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Climate change and increasing anthropogenic activities, such as over-exploitation of groundwater, are exerting unavoidable stress on groundwater resources. This study investigated the spatio-temporal variation of depth to groundwater level (DGWL) and the impacts of climatic (precipitation, maximum temperature, and minimum temperature) and anthropogenic (gross district product (GDP), population, and net irrigated area (NIA)) variables on DGWL during 1994–2020. The study considered DGWL in 113 observation wells and piezometers located in arid western plains (Barmer and Jodhpur districts) and semi-arid eastern plains (Jaipur, Ajmer, Dausa, and Tonk districts) of Rajasthan State, India. Statistical methods were employed to examine the annual and seasonal patterns of DGWL, and the generalized additive model (GAM) was used to determine the impacts of climatic and anthropogenic variables on DGWL. During 1994–2020, except for Barmer District, where the mean annual DGWL was almost constant (around 26.50 m), all other districts exhibited increase in DGWL, with Ajmer District experiencing the most increase. The results also revealed that 36 observation wells and piezometers showed a statistically significant annual increasing trend in DGWL and 34 observation wells and piezometers exhibited a statistically significant decreasing trend in DGWL. Similarly, 32 observation wells and piezometers showed an statistically significant increasing trend and 37 observation wells and piezometers showed a statistically significant decreasing trend in winter; 33 observation wells and piezometers indicated a statistically significant increasing trend and 34 had a statistically significant decreasing trend in post-monsoon; 35 observation wells and piezometers exhibited a statistically significant increasing trend and 32 observation wells and piezometers showed a statistically significant decreasing trend in pre-monsoon; and 36 observation wells and piezometers reflected a statistically significant increasing trend and 30 observation wells and piezometers reflected a statistically significant decreasing trend in monsoon. Interestingly, most of the observation wells and piezometers with increasing trends of DGWL were located in Dausa and Jaipur districts. Furthermore, the GAM analysis revealed that climatic variables, such as precipitation, significantly affected DGWL in Barmer District, and DGWL in all other districts was influenced by anthropogenic variables, including GDP, NIA, and population. As a result, stringent regulations should be implemented to curb excessive groundwater extraction, manage agricultural water demand, initiate proactive aquifer recharge programs, and strengthen sustainable management in these water-scarce regions. [ABSTRACT FROM AUTHOR]

Copyright of International Forestry Review is the property of Commonwealth Forestry Association 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.)

Natural resource managers may utilize remotely sensed data to monitor vegetation within their decision-making frameworks for improving habitats. Under binational agreements between the United States and Mexico, seven reaches were targeted for riparian habitat enhancement. Monitoring was carried out using Landsat 8 16-day intervals of the two-band enhanced vegetation index 2 (EVI2) for greenness and actual evapotranspiration (ETa). In-channel water was delivered in 2021 and 2022 at four places in Reach 4. Three reaches (Reaches 4, 5 and 7) showed no discernable difference in EVI2 from reaches that did not receive in-channel water (Reaches 1, 2, 3 and 6). EVI2 in 2021 was higher than 2020 in all reaches except Reach 3, and EVI2 in 2022 was lower than 2021 in all reaches except Reach 7. ET(EVI2) was higher in 2020 than in 2021 and 2022 in all seven reaches; it was highest in Reach 4 (containing restoration sites) in all years. Excluding restoration sites, compared with 2020, unrestored reaches showed that EVI2 minimally increased in 2021 and 2022, while ET(EVI2) minimally decreased despite added water in 2021–2022. Difference maps comparing 2020 (no-flow year) to 2021 and 2022 (in-channel flows) reveal areas in Reaches 5 and 7 where the in-channel flows increased greenness and ET(EVI2). [ABSTRACT FROM AUTHOR]

The focus of coal development in China has been strategically shifted westward. That realize green mining of coal resources and coordinated ecological development becomes one of the important measures to ensure national energy security. Most of the coal seams in the western region are buried shallowly, with thin overlying bedrock and thick coal seams, which is beneficial for large-scale underground mining or open-pit mining. However, the climate in the region is arid with little rainfall and fragile ecological conditions, which caused significant damage to the mining area and surrounding ecological environment on a large scale and with high intensity. Due to the unclear understanding of the evolution mechanism of ecological damage during the mining process and the post mining restoration mechanism, there is no mature restoration theory and method to guide it, which has become a major challenge restricting the high-quality development of coal in the region. We are focuse on the above-mentioned difficulties, which consider accurately surveying the geological and hydrogeological conditions and the ecological evolution characteristics of the entire coal mining cycle working face, that be helpful for elucidating the mechanism of overlying soil and rock damage caused by mining, the law of water resource loss and accumulation and cyclic transportation, the mechanism of ecological damage evolution and bearing capacity, and revealing the soil and rock layers, water resource circulation, and mechanism of ecological self-adaption in the post-mining area. By using the plant-microbial combination restoration method, a water-soil ecological three-dimensional coupling remediation theory was constructed for the synergy between artificial and natural restoration in underground and open-pit mines, and a new thinking on the mechanism of ecological restoration was proposed. That development of fissures is like loosening soil in farmland becomes a new opportunity for ecological restoration in shallow buried deep mining area, which promote the redistribution of water-soil-life. Meanwhile, utilizing microbial remediation technology to promote the coordinated forward direction development of water retention-quality improvement-capacity enhancement, practicing the thinking of developing “golden mountains and silver hills” and recreating “green mountains and clear waters” in the western fragile ecological area.

Changing land use from rangeland and forest to agricultural land and orchard can greatly affect the characteristics and fertility of the soil, especially in arid and semi-arid regions. In this study, seven major land-use types in Kohgiluyeh-and-Boyer-Ahmad province of southwest Iran were selected; these land types were orchards (grape), forests, rangelands, and agricultural lands which cultivated corn, beans, and rainfed and irrigated wheat containing five soil orders, namely Entisols, Inceptisols, Mollisols, Alfisols, and Vertisols. The samples were collected from the soil depths of 0-30 cm. Based on the results, the highest average content of organic carbon (OC) was detected in the forest (3.3%). It may thus be stated that there is a balance in forest soils between the rapid decomposition of soil organic matter and the rapid accumulation of litter due to plantation and also an abundance of litter. In all soil samples, the highest percentage of Fe and Mn were found in the residual (Res) fraction and the lowest percentage in the exchangeable (Ex) fraction. The highest and lowest amounts of Fe and Mn carbonate (Car) form were associated with forest and rangeland land uses. Different land uses had an important influence on the amount of the Fe form bound to organic compounds. In this way, the maximum amount of this form belonged to forest use which contained the highest amount of organic matter; the lowest amount of organic matter was related to rangeland use.

The nature of the Mesolithic in China has not been studied much due to the few well-context sites discovered and excavated during this period. The situation also restricts the understanding of human subsistence in the Mesolithic period in China, especially in the arid region. The present paper reports the flotation results at Locality 10 of the Pigeon Mountain site in Northwest China. Ten species of plants belonging to six families were identified, dominated by Agriophyllum squarrosum and Artemisia sieversiana. No firm evidence proves the domestication. Combined with the lithic artefacts in QG10, ancient people could utilize plant resources by constructing or expanding the food spectrum. It is the first systematic archaeobotany work in the Paleolithic site of Northwest China. The result reminds us that the enhanced utilization of wild plant resources is a vital subsistence for Mesolithic people in arid regions.

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.)

Rural areas are the main source of ecosystem services in arid and semi-arid areas, and ecosystem services are the background conditions for rural revitalization. In this study, the spatial pattern of key ecosystem services in the countryside was assessed, and the trade-offs and synergistic relationships among ecosystem services were investigated, using the Tacheng-Emin Basin in China as the study area. Finally, the types of ecological function zoning and development strategies for the countryside are proposed. The results showed that: (1) the area of ecological land was large, and the average land use intensity was 2.48, which belonged to the medium intensity. (2) The mean values of the six ecosystem services are all in the middle and lower classes, and the spatial distribution of the five ecosystem services is similar, except for food production. (3) Except for grain production, the other five ecosystem services showed positive feedback to elevation. The other five ecosystem services are synergistic, and there are trade-offs between grain production and other ecosystem services. In the nonlinear interaction mechanism of ecosystem services, the fluctuation constraint occupies the largest proportion. (4) At smaller spatial scales, there are more types of ecosystem service clusters. Combining the results of the study, the villages in the study area can be categorized into five types. This study formulates five priority levels of rural ecological revitalization and proposes different development recommendations for the sustainable development of each type of village. This study is helpful for the fine management of land resources and the revitalization of rural ecology and provides a reference for the sustainable development of ecosystem services in arid and semi-arid areas. • A 10-m resolution land use map was created based on the Random Forest. • Mountains have high ecosystem service values in arid and semi-arid areas. • There are trade-offs between grain production and other services in the study area. • Multiple non-linear relationships exist between ecosystem services. • Ecosystem service clusters are most diverse at the rural scale. [ABSTRACT FROM AUTHOR]

Agriculture is the most natural resource-intensive and climate-sensitive sector. This study examines the perceptions and attitudes of small family farmers toward climate change and identifies adaptation strategies supporting household food security in the Middle Eastern context, Lebanon. The study uses cross-sectional, primary data of households that own small family farms in the Central Bekaa region. The results show that the majority of the households believe that climate change is occurring, has adverse impacts on livelihoods, and is attributable to human factors. They perceived an increase in temperature and a decrease in rainfall patterns over the last 20 years. In response, the households used multiple agricultural practices to adapt to climate change. Based on the Household Food Insecurity Access Scale (HFIAS) scores, only 7.5% of the households were food secure, while 89% were mild to moderately food insecure. Generally, the households had modest access to nutritious diets. All the households used two or more environmentally sustainable agricultural practices. However, the use of multiple environmentally sustainable practices did not correlate with improved food security. This latter result may be due to the limited knowledge of the farmers about trade-offs between various climate change adaptation measures. The findings suggest the need to refocus research from the question of whether small family farmers are willing to adopt (or not) climate change adaptation practices to identifying those practices that are capable of balancing economic, social, and environmental goals in a specific context. [ABSTRACT FROM AUTHOR]

ABSTRACT: Sorghum as a drought tolerant crop provides an alternative opportunity towards increasing food production in the face of global climate change, mostly affecting Sub-Saharan Africa. Kenya is in the fore front in increasing the production of sorghum since its landmass is 80 percent arid and semi-arid. Few studies have evaluated farm and farmer related characteristics affecting adoption of sorghum production. Therefore, the objective of this study was to determine how selected factors affect the propensity of farmers to adopt sorghum production in Siaya County, Kenya. A total of 300 households were randomly selected as respondents in four sub-counties under sorghum production. Data was collected using semi-structured interview schedules administered to the selected farm households. The selected factors were subjected to descriptive analysis, while binary logistic regression model was applied for the quantitative analysis of the effect of these factors on adoption of sorghum production. The results of the regression analysis reveal that farm size, land size allocated to maize, beans and groundnut enterprise, land ownership and access to training significantly affected adoption of sorghum farming. The study underscores the significant impact of resource allocation decisions on uptake of sorghum production among farm households. Our findings show that farmers with larger farms are more likely to adopt sorghum production. However, due to industrial demand and food security potential of sorghum, we recommend that the extension service providers should also incentivize those with smaller farms to participate in sorghum production. Policies that will make sorghum enterprise more competitive over other crops, both at the farm and market level, are key. In addition, agricultural development policies should target provision of such services like training to streamline sorghum production in the arid and semi-arid areas in Kenya.

The biocrusts are organized by soil-surface communities of biota that live within or on the very top of soil surface and play an important role in soil conservation. They include lichens, mosses, fungi, cyanobacteria, eukaryotic algae, and other heterotrophic bacteria. The interaction between biocrusts and soil is very important and good awareness from that help to better manage soil specially in arid and semi-arid areas. The linkage between cyanobacteria species and soil physicochemical parameters and mineralogy in two geomorphic zones in the northeastern Iran was studied. Samples were collected in summer along a linear transect by using 50 x 50 cm quadrates for each study zone. Individual mineral soil particles were analyzed by a scanning electron microscopy (SEM). The amounts of Na, K, Ca, and Mg contents as well as EC and SOC altered significantly between two study zones. Biocrusts increased levels of organic carbon, pH, calcium carbonate, exchangeable sodium and potassium percentages. The main soil properties of SOC, CaCO3 and amount of clay changed among biocrust sand bare soils.

Freshwater ecosystems are of the most diverse ecosystems in the world, but anthropogenic disturbance and climate change are threatening the biodiversity of these habitats, particularly in the highly vulnerable arid regions. Understanding the compositional patterns in aquatic biota and discovering factors responsible for these patterns enable researchers to predict the impacts of environmental changes and reduce their destructive effects. As a first step for evaluating the conservation value of freshwater ecosystems in the arid areas of Central Iran, we investigated the phylogenetic beta diversity of Odonata assemblages and their response to climate, landscape, and local predictors. A total of 41 water bodies were surveyed and 42 species of Odonata were recorded. The distance matrices related to the total phylogenetic beta diversity of Odonata and the replacement and richness difference components were computed. Each of the three dissimilarity matrices were modelled by generalized dissimilarity modelling (GDM). The average phylogenetic beta diversity was high, and the replacement component had a higher contribution rather than the richness difference component. GDMs results showed that total phylogenetic beta diversity was strongly associated with climate and local predictors. The most influential variables observed were climate variables. Our findings indicated that even in extreme conditions, the freshwater ecosystems could support species with various phylogenetic histories. We emphasize the importance of man-made water bodies in supporting freshwater biodiversity in arid areas. Given the growing threat of habitat degradation and climate change, with no conservation plan, many vulnerable species may be in danger of localized extinction within the region. [ABSTRACT FROM AUTHOR]

Soil moisture is a vital resource that plays a critical role in arid and semi-arid areas. In the present study, a new approach was adopted to estimate surface soil moisture based on multi-index models using reflective and thermal indices as well as surface energy balance system–Iran (SEBS–Iran) in pastures and farmlands in Qom province, Iran in 2016–2017. To select the best model based on remote sensing (RS) indices, 12 models were designed and after analysis, the best ones were selected. Afterward, the results of the SEBS–Iran algorithm and the improved multi-index model [normalized multi-band drought index (NMDI), normalized difference vegetation index (NDVI), land surface temperature (LST) and the temperature vegetation dryness index (TVDI)] were calibrated with field data in the two studied fields (pastures and farmlands). The findings indicated that the multi-index model NMDI–TDVI–LST–NDVI (R = 0.95) and SEBS–Iran (R = 0.93) both had significant correlations with measured soil moisture. Regarding both models in farmlands and pastures, the SEBS–Iran regression model was closer to the line of fit, and R2 in the two fields was 0.95 and 0.96, respectively. Compared to SEBS–Iran, the multi-index model showed lower coefficient of determination in pastures (0.71) due to the higher accuracy of SEBS–Iran in areas with lower vegetation density. Generally, both methods were found to be suitable for soil moisture estimation. The multi-index model can be used to estimate soil moisture in densely vegetated areas on a large scale due to its simplicity and good accuracy. Moreover, the highly accurate SEBS–Iran model can be used even in sparsely vegetated areas. [ABSTRACT FROM AUTHOR]

Aims: The survival and distribution of plant species in the extreme environmental conditions of semi-arid regions is strongly dependent on traits associated with drought resistance. Seed weight may be particularly important, since larger seeds are predicted to promote survival in harsh environments, especially those of low soil moisture. Here, we test this hypothesis using data on the seed weight of 277 woody plant species in the semi-arid Caatinga biome of northeast Brazil. Methods: We used Structural Equation Models (SEM) to test for associations between seed weight and biophysical conditions, including temperature, precipitation, climatic seasonality, soil-vegetation interaction and soil compaction. Results: Species occurrence data were geographically biased due to large areas of the biome that remain under-collected. The strongest statistical association was between seed weight and soil compaction, with mean temperature of the driest quarter and aridity directly influencing soil compaction (and indirectly influencing seed weight). Conclusions: We conclude that the larger seeds of woody species in the Caatinga are primarily an adaptation to compacted soil, uneven distribution of rainfall and high temperatures, intrinsic conditions of the Caatinga biome. [ABSTRACT FROM AUTHOR]

In arid and semi-arid environments, soils are very fragile. Their degradation rapidly reduces the biological potential and disrupts the ecological and socio-economic balance. Living within a few millimetres of the soil surface, biocrusts are organised into communities of biota and play an important role in soil stability and preservation. They are mainly composed of cyanobacteria, lichens, mosses, fungi, eukaryotic algae and other heterotrophic bacteria. Soil-biocrusts interaction is therefore very important and a good knowledge of this interaction allows a better management of soils, especially in arid and semi-arid environments. Thus, the link between cyanobacteria species and physicochemical parameters and soil mineralogy was studied in two geomorphological zones of northeast of Iran. Cyanobacteria are the main photosynthetic component of biocrusts. Samples were collected in summer along a linear transect by using 50 x 50 cm quadrates for each study zone. Individual mineral soil particles were analysed by scanning electron microscopy (SEM). The amounts of Na, K, Ca and Mg as well as electrical conductivity and soil organic carbon are higher in the presence of biocrusts (Takhte Soltan site) than in their absence (Sabzevar Playa site). Biocrusts increased levels of organic carbon, pH, calcium carbonate, exchangeable sodium and potassium percentages. Results indicated that soil properties regarding soil organic carbon, CaCO3 and amount of clay changed among biocrust sand bare soils. This research considers further attention to biocrusts because of their multiple ecosystem roles and their importance in the constitution of dryland ecosystems. [ABSTRACT FROM AUTHOR]

The golf courses present major areas of grass that need high volumes of water for maintenance. In regions with arid climate, elevated water losses by evapotranspiration contrast with low rainfall. In the urban-touristic area of Los Cabos, 13 golf courses have been built in a distance of 40 km along the coast. This benefits private developers but golf courses provoke various environmental and social problems, including habitat loss, pollution of soils and aquifers, among others. Because the golf courses do not report their water demand, the annual water consumption was analyzed by indirect methods, using satellite imagery and geographic information systems. The obtained annual water demand of the 13 golf fields is 7.09 million m3, which is more than the whole water volume used for agriculture in this area. The findings suggest that the water consumption should be taken into account as an important environmental impact before the realization of new golf courses in Mexico. [ABSTRACT FROM AUTHOR]

Abstract The effects of precipitation patterns on the metabolism of soil microbes are poorly understood, especially in water-limited ecosystems where soil microorganisms play crucial roles in the turnover of soil organic carbon (SOC) and nutrients. We investigated the influence of the gradient levels of mean annual precipitation (MAP from 300 to 900 mm) on soil microbial metabolism in an arid and semi-arid grassland region located in Loess Plateau, China and identified relationships between microbial metabolic limitations and the variation of soil organic matter (SOM). Microbial metabolism in this arid and semi-arid region was limited by soil C and phosphorus (P) or nitrogen (N). Microbial C and P limitations decreased with the increase of MAP. Microbial C and P limitations were lowest in the areas with MAPs of 700–900 mm, whereas N limitation was observed in the areas with MAPs >700 mm. The results of a variation-partitioning analysis and partial least squares path modeling indicated that the microbial C and N/P limitations on regional scales were mainly determined by climate factors (MAP and mean annual temperature (MAT)), followed by vegetation biomass and soil properties. The extents of soil drying-rewetting processing caused by different MAPs directly affected microbial nutrient limitation. Our results suggested that the influence of precipitation variation on microbial metabolic limitation strongly governed SOM stability and that an increase in the rate of SOM decomposition with increasing precipitation could be caused by increased microbial nutrient limitation. SOM may be most stable at a MAP of 700 mm in the arid and semi-arid regions (300–900 mm MAP) where microbial nutrient limitation was lowest. This study provided novel insights into the responses of soil microbial metabolism to precipitation change and is an important step toward understanding the mechanisms of SOM stability in an arid and semi-arid grassland ecosystem under scenarios of precipitation variation. Graphical abstract Unlabelled Image Highlights • C and P limitation of soil microbes decreased as MAP increased (300 to 900 mm). • Microbial N limitation is observed in the areas of MAPs above 700 mm. • Precipitation is one of the most important drivers of microbial metabolic limitation. • SOM variations are correlated with microbial metabolic limitation. [ABSTRACT FROM AUTHOR]

The stability of the arable ecosystem plays a crucial role in the sustainable utilization of land resources and the efficiency of agricultural production. However, irrigated agriculture has led to severe desertification and salinization in arid and semi-arid areas, resulting in long-term low ecological stability of arable land. This study focuses on the arable ecosystem stability (AES) in the Hexi Corridor and constructs an AES evaluation model based on the pressure-buffer-response process. Using methods such as the revised wind erosion equation, remote sensing ecological index and path analysis to explore the spatiotemporal dynamics and driving mechanism of AES during the growing season (April–October). The results showed that the AES in the area was transitioning from a critical to stable state, with vulnerable arable land gradually decreasing while stable land increased. Stable arable land was concentrated in the middle reaches of the Heihe River basin, while arable land in the Shule River Basin was basically at critical level, a crucial area for wind erosion prevention. In the lower reaches of the Shiyang River Basin, much arable land was vulnerable to salinization, requiring urgent treatment. Complex climatic conditions and irrational irrigation patterns are the main causes of AES fluctuations. Agricultural engineering construction and favorable policy implementation can significantly improve AES. In addition, seasonal variability in wind erosion, salinization and AES was significant, with the worst in spring and the best in summer. Climate and vegetation factors have become the main factors affecting wind erosion and salinization. The fallow period before spring is a critical time for wind erosion control and salinity soil improvement. This study aims to provide theoretical guidance for the construction of agricultural production and ecological management in arid and semi-arid areas. [Display omitted] [ABSTRACT FROM AUTHOR]

The regional climate effects of vegetation change in arid and semi-arid regions of China, which has experienced serious grassland degradation, are investigated in this study using the Weather Research and Forecasting (WRF) regional climate model. Two long-term simulation experiments (from January 1, 1980 to March 1, 2010), one with the land cover derived from the original United States Geological Survey's (USGS) data (denoted as CTL) and the other (denoted as SEN) with a modification of the former one by vegetation degradation in arid and semi-arid regions of China, are undertaken to investigate the influence of land cover change on regional climate over arid and semi-arid regions of China. The possible mechanisms of how land cover change affects the regional climate in arid and semi-arid regions of China are also examined. The simulation results indicate that when compared with the observation datasets, the WRF model simulates the spatial pattern of observed temperature and precipitation quite well. After vegetation degradation over the arid and semi-arid regions of China, the net radiation and evaporation are reduced mainly within the degraded areas in summer, consistent with the reduction in precipitation and the increase in 2-m air temperature (T2 m). [ABSTRACT FROM AUTHOR]

New vegetation in barren areas offers possibilities for sequestering carbon in the soil. Arid and semi-arid areas (ASAs) are candidates for new vegetation. The possibility of agriculture in ASAs is reviewed, revealing the potential for cultivation by covering the surface with a layer of organic fibres. This layer collects more water from humidity in the air than does the uncovered mineral surface, and creates a humid environment that promotes microbial life. One possibility is to use large amounts of organic fibres for soil enhancement in ASAs. In the context of the European Commission Waste Framework Directive, the possibility of using textile waste from Sweden is explored. The costs for using Swedish textile waste are high, but possible gains are the sale of agricultural products and increased land prices as well as environmental mitigation. The findings suggest that field research on such agriculture in ASAs should start as soon as possible. [ABSTRACT FROM AUTHOR]

Water is a key element in building and maintaining regional ecosystems functions, particularly in arid and semi-arid regions, in which ecosystem productivity, surface energy balance, and water availability are closely interconnected. However, the effects of differences in soil moisture levels at different depths and humidity index involved MAT and MAP on plant diversity have received only scant attention. To determine effects of soil moisture and humidity index on both plant productivity and diversity of native grasslands on the Loess Plateau, China, a gradient analysis of soil moisture and above- and below-ground properties of plant communities showed that vegetation cover and above- and below-ground biomass were significantly and positively correlated to the levels of soil moisture. More specifically, the below-ground biomass was significantly and positively correlated to moisture in the top 10 cm layer of soil, whereas plant height, litter biomass, and root-to-shoot ratio were unrelated to the level of soil moisture. Plant diversity (richness index and the Shannon–Wiener diversity index) was significantly and positively correlated to a greater degree with moisture in the topsoil (0–5 cm layer) than in the subsoil, and was also closely correlated to the humidity index. Overall, changes in plant diversity in arid and semi-arid grassland ecosystems are closely determined by soil moisture and atmospheric humidity, and that higher moisture content in soil and higher atmospheric humidity favour greater plant diversity. [ABSTRACT FROM AUTHOR]

Soil moisture is fundamental to ecosystem sustainability in arid and semi-arid regions, and characterizing temporal variations in soil moisture levels in response to changes in land use is important in assessing whether vegetation that has been restored as part of ecological restoration can be sustained. Such an assessment is presented here based on 78 recent publications focused on China’s initiatives at ecological restoration including the ‘Grain for Green’ programme and the ‘Three Norths Shelter Forest System’ project. The study analysed 1740 observations at 83 sites in eight provinces in northern China to determine temporal and spatial variations in soil moisture and the causes of those variations. Changes in land use for restoration of ecosystems led to severe depletion in soil moisture levels – as low as 9%, determined gravimetrically – in the 0–100 cm layer of soil. The extent of depletion was influenced significantly by the choice of species for restoration (trees, shrubs, or grasses) and land use before the restoration. Deliberate restoration of vegetation may have the largest negative impact on soil moisture at sites that receive less than 600 mm of annual precipitation and may be practical only when it exceeds 600 mm. Afforestation decreased the levels of soil moisture significantly, whereas natural restoration had no significant effect on soil moisture. Therefore, natural restoration is the better option for maintaining the stability of water resources in arid and semi-arid regions. Afforestation would be a poor choice for places in which annual precipitation is close to or less than potential evapotranspiration but a better choice if annual precipitation is adequate. In planning revegetation initiatives, planners must understand that different environments support different vegetation types, and therefore require different solutions. [ABSTRACT FROM AUTHOR]

Broad-scale estimation of spatial changes in vegetation cover is of value in many areas of research and land-use management. There is currently no simple method available to estimate vegetation cover at the broad scale (above the level of individual vegetation-type mapping or modelling) that does not rely, at least in part, on remote sensing data. This means that for periods where this data is unavailable (pre 1980 and future forecasting) estimates of vegetation cover are also unavailable. De Martonne's simple Aridity Index (AI) requires only rainfall and temperature data however it is not widely applicable and regularly fails in arid and semi-arid regions. The Climate Aridity Vegetation Index ( CAVI ) has been developed in an attempt to overcome this limitation while retaining simplicity in the data required and in the calculation. The CAVI is based on readily available rainfall and temperature data and has been applied and tested across 12 years of monthly data across Australia. The CAVI estimates have then been validated by comparing them to the corresponding fractional cover satellite data. Performance is discussed in the context of using vegetation cover estimates in wind erosion research. The results were particularly encouraging in arid to semi-arid regions and can potentially be used as a surrogate for historical broad scale vegetation cover and possibly future projections. [ABSTRACT FROM AUTHOR]

ABSTRACT This work uses an aerosol-climate coupled system to study the direct climatic effects of dust aerosol on global arid (including hyper-arid) and semi-arid regions. Results show that dust aerosol can cause surface cooling over these regions. The cooling effects of dust aerosol are larger in the Northern Hemisphere (NH) than in the Southern Hemisphere (SH). This asymmetric cooling leads to a severer reduction in evaporation over the low latitudes of the NH compared with their counterpart areas in the SH. In addition, air descent is enhanced (or ascent is weakened) by dust aerosol over the low latitudes of the NH, whereas the reverse happens in the SH. With the anomalous in evaporation and circulation, precipitation is decreased (increased) over the arid and semi-arid areas in the NH (SH) by dust aerosol. Dust aerosol can decrease the potential evapotranspiration in arid and semi-arid regions mainly by decreasing the net radiation flux at the top of the atmosphere, which compensates for the decrease in precipitation caused by dust aerosol. Therefore, as the dominant aerosol in the arid and semi-arid regions, dust aerosol does not exacerbate the aridity over most of these regions. The effects of dust aerosol are indiscernible in the expansion of arid and semi-arid areas on a global scale. [ABSTRACT FROM AUTHOR]

In addition to drought intensity, drought magnitude (DM) is an important parameter in drought analysis. Therefore, in this study, the drought intensity and DM trends are investigated based on the standardized precipitation index (3, 6, 9, 12, 18 and 24 monthly SPI time series) from 1975 until 2005 in 25 synoptic weather stations located in arid and semi-arid regions of Iran. Although the DM is commonly computed for negative SPI values, for analysis the wet years besides drought conditions, this study has also involved positive SPI values and therefore, each time series was divided into four drought intensity conditions as follows: drought (D; SPI values less than −1), normal near drought (ND; SPI values more than −1 and less than 0), normal near wet (NW, SPI values more than 0 and less than +1), and wet (W; SPI values more than 1). The non-parametric rank-based Mann-Kendall test was used to detect trends of SPI values (drought intensity and DM) for 3, 6, 9, 12, 18 and 24 monthly time scales. Based on the results, a considerable percentage (50 %) of the stations at the level of 0.05 showed a significant trend with regards to drought intensity when compared with the DM trend (5.8 %). Generally, it can be said that the arid and semi-arid areas of Iran had a negative SPI trend and it means the more drought severities. Also, the more frequent significant positive DM trend in comparison to negative ones is a sign of increasing DM during the three past decades. [ABSTRACT FROM AUTHOR]

Drought is known as one of the main natural hazards especially in arid and semi-arid regions where there are considerable issues in regard to water resources management. Also, climate changes has been introduced as a global concern and therefore, under conditions of climate change and global warming, the investigation of drought severity trend in regions such as Iran which is mainly covered by arid and semi-arid climate conditions is in the primary of importance. Therefore, in this study, based on the application of Reconnaissance Drought Index (RDI) for assessment drought severities, and also the implementation of non-parametric Mann- Kendall statistics and Sen's slope estimator, the trends in different time series of RDI (3, 6, 9, 12, 18 and 24 monthly time series) were investigated. Results indicated the frequent decreasing trends in RDI time series particularly for long term time series (12, 18 and 24 monthly time series) than short term ones. Decreasing trend in RDI time series means the increasing trend in drought severities. Since the water resources especially ground water in most cases are affected by long term droughts, therefore, increasing trend in drought intensities in long term ones can be a threat for water resources management in surveyed areas. [ABSTRACT FROM AUTHOR]

Abstract: Water redistribution has a profound influence on dryland ecosystem function. This hydrological function is largely regulated by ecosystem engineers including biological soil crusts (biocrusts) which produce run-off, and burrowing animals, such as the greater bilby, whose pits capture water. We estimated the relative importance of these two ecosystem engineers in determining infiltration rates in a system where dune slopes shed water to adjacent interdune swales to maximize overall productivity. Also, we determined which biocrust property was most hydrologically important: total cover, composition, patch aggregation or spatial heterogeneity. While both biocrusts and burrowing animals equally affected the overall infiltration through macro- and micropores (under ponding), only biocrusts were important for the infiltration specifically via micropores (under tension). Of the studied biocrust properties, community composition was the strongest influence such that the greater the prevalence of early successional biocrust patches, the greater the infiltration rate. Greater total cover of biocrusts reduced infiltration, and the spatial properties were relatively unimportant. Although bilbies and biocrusts comparably influenced infiltration under ponding at the microscale, realistic cover of bilby pits at the landscape scale is unlikely to strongly impair the hydrological function of dunes. Reintroduction of the endangered bilby may enhance nutrient cycling and plant recruitment via its seed and resource capturing pits, without a concomitant disruption of hydrological function. In contrast, removal of biocrusts caused by, e.g., livestock trampling, is expected to strongly enhance infiltration in the run-off areas, strongly reducing ecosystem productivity at the landscape scale. [Copyright &y& Elsevier]

Abstract: The impacts of recurrent droughts have increased vulnerability and reduced the adaptive capacity of the people living in arid and semi-arid lands (ASALS) of Kenya. Current interventions are short-term and curative in nature, hence unsustainable. Some of the most arid and semi-arid lands are located within the Kenyan Rift system, which has an estimated geothermal potential of about 7000 to 10,000MWe, out of which only 200MWe has been developed, and about 5000MWe planned by 2030. Recent power sector reforms have built institutional structures that will accelerate development of geothermal energy. The paper analyses the potential use of geothermal energy resources in eastern Baringo lowlands between Lake Bogoria and Silali prospects, which has an estimated potential of >2700MWe, in creating the necessary adjustments needed to adapt to the impacts of recurrent droughts by locals. Opportunities for direct and indirect uses of geothermal energy exist in climate vulnerable sectors, such as, agriculture, fisheries, water, livestock production as well as alternative income generating activities such as, tourism, micro enterprises, aloe, honey and beeswax production, fabric dyeing and others using resources sourced from within a 50km radius. The possibility of accelerated geothermal development and proposed utilisation schemes in causing maladaptation if unsustainably implemented is also discussed. The paper draws a Lindal diagram adapted to the study area showing potential utilisation in the above sectors, and new flow diagram showing potential for cascaded use of geothermal hot water through the different processes. An estimated capacity of 100MWt and 100MWe can be used in the potential utilisation schemes discussed in this article to meet local adaptation and lighting needs and much less in a cascaded process. Potential barriers and possible solutions are also discussed. The study concludes that geothermal energy is a vital option for adaptation in the study area if sustainably used. [Copyright &y& Elsevier]

Photosynthetically active radiation ( Q) is a key variable in models of net primary productivity and carbon cycle modelling. The relationship between broadband global solar radiation ( R) and Q is investigated using 6 years of radiation data collected at 9 sites in arid and semi-arid regions of China. The dependence of Q/ R on aerosol optical depth (AOD) and water vapour content are also discussed. A simple and efficient all-weather empirically derived model is developed to estimate Q from R. The annual average daily Q in arid and semi-arid areas is 29.9 ± 11.7 and 27.3 ± 10.1 mol m d, respectively. The highest value (31.9 ± 11.3 mol m d) appears at Linze in the arid area. The lowest value (24.3 ± 9.7 mol m d) appears at Ansai in the semi-arid area. The results show that the monthly variation of the Q/ R ratio ranges from 1.69 ± 0.19 mol MJ in Aksu to 1.91 ± 0.08 mol MJ in Fukang. There is a small decreasing trend of the ratio of Q to R (PAR fraction) in arid and semi-arid regions because of the recent increase in fine aerosols. A simple and efficient empirically model suit for all-weather condition was developed to estimate Q from R. The slope a and intercept b of the regression line between estimated and measured values is close to 1 and zero, respectively. The application of the model to data collected from different locations also results in reasonable estimates of Q. [ABSTRACT FROM AUTHOR]

The objectives of this study are to compare reference evapotranspiration (ET0) computed using different forms of the Hargreaves (HG) equation with the standard FAO56PM; and to compare ET0 computed using the FAO56PM with limited data with the standard FAO56PM complete data set method. For this purpose, climatic data from 12 weather stations covering an area of ∼90 km2 of predominantly arid and semi-arid conditions are used. Ratios of ET0 estimated using the updated HG equation were closer to 1 when compared with the HG equations and ET0-est. Also, RMSE, ME and R 2 ranged from 0.235 to 0.526 mm day−1, −0.526 to 0.383 mm day−1, and 0.945 to 0.989, respectively. Therefore, the updated HG equation can be used for ET0 estimates instead of using the FAO56PM method with acceptable accuracy. In addition, it was found that the standard FAO56PM can be used with estimated solar radiation and humidity from temperature data and estimates of mean wind speed. In conclusion, this study produced two accurate methods that can be used to calculate monthly ET0 in conditions characterized by limited data, arid and semi-arid environments. [ABSTRACT FROM PUBLISHER]

Measurements of the broadband global solar radiation ( R) and total ultraviolet radiation (the sum of UV-A and UV-B) were conducted from 2005 to 2010 at 9 sites in arid and semi-arid regions of China. These data were used to determine the temporal variability of UV and UV/ R and their dependence on the water vapor content and clearness index. The dependence of UV/ R on aerosol optical depth (AOD) and water vapor content was also investigated. In addition, a simple and efficient empirically model suited for all-weather conditions was developed to estimate UV from R. The annual average daily UV level in arid and semi-arid areas is 0.61 and 0.59 MJ m d, respectively. The highest value (0.66 ± 0.25 MJ m d) was recorded at an arid area at Linze. The lowest value (0.53 ± 0.22 MJ m d) was recorded at a semi-arid area at Ansai. The highest daily value of UV radiation was measured in May, whereas the lowest value was measured in December. The monthly variation of the UV/ R ratio ranged from 0.41 in Aksu to 0.35 in Qira. The monthly mean value of UV /R gradually increased from November and then decreased in August. A small decreasing trend of UV/ R was observed in the arid and semi-arid regions due to recently increasing amounts of fine aerosol. A simple and efficient empirically model suit for all-weather condition was developed to estimate UV from R. The slope a and intercept b of the regression line between the estimated and measured values were close to 1 and zero, respectively. The relative error between the estimated and measured values was less than 11.5%. Application of the model to data collected from different locations in this region also resulted in reasonable estimates of UV. [ABSTRACT FROM AUTHOR]

Accurate estimation of the available potassium (K+) supplied by calcareous soils in arid and semi-arid regions is becoming more important. Exchangeable K+, determined by ammonium acetate (NH4OAc), might not be the best predictor of the soil K+ available to crops in soils containing micaceous minerals. The effectiveness of different extraction methods for the prediction of K-supplying capacities and quantity-intensity relationships was studied in 10 calcareous soils in western Iran. Total K+ uptake by wheat grown in the greenhouse was used to measure plant-available soil K+. The following methods extracted increasingly higher average amounts of soil K+: 0.025 M H2SO4 (45 mg K+ kg-1), 1 M NaCl (92 mg K+ kg-1), 0.01 M CaCl2 (104 mg K+ kg-1), 0.1 M BaCl2 (126 mg K+ kg-1), and 1 M NH4OAc (312 mg K+ kg-1). Potassium extracted by 0.01 M CaCl2, 1 M NaCl, 0.1 M BaCl2, and 0.025 M H2SO4 showed higher correlation with K+ uptake by the crop (P < 0.01) than did NH4OAc (P < 0.05), which is used to extract K+ in the soils of the studied area. There were significant correlations among exchangeable K+ adsorbed on the planar surfaces of soils (labile K+) and K+ plant uptake and K+ extracted by all extractants. It would appear that both 0.01 M CaCl2 and 1 M NaCl extractants and labile K+ may provide the most useful prediction of K+ uptake by plants in these calcareous soils containing micaceous minerals. [ABSTRACT FROM AUTHOR]

Abstract: Arid and semi-arid rangelands that serve as the resource basis for the livestock production system known as the pastoral production system in Ethiopia are under enormous threat. These rangelands cover about 62% of the national land area and employs approximately 27% of the population. A survey was conducted in two pastoral weredas (districts; Erer and Aysha) in the Shinile zone of the Somali region, with the aims of assessing the status and trends of rangeland degradation, and understanding the impact on livelihoods and perceptions of the pastoralists over a 60-year period (1944–1974 and 1974–2004). The year 1974 was taken as a reference due to the severe drought in the Horn of Africa. Three villages per wereda, 50 households per village and one elder pastoralist (70–75 years old) per household were randomly selected. The sample of elders consisted of 30% women and 70% men, who were interviewed using questionnaires and open discussions. The results revealed that drought, aridity and rangeland degradation have increased over time due to environmental degradation and mismanagement of rangeland resources. Changes in vegetation ecology have drastically (p<0.05) altered the livestock species composition in favour of camels and small ruminants rather than cattle. This has also influenced the planning and preference of pastoralists for different types of livestock. Poor and very poor households have emerged, and the below-medium wealth rank has disappeared, showing that poverty has increased over time. Traditional coping mechanisms are reported to be failing due to increasing environmental and rangeland degradation and lack of national policies to minimize or solve the problems. These findings offer a new perspective for communal rangeland management research, particularly in arid and semi-arid areas. [Copyright &y& Elsevier]

Study of the groundwater samples from Tajarak area, western Iran, was carried out in order to assess their chemical compositions and suitability for agricultural purposes. All of the groundwaters are grouped into two categories: relatively low mineralized of Ca–HCO3 and Na–HCO3 types and high mineralized waters of Na–SO4 and Na–Cl types. The chemical evolution of groundwater is primarily controlled by water–rock interactions mainly weathering of aluminosilicates, dissolution of carbonate minerals and cation exchange reactions. Calculated values of pCO2 for the groundwater samples range from 2.34 × 10−4 to 1.07 × 10−1 with a mean value of 1.41 × 10−2 (atm), which is above the pCO2 of the earth’s atmosphere (10−3.5). The groundwater is oversaturated with respect to calcite, aragonite and dolomite and undersaturated with respect to gypsum, anhydrite and halite. According to the EC and SAR the most dominant classes (C3-S1, C4-S1 and C4-S2) were found. With respect to adjusted SAR (adj SAR), the sodium (Na+) content in 90% of water samples in group A is regarded as low and can be used for irrigation in almost all soils with little danger of the development of harmful levels of exchangeable Na+, while in 40 and 37% of water samples in group B the intensity of problem is moderate and high, respectively. Such water, when used for irrigation will lead to cation exchange and Na+ is adsorbed on clay minerals while calcium (Ca2+) and magnesium (Mg2+) are released to the liquid phase. The salinity hazard is regarded as medium to high and special management for salinity control is required. Thus, the water quality for irrigation is low, providing the necessary drainage to avoid the build-up of toxic salt concentrations. [ABSTRACT FROM AUTHOR]

Abstract: The performance of a crop simulation model (agricultural production systems simulator model, APSIM-Nwheat) was tested using data obtained from several locations in the rain-fed environments of West Asia and North Africa (WANA) in Morocco and Jordan. The model was able to simulate wheat grain yields reasonably well except at one site in one season in Morocco. The model was subsequently used to analyze the effect of soil type (soil water-holding capacity), rate and timing of nitrogen (N) fertiliser, initial soil moisture storage, cultivars (early versus late), sowing dates and density and supplemental irrigation (SI) in optimizing wheat production using 20 years of historical weather records from Morocco. The simulation indicated that yields were often limited by the amount and timing of rainfall. While the effect of N fertiliser was minimal or detrimental in dry years, it improved grain yields in wet years and when crops were sown early combined with pre-sown stored plant available water in the soil. The analysis showed that early sowing is important for achieving high yields by avoiding terminal water deficit. There is little difference between grain yields when current practice of about 300plants/m2 was compared with a density of 150plants/m2. This implies that there is scope for reducing current planting density to save seeds without reducing yields. The simulation analysis highlighted that 40mm of SI at sowing significantly improved average grain yields as a result of enabling early crop establishment, in particular with a N fertiliser application of 40kgN/ha. The analysis indicated that wheat grain yields in the arid and semi-arid rain-fed regions of WANA can be improved compared to current yield levels by adjusting N management to soil type, pre-sowing soil water availability, sowing opportunity and the availability of SI. [Copyright &y& Elsevier]

Abstract: It is difficult to conduct the assessment of dust storms under the influence of land surface indices with accurate statistical theory in the dust source region of China due to problems, especially those that emerge in the data of land surface that has no accurate data for soil moisture and hardness from meteorological records, no quantitative data for dust emission and a deficient proper theory using the capacity to combine quantitative data with qualitative data. This paper selected Erlianhaote of Inner Mongolia in northern China as a study example, and compiled the data of land surface condition of soil moisture and hardness as well as the data of dust storms and wind during 2001–2003. The authors determined the threshold value from the influences in different land patterns on dust emission processes by discrimination, quantitatively described the integrated influence of wind speed and soil moisture as well as soil hardness impact on dust storms using Hayashi''s quantification theory type 2, and also discussed the related problems of potential errors in the data sets. This theorem could provide the obvious numeral materials about multi-factor cause–effect relationship for decision making and is useful in the quantificational assessment for factors impacting dust storms during the study period. Land surface condition diversity research had obvious scale effect characteristics. A clear evidence is that the combined contribution of soil moisture and hardness in dust emission is 48.79% of that of total contribution of wind speed, approximately the same as that of wind speed. [Copyright &y& Elsevier]