas decreased the amount of available water for downstream agricultural areas by 6–24%. Potential changes in the water availability due to the land cover changes then affected the yield of dry bean grown in the downstream irrigation areas, from −42–24% under the deforestation and afforestation scenarios. The study demonstrated how improved hydrologic stability due to an increase in tree cover could promote agricultural production. It also showed that afforestation could be an effective way to manage both the natural and agricultural resources in Haiti, improving the environmental sustainability of the watershed and the economic sustainability of local smallholder farmers.

Is variation in inter-annual precipitation a mechanism for maintaining plant metabolic diversity?

In order for diverse species to coexist in ecological communities, they must vary in ways that reduce competition. Often, this is done by some form of spatial niche separation where small differences in environment allow for coexistence among species. However, temporal separation of resources could also be a factor in driving community diversity. Here, we ask whether inter-annual variation in growing season precipitation could provide sufficient variation in water availability to allow plant species with different intrinsic metabolism to co-occur. We hypothesized that species would differentially respond to soil water availability, and that species with a metabolic strategy to conserve water at the expense of carbon gain would grow better in dry conditions relative to species with a metabolic strategy to gain carbon at the expense of foliar water loss. We measured above-ground biomass and leaf-level metabolism using carbon and oxygen stable isotope ratios for seven Asteraceae species across five experimental water treatments. Species differentially responded to variation in growing season water availability and, importantly, how they responded could be explained by differences in metabolism. Water-conservative species grew best in the dry treatments and had lower growth in wet treatments. Carbon-acquisitive species displayed the opposite pattern, with maximal growth in wet treatments and steep declines in dry treatments. Metabolic differences among co-occurring species may help explain temporal variation in growth, and could provide an underlying physiological mechanism for long-term dynamics that promote biodiversity.

Grapevine responses to site-specific spatiotemporal factors in a Mediterranean climate

Water availability in vineyards varies in space and time. The spatiotemporal variability of water availability to vines is affected by terrain, meteorology, and irrigation. This study aimed to analyze the response of vegetative and reproductive attributes of vines to spatiotemporal variability in water availability. We quantified the spatial autocorrelation of terrain covariates and grapevine attributes and determined the relative influence (RI) of the covariates on these attributes. In each of four growing seasons (2017–2020), in a Vitis vinifera cv. “Sauvignon Blanc” vineyard, five vegetative and reproductive attributes were collected for 240 vines. Terrain covariates included elevation, slope, aspect, topographic wetness index, and categorical landforms; and meteorological covariates consisted of annual rainfall and chilling hours. A Moran’s I statistic was computed for each spatial covariate and each grapevine attribute during each season to define temporal changes in spatial variability. A multivariate analysis using gradient boosted regression trees algorithm was applied to extract the RI of the covariates. The results showed high spatial autocorrelation of the terrain covariates and a strong negative shift in spatial dependency of the grapevine attributes throughout the experiment. Yield and number of clusters per vine were highly affected by seasonal precipitation (RI of 46.15% and 42.59%), while changes in inter-seasonal cluster weight and pruning weight were highly subjected to irrigation amounts (RI of 23% and 26.66%), with complementary terrain influences. The number of canes per vine was mainly affected by terrain characteristics. Long-term changes in grapevine attributes depended on meteorological shifts, while higher precipitation amounts were associated with weaker responses of vines to irrigation strategies. The spatial patterns of terrain affected water distribution in the vineyard and controlled the spatial dynamics of grapevine attributes. Knowledge regarding the space-time trends of water availability effects on grapevine attributes may assist decision making of irrigation practices in vineyards.

Grand Challenges of Hydrologic Modeling for Food-Energy-Water Nexus Security in High Mountain Asia

Climate-influenced changes in hydrology affect water-food-energy security that may impact up to two billion people downstream of the High Mountain Asia (HMA) region. Changes in water supply affect energy, industry, transportation, and ecosystems (agriculture, fisheries) and as a result, also affect the region's social, environmental, and economic fabrics. Sustaining the highly interconnected food-energy-water nexus (FEWN) will be a fundamental and increasing challenge under a changing climate regime. High variability in topography and distribution of glaciated and snow-covered areas in the HMA region, and scarcity of high resolution (in-situ) data make it difficult to model and project climate change impacts on individual watersheds. We lack basic understanding of the spatial and temporal variations in climate, surface impurities in snow and ice such as black carbon and dust that alter surface albedo, and glacier mass balance and dynamics. These knowledge gaps create challenges in predicting where and when the impact of changes in river flow will be the most significant economically and ecologically. In response to these challenges, the United States National Aeronautics and Space Administration (NASA) established the High Mountain Asia Team (HiMAT) in 2016 to conduct research to address knowledge gaps. This paper summarizes some of the advances HiMAT made over the past 5 years, highlights the scientific challenges in improving our understanding of the hydrology of the HMA region, and introduces an integrated assessment framework to assess the impacts of climate changes on the FEWN for the HMA region. The framework, developed under a NASA HMA project, links climate models, hydrology, hydropower, fish biology, and economic analysis. The framework could be applied to develop scientific understanding of spatio-temporal variability in water availability and the resultant downstream impacts on the FEWN to support water resource management under a changing climate regime.

Simulation of future climate scenarios and the impact on the water availability in southern Brazil

Water is an essential natural resource that is being impacted by climate change. Thus, knowledge of future water availability conditions around the globe becomes necessary. Based on that, this study aimed to simulate future climate scenarios and evaluate the impact on water balance in southern Brazil. Daily data of rainfall and air temperature (maximum and minimum) were used. The meteorological data were collected in 28 locations over 30 years (1980-2009). For the data simulation, we used the climate data stochastic generator PGECLIMA_R. It was considered two scenarios of the fifth report of the Intergovernmental Panel on Climate Change (IPCC) and a scenario with the historical data trend. The water balance estimates were performed for the current data and the simulated data, through the methodology of Thornthwaite and Mather (1955). The moisture indexes were spatialized by the kriging method. These indexes were chosen as the parameters to represent the water conditions in different situations. The region assessed presented a high variability in water availability among locations; however, it did not present high water deficiency values, even with climate change. Overall, it was observed a reduction of moisture index in most sites and in all scenarios assessed, especially in the northern region when compared to the other regions. The second scenario of the IPCC (the worst situation) promoting higher reductions and dry conditions for the 2099 year. The impacts of climate change on water availability, identified in this study, can affect the general society, therefore, they must be considered in the planning and management of water resources, especially in the regional context

Climate change and reservoir sedimentation implications for irrigated agriculture in the Indus Basin Irrigation System in Pakistan

Pakistan relies greatly on the water of the Upper Indus basin (UIB) for its vast agriculture in the Indus Basin Irrigation System (IBIS). There are already concerns about the extent of unsustainable water use in the IBIS, particularly of groundwater, and these concerns are likely to increase in the future due to population increase and associated increased demand for food. In addition, climate change, continuing reservoir sedimentation in the major dams, and other impacts on water supply and demand are likely to have an impact on the practical implementation of the landmark inter-provincial Water Apportionment Accord (the Accord), which governs surface water allocation in the IBIS. There is, therefore, a need to assess the sustainability of irrigation in light of the potential variations of water availability in the basin under a series of plausible climate change and reservoir sedimentation scenarios.In this paper, we examine the impact of continuing reservoir sedimentation and climate change by 2050 on the water balance of canal commands in the IBIS. Firstly, we used a river system model, the first to include water management rules as in the Accord, to propagate climate induced changes on flows in the UIB and their impact on IBIS flow regulation and canal deliveries (Icw), with and without reservoir sedimentation. Secondly, we used a selection of General Circulation Models (GCMs) that showed skill at simulating the local climate of the IBIS to assess the projected changes to rainfall (Pn) and evapotranspiration (ETa). The analysis revealed that water balances in IBIS canal command areas are more significantly affected by changed inflows from the UIB than by localised climate induced changes (i.e. Pn and ETa). Continuing reservoir sedimentation in the dams to 2050 will diminish the capacity of the system to store flows during the wet summer Kharif season for its later release in the dry winter Rabi season. This will decrease the supply of Icw in the Rabi season to the downstream IBIS areas in Sindh and Balochistan provinces, and potentially increase supplies in the Kharif season. The impact of reservoir sedimentation on the Rabi water supply (33 mm (13%) decrease in median Icw, equivalent to 1.89 km3), is greater than the impact of projected localised climate change within the IBIS (2 mm (12%) decrease in median Pn, equivalent to 0.13 km3). Sedimentation combined with climate change decreases the median Icw by 51 mm (20%, equivalent to 2.91 km3) in Rabi in the low flow scenario and increases it by 48 mm (8%, equivalent to 2.72 km3) in Kharif in the high flow scenario. In the upstream Punjab province, however, reservoir sedimentation will have limited impact by 2050 due to lower ETa in Rabi and the availability of groundwater. Continued reservoir sedimentation beyond 2050 will also affect Punjab, again diminishing the supply of Icw in Rabi and increasing it in Kharif. Concurrently, declining Icw could lead to a substantial reduction in crop areas in the Rabi season. To avoid this undesirable scenario, Pakistan needs to explore both demand and supply management options to achieve food and economic security, as well as controlling sedimentation rates in reservoirs.

Responses in Growth and Anatomical Traits of Two Subtropical Tree Species to Nitrogen Addition, Drought, and Their Interactions.

Nitrogen (N) deposition and drought are two major stressors that influence tree growth and propagation. However, few studies have investigated their interactions. In this study, saplings of the two co-occurring species Ormosia pinnata (leguminous) and Schima superba (non-leguminous) were cultivated under two N addition rates (0 and 80 kg N ha–1 year–1) with well-watered (WW, 80% of field capacity), moderate drought (MD, 60% of field capacity), and severe drought conditions (SD, 40% of field capacity). We examined their growth, as well as multiple anatomical and non-structural carbohydrate (NSC) responses, after 2 years. Results revealed that N addition significantly promoted the growth of MD-stressed S. superba, whereas no significant effect was detected in O. pinnata. Decreased leaf water potential (both Ψmd and Ψpd) was also observed with N addition for both species under MD, but not under SD. Furthermore, the application of N positively impacted drought adaptive responses in the stem xylem of S. superba, showing decreased stem xylem vessel diameter (DH), theoretical hydraulic conductivity (Kth), and increased vessel frequency (VF) upon drought under N addition; such impacts were not observed in O. pinnata. Regarding leaf anatomy, N addition also caused drought-stressed S. superba to generate leaves with a lower density of veins (VD) and stomata (SD), which potentially contributed to an enhanced acclimation to drought. However, the same factors led to a decrease in the palisade mesophyll thickness (PMT) of SD-stressed O. pinnata. Moreover, N addition increased the xylem soluble sugar and starch of MD-stressed O. pinnata, and decreased the xylem soluble sugar under SD for both species. The results suggest that N addition does not consistently modify tree growth and anatomical traits under variable water availability. S. superba appeared to have a greater capacity to be more adaptable under the future interactive effects of N addition and drought due to major modifications in its anatomical traits.

Local and non-local controls on seasonal variations in water availability and use by riparian trees along a hydroclimatic gradient

As global climate change continues to impact regional water cycles, we may expect further shifts in water availability to forests that create challenges for certain species and biomes. Lowland deciduous riparian forests are particularly vulnerable because tree species cannot migrate out of the stream corridor, and they rely on root zone water availability that is controlled by variations in both local climate conditions (e.g. precipitation, evaporation, and infiltration) and non-local hydroclimatic forcing (e.g. streamflow, snowmelt, recharge). To determine how the seasonal water source usage of riparian trees is controlled by local versus non-local variability in hydroclimatic regime, we reconstructed the seasonal oxygen isotope (δ 18 O) signature of water used by two riparian tree species with contrasting rooting depths, comprising ∼800 δ 18 O tree-ring cellulose measurements from 12 tree-level decadal time-series at sub-annual resolution (six samples per year), along a strong hydroclimatic gradient within the Rhône River basin, SE France. These results were evaluated alongside δ 18 O measurements made from potential endmember water sources and independent hydroclimatic metrics. Thus we characterize the seasonal evolution of both potential water availability at distinct rooting depths and tree water source use and investigate the generalized riparian tree response to seasonal variations in local versus non-local hydroclimatic forcing over a decade. We show: (a) distinct seasonal water use between species, based on differential access to groundwater; (b) substantial source switching in both species based on evolving water availability; and (c) that riparian trees are more dependent on locally controlled soil moisture with distance downstream, creating increased vulnerability to locally increasing temperatures. We also find that deeply rooted trees in lowland riparian floodplains are potentially vulnerable to climate change because of their high dependence on water supply from mountains. This effect is more pronounced downstream, where seasonal water table decline may lead to loss of water required for deeply rooted trees.

Understanding uptake of community groundwater monitoring in rural Brazil

Resource monitoring is often cited as important for effective common pool resources management. In practice, not all monitoring interventions are successful, particularly when the resource, such as groundwater, is challenging to monitor and measure. We conducted a field experiment on groundwater monitoring in Ceará, Brazil, where communities are increasingly reliant on groundwater yet do not engage in monitoring. Despite careful implementation, uptake of monitoring within the 80 treatment communities was low. To unpack this low uptake, we conduct multimethods exploratory research. We find that uptake is less likely in communities facing high coordination costs, either within the community leadership or across the broader community. Uptake is also less likely when there are physical barriers to monitoring, when there are more substitutes for groundwater, and when there is lower variability in water availability. Our findings can inform future monitoring interventions in similar contexts worldwide.

Water availability controls crustal melting temperatures

Although the capacity for water to lower the solidus during crustal melting is well recognised, a modern consensus is that most granitic magmas are generated under fluid-absent melting conditions at temperatures ≥850 °C, and that water has little influence on crustal melting temperatures. By contrast, we show that granite magmas produced in different tectonic settings equilibrated in the crust at significantly different temperatures, ranging between 700 and 1000 °C, depending on water availability during melting. On a molecular scale, the process that lowers the solidus is similar to hydroxylation, i.e. the depolymerization of the aluminosilicate framework melt by complexing of OH− ions with the melt network formers, Si4+ and Al3+. On a larger scale, the process is “water fluxing”, which is consistent with the growing realisation that many granitic magma reservoirs form under protracted, cool-storage conditions, and consistent with the typically low (100–200 ppm) Zr content (hence low zircon saturation temperatures) of granitic magmas. Global compilations of common igneous and sedimentary rocks also show that Zr contents are consistently in the range of 100–200 ppm, indicating that average Zr contents do not change significantly during crustal differentiation. Such low average contents are most easily reconciled with models of low-T silicic melt generation and entrainment of refractory or antecrystic zircon in the magma. Low-K, I-type (Cordilleran) granitic magmas are cooler and much more voluminous than A-type magmas because they are hydrous, although transiently heated by mafic magma infusions. In turn, water availability is tectonically controlled, occurring in most suprasubduction (SSZ) environments where mantle-derived water drives melting of orogenic crust already elevated in heat flux (>75 mWm−2), typical of upper amphibolite facies conditions. However, within intraplate environments, where melting proceeds by high-T, hydrate-breakdown melting, crustal temperatures are not buffered during water fluxing and rise to granulite facies and ultrahigh temperature (UHT) conditions, particularly for refractory protoliths, producing ferroan, alkalic A-type granites and charnockites in deep crustal hot zones (DCHZ). The combination of tectonic setting, contrasting source rocks, and variation in water availability, controls the compositional diversity of granitic magmas.

Sensitivity analysis and parameter estimation of anthropogenic water uses for quantifying relation between groundwater overuse and water stress in Mongolia

In Mongolia, overuse and degradation of groundwater is a serious issue, mainly in the urban and economic hub in Ulaanbaatar, and the Southern Gobi mining hub. The authors have recently applied a process-based eco-hydrology model, NICE (National Integrated Catchment-based Eco-hydrology) to these two contrasting river basins in order to explicitly quantify spatio-temporal variations in water availability. In this study, they further extended the model to couple with inverse method for sensitivity analysis and parameter estimation of anthropogenic water uses (NICE-INVERSE). The model quantified the spatio-temporal variations of livestock water use in these river basins in comparison with the estimated values by aggregating statistical data, GIS data, observation data, and field surveys in their previous studies. The amount of water use by animals were generally small for each soum (district), and could also be heavily returned back to the ecosystems. The result also showed a temporal decreasing trend of unit water use in some typical livestock (cattle, sheep, and goats), suggesting a substantial increase in water stress due to local-regional eco-hydrological degradation by urbanization and mining. These results clarified the substantial increase in water stress of groundwater degradation was mainly caused by urbanization and mining locally in addition to climatic change. Sensitivity analysis and inverse estimation of model parameters helped to improve the accuracy of hydrologic budgets in basins. This methodology is powerful for evaluating spatio-temporal variations of water availability in regions with fewer inventory data on urbanization, mining, and livestock.

Impact of temperature and water availability on microwave-derived gross primary production

Abstract. Vegetation optical depth (VOD) from microwave satellite observations has received much attention in global vegetation studies in recent years due to its relationship to vegetation water content and biomass. We recently have shown that VOD is related to plant productivity, i.e., gross primary production (GPP). Based on this relationship between VOD and GPP, we developed a theory-based machine learning model to estimate global patterns of GPP from passive microwave VOD retrievals. The VOD-GPP model generally showed good agreement with site observations and other global data sets in temporal dynamic but tended to overestimate annual GPP across all latitudes. We hypothesized that the reason for the overestimation is the missing effect of temperature on autotrophic respiration in the theory-based machine learning model. Here we aim to further assess and enhance the robustness of the VOD-GPP model by including the effect of temperature on autotrophic respiration within the machine learning approach and by assessing the interannual variability of the model results with respect to water availability. We used X-band VOD from the VOD Climate Archive (VODCA) data set for estimating GPP and used global state-of-the-art GPP data sets from FLUXCOM and MODIS to assess residuals of the VOD-GPP model with respect to drought conditions as quantified by the Standardized Precipitation and Evaporation Index (SPEI). Our results reveal an improvement in model performance for correlation when including the temperature dependency of autotrophic respiration (average correlation increase of 0.18). This improvement in temporal dynamic is larger for temperate and cold regions than for the tropics. For unbiased root-mean-square error (ubRMSE) and bias, the results are regionally diverse and are compensated in the global average. Improvements are observed in temperate and cold regions, while decreases in performance are obtained mainly in the tropics. The overall improvement when adding temperature was less than expected and thus may only partly explain previously observed differences between the global GPP data sets. On interannual timescales, estimates of the VOD-GPP model agree well with GPP from FLUXCOM and MODIS. We further find that the residuals between VOD-based GPP estimates and the other data sets do not significantly correlate with SPEI, which demonstrates that the VOD-GPP model can capture responses of GPP to water availability even without including additional information on precipitation, soil moisture or evapotranspiration. Exceptions from this rule were found in some regions: significant negative correlations between VOD-GPP residuals and SPEI were observed in the US corn belt, Argentina, eastern Europe, Russia and China, while significant positive correlations were obtained in South America, Africa and Australia. In these regions, the significant correlations may indicate different plant strategies for dealing with variations in water availability. Overall, our findings support the robustness of global microwave-derived estimates of gross primary production for large-scale studies on climate–vegetation interactions.

Spatial and temporal dynamics of suspended particles and E. coli in a complex surface-water and karst groundwater system as a basis for an adapted water protection scheme, northern Vietnam

Karst aquifers in subtropical regions are characterized by high variability of water availability and quality due to changes associated with rainy and dry seasons. An additional challenge for water management is the combination of surface-water and karst groundwater systems since high spatiotemporal dynamics cause high variability of water quality. In these cases, adapted protection strategies are required. In this study, a protection approach for the catchment of a river-water diversion point in a rural area in northern Vietnam is developed. The variability of water quality was evaluated by rainy and dry season synoptic surveys of suspended particles and microbial contamination at 49 sites and time series at three sets of paired sites under constant hydraulic conditions. The anthropogenic land-use activities in the catchment were mapped to identify potential contamination sources and to highlight the challenging combination of surface-water and karst groundwater management. The analyzed data indicate differences in water quality between the dry and rainy seasons and a higher influence on water quality from land use than from hydrologic conditions. Furthermore, the results suggest a high risk of contamination resulting from residential areas, agriculture, and livestock farming, and reveal the necessity of implementation of appropriate measures such as restricted farming and the hook-up of buildings to municipal sewage disposal. Finally, the data show that water quality can be improved by adjusting water withdrawals by the time of day. The applied methods can be transferred to other surface-water and karst groundwater systems in similar subtropical environments.

The impact of shifting Köppen-Geiger climate zones on soil organic carbon concentrations in Australian grasslands

The factors determining the spatial distribution of soil organic carbon (SOC) at large-scales closely align with bioclimate regions; reflecting climate, ecosystem and soil properties. Recent studies of the Köppen-Geiger climate zones of Australia have highlighted an extension of the hot, arid, steppe environment from central Australia into the southeast (SE) under future climate change scenarios (2071–2100 under RCP 8.5). As SOC concentrations are highest in Australia's SE, it is important the effect of this shift is quantified. This study assesses this and how changes in the factors that control SOC formation may alter SOC concentrations. Field measured SOC concentrations were compared to current climate, soil, topography, vegetation, and soil erosion variables for 12 grassland sites from SE to NW Australia. SOC concentrations ranged from 0.39% in northwest (NW) and Central Australia to as high as 6.88% in the SE. Using regression analyses; temperature, elevation and Normalised Difference Vegetation Index were found to be the only significant drivers (α = 0.95) of SOC across the sites. Partial correlation analyses then identified temperature, elevation and clay content as imparting a significant effect on the relationships between SOC and water availability variables. This indicates that an extension of the arid environment into SE Australia may lead to a decrease in SOC (up to 1.12%), as mean annual temperature exceeds threshold values that limit SOC concentration. This is significant as the majority of Australia's SOC is stored in this area and these environments exert a strong influence on global carbon cycling.

A stable isotope and functional weed ecology investigation into Chalcolithic cultivation practices in Central Anatolia: Çatalhöyük, Çamlıbel Tarlası and Kuruçay

The integration of stable isotope analysis of crop remains with the ecological analysis of archaeological weed flora allows for a detailed reconstruction of crop husbandry and arable growing conditions. This paper presents the first such study for developed Neolithic and Chalcolithic Central Anatolia, exploring crop husbandry at the large (8 ha) early 6th millennium BC site of Çatalhöyük West and the last phases of the preceding Neolithic Çatalhöyük East, located on the western end of the Konya Plain, and the small 4th millennium sites of Çamlıbel Tarlası (0.25 ha), located in the loop of the Kızılırmak river, and Kuruçay Höyük (~1 ha), located on the shore of Lake Burdur. The results reveal the mosaic nature of Çatalhöyük cultivation; the complex ecosystem, naturally 15N enriched, was additionally anthropogenically improved, while inhabitants also chose to cultivate barley in drier conditions to the wheats and pulses. The smaller, Late Chalcolithic site of Çamlıbel Tarlası cultivated each individual crop species in variable conditions instead of selecting a specific species for cultivation in drier or wetter conditions. Each single species was cultivated in conditions with a wide range of water availabilities while receiving low-level manure application. Variation in water availability is possibly a consequence of the variable topography surrounding the site, with the hills potentially used for cultivation, providing a wide range of conditions due to their slope. Functional weed ecology complements the isotopic data, indicating the wider range of cultivation intensities surrounding Çatalhöyük West, compared with more consistent, narrower ranges of growing conditions at Çamlıbel Tarlası and Kuruçay Höyük. Settlement date, site size and environment seem to be key contributing factors shaping the method used to cultivate crops at these Chalcolithic sites. The larger, earlier community of Çatalhöyük West, located in a complex riverine ecosystem around the dryland anabranching channels of the Çarşamba river, cultivated species in different conditions and maintained a range of crop husbandry intensities, potentially reflecting differential access to limited resources. The smaller Late Chalcolithic sites, with communities consisting of one household to several households and located in less complex ecosystems with higher precipitation, maintained more stable crop growing conditions and management intensities. This is plausibly a consequence of equal access and sharing of critical resources for crop cultivation, such as labour, manure and land, coupled with the adequate precipitation rates.

Groundwater Recharge for Water Security

The Arizona Water Banking Authority (AWBA) was established in 1996 to make full use of Arizona’s Colorado River entitlement. It aims to address groundwater depletion in central Arizona and to protect Colorado River water users against future shortages due to interannual variability in water availability. Each year, the AWBA pays the costs to deliver any of the state’s unused entitlement to Colorado River water into central and southern Arizona and to store that water underground. The AWBA stores water on behalf of Central Arizona Project municipal subcontractors, other mainstream municipal Colorado River water rights holders, and tribal entities. Through its interstate banking agreements, the AWBA can also store water on behalf of the states of Nevada and California. Water stored by the AWBA is accounted for using Arizona’s statutorily created system of long-term storage credits (LTSCs), which allow future pumping of stored water within the same hydrologic basin. During shortage conditions in the Lower Basin of the Colorado River, the AWBA will distribute the LTSCs, enabling recipients to pump groundwater that otherwise would not be permitted. In this way, the AWBA serves as a unique insurance mechanism against shortages for users of Colorado River water in Arizona and the Lower Basin. To date, the AWBA’s focus has been on storage, yet in the coming years, its activities will shift to recovery, and it will need to confront additional challenges associated with matching supplies with demands and limitations on water available for recharge.

A fragile soil moisture environment exacerbates the climate change-related impacts on the water use by Mongolian Scots pine (Pinus sylvestris var. mongolica) in northern China: Long-term observations

Characterizing the soil moisture environment in the plantation ecosystems may provide substantial information for judging the stability of forests in relation to climate change. In this study, we explored the level and the variations of water availability, as well as their influence on tree water use in the long-term. This was achieved by monitoring in particular the volumetric soil water content (θ), the groundwater level, the atmospheric vapor pressure deficit (VPD), and the sap flux-based forest transpiration (Tr) in a sand-fixation plantation of Mongolian Scots pine in northern China. The results showed a significant inter- and intra-annual variability of annual precipitation (Pr), for an average (±standard deviation) of ~ 476 ± 139 mm over the past 16-year study period. The inter-annual variations of the groundwater level showed a general downward trend, decreasing from −4.82 to −6.13 m. The relative extractable soil water (REW) between 0−1 m and between 1−2 m depth along soil profile was only 0.29 ± 0.14 and 0.16 ± 0.08, respectively, indicating a decreasing of soil moisture capacity and of the moisture depletion patterns with depth. The statistics relative to the past seven years (between 2013−2019) indicate an average Tr of 193 ± 59 mm for Mongolian Scots pines. Notably, their transpiration capability (Tr/VPD) declined with the decrease of REW0−1 m: the boundary curve showed a clear exponential decline. The threshold value of REW0–1 m (deduced from an abrupt decrease of Tr/VPD) was ~ 0.41 and 0.35 at the daily and monthly timescales, respectively. The average Tr/Pr value was 0.42 (maximum = 0.60) and Tr accounted on average for 55% of the total evapotranspiration (maximum = 77%). Soil drought prevailed at the study site; however, we did not notice a heavy use of soil water resources by Mongolian Scots pine. The results, overall, underlined the causes rather than the consequences of the observed soil moisture conditions, which are leading to the degradation of Mongolian Scots pine. Forest management measures causing moderate disturbance are hence recommended for mitigating the water competition between Mongolian Scots pine and sub-canopy vegetation.