Unfolding the dynamics of ecosystems undergoing alternating wet-dry transitional states.

A significant fraction of Earth's ecosystems undergoes periodic wet-dry alternating transitional states. These globally distributed water-driven transitional ecosystems, such as intermittent rivers and coastal shorelines, have traditionally been studied as two distinct entities, whereas they constitute a single, interconnected meta-ecosystem. This has resulted in a poor conceptual and empirical understanding of water-driven transitional ecosystems. Here, we develop a conceptual framework that places the temporal availability of water as the core driver of biodiversity and functional patterns of transitional ecosystems at the global scale. Biological covers (e.g., aquatic biofilms and biocrusts) serve as an excellent model system thriving in both aquatic and terrestrial states, where their succession underscores the intricate interplay between these two states. The duration, frequency, and rate of change of wet-dry cycles impose distinct plausible scenarios where different types of biological covers can occur depending on their desiccation/hydration resistance traits. This implies that the distinct eco-evolutionary potential of biological covers, represented by their trait profiles, would support different functions while maintaining similar multifunctionality levels. By embracing multiple alternating transitional states as interconnected entities, our approach can help to better understand and manage global change impacts on biodiversity and multifunctionality in water-driven transitional ecosystems, while providing new avenues for interdisciplinary studies.

Can we identify tipping points of resilience loss in Mediterranean rangelands under increased summer drought?

Mediterranean ecosystems are predicted to undergo longer and more intense summer droughts. The mechanisms underlying the response of herbaceous communities to such drier environments should be investigated to identify the resilience thresholds of Mediterranean rangelands. A 5-year experiment was conducted in deep and shallow soil rangelands of southern France. A rainout shelter for 75 days in summer imposed drier and warmer conditions. Total soil water content was measured monthly to model available daily soil water. Aboveground net primary production (ANPP), forage quality, and the proportion of graminoids in ANPP were measured in spring and autumn. Plant senescence and plant cover were assessed in summer and spring, respectively. The experimental years were among the driest ever recorded at the site. Therefore, manipulated summer droughts were drier than long-term ambient conditions. Interactions between treatment, community type, and experimental year were found for most variables. In shallow soil communities, spring plant cover decreased markedly with time. This legacy effect, driven by summer plant mortality and the loss of perennial graminoids, led to an abrupt loss of resilience when the extreme water stress index exceeded 37 mm 10 day-1, characterized by a reduction of spring plant cover below 50% and a decreased ANPP in rainy years. Conversely, the ANPP of deep soil communities remained unaffected by increased summer drought, although the presence of graminoids increased and forage nutritive value decreased. This study highlights the role of the soil water reserve of Mediterranean plant communities in modulating ecosystem responses to chronically intensified summer drought. Communities on deep soils were resilient, but communities on shallow soils showed a progressive, rapid, and intense degradation associated with a loss of resilience capacity. Notably, indexes of extreme stress were a better indicator of tipping points than indexes of integrated annual stress. Considering the role of soil water availability in other herbaceous ecosystems should improve the ability to predict the resilience of plant communities under climate change.

Root pH variation of herbaceous plants among plant functional groups in response to climate and soil gradients on the Tibetan alpine grasslands.

Plant pH is an emerging functional trait that plays important roles in physiological processes and nutrient cycling. However, how root pH varies among plant functional groups (PFGs) and the regulatory factors on a large scale remain unclear. Therefore, we quantified root pH variation of herbaceous plants in four PFGs from 20 sites on the Tibetan Plateau along a 1600 km transect and explored the correlations between root pH and different PFGs, climate and soil conditions. The results showed that the root pH of herbaceous plants was slightly acidic (6.46 ± 0.05). Grasses had the highest root pH (6.91 ± 0.10) across all functional groups (p < .05), whereas legumes had the lowest (5.90 ± 0.08; p < .05). The root pH decreased with mean annual precipitation, aridity index, soil water content and soil stress coefficient, whereas the significant positive correlation with soil pH. PFGs, climate and soil explained 5.39, 11.15 and 24.94% of the root pH variance, respectively. This study provided a comprehensive analysis of root pH patterns in herbaceous plants over a large spatial scale. Root pH was controlled by the combined influence of PFGs, climate and soil properties, with moisture status being the main influential factor. In contrast to the leaf pH, the root pH of herbaceous plants is strongly affected by the soil pH along environmental gradients. Our findings provide new insights into root functional traits and survival strategies of herbaceous plants in alpine ecosystems.

Topography-driven microclimate gradients shape forest structure, diversity, and composition in a temperate refugial forest.

Macroclimate drives vegetation distributions, but fine-scale topographic variation can generate microclimate refugia for plant persistence in unsuitable areas. However, we lack quantitative descriptions of topography-driven microclimatic variation and how it shapes forest structure, diversity, and composition. We hypothesized that topographic variation and the presence of the forest overstory cause spatiotemporal microclimate variation affecting tree performance, causing forest structure, diversity, and composition to vary with topography and microclimate, and topography and the overstory to buffer microclimate. In a 20.2-ha inventory plot in the North American Great Plains, we censused woody stems ≥1 cm in diameter and collected detailed topographic and microclimatic data. Across 59-m of elevation, microclimate covaried with topography to create a sharp desiccation gradient, and topography and the overstory buffered understory microclimate. The magnitude of microclimatic variation mirrored that of regional-scale variation: with increasing elevation, there was a decrease in soil moisture corresponding to the difference across ~2.1° of longitude along the east-to-west aridity gradient and an increase in air temperature corresponding to the difference across ~2.7° of latitude along the north-to-south gradient. More complex forest structure and higher diversity occurred in moister, less-exposed habitats, and species occupied distinct topographic niches. Our study demonstrates how topographic and microclimatic gradients structure forests in putative climate-change refugia, by revealing ecological processes enabling populations to be maintained during periods of unfavorable macroclimate.

Soil-plant-gall relationships: from gall development to ecological patterns.

The adaptive nature of the galler habit has been tentatively explained by the nutrition, microenvironment, and enemy hypotheses. Soil attributes have direct relationships with these three hypotheses at the cellular and macroecological scales, but their influence has been restricted previously to effects on the nutritional status of the host plant on gall richness and abundance. Herein, we discuss the ionome patterns within gall tissues and their significance for gall development, physiology, structure, and for the nutrition of the gallers. Previous ecological and chemical quantification focused extensively on nitrogen and carbon contents, evoking the carbon-nutrient defence hypothesis as an explanation for establishing the plant-gall interaction. Different elements are involved in cell wall composition dynamics, antioxidant activity, and regulation of plant-gall water dynamics. An overview of the different soil-plant-gall relationships highlights the complexity of the nutritional requirements of gallers, which are strongly influenced by environmental soil traits. Soil and plant chemical profiles interact to determine the outcome of plant-herbivore interactions and need to be addressed by considering not only the soil features and galler nutrition but also the host plant's physiological traits. The quantitative and qualitative results for iron metabolism in gall tissues, as well as the roles of iron as an essential element in the physiology and reproduction of gallers suggest that it may represent a key nutritional resource, aligning with the nutrition hypothesis, and providing an integrative explanation for higher gall diversity in iron-rich soils.

Fine Root Density Dynamics and Carbon Stock of Eucalyptus spp.: Interplay of Age, Genotype, and Edaphoclimatic Conditions.

Roots play a fundamental role in forest ecosystems, but obtaining samples from deep layers remains a challenging process due to the methodological and financial efforts required. In our quest to understand the dynamics of Eucalyptus roots, we raise three fundamental questions. First, we inquire about the average extent of the roots of two contrasting Eucalyptus genotypes. Next, we explore the factors that directly influence the growth and depth of these roots, addressing elements such as soil type, climate, and water availability. Lastly, we investigate how the variation in Eucalyptus species may impact root growth patterns, biomass, and carbon stock. In this study, we observed that the maximum root depth increased by an average of 20% when genotypes were grown on sites with higher water availability (wet site). E. urophylla stands had a higher biomass and carbon stock (5.7 Mg C ha-1) of fine roots when cultivated on dry sites (annual rainfall~727 mm) than the wet sites (annual rainfall~1590 mm). In E. grandis × E. camaldulensis stands, no significant differences were observed in the stock of fine root biomass (3.2 Mg C ha-1) between the studied environments. Our results demonstrated that genotypes with greater drought tolerance (E. grandis × E. camaldulensis) tend to maintain higher stocks of fine root biomass (3.2-6.3 Mg ha-1) compared to those classified as plastic (E. urophylla), regardless of the edaphoclimatic conditions of the cultivation site. Finally, our research helps understand how Eucalyptus trees adapt to their environment, aiding sustainable forest management and climate change mitigation. We also provide a practical tool to estimate underground biomass, assisting forest managers and policymakers in ensuring long-term forest sustainability.

Investigating the water availability hypothesis of pot binding: small pots and infrequent irrigation confound the effects of drought stress in potato (Solanum tuberosum L.).

To maximise the throughput of novel, high-throughput phenotyping platforms, many researchers have utilised smaller pot sizes to increase the number of biological replicates that can be grown in spatially limited controlled environments. This may confound plant development through a process known as "pot binding", particularly in larger species including potato (Solanum tuberosum), and under water-restricted conditions. We aimed to investigate the water availability hypothesis of pot binding, which predicts that small pots have insufficient water holding capacities to prevent drought stress between irrigation periods, in potato. Two cultivars of potato were grown in small (5 L) and large (20 L) pots, were kept under polytunnel conditions, and were subjected to three irrigation frequencies: every other day, daily, and twice daily. Plants were phenotyped with two Phenospex PlantEye F500s and canopy and tuber fresh mass and dry matter were measured. Increasing irrigation frequency from every other day to daily was associated with a significant increase in fresh tuber yield, but only in large pots. This suggests a similar level of drought stress occurred between these treatments in the small pots, supporting the water availability hypothesis of pot binding. Further increasing irrigation frequency to twice daily was still not sufficient to increase yields in small pots but it caused an insignificant increase in yield in the larger pots, suggesting some pot binding may be occurring in large pots under daily irrigation. Canopy temperatures were significantly higher under each irrigation frequency in the small pots compared to large pots, which strongly supports the water availability hypothesis as higher canopy temperatures are a reliable indicator of drought stress in potato. Digital phenotyping was found to be less accurate for larger plants, probably due to a higher degree of self-shading. The research demonstrates the need to define the optimum pot size and irrigation protocols required to completely prevent pot binding and ensure drought treatments are not inadvertently applied to control plants.

Characteristics and drivers of vegetation productivity sensitivity to increasing CO2 at Northern Middle and High Latitudes.

Understanding and accurately predicting how the sensitivity of terrestrial vegetation productivity to rising atmospheric CO2 concentration (ß) is crucial for assessing carbon sink dynamics. However, the temporal characteristics and driving mechanisms of ß remain uncertain. Here, observational and CMIP6 modeling evidence suggest a decreasing trend in ß at the Northern Middle and High Latitudes during the historical period of 1982-2015 (-0.082 ± 0.005% 100 ppm-1 year-1). This decreasing trend is projected to persist until the end of the 21st century (-0.082 ± 0.005% 100 ppm-1 year-1 under SSP370 and -0.166 ± 0.006% 100 ppm-1 year-1 under SSP585). The declining ß indicates a weakening capacity of vegetation to mitigate warming climates, posing challenges for achieving the temperature goals of the Paris Agreement. The rise in vapor pressure deficit (VPD), that triggers stomata closure and weakens photosynthesis, is considered as the dominated factor contributing to the historical and future decline in ß, accounting for 62.3%-75.2% of the effect. Nutrient availability and water availability contribute 15.7%-21.4% and 8.5%-16.3%, respectively. These findings underscore the significant role of VPD in shaping terrestrial carbon sink dynamics, an aspect that is currently insufficiently considered in many climate and ecological models.

Field Examinations on the Application of Novel Biochar-Based Microbial Fertilizer on Degraded Soils and Growth Response of Flue-Cured Tobacco (Nicotiana tabacum L.).

Southwestern China is receiving excessive chemical fertilizers to meet the challenges of continuous cropping. These practices are deteriorating the soil environment and affecting tobacco (Nicotiana tabacum L.) yield and quality adversely. A novel microbially enriched biochar-based fertilizer was synthesized using effective microorganisms, tobacco stalk biochar and basal fertilizer. A field-scale study was conducted to evaluate the yield response of tobacco grown on degraded soil amended with our novel biochar-based microbial fertilizer (BF). Four treatments of BF (0%, 1.5%, 2.5% and 5%) were applied in the contaminated field to grow tobacco. The application of BF1.5, BF2.5 and BF5.0 increased the available water contents by 9.47%, 1.18% and 2.19% compared to that with BF0 respectively. Maximum growth of tobacco in terms of plant height and leaf area was recorded for BF1.5 compared to BF0. BF1.5, BF2.5 and BF5.0 increased SPAD by 13.18-40.53%, net photosynthetic rate by 5.44-60.42%, stomatal conductance by 8.33-44.44%, instantaneous water use efficiency by 55.41-93.24% and intrinsic water use efficiency by 0.09-24.11%, while they decreased the intercellular CO2 concentration and transpiration rate by 3.85-6.84% and 0.29-47.18% relative to BF0, respectively (p < 0.05). The maximum increase in tobacco yield was recorded with BF1.5 (23.81%) compared to that with BF0. The present study concludes that the application of BF1.5 improves and restores the degraded soil by improving the hydraulic conductivity and by increasing the tobacco yield.

Assessing future intra-basin water availability in madagascar: Accounting for climate change, population growth, and land use change.

The Major River Basins in Madagascar (MRBM) play a crucial role in providing water to the Malagasy population as well as the ecosystem. Little is known about the impact of climate change on these basins, and it is not clear what factors have the most significant impact on them. There are two central objectives of this study: 1. To assess the future potential water available for daily life and agriculture use across the MRBM. 2. To compare the projected change within the MRBM with the historical trends analysis and identify the water-stressed basins. In this paper, a new method for assessing the future available Intra-basin water resources combined with the impacts of climate change, land use, and population is proposed. Three imbalance indicators are introduced to quantify the spatial availability (indicator N°1), distribution (indicator N°2), and variability (indicator N°3) of the Potential Water Resources (PWR) available and have been applied to the MRBM. Under the SSP2-4.5 scenario, results showed a decreasing trend of the PWR in most of the basins by 2050 with a rise in evapotranspiration and a decline in precipitation. The increasing trend and uneven distribution of the population and agricultural land upstream/downstream are found to cause the reduction of the PWR available per capita (by 37 %) and agriculture area (by 69 %) across the MRBM. This study predicts water scarcity for most of the basins by 2050, especially in the Mangoro and Onilahy Basins. Upstream populations are expected to grow in Mahajamba, Mahavavy, Betsiboka, Manambolo, Tsiribihina, Mangoro, Onilahy, Mananara, and Mandrare basins, along with an expansion of the downstream agricultural land in Sofia, Betsiboka, Manambolo, Mangoky, and Mandrare basins. These findings enhance the cause-effect relationship between climate change, land use change, population growth, and water scarcity in the MRBM. Urgent action is therefore needed for an efficient and sustainable management of these water-stressed basins.

Enhancing reclaimed water distribution network resilience with cost-effective meshing.

Water Distribution Networks (WDNs) are critical infrastructures that ensure a continuous supply of safe water to homes. In the face of challenges, like water scarcity, establishing resilient networks is imperative, especially in regions vulnerable to water crises. This study evaluates the resilience of network designs through graph theory, including its hydraulic feasibility using EPANET software, an aspect often overlooked. Novel mathematical algorithms, including Resilience by Design (RbD) and Resilience-strengthening (RS) algorithms, provide cost-effective and resilient network designs, even with budget constraints. A novel metric, Water Availability (WA), is introduced to offer a comprehensive measure of network resilience, thereby addressing ongoing discrepancies in resilience evaluation methods. Practical benefits are illustrated through a case study in which a resilient-by-design reclaimed water network is created, and an existing equivalent non-resilient network is improved. The resilient-by-design network demonstrates remarkably better results compared to the equivalent non-resilient design, including up to a 36 % reduction in the probability of service disruptions and a nearly 65 % decrease in the annual average unserved water due to service disruptions. These findings underscore the enormous advantages of a resilience-focused network design approach. When compared to the equivalent non-resilient design, the resilient-by-design network generated effectively safeguards up to a significant 91,700m3 of water from the impacts of water disruption events over a 50-year operational period. In addition, the resilient-by-design WDN solution incurs a subtle decrease in overall costs compared to consuming tap water from the drinking WDN baseline over a 50-year operational period. These findings highlight the cost-effectiveness of the approach, even offering financial benefits. This paper builds on our previous research by expanding its scope to include resilience considerations, providing algorithms that can be easily adapted from reclaimed to drinking WDNs. Ultimately, we contribute to the enhancement of water resource management and infrastructure planning in ever-evolving urban environments.

Replacing nitrogen in mineral fertilizers with nitrogen in maize straw increases soil water-holding capacity.

Soil water-holding capacity decreases due to long-term mineral fertilizer application. The objective of this study was to determine how replacing mineral fertilizer with maize straw affected the soil water retention curve, soil water content, soil water availability, and soil equivalent pore size. Replacement treatments in which 25% (S25), 50% (S50), 75% (S75), and 100% (S100) of 225 kg ha-1 nitrogen from mineral fertilizer (CK) was replaced with equivalent nitrogen from maize straw were conducted for five years in the Loess Plateau of China. The Gardner model was used to fit the soil water retention curve and calculate the soil water constant and equivalent pore size distribution. The results indicated that the Gardner model fitted well. Replacing nitrogen from mineral fertilizer with nitrogen from straw increased soil specific water capacity, soil readily available water, soil delayed available water, soil available water, soil capillary porosity, and soil available water porosity over time. S25 increased field capacity and wilting point from the fourth fertilization year. S50 enhanced soil readily available water, soil delayed available water, soil available water, and soil available water porosity from the fifth fertilization year, whereas S25 and S75 increased these from the third fertilization year or earlier. Soil specific water capacity, soil readily available water, soil delayed available water, soil available water, soil capillary porosity, and soil available water porosity could better reflect soil water-holding capacity and soil water supply capacity compared with field capacity and wilting point.

Intra- and interspecific diversity in a tropical plant clade alter herbivory and ecosystem resilience.

Declines in biodiversity generated by anthropogenic stressors at both species and population levels can alter emergent processes instrumental to ecosystem function and resilience. As such, understanding the role of biodiversity in ecosystem function and its response to climate perturbation is increasingly important, especially in tropical systems where responses to changes in biodiversity are less predictable and more challenging to assess experimentally. Using large-scale transplant experiments conducted at five neotropical sites, we documented the impacts of changes in intraspecific and interspecific plant richness in the genus Piper on insect herbivory, insect richness, and ecosystem resilience to perturbations in water availability. We found that reductions of both intraspecific and interspecific Piper diversity had measurable and site-specific effects on herbivory, herbivorous insect richness, and plant mortality. The responses of these ecosystem-relevant processes to reduced intraspecific Piper richness were often similar in magnitude to the effects of reduced interspecific richness. Increased water availability reduced herbivory by 4.2% overall, and the response of herbivorous insect richness and herbivory to water availability were altered by both intra- and interspecific richness in a site-dependent manner. Our results underscore the role of intraspecific and interspecific richness as foundations of ecosystem function and the importance of community and location-specific contingencies in controlling function in complex tropical systems.

Adaptive strategies to enhance water security and resilience in low- and middle-income countries: A critical review.

The water sector is facing unprecedented pressures as increased environmental and anthropogenic challenges, such as climate change and rapid urbanization, impact the availability and predictability of safe drinking water. There is a need for practitioners and policymakers to integrate water security and resilience (WS&R) factors into programming to sustain investments in drinking water systems to support associated economic, security, and public health benefits. In response to intensifying impacts from WS&R risks, communities around the world are developing adaptive strategies, and a critical review of these strategies may provide lessons that can be implemented at scale. In this critical review, we systematically screened over 9000 peer-reviewed and grey literature articles and extracted data from relevant studies that propose, pilot, and/or evaluate adaptations in low- and middle-income countries (LMICs) and evaluated the suitability of each adaptation for different contexts. We created a portfolio of adaptive strategies from over 75 LMICs to inform practitioners and policymakers in enhancing the resilience of drinking water systems. Over 20 adaptations were identified, including strategies such as stormwater management, wastewater reuse, non-revenue water reductions, water pricing, and public awareness campaigns. We categorized adaptations by function (improving water management, augmenting existing supplies, reducing water demand) and scale (household, municipal, regional) to provide recommendations tailored to local needs. For each adaptation, we highlighted associated strengths, weaknesses, barriers to adoption, and enabling environments for successful implementation. We propose a novel decision-support tool, called STEP WS&R, that provides a consistent and replicable process for informing high-level investment and policy choices around WS&R. This critical review presents recommendations for practitioners and policymakers to invest in WS&R adaptations, catered to shared risks and contexts.

Interactive Effects of Microbial Fertilizer and Soil Salinity on the Hydraulic Properties of Salt-Affected Soil.

Significant research has been conducted on the effects of fertilizers or agents on the sustainable development of agriculture in salinization areas. By contrast, limited consideration has been given to the interactive effects of microbial fertilizer (MF) and salinity on hydraulic properties in secondary salinization soil (SS) and coastal saline soil (CS). An incubation experiment was conducted to investigate the effects of saline soil types, salinity levels (non-saline, low-salinity, and high-salinity soils), and MF amounts (32.89 g kg-1 and 0 g kg-1) on soil hydraulic properties. Applied MF improved soil water holding capacity in each saline soil compared with that in CK, and SS was higher than CS. Applied MF increased saturated moisture, field capacity, capillary fracture moisture, the wilting coefficient, and the hygroscopic coefficient by 0.02-18.91% in SS, while it was increased by 11.62-181.88% in CS. It increased soil water supply capacity in SS (except for high-salinity soil) and CS by 0.02-14.53% and 0.04-2.34%, respectively, compared with that in CK. Soil available, readily available, and unavailable water were positively correlated with MF, while soil gravity and readily available and unavailable water were positively correlated with salinity in SS. Therefore, a potential fertilization program with MF should be developed to increase hydraulic properties or mitigate the adverse effects of salinity on plants in similar SS or CS areas.

Decoding autumn phenology: Unraveling the link between observation methods and detected environmental cues.

Leaf coloring and fall mark the end of the growing season (EOS), playing essential roles in nutrient cycling, resource allocation, ecological interactions, and as climate change indicators. However, understanding future changes in autumn phenology is challenging due to the multitude of likely environmental cues and substantial variations in timing caused by different derivation methods. Yet, it remains unclear whether these two factors are independent or if methodological uncertainties influence the environmental cues determined. We derived start of growing season (SOS) and EOS at a mixed beech forest in Central Germany for the period 2000-2020 based on four different derivation methods using a unique long-term data set of in-situ data, canopy imagery, eddy covariance measurements, and satellite remote sensing data and determined their influence on a predictor analysis of leaf senescence. Both SOS and EOS exhibited substantial ranges in mean onset dates (39.5 and 28.6 days, respectively) across the different methods, although inter-annual variations and advancing SOS trends were similar across methods. Depending on the data, EOS trends were advanced or delayed, but inter-annual patterns correlated well (mean r = .46). Overall, warm, dry, and less photosynthetically productive growing seasons were more likely to be associated with a delayed EOS, while colder, wetter, and more photosynthetically productive vegetation periods resulted in an earlier EOS. In addition, contrary to recent results, no clear influence of pre-solstice vegetation activity on the timing of senescence was detected. However, most notable were the large differences in sign and strength of potential drivers both in the univariate and multivariate analyses when comparing derivation methodologies. The results suggest that an ensemble analysis of all available phenological data sources and derivation methods is needed for general statements on autumn phenology and its influencing variables and correct implementation of the senescence process in ecosystem models.

Nitrogen addition does not alter symmetric responses of soil respiration to changing precipitation in a semi-arid grassland.

Concurrent changing precipitation regimes and atmospheric nitrogen (N) deposition can have profound influences on soil carbon (C) cycling. However, how N enrichment regulates the responses of soil C fluxes to increasing variability of precipitation remains elusive. As part of a field precipitation gradient experiment with nine levels of precipitation amounts (-60 %, -45 %, -30 %, -15 %, ambient precipitation, +15 %, +30 %, +45 %, and +60 %) and two levels of N addition (0 and 10 g N m-2 yr-1) in a semi-arid temperate steppe on the Mongolian Plateau, this work was conducted to investigate the responses of soil respiration to decreased and increased precipitation (DP and IP), N addition, and their possible interactions. Averaged over the three years from 2019 to 2021, DP suppressed soil respiration by 16.1 %, whereas IP stimulated it by 27.4 %. Nitrogen addition decreased soil respiration by 7.1 % primarily via reducing microbial biomass C. Soil respiration showed symmetric responses to DP and IP within all the four precipitation variabilities (i.e., 15 %, 30 %, 45 %, and 60 %) under ambient N. Nevertheless, N addition did not alter the symmetric responses of soil respiration to changing precipitation due to the comparable sensitivities of microbial biomass and root growth to DP and IP under the N addition treatment. These findings indicate that intensified precipitation variability does not change but N addition could alleviate soil C releases. The unchanged symmetric responses of soil respiration to precipitation variability under N addition imply that N deposition may not change the response pattern of soil C releases to predicted increases in precipitation variability in grasslands, facilitating the robust projections of ecosystem C cycling under future global change scenarios.

Mesic vegetation persistence: A new approach for monitoring spatial and temporal changes in water availability in dryland regions using cloud computing and the sentinel and Landsat constellations.

Climate change and anthropogenic activity pose severe threats to water availability in drylands. A better understanding of water availability response to these threats could improve our ability to adapt and mitigate climate and anthropogenic effects. Here, we present a Mesic Vegetation Persistence (MVP) workflow that takes every usable image in the Sentinel (10-m) and Landsat (30-m) archives to generate a dense time-series of water availability that is continuously updated as new images become available in Google Earth Engine. MVP takes advantage of the fact that mesic vegetation can be used as a proxy of available water in drylands. Our MVP workflow combines a novel moisture-based index (moisture change index - MCI) with a vegetation index (Modified Chlorophyll Absorption Ratio Vegetation Index (MCARI2)). MCI is the difference in soil moisture condition between an individual pixel's state and the dry and wet reference reflectance in the image, derived using 5th and 95th percentiles of the visible and shortwave infra-red drought index (VSDI). We produced and validated our MVP products across drylands of the western U.S., covering a broad range of elevation, land use, and ecoregions. MVP outperforms NDVI, a commonly-employed index for mesic ecosystem health, in both rangeland and forested ecosystems, and in mesic habitats with particularly high and low vegetation cover. We applied our MVP product at case study sites and found that MVP more accurately characterizes differences in mesic persistence, late-season water availability, and restoration success compared to NDVI. MVP could be applied as an indicator of change in a variety of contexts to provide a greater understanding of how water availability changes as a result of climate and management. Our MVP product for the western U.S. is freely available within a Google Earth Engine Web App, and the MVP workflow is replicable for other dryland regions.

Dataset of temporal trends of surface water area across India's rivers and basins.

This dataset [1] quantifies the extent and rate of annual change in surface water area (SWA) across India's rivers and basins over a period of 30 years spanning 1991 to 2020. This data has been derived from the Global Surface Water Explorer, which maps historical terrestrial surface water occurrence globally using the Landsat satellite image archive since 1984, at a spatial resolution of 30 m/pixel and a temporal resolution of once a month. This monthly time-series was used to create annual composites of wet-season (October, November, December), dry-season (February, March, April), and permanent (October, November, December, February, March, April) surface water extent, which were then used to estimate annual rates of change. To estimate SWA trends for both river networks and their basins, we conducted our analysis at two spatial scales - (1) cross-sectional reaches (transects) across river networks, and (2) sub-basins within river catchments. For each reach and sub-basin (henceforth basin), temporal trends in wet-season, dry-season, and permanent SWA were estimated using the non-parametric Sen's slope estimator. For every valid reach and basin, the temporal timeseries of invalid or missing data was also computed as a fractional area to inform the level of certainty associated with reported SWA trends estimates. In addition to a Zenodo data repository, this data [1] is presented as an interactive web application (https://sites.google.com/view/surface-water-trends-india/; henceforth Website) to allow users to visualize the trends of permanent, wet-season, and dry-season water along with the extent of missing data for individual transects or basins across India. The Website provides a simple user interface to enable users to download seasonal time-series of SWA for any region of interest at the scale of the river network or basin. The Website also provides details about accessing the annual permanent, dry and wet season composites, which are stored as publicly accessible cloud assets on the Google Earth Engine platform. The spatial (basin and reach) and temporal (wet season, dry season, and permanent water scenarios) scales of information provided in this dataset yield a granular understanding of water systems in India. We envision this dataset to serve as a baseline information layer that can be used in combination with other data sources to support regional analysis of hydrologic trends, watershed-based analysis, and conservation planning. Specific applications include, but are not limited to, monitoring and identifying at-risk wetlands, visualizing and measuring changes to surface water extent before and after water infrastructure projects (such as dams and water abstraction projects), mapping drought prone regions, and mapping natural and anthropogenic changes to SWA along river networks. Intended users include, but are not limited to, students, academics, decision-makers, planners, policymakers, activists, and others interested in water-related issues.