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Elevated soil nitrogen (N) resulting from pollution, fertilizer and woody encroachment in grasslands enhances invasion pressures from weedy plant species. Sawdust, sucrose and other labile carbon (C) sources can be used as a soil amendment to combat the growth of fast‐growing, invasive non‐native plants by immobilizing soil N.Here, we present a systematic review of 83 publications, and a meta‐analysis from 48 publications. Using hierarchical mixed‐effects meta‐analytic models, we synthesized 655 responses from native plants and 486 responses from non‐native weeds to quantify the overall effect of C addition. We explored the possible explanations for variation in effect, such as differences in study conditions and how C was applied.Carbon addition studies were almost exclusively reported from the United States, Australia and Canada (93%). The majority of papers (63%) did not include any cost information.Overall, C addition significantly decreased non‐native weed abundance, but did not significantly affect native plant abundance. A C application rate of at least 210 g C m−2 year−1 (5 Mg sucrose ha−1 year−1 or 4.6 Mg sawdust ha−1 year−1) decreased non‐native weed abundance, but a rate of 2110–3000 g C m−2 year−1 (50–71 Mg sucrose ha−1 year−1 or 46–65 Mg sawdust ha−1 year−1) was required to significantly increase native plant abundance. Carbon addition was most effective in the western USA and southeastern Australia, and when used to suppress non‐native grasses (annual or perennial) and annual forbs. Simultaneous seeding of native species prevented an overall decrease in native plant abundance.Synthesis and application. When there is a nearby and inexpensive source of C available, we recommend C addition with simultaneous seeding of native species to control invasive non‐native grasses and annual forbs in semi‐arid and arid regions of the western USA and southeast Australia. In contrast to other weed control measures, especially herbicide, C addition does not significantly harm native perennial plants. Future studies should implement longer‐term monitoring, establish larger plots and include cost analysis to improve guidance for land managers. [ABSTRACT FROM AUTHOR]

Secondary salinisation of soil and water resources is an acute management issue over large parts of Australia. This paper focusses on the situation in the Liverpool Plains, where secondary soil salinity is on the increase due to rising saline groundwater tables. The Liverpool Plains are famous for the vast alluvial floodplains where self-mulching black clays provide the production basis for an extensive dryland cropping industry. The farmers there are asking how best to manage their resources under the present hydrological conditions, and are concerned whether their businesses will remain viable in the future. A multi-period programming model is applied to a model farm situation. The objective function reflects the economic paradigm of farming. The model includes a simulation sub-routine which links land use, rainfall and lateral groundwater flow into a point water balance and estimates the salt-affected area. A feedback relationship applies between soil salinity and land productivity. The results of the model suggest that the prevailing cropping practices that rely on long fallowing for soil moisture retention are sub-optimal. Increased cropping frequency increases farm income and reduces on-farm recharge to groundwater. Diversification into lucerne is favourable for the same reasons. Unless trees have commercial value, tree planting is not a favoured option except on salt-affected land. The farm achieves complete on-farm recharge control. However, assuming that the groundwater table rises at a rate of 10 cm per year independent of on-farm recharge, salinisation continues despite these land management changes. The subsequent land productivity losses render the model farm financially unviable in the medium term. Sustaining the productivity of the Liverpool Plains is an issue of reducing recharge to the groundwater system by changing land-use practices throughout the entire catchment. © 1997 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Snowmelt floods are highly hazardous meteorological disasters that can potentially threaten human lives and property. Hence, snowmelt susceptibility mapping (SSM) plays an important role in flood prevention systems and aids emergency responders and flood risk managers. In this paper, a method of identifying snowmelt flood hazards is proposed, and a large‐scale snowmelt flood hazard zonation scheme based on historical recordings and multisource remote sensing data is established. To assess the quality of our approach, the proposed model was tested in the cold and arid region of Xinjiang, China. Overall, 140 historical snowmelt flood events and 27 explanatory factors were selected to construct a geospatial dataset for SSM of the contemporary period. GridSearchCV was used to comprehensively search the candidate parameters from the grid of given parameters obtained with the random forest (RF) algorithm. Then, the geospatial dataset was divided into two subsets: 70% for training and 30% for testing. Next, SSM results were obtained with the RF algorithm using optimized parameters. The results indicate that our optimized RF classifier performs well for the task of SSM, with a high AUC value (0.975) for the test dataset. The validation and analysis suggest that the proposed method can efficiently identify snowmelt flood hazards in undersampled arid areas at a regional scale. [ABSTRACT FROM AUTHOR]

As typical of I Restoration Ecology i , the thematic series includes high quality papers that address critical research issues, consider practical solutions, or provide policy guidance for the restoration of arid lands. This issue of I Restoration Ecology i is part of the thematic series on arid land (dryland) restoration. Literature cited 1 Hallett JG, Omar SAS (2020) Restoration ecology of arid lands (RE-AL). [Extracted from the article]

Numerical solution of the one‐dimensional Richards equation (RE) accurately partitions precipitation into infiltration and runoff in capillary dominated soils. However, its application sometimes requires significant computational effort and presents reliability challenges. The Green and Ampt (G&A) approach represents a conservative and efficient method to calculate one‐dimensional infiltration but is limited to deep, well drained, uniform, non‐layered soils for a single rainfall event. The original G&A model and subsequent advancements represent wetting fronts as discrete objects, rather than discretizing the model domain in space, yielding a computationally simpler model than the RE. This paper describes an extension of the G&A method into layered soils on a continuous basis that we call Layered Green and Ampt with Redistribution (LGAR). Assumptions employed in the derivation include: uniform soil hydraulic properties within layers, single‐valued capillary head at the interface between soil layers, and no influence of groundwater table on soil moisture. Wetting fronts advance due to the combined effects of gravity and wetting front capillary drive in a layered soil profile. Results of multi‐month continuous LGAR simulations of infiltration using forcing and soil hydraulic data from USDA SCAN sites are compared against infiltration calculated using the HYDRUS‐1D RE solver using standard metrics. The assumptions employed in deriving the LGAR method limit its application to situations where cumulative potential evapotranspiration is greater than cumulative precipitation, typical of arid or semi‐arid conditions. LGAR is a mass‐conservative, computationally efficient, reliable and reasonably accurate method for simulating infiltration over extended time periods compared to the numerical solution of the RE in layered soils in arid and semi‐arid regions. Plain Language Summary: In arid and semi‐arid regions the groundwater table is typically far below the land surface, and the process of infiltration divides rainfall into soil moisture and surface runoff. Previous extensions of the Green and Ampt (1911, https://doi.org/10.1017/s0021859600001441) infiltration method allow accurate calculation of infiltration into a layered soil for short time periods. This paper shows a novel extension that calculates infiltration in layered soils on a continuous basis using a Green and Ampt like method. This development represents an advance because it provides an accurate, mass‐conserving, computationally efficient and reliable method to calculate infiltration in arid and semi‐arid landscapes where stormflow generation is often dominated by layered soil properties. Key Points: The Richards equation (RE) is widely used to simulate infiltration but often presents computational challengesWe developed a Layered Green and Ampt with Redistribution (LGAR) approach that compares well against RE infiltration predictionsThe LGAR method is unconditionally stable with guaranteed mass conservation and is designed for semi‐arid and arid areas [ABSTRACT FROM AUTHOR]

Literature cited 1 Hallett JG, Omar SAS (2020) Restoration ecology of arid lands (RE-AL). As typical of I Restoration Ecology i , the thematic series includes high quality papers that address critical research issues, consider practical solutions, or provide policy guidance for the restoration of arid lands. This issue of I Restoration Ecology i is part of the thematic series on arid land (dryland) restoration. [Extracted from the article]

Simple models continue to be important for continental‐scale floodwater depth mapping due to the prohibitively expensive cost of calibrating and applying hydrodynamic models. This paper investigates the accuracy of three simple models for floodwater depth estimation from remote sensing derived water extent and/or Digital Elevation Models (DEMs) in semiarid regions. The three models are Height Above Nearest Drainage (HAND; Nobre et al., 2011, https://doi.org/10.1016/j.jhydrol.2011.03.051), Teng Vaze Dutta (TVD; Teng et al., 2013, http://hdl.handle.net/102.100.100/97033?index=1), and Floodwater Depth Estimation Tool (FwDET; Cohen, Brakenridge, et al., 2018, https://doi.org/10.1111/1752-1688.12609). The model accuracy and nature of errors are established using industry's best practice hydrodynamic models as benchmarks in three regions in eastern Australia. The overall results show that FwDET tends to underestimate (by 0.32 m at 50th percentile) while HAND and TVD overestimate floodwater depth for almost all floods (by 0.97 and 0.98 m, respectively). We quantify how switching DEM from 5 m LiDAR to national or global data sets DEM‐H (Gallant et al., 2011, https://ecat.ga.gov.au/geonetwork/srv/eng/catalog.search#/metadata/72759), MERIT (Yamazaki et al., 2019, https://doi.org/10.1029/2019WR024873), or FABDEM (Hawker et al., 2022, https://doi.org/10.1088/1748-9326/ac4d4f) can affect different models differently; and we evaluate model performance against reach geomorphology and magnitude of flood events. The findings emphasize the importance of choosing a model that is fit for the intended application. By describing the applicability, advantages, and limitations of these models, this paper assists practitioners to choose the most appropriate model based on characteristics of their study area, type of problems they try to solve, and data availability. Plain Language Summary: We have assessed the performance of three simple models for estimating floodwater depth by evaluating their accuracy against different Digital Elevation Model inputs, characteristics of study area, and magnitude of flood events. Our results emphasize that selection of an appropriate model depends on the circumstances. This study provides recommendations for future studies that enhance remote sensing‐based flood maps with water depth, making use of the growing number of publicly available remote sensing water extent and digital elevation data sets globally. All the methods have been coded in Python and are freely available at https://github.com/csiro-hydroinformatics/water-depth-estimation. Key Points: We assessed three simple models for estimating floodwater depth by comparing their results with those of hydrodynamic modelsThe model performance was evaluated against reach geomorphology, magnitude of flood events, and different Digital Elevation Model inputsThe results emphasize that a model should be chosen for the intended application. Guidelines provided for possible applications [ABSTRACT FROM AUTHOR]

Biological soil crusts (biocrusts) are complex communities of micro‐ and macro‐organisms dwelling at the soil surface in dryland regions worldwide, which contribute to important ecological functions in these areas. Biocrusts may reach different developmental stages, associated to autogenic succession of specific phototrophic organisms. However, notwithstanding the large amount of existing literature, little is known regarding the relationship between biocrust stages of development and soil nutrient dynamics. In this opinion paper, we specifically focused on soil nitrogen, and compared the total nitrogen content and potential nitrogenase activity of different developmental types of biocrust (‐covered) soils. Based on published reports, we looked at a possible relationship between nitrogen content at the soil surface and biocrust development, discussing the potential mechanisms leading to the observed soil nitrogen content heterogeneity. The results showed that a higher nitrogen content remained associated to the presence of moss‐dominated biocrusts, and this biocrust morphotype was characterized by a lower potential nitrogenase activity compared to the cyanobacteria‐ and/or lichen‐dominated biocrusts. We hypothesized that these seemingly contradictory findings might be attributed to three potential mechanisms: nitrogen inheritance, nutrient retention and nutrient transfer, which we hereby examined one by one. Altogether, our opinion supports the theory of biocrust succession from incipient cyanobacteria‐dominated stages to more 'mature' stages dominated by mosses. We stress how the heterogeneous distribution of soil nitrogen, which is closely related with biocrust development and community types, eventually affects regional and even global nitrogen dynamic and storage. [ABSTRACT FROM AUTHOR]

Global food demand is expected to increase in the next decades, pushing agricultural expansion and deforestation. However, food production in agricultural lands is just one dimension of food security, to which forest goods and services also contribute. In this paper, we aimed to explore the relationship between forest cover and food security. We hypothesized that food security is improved by both human‐made and green infrastructure combined. To test this relationship, we explore the relationships between forest cover and a multidimensional index of food security that included both socioeconomic and natural variables taken from Brazilian official databases for 1141 municipalities of the Brazilian Caatinga (a seasonally tropical dry forest). The index was formed by 12 principal components axes (12 PCs) and we found that financial poverty (PC 1) and economic inequality (PC 2) were the main determinants of food insecurity in Caatinga. We found that lowest food security values were found in two contrasting contexts: one is represented by poor and unequal municipalities with high forest cover while the other refers to poor and less unequal municipalities but with little forest cover. Municipalities with intermediate levels of forest cover had slightly higher food security, a consistent pattern across time (2006–2017). Win–win scenarios where both forest cover and food security increased with time were almost as common as lose–lose situations (25% and 22% respectively). This suggests a sort of balance between forests and human‐made land uses and reinforces that natural capital contributes to food security. Zero‐hunger is a main issue for sustainable development goals, and our results adds to the notion that both sustainable use of forests and socioeconomic improvements must coexist rather than being treated as antagonistic policies. [ABSTRACT FROM AUTHOR]

The Caspian Sea level (CSL) is strongly sensitive to climate‐induced changes in its water balance components, especially evaporation from its surface as the main expenditure component of the Caspian Sea's (CS) water budget. Projecting evaporation and determining associated uncertainties obtained from such studies are critical for reliably predicting future CSL fluctuations and developing mitigation and adaptation strategies. This paper studies the projected changes in evaporation from the CS using 18 global climate models (GCMs) from the latest Coupled Model Intercomparison Project phase 6 (CMIP6) and Meyer's semi‐empirical formula. Future evaporation projections are constructed employing a weighted combination of the top‐ranked GCMs, including all ensemble members of selected individual models in a probabilistic framework. This study estimates late 21st century median evaporation of 945, 1016, 1105 and 1173 mm under the low‐emission, medium‐emission, medium‐to‐high emission and high‐emission scenarios, respectively. The weighted multimodel ensemble suggests CS's annual mean evaporation is projected to substantially increase by 3.9%, 13.2%, 20% and 27.9% under SSP1‐2.6, SSP2‐4.5, SSP3‐7.0 and SSP5‐8.5, respectively, for the late 21st century against the reference period. According to the spatial distribution of evaporation, arid eastern regions of CS experience higher evaporation than semi‐arid western and southwestern temperate regions. Additionally, the northwestern continental regions experience the least evaporation over the CS. [ABSTRACT FROM AUTHOR]

Rodents are one of the most abundant and diverse groups of mammals in arid zones. Their population and community dynamics are closely linked to climatic factors and pulses of primary productivity activation. In the future, climatic conditions in arid ecosystems could become more extreme as a consequence of climate change, which could affect the species that inhabit these regions. In this paper, we review the literature on the ecological response of rodents in the world's arid zones, at the population and community levels, to climatological factors (temperature and precipitation), climatic events and the possible impact of climate change. We used the PRISMA protocol to systematically search the literature, and the “vote‐counting” method to count positive, null or negative responses of the rodents. At the population level, rodent density and abundance responded positively to precipitation, while biomass responded negatively and reproduction responded positively to increasing temperature. At the community level, rodent density, biomass and diversity increased after rainfall. El Niño events were positively related to rodent population increases. In contrast, intense storms affected the survival of some species. Rodents with physiological adaptations suited to living in arid areas, for example, the heteromyids, responded positively to precipitation and could suffer fewer negative ecological consequences in the future when exposed to increased temperature and changes in precipitation. [ABSTRACT FROM AUTHOR]

Drought seriously endangers the development of agro‐pastoral ecotone in arid and semi‐arid regions. However, drought evolution characteristics of semi‐arid sandy grassland and its drivers are not well understood in the complex climate change context. Thus, in this paper, the revised standardized precipitation evaporation indices on one‐month (SPEI‐1) and growing‐season (SPEI‐6) scale, flash drought and dry spells (DS) were calculated as drought indicators, and the temporal variabilities and meteorological drivers of drought in Horqin Sandy Land during the growing period (April–September) from 2007 to 2021 were studied. The results showed that SPEI‐1 and SPEI‐6 exhibited negative trends and periodic change. This drought aggravation was manifested in increased grades and numbers of drought months. Flash droughts can occur every month during the growing season. And its occurrence was not only positively correlated with all drought events in frequency but also synchronized in time. The increased number of DS showed an asymmetrical shift towards 7‐day‐and‐longer DS. SPEI sensitivity to precipitation (P) was noticeably higher than to atmospheric evapotranspiration demand (AED) at both monthly and growing season scales. SPEI sensitivity to AED was modulated by P amounts, which was higher during low P period. Apart from the amounts of P and AED, their temporal variability also strongly determined how they affect the drought severity. P was also the main driver for flash drought and long DS, but AED with larger amount and higher variability is the reason for their aggravation. Our results demonstrate the complexity of drought intensification in semi‐arid sandy grasslands and highlight the important role of AED anomalies in it. [ABSTRACT FROM AUTHOR]

Groundwater exploitations in semi‐arid regions result in significant declines of groundwater levels and streamflow and even trigger seasonal streamflow drying up, which may bring adverse impacts on riparian ecosystems. It is critical to explore future streamflow changes caused by variable climate scenarios and groundwater exploitation intensities; however, a comprehensive assessment of the streamflow drying up frequency remains lacking. Furthermore, the thresholds of controlling factors beyond which streamflow drying up occurs have rarely been explored. Here we develop an integrated surface water‐groundwater model for the Taoer River Basin (TRB), a typical semi‐arid watershed in northeast China. We apply the model to multiple future scenarios to reveal the frequency of potential streamflow drying up and explore the thresholds of controlling factors of streamflow drying up based on a decision tree method. We find that the groundwater level in the lower region of the TRB (LTRB) is hard to recover to the riverbed elevation and the streamflow drying up frequency is still high unless the groundwater exploitation is reduced by 50%. However, this leads to a competition between the ecological and economic objectives. Our results also show that the streamflow drying up frequency in the LTRB is very sensitive to the upstream water inflow that can be regulated through the reservoir operation or inter‐basin water diversion, indicating the importance of a basin scale strategic management. The findings of this paper can help policy makers sustainably exploit water resources in semi‐arid regions. [ABSTRACT FROM AUTHOR]

The paper aims to focus on climatic risk as a potential determinant of temporary labour migration in Semi‐Arid Tropics (SAT) village in India for the year 2013–2014. Specifically, we address the question of how households use temporary labour migration as a coping mechanism to minimise the risk posed by climate variables such as drought, floods, cyclone etc. In doing so, the paper uses a binary choice model (logistic regression) to examine the potential socioeconomic and demographic factors along with climatic risk that determine the probability of migration of workers in select Indian semi‐arid villages. The paper uses data from International Crops Research Institute for the Semi‐Arid Tropics (ICRISAT). The results show that among all climatic risk anomalies, maximum households in SAT villages are affected by drought risk. It is accounted that 69% of households are influenced by the drought risk. With respect to compensation of climatic risk, around 17% of non‐migrant households received government support, while only 9% of migrant households received such assistance in this study. Also, the logistic regression models predict that the probability of household having any temporary migrants is significantly determined by climatic risk along with other demographic and socio‐economic factors. To the best of the authors' knowledge, perhaps this is the first paper that makes a direct approach of linking climatic risk with temporary labour migration in semi‐arid tropics region of India. [ABSTRACT FROM AUTHOR]

Global drylands face a host of urgent human and environmental challenges with far-reaching impacts. Improving smallholder agriculture remains a key development pathway to tackle these challenges. The dryland development paradigm (DDP), introduced in 2007, presented a highly influential framework for dryland development based on systems research. This paper empirically derives a new, updated DDP. It assesses recent, cutting-edge dryland science, combining literature review with qualitative and quantitative analysis of research published by the world's largest dryland science and development research initiative. The new DDP comprises eight characteristics that are distilled into three integrative principles: Unpack, Traverse and Share. The new DDP is applied and tested to identify key dryland knowledge and development gaps. A future research agenda is then elucidated, grounded in a research in development approach, in which research anchored in the three integrative principles is embedded within the context it seeks to improve. Supported by greater trans-disciplinarity and knowledge co-production, operationalization of the new DDP can deliver both novel scientific insights and development impact in line with the aspirations of the 2030 Sustainable Development Goals. © 2017 The Authors. Land Degradation & Development Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Spatial analysis is paramount for understanding, monitoring, and conserving ancient settlements and cultural landscapes. Advancing remote sensing and prospection techniques are expanding the methodological frame of archaeological settlement analysis by enabling remote, landscape‐scale approaches to mapping and investigation. Whilst particularly effective in arid lands and areas with sparse or open ground cover, such as vegetation and buildings, these approaches remain peripheral in tropical environments because of technical and contextual challenges. In tropical Eastern Africa, for example, scales, resolution and visibility are often compromised by thick vegetation cover, inadequate access to, if not lack of, imagery resources and technologies, and the availability of comparative archaeological data for interpretation. This paper presents the initial results of spatial analysis, using historic landscape characterisation, remote sensing, published and legacy data, and a pilot ground survey to examine the earliest settlement of Zanzibar, Unguja Ukuu. Comparing multiple strands of evidence in a Geographic Information System (GIS), we use each as a test on the others to draw out the strengths and weaknesses of each technique in the context of tropical and coastal Eastern Africa. Drone photogrammetry, geophysical prospection, and ground survey were compared with legacy remote sensing resources and the results of a coring survey conducted across the site during the 1990s into a GIS platform to produce multi‐phase hypothetical maps of the archaeological site in the context of its potential resource landscape. These were then tested against the results of recent excavations. The discussion highlights the challenges and potential of combining these techniques in the context of Eastern Africa and provides some suggested methods for doing so. We show that remote sensing techniques give an insight into current landscapes but are less useful in understanding or modelling how sites would have fitted into their surroundings in the past, when conditions were potentially very different. [ABSTRACT FROM AUTHOR]

Aim: Stemflow has been increasingly recognized as an indispensable component in water and nutrient budgets within vegetated ecosystems. Here we aim to quantify the stemflow percentage (St, %) of incident precipitation (i.e. stemflow production) at a global scale, and to provide a systematic evaluation on how biotic and abiotic factors affect St. Location: Global. Time period: 1970–2019. Major taxa studied: Woody plants (trees and shrubs). Methods: We compiled a global stemflow dataset from 234 peer‐reviewed papers, which included 488 observations of St and the related biotic (stand characteristics) and abiotic factors (climate variables) at 283 sites within terrestrial woody plant ecosystems. We explored the global pattern of St and performed a machine learning method (boosted regression trees) to model the effects of biotic and abiotic variables on St. Results: Globally, the median (interquartile range, IQR) St was 2.7% (1.0–6.3%). We found that St in arid zones (type B in the Köppen‐Geiger climate classification) was significantly higher (p <.01) than in other climate types, and we also detected a significant difference (p <.01) in St between trees (median: 2.4%; IQR: 1.0–5.3%) and shrubs (median: 7.2%; IQR: 5.2–11.9%). Predictor variables that substantially accounted for the explained deviance of the final model included vegetation height (27.0%), mean annual precipitation (16.1%), mean annual temperature (14.4%), stand density (10.8%), stand age (8.9%) and bark type (5.5%). In contrast, leaf area index, diameter at breast height, basal area, phenology type, life‐form and leaf type were classified as low importance. Main conclusions: Our synthesis provides a cross‐site comparison of St, and gives a holistic view on how climate variables and stand characteristics contribute to and affect global stemflow production. [ABSTRACT FROM AUTHOR]

In this paper I analyse the making and unmaking of amphibious urban modernity in Recife in the Northeast of Brazil in the first half of the 20th century. I argue that the transformation of the city was predicated on an absorptive and eradicative notion of whiteness that required the enclosure of wet, amphibious space to make dry land. The process of urban transformation proceeded not only through a racial division of space, but through a racial division of nature. In this paper I analyse the making and unmaking of amphibious urban modernity in Recife in the Northeast of Brazil between 1920 and 1950. I argue that the transformation of the city was predicated on an absorptive and eradicative notion of whiteness that necessitated the creation of dry, enclosed land. The process of urban transformation proceeded not only through a racial division of space, but through a racial division of nature. Racialised groups, and the houses, marshlands, and mangroves where they lived were subject to eradication not only as spaces but as ecologies and landscapes. Brazilian racial thought in the period was fundamentally imbricated with ideas about nature. Histories of coloniality, indigeneity, enslavement, and escape meant that forests, wetness, and the spectre of commonly held land were understood as threats to whiteness and its self‐association with order, enclosure, purity, and dryness. To answer why the division between the wet and the dry was so important, and why whiteness needed dryness, I turn back to philosophical investigations of the foundational myth of Brazil. I argue that a peculiarly Brazilian philosophy of nature, which drew racial lines within nature itself, underpinned a familiar, if uncanny, white supremacy that ordered society along the material and symbolic contours of race. Under colonial modernity, this philosophy translated into a division of the pure – rational, cleansed, dry, modern, urban space – from the impure – muddy, fearful, tangled, forested landscape. Under the conditions of dependent capitalism, the process on which this racial division of nature relied was enclosure. Identifying the historical process of the racial division of nature is of particular significance in Brazil, given the still flowing undercurrents of racial oppression and environmental plunder. [ABSTRACT FROM AUTHOR]

Wetlands in arid or semiarid zones are vital for maintaining biodiversity but face growing threats. Flooding regime variability is a key driver of ecological dynamism in these systems, dictating primary productivity on a large spatial scale. The functional composition or diversity of wetland-dependent bird species has been found to be sensitive to fluctuations in hydrological regimes and can thus be indicative of cascading ecosystem responses associated with climate change. In this paper, we investigate whether large-scale changes in inundation and fire--a significant additional biodiversity determinant in (semi-)arid landscapes--are reliable predictors of functional group responses of wetland-dependent birds along a perennial channel of the Okavango Delta, Botswana. We fit generalized additive models (GAMs) to 6 years of bird survey data collected along ~190-km-long annual transects and use remotely sensed landscape-level inundation estimates, as well as spatiotemporal distance to fire, to predict the responsiveness of seven trait-based functional group abundances. During the surveys, a total of 89 different wetland-dependent bird species were recorded, including 76 residents, across all years, with below-surface feeding waders consistently the most abundant functional group. Including estimated spatiotemporal variability in flooding and fire, as well as their interactions, improved model fit for all seven functional groups, explaining between 46.8% and 68.3% of variability in functional group abundances. Covariates representing longer-term variability in inundation generally performed better than shorter-term ones. For example, variability in inundation over the 5 months preceding a survey best predicted the responses of all functional groups, which also all exhibited responsiveness to the interaction between flooding and fire. We were able to interpret the responses of individual functional groups, based on the resource exploitation assumption. Overall, our results suggest that perennial waters in dryland wetlands offer functional refugia to wetland-dependent birds and highlight the indicative power of large-scale traitbased bird monitoring. Our findings demonstrate the potential utility of such a monitoring regime for dryland wetland ecosystems vulnerable to industrial-scale anthropogenic pressure and associated climate change. [ABSTRACT FROM AUTHOR]

Sand dams are simple and effective structures built across ephemeral riverbeds in arid/ semiarid regions to harvest water within sand pores and increase water availability and quality for rural communities. The complex morphological, hydrological, social, and economic conditions that make sand dams a beneficial tool for water resilience are largely influenced by the siting phase. Proper location of a sand dam can reduce communities' travel time to water points, reduce water conflicts, and increase food security through expansion of irrigated agriculture. On the other hand, a misplacement of sand dams can, at worst, increase disparities in water access and increase local conflicts. To approach a viable siting of sand dams, most projects are developed and delivered with the community through a bottom‐up approach. However, in the case of large‐scale projects, remote sensing and biophysical analysis are the dominant approach, leaving the socio‐economic component at the margins of the siting strategy and eventually affecting the benefits to local communities. In this paper, we propose a large‐scale participatory methodology to sand dams siting, which draws on mixed‐methods connecting the conventional top‐down biophysical analysis with bottom‐up participatory research. We first describe the generic approach developed for sand dams siting in Namibe, a semi‐arid region of Southwest of Angola, then we draw on our case to propose a generic approach to large‐scale participatory siting beyond Namibe. [ABSTRACT FROM AUTHOR]

Anthropogenic disturbances and climate change are expected to reorganize biodiversity on multiple ecological levels from populations to ecosystems, especially in arid and semiarid regions due to environmental filtering imposed by water stress. This paper examines the individual and combined effects of chronic anthropogenic disturbance and increased aridity on the structure of fruit-feeding butterfly assemblages in a human-modified landscape of Caatinga dry forest, in the northeast of Brazil. Butterflies were recorded monthly across old-growth forest stands and their assemblages were described in terms of taxonomic and functional community-level attributes confronted to different levels of chronic disturbance and aridity. Butterfly assemblages were species-poor but had high species replacement (turnover) along both the chronic disturbance and aridity gradients. We observed a negative effect of aridity on alpha and beta diversity of butterfly assemblages. Butterfly assemblages across forest stands exposed to high levels of chronic disturbance and aridity had a nested structure. Functional diversity (Rao's Q) and the community-weighted means (CWM) of ocellus-bearing species and monocot-feeding larvae were negatively and positively affected by increased aridity and chronic disturbance, respectively. Our findings suggest that aridity and its combination with chronic disturbance have a drastic effect on the structure of butterfly assemblages in the Caatinga dry forest. These findings highlight that rainfall and chronic disturbances as major drivers of biological reorganization in human-modified landscapes. As aridity increases, Caatinga tends to support taxonomically and functionally impoverished and highly distorted assemblages. [ABSTRACT FROM AUTHOR]

Reservoirs are the key infrastructure of water resources management. A controlling variable of reservoir operation is evaporation, which in semi‐arid and arid regions may consume a large fraction of reservoir storage annually. This paper assesses the role of evaporation and the choice of evaporation methods on reservoir operation. The operation of the reservoir is calculated with the standard operation policy (SOP). Several efficiency criteria are employed to rank the evaporation‐calculation methods with the technique for the order of preference by similarity to ideal solution (TOPSIS). The method presented in this paper is illustrated by applying its application to Karkheh reservoir, the largest in Iran. [ABSTRACT FROM AUTHOR]

Investigating the spatio‐temporal patterns of desertification and its driving mechanisms is crucial for efforts to improve the ecology and environment and combat desertification. Based on meteorological and satellite remote sensing data, this paper analyzed the dynamic characteristics of desertification in the Hexi region of arid and semiarid land in Northwest China from 2000 to 2018 using a dimidiate pixel model; revealed the relationship between desertification evolution characteristics and climatic variations and anthropogenic events based on the change characteristics of net primary productivity (NPP); and then clarified the response of desertification to climatic variations and anthropogenic events using a geodetector model. Outcomes show that: (1) overall desertification in Hexi region is at a serious level, but during the study period, severe desertification decreased, mainly concentrated in the east and southwest, and non‐desertification increased, mainly near the Qilian Mountains and Shule River basin; (2) there were both spatial and temporal dynamics during the study period, with severe desertification decreasing by 11% and moderate, light, and non‐desertification increasing by 3%, 5%, and 3% respectively; (3) during 2000–2005, human activities, climate change, and their joint contribution to desertification reversal were similar, i.e., 23%, 40%, and 36%, and the former two contributed equally to desertification expansion, 38% and 41%, respectively; climate change predominated in desertification reversal in 2005–2010 and 2015–2018, while human activities predominated in desertification expansion; human activities predominated in desertification reversal and climate change predominated in desertification expansion in 2010–2015. This research can provide a theoretical basis and technical support for ecological and environmental management and sustainable socio‐economic development in arid and semiarid regions. [ABSTRACT FROM AUTHOR]

Filistatids, the crevice weavers, are an ancient family of cribellate spiders without extant close relatives. As one of the first lineages of araneomorph spiders, they present a complicated mixture of primitive and derived characters that make them a key taxon to elucidate the phylogeny of spiders, as well as the evolution of phenotypic characters in this group. Their moderate diversity (187 species in 19 genera) is distributed mainly in arid and semi‐arid subtropical zones of all continents, except Antarctica. The objective of this paper is to generate a comprehensive phylogenetic hypothesis for this family to advance the understanding of its morphological evolution and biogeography, as well as lay the basis for a natural classification scheme. By studying the morphology using optical and electronic microscopy techniques, we produced a matrix of 302 morphological characters coded for a sample of 103 species of filistatids chosen to represent the phylogenetic diversity of the family. In addition, we included sequences of four molecular markers (COI, 16S, H3 and 28S; 3787 aligned positions) of 70 filistatid species. The analysis of the data (morphological, molecular, and combined) consistently indicates the separation of the Filistatidae into two subfamilies, Prithinae and Filistatinae, in addition to supporting several groups of genera: Filistata, Zaitunia and an undescribed genus from Madagascar; Sahastata and Kukulcania; all Prithinae except Filistatinella and Microfilistata; Antilloides and Filistatoides; a large Old World group including Pritha, Tricalamus, Afrofilistata, Labahitha, Yardiella, Wandella and putative new genera; and a South American group formed by Lihuelistata, Pikelinia and Misionella. Pholcoides is transferred to Filistatinae and Microfilistata is transferred to Prithinae, and each represents the sister group to the remaining genera of its own subfamily. Most genera are valid, although Pikelinia is paraphyletic with respect to Misionella, so we consider the two genera as synonyms and propose a few new generic combinations. Considering the new phylogenetic hypothesis, we discuss the evolution of some morphological character systems and the biogeography of the family. The ages of divergence between clades were estimated using a total‐evidence tip‐dating approach by including fossils of Filistatidae and early spider clades; this approach resulted in younger age estimates than those obtained with traditional node‐dating. Filistatidae is an ancient family that started diversifying in the Mesozoic and most genera date to the Cretaceous. Clades displaying transcontinental distributions were most likely affected by continental drift, but at least one clade shows unequivocal signs of transoceanic long‐distance dispersal. [ABSTRACT FROM AUTHOR]

Restoration efforts in dryland systems are often limited by a complex range of environmental variables and chronically low establishment of seeded native species. Methods for restoring large tracts of degraded drylands in the western United States and southwestern Australia have not advanced substantially since the early 1900s despite continuous efforts to improve success. Historic agricultural practices used in large‐scale restoration efforts are often unsuccessful. A multidisciplinary approach toward problem resolution is necessary for future advancements in restoration applications and methods. Specifically, agricultural technologies such as seed enhancements should be applied to native restoration approaches. Seed enhancement technologies, such as activated carbon coating and extruded pelleting, are novel in the restoration context. However, their use is increasingly recognized as an opportunity to overcome current limitations to restoration efforts. At this early juncture in the development of seed enhancement technologies within restoration, we reflect on the need to tailor current agricultural technologies in light of the differences between agricultural and restoration contexts and reconceptualize our approach to seed enhancement technologies. In this paper, we provide a guide for the development of seed enhancement technologies in ecological restoration. [ABSTRACT FROM AUTHOR]

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dynamic changes in soil organic carbon (SOC) have become a popular topic in global research on organic carbon as part of the increasing attention being paid to food security and reducing greenhouse gas emissions. In this paper, the semiarid regions of China were selected as a research focus, and SOC data from 1980 to 2015 were analysed using IBM SPSS Statistics 20.0 software. SOC in farmland varied according to cultivated land type, mulching material type and planting method in the studied regions. The SOC content is 10.3–10.8 g kg−1 in supplementally irrigated land and flat dry land, 7.1–8.7 g kg−1 in terraced dry land and river beach land, and 6.2–6.4 g kg−1 in sloping dry land. The SOC content increased to 16.1–17.4 g kg−1 when crop stalks were used as mulch. The increase was only 11.5–13.5 g kg−1 in soils mulched with film or sandstone. The SOC value in wheat, maize and potatoes sown on single or double ridges was 2.4%–3.2%, 35.7%–36.4% and 4.4%–4.8%, respectively, which are higher than the values for wheat, maize and potatoes sown using the flat planting method. The SOC sequestering potential also varied according to the previously noted factors and was improved from 224.1% to 383.8% depending on cultivated land type, from 96.5% to 182.3% depending on mulching material type and from 96.1% to 191.3% depending on planting method. The SOC sequestering potential can be improved by 453.2%–757.4% with the integration of the optimal cultivated land type, mulching material type and planting method. Thus, there is substantial soil carbon sequestration potential in China's semiarid regions. [ABSTRACT FROM AUTHOR]

Pasturelands are globally extensive, sensitive to climate, and support livestock production systems that provide an essential source of food in many parts of the world. In this paper, we integrate information from remote sensing, global climate, and land use databases to improve understanding of the resilience and resistance of this ecologically vulnerable and societally critical land use. To characterize the effect of climate on pastureland productivity at global scale, we analyze the relationship between satellite‐derived enhanced vegetation index data from MODIS and gridded precipitation data from CHIRPS at 3‐ and 6‐month time lags. To account for the effects of different production systems, we stratify our analysis by agroecological zones and by rangeland versus mixed crop‐livestock systems. Results show that 14.5% of global pasturelands experienced statistically significant greening or browning trends over the 15‐year study period, with the majority of these locations showing greening. In arid ecosystems, precipitation and lagged vegetation index anomalies explain up to 69% of variation in vegetation productivity in both crop‐livestock and rangeland‐based production systems. Livestock production systems in Australia are least resistant to contemporaneous and short‐term precipitation anomalies, while arid livestock production systems in Latin America are least resilient to short‐term vegetation greenness anomalies. Because many arid regions of the world are projected to experience decreased total precipitation and increased precipitation variability in the coming decades, improved understanding regarding the sensitivity of pasturelands to the joint effects of climate change and livestock production systems is required to support sustainable land management in global pasturelands. Plain Language Summary: Pastures, which provide food for livestock, are the most extensive land use on the planet, and their productivity depends on the timing and amount of rainfall they receive. In this paper, we use data on vegetation productivity, rainfall, and land use in order to determine the ability of pastures to remain unaffected by a disturbance and the time required for pastures to recover following a disturbance. To determine the effects of rainfall on pastures, we analyze the relationship between productivity and rainfall at 3‐ and 6‐month time intervals. We also take into account pasture management and whether pastures are located in dry or humid areas of the world. In dry regions, rain from the current season, rain from the last two seasons, and vegetation productivity from the previous growing season explain nearly 70% of current season vegetation productivity. Pastures in Australia are least capable of withstanding rainfall deficits, while pastures in Latin America recover more slowly after drought compared to other regions. Dry regions of the world are predicted to receive less rain less regularly in the coming decades, so improved understanding of the sensitivity of pastures to expected changes in rainfall will help support sustainable management of global pastures. Key Points: In Australia, pasturelands have both low resistance and low resilience relative to other regions across the worldSouthern South America has the lowest resilience globally, which is indicative of slow vegetation recovery after a disturbanceA total of 14.5% of global pasturelands experienced greening or browning trends, with the majority of these locations showing greening [ABSTRACT FROM AUTHOR]

The paper aims to study the physio‐chemical parameters of Wadi Feiran groundwater and classify it for use for drinking and irrigation. Twenty water samples collected from the WF have revealed a number of physio‐chemical parameters such as pH, TDS, SAR, EC, ions (Na+, Mg+2, Ca+2, K+, Cl−, SO4−2, NO3−, and HCO3−), and trace elements (U, Pb, Cd, Zr, and Fe). The study clarified that the major ion parameters are within the permissible limits according to WHO 2018, except for Ca+2, Cl−, SO4−2, and NO3−, but trace elements have high concentrations, except for Zn. To recognize the association between groundwater quality parameters and their collective impact on whole groundwater quality, correlation coefficient, factor, and cluster multivariate statistical analyses were carried out and confirmed with the constructed LU/LC map. These revealed that the increase of TDS, EC, Cl, SO4, Na, Mg, and NO3 is attributed to rainfall, leakage of municipal sewage Nile water, and human actions. GIS approaches were used to create thematic layers from groundwater physio‐chemical parameters, which were then weighted and combined to produce a groundwater quality model. This model was classified into potable, marginal, and un‐potable water. Potable and marginal water can be used for drinking and irrigation, but un‐potable water can only be used for irrigation. [ABSTRACT FROM AUTHOR]

With rapid urbanization and industrial development, waste discharges in west central Tunisia have multiplied. The focus here is on the waste manifestation from the National Company of Cellulose and Alfa Paper (SNCPA), which has been considered as a serious pollutant affecting natural resources as surface and groundwaters, human health and hygiene in the Kasserine land of semi‐arid climate. In order to preserve the quality assurance of available groundwater and determine its suitability for domestic an agricultural needs, a hydrogeochemical analysis was carried out to 30 samples for water samples taken from various source points of the study area (2018). This study attempt to assess the hydrogeochemical characteristics and ionic concentration with respect to WHO (2017) and Tunisian (NT.09.14) standards in the El Arich aquifer, in association with multivariate‐statistical‐analysis. Also DRASTIC model index was integrated with geographical information system (GIS) tools for the evaluation of the aquifer vulnerability to pollution. Results highlighted that only 17.65% of the groundwater samples are suitable for consumption purposes based on TDS, EC, Na+, K+, SO42–, and F–. The modeling of equilibrium geochemical processes elucidated that the groundwater's along flow‐paths are mostly in the oversaturated condition with respect to carbonate minerals, but they are undersaturated with evaporatic minerals. Based on some pre‐specified criteria and the validation by the water quality risk indices for soil salinization, the final vulnerability map shows four classes of vulnerability: very high, high, moderate, and low, depending on the intrinsic properties. HCA and FA suggest that high mineralization were related to rock‐water interactions and anthropogenic impact from the effluents discharged by the SNCPA. This multidisciplinary analysis would provide an overview for decision making authorities to take necessary action for the sustainable management and future planning in groundwater resource. [ABSTRACT FROM AUTHOR]

In this paper, the spatio-temporal variation characteristics of the daily maximum boundary layer height (BLH) and precipitation (Prec) from 1900 to 2010 are analysed by using ERA-20C reanalysis data with mathematical statistical methods. However, since time-scale variation of boundary layer processes is very short and precipitation is also a discontinuous variable, to further understand the influence of BLH on precipitation, appropriate individual cases need to be selected for more in-depth analysis. These three sub-regions are extreme arid (annual average Prec < 25mm), arid (25mm < annual average Prec <250mm), and semi-arid (250mm < annual average Prec < 500mm), as shown by the white contours in Figure 1. The white contours represent the average annual precipitation from 1900 to 2010, and the shaded colours represents the daily trend rates. gl 1 TableThe climate tendency rate and correlation coefficient (r) between the daily maximum boundary layer height and precipitation in the three sub-regions. [Extracted from the article]

Fog microphysics characteristics play an important role in fog life cycle, radiation and visibility. Measurements of fog microphysics are important in understanding these processes and improving existing model parameterization schemes. From 28 January to 17 February 2021, we carried out the first measurements of fog microphysics in the arid region of the United Arab Emirates and present initial results in this paper. Five events occurred, the longest lasting about 4 hr 28 min and the remaining lasting 2 hr or less. In this study, the meteorological conditions at synoptic scale associated with the formation of fog, are presented as well as the microphysics characteristics of fog. Maximum cloud droplet count ranged from 80 to 700 cc, Liquid Water Content (LWC) from 0.06 to 0.58 g m−3 and the Median Volume Diameter reached 25 μm in all the cases. The estimated Liquid Water Path reached a maximum of 100 g m−2. The size distribution was bimodal for all visibility classes of mist, fog and thick fog with modes at around 4.5 μm and between 22 and 25 μm. The droplet size distribution broadened as the mature phase progressed, demonstrating a decrease in droplets in the 6–16 μm range and an increase in droplets above 19 μm. During the mature stage, droplet growth was observed with no associated decrease in LWC, suggesting growth by collision and coalescence was occurring. However, LWC did increase concurrently suggesting droplet growth by condensation was also taking place. Plain Language Summary: During the cold season of each year, desert regions experience the formation of radiation fog due to the rapid cooling of the desert surface at night. Cities built on the fringes of major desert regions, such as the United Arab Emirates (UAE) cities, witness very poor visibility due to seasonal fog formation. The fog impacts air and road traffic and disrupts the daily life. Fog microphysics characteristics play a key role in fog life cycle, radiation and visibility. Measurements of fog microphysics are important to understand and improve existing model parameterization schemes for a more accurate forecast of fog occurrence and life cycle. We carried out the first fog microphysics measurements over the UAE, an arid region on the Arabian Peninsula, where fog is a frequent occurrence in winter months. Results from this study are the first of their kind in the region and are expected to advance the current knowledge on fog dynamics and characteristics. Key Points: First microphysical measurements of radiation fog in the United Arab Emirates, a warm, arid region in the subtropicsThe cloud droplet size distribution was bimodal for all visibility classes, with modes at around 4.5 μm and between 22 and 25 µmDroplet growth was observed to be due to collision, coalescence and condensation [ABSTRACT FROM AUTHOR]

Seasonally dry forests in tropical regions show over 300% inter‐annual biomass variability that directly affects the runoff and erosion dynamics. However, biomass fluctuation is mostly overlooked in hydrosedimentological analysis, including in connectivity analysis. The aim of this paper is to understand how the dryland vegetation seasonality in Brazilian drylands affects the potential runoff and sediment connectivity using the Index of Connectivity (stream and outlet targets). Two main analytical steps were used to identify the influence of dry forest biomass fluctuation on connectivity: Creation of vegetation scenarios based on the relationship between rainfall patterns and NDVI fluctuations (Landsat images); Identification of the effect of the vegetation scenarios on Index of Connectivity. The method was applied to a 90 km2 watershed in NE Brazil, creating a daily vegetation classification using five vegetation scenarios related to rainfall parameters, with average NDVI values from 0.18 during very dry scenarios (<20 mm of antecedent rainfall) to 0.62 in very wet scenario (>500 mm of antecedent rainfall). The primary connectivity behaviour is controlled by a continuous connectivity decrease, reaching 32%, related to increase of humidity and vegetation biomass. At the same time, due to rainfall irregularity, high magnitude rainfall events can occur even during very dry scenarios, when the watershed shows very high potential connectivity. It indicates that connectivity in runoff‐dominated regions is temporally variable due to the highly seasonal vegetation and variable incidence of intense rainstorms. [ABSTRACT FROM AUTHOR]

Within tribe Gnaphalieae (Asteraceae), the Australasian clade is one of the four major clades. In Australia, the Gnaphalieae account for 488 species or approximately half of the native Asteraceae, encompassing wide ecological and morphological diversity including shrubs, everlasting paper daisies, cudweeds, alpine cushion plants, and ephemeral herbs in the arid zone. The evolution of the Australasian clade is still poorly understood. The most detailed previous infratribal classification of Gnaphalieae has recently been revised, resulting in the recognition of two subtribes, with all Australian species placed in subtribe Gnaphaliinae. The most comprehensive previous phylogeny of Australian Gnaphalieae used high‐copy ribosomal and chloroplast markers but showed limited resolution and branch support. We used conserved ortholog set data produced with sequence capture and 53 chloroplast genes to infer nuclear and chloroplast likelihood phylogenies for Australian Gnaphalieae, generating data for at least one species each from 80 of the 86 native genera. Four major clades were resolved: the Euchiton clade of cudweed‐like and alpine perennial species; the shrubby Cassinia clade; the predominantly perennial and eastern Australian Waitzia clade; and the predominantly ephemeral and western Australian to Eremaean Angianthus clade. The Cassinia, Waitzia, and Angianthus clades are largely congruent with "groups" in a previous morphological analysis and classification of Gnaphalieae. Analysis of ancestral ranges implied the temperate Southeast of Australia as the most likely area of origin for the Australian Gnaphalieae as a whole and for three of the four major clades. The Angianthus clade was implied to be ancestrally Eremaean, with a major secondary radiation originating in southwestern Australia. Our broadly sampled phylogeny provides a framework to inform sampling and design of future studies to test the circumscription of genera. [ABSTRACT FROM AUTHOR]

Abstract: Cultivated oases play an important role in supporting human civilization in arid regions. Few quantitative analyses have been conducted on the influence of natural disturbances and human interventions on this fragile system over a long timescale. This paper presents an empirical study to investigate the quantitative relationship between cultivated oasis evolution and a set of natural and human factors in Heihe River Basin (HRB) over a timeframe of approximately 2,000 years (206  BC–1949 AD). Multiple data sources, including documentary records, historical atlas reconstruction data, and published papers, were used. Stepwise multiple linear regression analysis was adopted to quantify any significant contributions of the selected variables. The results showed that cultivated oasis in the HRB had experienced substantial fluctuations. Population size, agricultural policies, military clashes, and grain yield per unit area were 4 major human related factors determining historical cultivated oasis development, while flood was the only significant natural factor. In combination of similar studies in recent decades, this study shows that the dynamics of oasis development and its transition is important for determination of the sustainable size of a cultivated oasis in the HRB. [ABSTRACT FROM AUTHOR]

The ability of people to respond successfully to environmental variability is determined by their existing vulnerabilities and social‐ecological relationships. At the same time, dominant policy and scholarly approaches to adaptation remain apolitical and pay inadequate attention to the links between structural vulnerability and adaptive capacity. Using a case study from the dynamic wetland environment of the Okavango Delta, Botswana, this paper draws on work in political ecology, vulnerability studies, and the emerging field of transformative adaptation to emphasise the need for an anticipatory approach to adaptation. While flooding variability is an inherent part of life in the Okavango Delta, high floods in 2009, 2010 and 2011 displaced hundreds of residents from their homes and inundated many floodplain agricultural fields past the point of production. A combination of household interviews, participant observation sessions, and household surveys was used to investigate the impacts of these flooding events, responses to them, and the implications of those responses. Findings reveal that the Government of Botswana began to regulate wetland‐based livelihoods more strictly during the years the high floods occurred, and to encourage residents to switch permanently to dryland livelihoods. While these state‐sponsored strategies appear to be practical responses to flooding variability, they ultimately result in decreased adaptive capacity for some people, especially members of the Bayei tribe. This group typically subsists from wetland‐based livelihoods and has strong cultural ties to the waters of the Delta. By situating these findings within the historical context of marginalisation of ethnic minorities and rural communities in the country, and considering them in the light of predictions of future increases in environmental variability in the Okavango Delta, the paper identifies sites of potential transformation that would lead to improved adaptive capacities for vulnerable groups, in advance of the most significant impacts of climate change. [ABSTRACT FROM AUTHOR]

Estimation of the infiltration/natural recharge to groundwater from rainfall is an important issue in hydrology, particularly in arid regions. This paper proposes the application of The Natural Resources Conservation Service (NRCS) mass balance model to develop infiltration (F)–rainfall (P) relationship from flash flood events. Moreover, the NRCS method is compared with the rational and the Ф‐index methods to investigate the discrepancies between these methods. The methods have been applied to five gauged basins and their 19 sub‐basins (representative basins with detailed measurements) in the southwestern part of Saudi Arabia with 161 storms recorded in 4 years. The F–P relationships developed in this study based on NRCS method are: F = 39% P with R2 = 0.932 for the initial abstraction factor, λ = 0.2. However, F = 77% P with R2 = 0.986 for λ = 0.01. The model at λ = 0.01 is the best to fit the data, therefore, it is recommended to use the formula at λ = 0.01. The results show that the NRCS model is appropriate for the estimation of the F–P relationships in arid regions when compared with the rational and the Ф index methods. The latter overestimates the infiltration because they do not take λ into account. There is no significant difference between F–P relationships at different time scales. This helps the prediction of infiltration rates for aquifer recharge at ungauged basins from monthly and annual rainfall data with a single formula. [ABSTRACT FROM AUTHOR]

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper provides a survey of ancient and traditional rainwater harvesting applications as effective climate adaptation strategies. Rainwater harvesting has a more significant past than a present. The fifteen identified ancient and traditional rainwater harvesting practices and the societies that practiced them may provide a key water conservation strategy for the future in vulnerable regions found in the dry-wet, semi-arid, and arid climatic regions. In the past several decades, there has been a call from scientific and non-governmental organization communities to combine modern water systems and old rainwater harvesting methods or to modernize the existing rainwater harvesting knowledge to benefit human settlements facing water scarcity. [ABSTRACT FROM AUTHOR]

In extremely arid regions, deeply buried phreatic water evaporates during the daytime from March to November in the northern hemisphere. It has been found that the earth–air undergoes 'autonomous breathing' and 'passive breathing', respectively caused by the changes of temperature and atmospheric pressure. In this paper, the effects of these breathing modes on phreatic evaporation (PhE) were investigated as well as the responsible mechanisms. Quantitative estimates suggest that the direct contribution from autonomous breathing is only 0.55 g·m−2·yr−1. Passive breathing pumps water vapour upwards from the deeply buried phreatic water table. Film water on the soil continuously migrates in pulsation from deep layers to the upper layer. Na2SO4 in the shallow soil absorbs moisture from the earth–air at night and decomposes during the day, forming water vapour, which is critical to the occurrence of PhE. The diurnal PhE process can be elucidated in detail by the bimodal variation in the atmospheric pressure. PhE occurs mainly from 10:00 to 17:00 during daytime from March to November, which correlates with passive breathing of the earth–air. The amplitude of atmospheric fluctuation determines the amount of earth–air that outflows, while temperature determines the water vapour concentration. In calculation, PhE is equal to the net absolute humidity (AH) times the amount of earth–air. There is 1.55 mm·year−1 of PhE caused by daily peak→valley differences, and about 2.97 mm·year−1 in estimation caused by numerous atmospheric fluctuations smaller than 2.84 hPa. The results coincide with the actual amount of PhE monitored of 4.52 mm·year−1. Therefore, the amount of PhE is proportional to the range and frequency of fluctuation in external atmospheric pressure, and is also positively related to soil temperature, salt content, water content, porosity, and vadose zone thickness. [ABSTRACT FROM AUTHOR]

The Yangtze River Basin has periodically been subject to torrential rains and floods. It is of great significance to characterize the extreme precipitation patterns to learn about frequent flood characteristics in the Yangtze River Basin. Commonly, spatiotemporal characteristics of extreme precipitation was studied by regional frequency analysis method with site data. Spatial sparse site data may cause imprecise divisions of homogeneous regions. In this paper, the spatiotemporal characteristics of extreme precipitation was studied by regional frequency analysis with corrected satellite‐based grid precipitation data (Global Land Data Assimilation System, GLDAS) rather than site data. The results show that: (1) The corrected GLDAS daily precipitation data had greatly improved its ability to capture extreme precipitation events in Yangtze River Basin, as the data average accuracy increased from 0.215 before correction to 0.849 after correction. It is feasible to use satellite‐based grid precipitation data to replace the site data for the regional frequency analysis of extreme precipitation. (2) The Yangtze River Basin was categorized into seven homogeneous regions for the annual maximum 1‐day (RX1DAY) index with an automatic subjective adjustment method. (3) The regional growth curves and quantiles of the Yangtze River Basin were drawn for the return period for 2–100 years. (4) Spatial patterns of extreme daily precipitation series with a return period of 100 years indicated that the precipitation amount increases gradually from the upper to the lower Yangtze River Basin, from the "arid zone" to the "wet zone" and then to the "special wet zone", and the 100‐year return level of RX1DAY varied from 30.3 to 301.8 mm. There were three main precipitation centres, the Sichuan Basin, Dongting Lake Basin, and a great triangle area covering the Poyang Lake Basin and the south foot of Dabie Mountain. [ABSTRACT FROM AUTHOR]

Studies about evaluations of different rainfall estimation methods are important as they are usually applied in works related to water resources availability, public supply, watering, animal water supply, hydroelectric power generation, drought episodes' evaluation, among others. Studies that cover the entire area of the Brazilian semiarid within this scope are still scarce. In this context, the objective of this paper was to evaluate seven rain estimation methods, from different approaches, with the aid of statistical analysis. The focus was on the long term, using 30 years of data in monthly scale, in order to verify the methods performance in estimating the spatiotemporal behaviour of rainfall compared to data measured in situ, coming from rainfall and meteorological stations. The evaluation process was based on the random selection of training and testing stations, with the first being used to interpolate rainfall data using different methods, and the latter used to evaluate this estimates with the aid of statistical analysis. Finally, the results were standardized, interpreted and discussed. Of all the estimation methods evaluated, CHIRPS obtained the best performance when compared to field stations data used as test. From the results obtained, there is evidence that the best performance is due to the incorporation of several distinct data sources derived from in situ stations, geostationary satellite infrared sensor estimates and physiographic predictors. This information is not fully present in other evaluated methods. The worst estimation performances were in the eastern side of the Brazilian semiarid, an area that receives moisture from the Atlantic Ocean and has significant topographic variations, due to the set of the complex relief mountains present in the northeast coast of Brazil. [ABSTRACT FROM AUTHOR]

Land degradation has become a most pressing issue in drylands. Although crop and livestock production have been the dominant sources of income, there is an increasing realisation that alternative livelihood options need to be explored to ensure both environmental and economic sustainability. This paper provides a systematic review of alternative livelihood strategies currently adopted for improving livelihood conditions of dryland dwellers in different parts of the world. Although drylands encompass a vast social and geographic terrain and represent a heterogeneous socio-economic environment, this paper has been able to document some general lessons applicable to rural drylands for diversifying livelihood opportunities and promoting rural development while minimising the pressure from intensive land-based activities. The paper concludes with a discussion on how international development policies can move forward in the fight against land degradation and in helping achieve poverty reduction through investments in sustainable land management and alternative livelihood strategies. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Managed aquifer recharge (MAR) has been gaining adoption within the mining industry for managing surplus water volumes and reducing the groundwater impacts of dewatering. This paper reviews MAR for mining and includes an inventory of 27 mines using or considering MAR for current or future operations. Most mines using MAR are in arid or semi‐arid regions and are implementing it through infiltration basins or bore injection to manage surplus water, preserve aquifers for environmental or human benefit, or adhere to licensing that requires zero surface discharge. Surplus water volumes, hydrogeological conditions, and economics play a pivotal role in the feasibility of MAR for mining. Groundwater mounding, well clogging, and interaction between adjacent mines are common challenges. Mitigation strategies include predictive groundwater modeling, extensive monitoring programs, rotation of infiltration or injection facilities, physical and chemical treatments for clogging, and careful location for MAR facilities in relation to adjacent operations. Should water availability alternate between shortage and excess, injection bores may be used for supply, thus reducing costs and risks associated with drilling new wells. MAR, if applied strategically, also has the potential to accelerate groundwater recovery post‐mine closure. The success of MAR for mining is emphasized by mines opting to increase MAR capacity alongside dewatering expansions, as well as prospective mines proposing MAR for future water requirements. Upfront planning is the key to maximizing MAR benefits. Improved information sharing could help increase awareness and uptake of MAR as an effective and sustainable mine water management tool. [ABSTRACT FROM AUTHOR]

Despite several studies showing the effect of access to markets and weather conditions on crop production, we know quite little on whether and how livestock production systems respond to variation in weather risk and access to markets. In this paper, we study whether and how livestock production responds to (access to) markets and varying weather risk. We also explore whether such responses vary across livelihood zones and livestock production systems. We study these research questions using households' livestock production, ownership, and marketing decisions of households in Ethiopia. We find that households living close to markets are more likely to engage in market‐oriented livestock production and use modern livestock inputs. We also find that households exposed to more unpredictable weather are less likely to engage in livestock production for markets, rather they are more likely to engage in livestock production for precautionary savings and insurance. Furthermore, greater rainfall uncertainty influences livestock portfolio allocation toward those which can be easily liquidated while also discouraging investment in modern livestock inputs. However, these responses and patterns vary across livelihood zones and production systems; most of these stylized responses and impacts are more pronounced and significant in the arid and semi‐arid lands of Ethiopia, where livestock herding remains a dominant source of livelihood. Those households relying only on livestock production seem more sensitive and responsive to weather risk and weather shocks. The heterogeneity in responses and impacts of weather risk among farming systems and livelihoods highlights the need for more tailored livestock sector policies and interventions. [ABSTRACT FROM AUTHOR]

Groundwater‐dependent ecosystems are often defined by the presence of deeply rooted phreatophytic plants. When connected to groundwater, phreatophytes in arid regions decouple ecosystem net primary productivity from precipitation, underscoring a disproportionately high biodiversity and exchange of resources relative to surrounding areas. However, groundwater‐dependent ecosystems are widely threatened due to the effects of water diversions, groundwater abstraction, and higher frequencies of episodic drought and heat waves. The resilience of these ecosystems to shifting ecohydrological–climatological conditions will depend largely on the capacity of dominant, phreatophytic plants to cope with dramatic reductions in water availability and increases in atmospheric water demand. This paper disentangles the broad range of hydraulic traits expressed by phreatophytic vegetation to better understand their capacity to survive or even thrive under shifting ecohydrological conditions. We focus on three elements of plant water relations: (a) hydraulic architecture (including root area to leaf area ratios and rooting depth), (b) xylem structure and function, and (c) stomatal regulation. We place the expression of these traits across a continuum of phreatophytic habits from obligate to semi‐obligate to semi‐facultative to facultative. Although many species occupy multiple phreatophytic niches depending on access to groundwater, we anticipate that populations are largely locally adapted to a narrow range of ecohydrological conditions regardless of gene flow across ecohydrological gradients. Consequently, we hypothesize that reductions in available groundwater and increases in atmospheric water demand will result in either (a) stand replacement of obligate phreatophytic species with more facultative species as a function of widespread mortality in highly groundwater‐dependent populations or (b) directional selection in semi‐obligate and semi‐facultative phreatophytes towards the expression of traits associated with highly facultative phreatophytes in the absence of species replacement. Anticipated shifts in the expression of hydraulic traits may have profound impacts on water cycling processes, species assemblages, and habitat structure of groundwater‐dependent woodlands and riparian forests. [ABSTRACT FROM AUTHOR]

With nearly a quarter of global dryland systems considered to be degraded, the level and scale of degradation often exceed the thresholds for autogenic recovery, requiring human intervention to ensure that ecosystem biodiversity, structure, and function can be improved. A 'Think Tank' workshop focusing on advancing the ecological approaches to large-scale restoration in degraded environments was held at Kings Park and Botanic Garden, Western Australia. Acknowledging that adaptive and broadly multidisciplinary strategies are paramount to achieving restoration in a repeatable and cost-effective manner, the workshop served as a forum to bring together plant scientists, ecologists, engineers, and environmental managers involved in dryland restoration from around the globe. This introductory paper to this special issue summarizes important contemporary challenges facing dryland restoration worldwide, offers a synthesis of the fundamental workshop themes, and provides a contextual overview for the series of invited papers in this issue, comprising reviews and case studies in seed and restoration technologies. [ABSTRACT FROM AUTHOR]

Environmental factors such as temperature and humidity influence the distribution of free‐living organisms. As climates change, the distributions of these organisms change along with their associated parasites, mutualists and commensals. Less studied, however, is the possibility that environmental conditions may directly influence the distribution of these symbionts even if the hosts are able to persist in altered environments. Here, we investigate the diversity of parasitic lice (Insecta: Phthiraptera) on birds in arid Utah compared to the humid Bahamas. We quantified the parasite loads of 500 birds. We found that the prevalence, abundance and richness of lice was considerably lower among birds in Utah, compared to the Bahamas, despite sampling greater host taxonomic richness in Utah. Our data suggest that as climates change, birds in arid regions will have less diverse louse communities over time, potentially relieving birds of some of the cost of controlling these ectoparasites. Conversely, birds in more humid regions will see an increase in louse diversity, which may require them to invest more time and energy in anti‐parasite defense. Additional research with other ectoparasites of birds and mammals across different environmental conditions is needed to more fully understand how climate change may reshape parasite communities, and how these changes could influence their hosts. [ABSTRACT FROM AUTHOR]

This paper investigates the extreme wet‐bulb temperatures (TWs) in China, with a focus on understanding the relative contributions of temperature and moisture to the extremes. Analysis of station observations shows that daily extreme temperatures (T), specific humidity (q), and TWs generally co‐occur in Southeastern China, while extreme TW and T rarely overlap in the arid and semiarid North and Northwest China. Overall, q contributes more than T to extreme TWs, especially in North and Northwest China. Based on the relative contributions of q and T, regional extreme TW events are classified as q dominated and T dominated, respectively, to study their large‐scale environment. Cluster analysis of global reanalysis data shows that extreme TWs are generally accompanied by increased surface air temperature and humidity, concomitant with anomalous high pressure and notable water vapor flux convergence. However, important differences are also seen in the large‐scale environment during q‐dominated and T‐dominated extreme TWs. During q‐dominated extreme TWs, the large‐scale environment favors convection, as indicated by ascending motions, decreased downward solar radiation as well as increased precipitable water and near‐surface relative humidity. In contrast, during T‐dominated extreme TWs, convection is inhibited by the large‐scale environment that features descending motion and increased downward solar radiation, decreased precipitable water, and decreased relative humidity. Consistent with the contrasting environments, we demonstrate that T‐dominated extreme TWs tend to last longer than q‐dominated extremes. Given the significant role of moisture in extreme TWs, more research is needed to understand its impacts on heat stress now and in the future. Key Points: Extreme wet‐bulb temperatures in China are investigated using observations, considering both the role of temperatures and moistureMoisture contributes more to extreme wet‐bulb temperatures than temperature in most regions of ChinaThe environment during moisture‐/temperature‐dominated extreme wet‐bulb temperatures tends to be convection favored/convection inhibited. [ABSTRACT FROM AUTHOR]

Agriculture production in study areas benefits from the use of ridge‐furrow rainwater harvesting (RFRH) to supplement rainfall in the absence of irrigation from imported sources. However, it is necessary to select suitable fodder plants for use with RFRH in this climate. In this paper, 10 treatments (3 ridge widths × 3 ridge‐mulching materials + flat planting [FP] as control) in a complete random design were applied in a 3‐yr field experiment for alfalfa (Medicago sativa L.) and oat (Avena sativa L.) production, respectively. Ridges mulched with plastic film (PF) and ridges mulched with biodegradable film (BF) had positive effects on fodder, grain yields, and water use efficiency (WUE), but ridges with manually compacted soil (MCS) had a negative effect on yield and WUE in the most cases. Fodder, grain yields, and WUE decreased as ridge width increased. For oats, the decrease of WUE of MCS was 1.31 kg ha−1 mm−1, but the increase of WUE of BF and PF was 0.83 and 1.25 kg ha−1 mm−1, respectively, compared with that of FP over 3 yr. For alfalfa, the increase of WUE of MCS, BF, and PF was, respectively, 0.22, 5.62, and 6.33 kg ha−1 mm−1. The RFRH systems, especially PF and BF, produced oat and alfalfa fodders with increased crude protein content and decreased acid and neutral detergent fiber content. The average alfalfa fodder yield was 1.37 times greater than that of oats, whereas the average WUE of alfalfa was 2.62 times greater than that of oats. Alfalfa fodder contained higher crude proteins and lower neutral detergent fiber content than oat fodder and had similar acid detergent fiber. It is more economic to harvest oat fodder than to harvest oat grain, and it is more economic to produce alfalfa than to produce oats. [ABSTRACT FROM AUTHOR]