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Abstract: Concern about climate and its impact on human populations in the Sahel since the 1970s was an immediate response to the most recent of recurrent drought periods. Understanding the relative impact of this drought on rural life in the Sahel is, however, not straightforward. This is due to the fact that climate is only one of many factors influencing local adaptation strategies to environmental changes. Another explanation could be that climate in many rural communities in the Sahel is simply no longer the primary worry. The argument presented in this paper, supported by data from a small village in northern Burkina Faso, is that the villagers there are ‘beyond climate’ as their current livelihood strategies are increasingly climate independent. People have over the past decades engaged in livelihood diversification in order to negate the negative impact of climate variability on agriculture. In order to analyse the temporal perspective of climate–livelihood interaction, the paper employs human–environmental timelines. The results document the multiplicity of exposures shaping decisions in the village. While significant correlation exists between recent livelihood diversifications and major climatic events, it is equally obvious that recent political developments and the economic flow of project activities are crucial factors of change. [Copyright &y& Elsevier]

Abstract: Southern South America (SSA) has today a high diversity of climates, environments, biomes, and biotas, as a result of the complex interaction through time of plants and animals with the geological forces (e.g. plate tectonics, sea-level changes, glaciations) that modulated the geography of the continent. Arid biomes are well represented in SSA today, but were arid biomes similarly important in the geologic past? How long in time can be found major arid biomes in SSA? With the aim of replaying these questions, in this paper we summarized the paleoenvironmental changes of SSA through Cenozoic, emphasizing the relationships between biomes and the geological forces that, through different climatic-environmental factors, have driven its evolution. We define SSA the south of the 15°S area. We prefer this geographical delimitation because with it we can see and follow the history of the biogeographic (historic and ecologic) relationships of Patagonian biota with the rest of the South American biota. Additionally, with this delimitation we possess the most complete Cenozoic South American land-mammal fossil record. We use biomes because biomes are taxon-free analytical units, and their pattern of change can be traced through time independently of the taxa present at different geological periods. Data on plate tectonics, volcanism, sea-level changes, marine paleotemperatures, and glaciations were taken from literature. To analyse the pattern of change of southern South American climates and environments through the Cenozoic, we used the fossil record of land-mammals as information source. When available, the record of vascular plants were used to contrast the inferences derived from land-mammals. Finally, we used standard geologic divisions (i.e. Epochs) as chronological units. The main conclusion of this paper is that from Early Paleocene to Late Pleistocene, southern South American climatic conditions changed from warm, wet, and non-seasonal, to colder, dryer, and seasonal. Concomitantly, biomes changed from tropical forest to steppes, across a sequence constituted by subtropical forests, woodland savanna, park-savanna, and grassland savanna. During the Quaternary, and as a consequence of glacial cycles, cold and dry conditions were interrupted by warmer and wet periods. Accordingly, several pulses of expansion and retraction of steppes (and, concomitantly, advances and retreats of the northern tropical forests) are recorded. This cyclic pattern of changes produced the provincialism that has characterized the South American biota from Early Pleistocene to the present. [Copyright &y& Elsevier]

Groundwater resources are essential to underpin the daily life of communities in remote regions. Hydrogeological studies in these areas are complex, largely due to the absence of long water table records and to the difficulties involved in accessing some relevant locations. This hampers attempts to manage local resources. Devising cost-effective methods to explore these aquifers is important to understand how they work and to come up with adequate protection strategies. This paper deals with the joint application of Geographic Information Systems (GIS) tools and numerical groundwater models to explore groundwater resources in desert areas. The method is illustrated through its application to Erg Chebbi, a water table aquifer located in southern Morocco, which supplies drinking and irrigation water for local communities while also underpinning agriculture and tourism. The geometry of the aquifer was established based on existing cartography, GIS and a field survey. This led to the development of a steady-state numerical model. Modeling results suggest that the aquifer has been depleted by almost 30% due to groundwater extractions in less than 50 years. The average drawdown was found to be in the order of three meters. This corresponds to a total depletion in the order of 20-60 Mm3. [ABSTRACT FROM AUTHOR]

Abstract: The Namib Desert is an ancient desert on the west coast of southern Africa. The Namib has unique endemic biodiversity and scenic landscapes, with a major part contained in the Namib Naukluft Park and the adjacent Dorob National Park, together forming a major tourism attraction in Namibia. There are currently large exploration and mining developments in the central Namib, fuelled by rising global demand for uranium. Mining contributes significantly to the Namibian GDP, but through destruction of habitats and ecological processes, may cause environmental degradation and loss of ecosystem services. Additionally, Namibia stands to lose a significant part of the biological diversity that makes it unique. These direct impacts are occurring in the context of regional climatic changes that are predicted to have their own severe impacts on biodiversity. A number of tools exist to counter these impacts, among which ecological restoration is an important one. Yet the extent of the damage to ecological processes and functions of the Namib, the interactions with climate change and the mechanisms through which the impacts will occur are still not well known. There is thus a crucial need for a better understanding of these arid ecosystems and their response to disturbance, to devise better restoration techniques, and to inform decision makers about management options. This paper analyses the extent of the threats to the central Namib''s ecosystems and biodiversity due to mining, identifies critical knowledge gaps for restoration, defines policy needs, and proposes a broad strategy which is intended to be a framework for research, planning and management for sustainable use of this unique desert. [Copyright &y& Elsevier]

Abstract: Soil fauna are considered to be an important determinant of the litter decomposition in terrestrial ecosystems. However, the contributions of soil macrofauna and mesofauna to litter decomposition in semi-arid environments are not well-recognized. In this paper, litterbags with different mesh sizes (4.7 mm, 2 mm and 0.01 mm) were employed to examine the intraspecific differences in the decomposition of Stipa baicalensis, Achnatherum avinoides, Lespedeza davurica and Agropyron cristatum. In addition, the effects of soil macrofauna and mesofauna on litter decomposition were determined in Songnen sandy land. The results of this study showed that Prostigmata, Psocidae and Oribatida were dominant fauna in the litterbags. Significant intraspecific differences were found in litter decomposition rates, and the process of litter decomposition can be separated into two apparent stages. Ac. avinoides exhibited the highest contribution rate to litter decomposition, followed by Ag. cristatum, L. davurica and S. baicalensis. Contribution rates of macrofauna and mesofauna to litter decomposition were different. The rate of litter decomposition was positively correlated with the group density of fauna. Our results suggested that both macrofauna and mesofauna could accelerate litter decomposition and, consequently, nutrient cycling in semi-arid ecosystems, although their functional roles were different in litter decomposition. [Copyright &y& Elsevier]

Abstract: The changing climate is affecting biological and physical processes occurring in the biosphere, including the biogeochemical cycles of water and carbon. The response of ecosystem carbon exchange to changes in temperature and the water balance is still very uncertain, a fact that highlights the need for research in order to understand the role of the biosphere in the future global carbon budget. South east Spain is on the borderline between the tropical and mid-latitude climate zones, with climates ranging from sub-humid to arid, and the majority representing the driest area in Europe. Initial predictions on climate change for this region point to decreases in total precipitation and the number of precipitation events, meaning a decrease in water availability underlining the vulnerability of the region to desertification. This region, due to these special climatic conditions, has been the subject of experimental carbon and water field research in recent years. This paper defines the state of the art of carbon and water balance measurement and modelling studies in this region, analyses the different processes involved in aggregate exchanges (vegetation and soil; net ecosystem carbon balance–evapotranspiration, photosynthesis–transpiration, soil respiration–evaporation), and identifies needs for future research. [Copyright &y& Elsevier]

Abstract: Many Mediterranean streams in arid and semiarid areas are naturally saline systems due to the presence of evaportic rocks of Miocene or Triassic origin. Despite the fact that these aquatic ecosystems are rare in Europe, they are common in southeast of Spain. The environmental constraints of these semiarid saline streams are imposed by both geological and climatic conditions. This paper is a compilation and summary of the principal results obtained from various studies on semiarid saline streams in the Iberian southeast. Available data for these typical environments in the region covers diverse issues such as those regarding their physical and chemical features, typology, biodiversity, community structure and ecosystem functioning, as well as different ecological and evolutionary aspects of their biota (e.g. ecophysiological responses, life cycles and phylogeography). Issues concerning the conservation of these habitats, such as the main human uses, impacts, threats and their management are also summarised. Finally, topics in need of further research are provided. The current knowledge of saline streams in southeastern Spain highlights the physical and ecological singularity of these environments, and their high conservation value. Saline streams are particularly interesting due to their halotolerant/halophilic biota and high number of rare and endemic species. [Copyright &y& Elsevier]

Abstract: The goal of this paper is to provide a general description of the terrestrial arthropod fauna of arid areas of SE Iberian Peninsula. The available data show that invertebrate communities in these environments are dominated by arthropods and that the composition of the assemblages are similar to those described in other arid regions of the world. The number of species of different arthropod groups (Coleoptera, Hymenoptera, Orthoptera, Lepidoptera, Araneae) in these environments show that arid regions of SE Iberian Peninsula are inhabited by a diverse terrestrial arthropod fauna. An ecological feature of arthropod communities in arid zones of SE Spain is the spatial and temporal variability of assemblage composition at different scales, a characteristic of faunal assemblages in arid environments. Similarity in composition of assemblages between sites (Beta diversity) shows a high variability in faunal composition between apparently similar environments. The distribution patterns of species show that 8.4–9.6% of the species in these environments are local and SE Iberian Peninsula endemics. A number of eremic Mediterranean or Palaearctic species are also associated exclusively with these environments, highlighting the singularity of the invertebrate fauna in these arid habitats. Differences in assemblage composition of arid areas with more mesic surrounding environments show that arid zones of SE Spain are inhabited by a distinct fauna, increasing faunal diversity in SE Spain. A recent analysis of endangered and threatened invertebrate species in southern Spain recognizes the arid environments of SE Spain as priority areas for conservation, where habitat loss and fragmentation, changes in agricultural and grazing uses, and inadequate management constitute the main threats. We conclude that the fauna of the SE Iberian arid zones represents an important component of the high ecological diversity of the Mediterranean ecosystem in SE Spain, not only because of their arthropod diversity but also due to the important implications that these areas have for conservation in the entire SE region of the Iberian Peninsula. [Copyright &y& Elsevier]

Abstract: Monitoring changes in soil and vegetation is crucial in fragile Mediterranean semiarid environments. To identify early perturbation warnings using radiometric techniques, the spectral variability of the ecosystem components must be understood and the ranges of their natural variability established. This paper aims to assess the potential of hyperspectral information for analysing spectral variability and to provide guidelines for using spectroscopy to monitor semiarid environments. Spectral field measurements of different soil (volcanic and calcareous), vegetation (esparto and dwarf palm) and natural mixtures (NPV and BSC) were acquired; spectral assessment focused on albedo, spectral shape and absorption bands. Results show high variability of soil background between and within soil typologies. The presence of biotic elements masks the distinctive characteristics between soil typologies, making combination of the VIS-NIR and SWIR regions necessary for correct discrimination and quantification of soil properties. Plant species are discriminated by taking advantage of their spectral properties based on the differences in absorption by chlorophyll, water and lignin. In summer, these differences are more significant, predictably due to their specific survival strategies. Radiometric techniques enable discrimination of ecosystem components, although the high variability of the landscape and subtle differences between components makes it necessary to use high-spectral resolution information. [Copyright &y& Elsevier]

Abstract: In this paper we summarize the surface characteristics for six locations in western Mexico and southwestern USA (from a subhumid climate in Jalisco, Mexico to the Sonoran Desert climate in Arizona, USA), that lie along a meridional transect within the North American Monsoon (NAM) core region using available MODerate Resolution Imaging Radiometer (MODIS) satellite data and supplementary surface instrumental data for two of these sites in Sonora, Mexico. The climate analysis for each site is carried out for the period 2000–2008, that includes all available MODIS data. A comparison of seasonal and annual variability in surface conditions for the enhanced vegetation index (EVI), albedo and land surface temperature (LST) at each site is presented. With the help of available surface data from field observations, a more detailed analysis of Rayón and Rosario de Tesopaco sites is presented. The qualitative behavior and climate response of three types of vegetation: desert shrub, subtropical shrub, and tropical deciduous forest ecosystems are analyzed under the influence of the NAM summer wet season. The onset of the NAM warm wet season in early summer, is one of the main precursors of generalized EVI growth in all the NAM region. At all the sites, it is observed that the mean daytime LST cools several degrees as the NAM fully develops. During the warm wet season, in the case of open and sparse vegetation regions such as desert shrub and subtropical shrub, albedo values fall slightly during the NAM season, while in closed and dense tropical deciduous forest regions albedo shows a slight increase. Differences in soil reflectivity at these sites are probably responsible for this rather unexpected behavior. Additionally it is found that, desert shrub and subtropical shrub regions in northern latitudes show large LST and small EVI/albedo seasonal variability, whilst tropical deciduous forests in lower latitudes show much larger EVI/albedo and smaller LST seasonal variability. Thus MODIS data proves to be a valuable tool for assessing the dynamics of seasonal and interannual surface characteristics helpful in determining climate patterns. [Copyright &y& Elsevier]

Abstract: Temporal variation of aboveground net primary production (ANPP) of arid ecosystems has been associated with precipitation regimes with different results. The objective of this paper was to characterize the relationship between interannual variation of annual and seasonal Normalized Difference Vegetation Index (NDVI), as a surrogate for ANPP, and precipitation in the steppes of Northern Patagonia. In 11 sites encompassing a wide range of conditions and vegetation physiognomies, we studied a 20-year monthly data set of NDVI and precipitation. We took into account the precipitation of current, as well as previous periods of variable length. Interannual variation of annual NDVI was little correlated with annual precipitation, either current or previous. In contrast, it was highly and widely correlated with precipitation accumulated during a few months of the previous growing season. Interannual variation of seasonal NDVI was little correlated with current seasonal precipitation. In contrast, it was significantly correlated with precipitation accumulated during previous periods of variable length according to the season and site under consideration. NDVI was more tightly coupled with precipitation in drier ecosystems. Lags of response between NDVI and precipitation provide an opportunity for forecasting ANPP and suggest even longer lags between climatic variation and herbivore performance. [Copyright &y& Elsevier]

Abstract: The aim of this study is to explore the environmental factors that determine plant community distribution in northeast Algeria. This paper provides a quantitative analysis of the vegetation–environment relationships for a study site in the Chott El Beida wetland, a RAMSAR site in Setif, Algeria. Sixty vegetation plots were sampled and analysed using TWINSPAN and Detrended Correspondence Analysis (DCA) in order to identify the principal vegetation communities and determine the environmental gradients associated with these. 127 species belonging to 41 families and 114 genera were recorded. Six of the recorded species were endemic representing 4.7% of the total species. The richest families were Compositae, Gramineae, Cruciferae and Chenopodiaceae. Therophytes and hemicryptophytes were the most frequent life forms. The Mediterranean floristic element is dominant and is represented by 39 species. The samples were classified into four main community types. The principal DCA axes represent gradients of soil salinity, moisture and anthropogenic pressure. The use of classification in combination with ordination techniques resulted in a good discrimination between plant communities and a greater understanding of controlling environmental factors. The methodology adopted can be employed for improving baseline information on plant community ecology and distribution in often critically endangered Mediterranean wetland areas. [Copyright &y& Elsevier]

Abstract: Descriptions of the spatial distribution of nodules and their relationship with the distribution of roots are extremely rare in leguminous shrubs of arid ecosystems. In this paper we show that in the Patagonian arid steppe the spatial distribution of nodules of Adesmia volkmanni Philippi (ex- A. campestris) paralleled that of their roots. Nodules and roots of A. volkmanni were concentrated in intermediate (70–90cm) soil layers, but did not appear to be biologically active (no visual signs of leg-haemoglobin). In addition, leaves showed the same natural 15N abundance (δ 15N) than those of another native shrub species, Mulinum spinosum, a known non-fixer with the same rooting and phenological patterns. However, high leaf N content, presence of nodules, and clear isotopic differences between the two species in a more humid site suggest that nitrogen fixation could occur in some favourable years in Adesmia volkmanni plants of xeric sites. [Copyright &y& Elsevier]

Abstract: The temporary wetlands of Eastern Mauritania in the Sahel region of Africa, are productive systems in an arid environment. Traditionally managed wetlands provide habitats for a wide range of plant and animal species and support local livelihoods through multiple land use. The heterogeneity and socio-economic importance of the wetlands is reflected in a cultural nomenclature, but the land use, environmental and biological basis of the nomenclature has not been studied. In this paper, the cultural typology is described from a structured field survey of site biophysical and land use attributes recorded in a regional site inventory. A numerical classification of inventory sites based on the plant species used for food and materials (resource species), showed that it was significantly associated with the cultural typology. Ordination of the sites showed that key underlying environment gradients significantly influencing resource species composition were water availability and land use intensity. Each cultural type occupied a unique location in ordination space corresponding to its hydrology and land use. A site ordination based on animal wildlife species composition showed that the duration of standing water was a key significant explanatory variable, with land use intensity of secondary importance. Analysis supports the view that traditional land use is based on understanding environment, plant growth and wildlife interactions and that this is the basis of sustainable management. Recent schemes to develop single-use agricultural systems by changing wetland shape and hydrology do not take cultural typology or traditional use systems into account. We propose that decisions on land use change at site and regional landscape scales would benefit from considering traditional management practices and that the cultural typology can be used as an indicator of site development potential. [Copyright &y& Elsevier]

Abstract: The objective of this paper is to examine the spatial variability of islands of enhanced hydrologic activity and its application to remediation of degraded arid and semi-arid ecosystems. Factors causing high spatial variability of water in arid regions include precipitation, soil, physiography, and vegetation. Inherent heterogeneity of arid lands causes areas of runoff and run-on which lead to development of islands of hydrologically enhanced biotic productivity. These hydrologic islands are observed at the individual plant scale as well as in large area patterns of banded vegetation, playettes and playas, and beaded drainage networks where run-on and infiltration stimulate vegetation growth. To remediate degraded rangeland, it may be prudent to mimic nature by diverting water to target areas to create patterns similar to natural islands of hydrologically enhanced biotic productivity. Installation of structures such as water ponding dikes can promote changes to natural vegetation patterns at a landscape scale. [Copyright &y& Elsevier]

Abstract: Aeolian processes are tightly linked to soil and vegetation change in arid and semi-arid systems at multiple spatial and temporal scales. Wind influences patterns of vegetation and soil within the landscape, and these patterns control wind erosion at patch to landscape scales. Aggregated at larger scales, patterns in soil and vegetation distributions influence global distributions of dust and its biogeochemical impacts. Understanding the controls on aeolian processes is therefore important not only in understanding the biogeochemistry and land cover patterns in dryland environments, but also in understanding global land cover, climate, and biogeochemistry. Although the microscopic physics that control aeolian processes are well understood, the controls on these processes in real landscapes are poorly constrained, particularly for structurally complex plant communities such as shrub-invaded grasslands. This paper reviews the controls on aeolian processes and their consequences at plant-interspace, patch-landscape, and regional–global scales. Based on this review, we define the requirements for a cross-scale model of wind erosion in structurally complex arid and semi-arid ecosystems. [Copyright &y& Elsevier]

Abstract: Species diversity influences plant community structure and function. This paper examines the patterns and dynamics of species diversity along a chronosequence of vegetation recovery on sand dunes in a semi-arid region to assess the probability of vegetation recovery via succession, and provides some implications for revegetation practices in this region. Species richness and diversity indices gradually increased with succession, except for a decline in the community of 18 years, which is attributed to the strong dominance of Artemisia halodendron. In each stage of the restoration process, there was a dominant species with particular life history traits which contribute to the dominance of this species. Species replacement and habitat changes were the main drivers of succession, while plant species and community succession drove the process of vegetation recovery. Results showed that restoration via succession holds promise for vegetation recovery and desertification control within protected, fenced enclosures. [Copyright &y& Elsevier]

Abstract: We investigated the effects of winter and summer drought on a shrub/grass community of the Colorado Plateau in western North America, a winter-cold, summer-hot desert that receives both winter and summer precipitation. Summer, winter and yearlong drought treatments were imposed for 2 consecutive years using rainout shelters. We chose three perennial species for this study, representing different rooting patterns and responsiveness to precipitation pulses: Oryzopsis hymenoides, a perennial bunch grass with shallow roots; Gutierrezia sarothrae, a subshrub with dimorphic roots; and Ceratoides lanata, a predominantly deep-rooted woody shrub. Growth for all three species was far more sensitive to winter than to summer drought. The primary reason was that plants did not grow in summer and also did not appear to use summer-assimilated carbon to support growth in the following spring. We hypothesize that the relative scarcity and uncertainty of summer rain on the Colorado Plateau prevents most species from evolving adaptations that would improve their use of summer rain. Together with the results of the companion paper, which focused on plant water relations, we conclude that variation in fall to spring precipitation would have strong effects on primary productivity, and could cause reversible fluctuations in community composition, while increased variation in summer precipitation, through causing high rates of mortality among shallow-rooted species in dry years, has the potential to cause lasting and perhaps irreversible community change, especially if coinciding with the invasion of western landscapes by cheatgrass, tumble weed and other grazing tolerant exotics. [Copyright &y& Elsevier]

The Israel–Egypt border region composed of longitudinal sand dunes is a very unique arid environmental ecosystem in the world: the Israeli side with much more vegetation cover has notably higher land surface temperature (LST) during daytime than the Egyptian side where bare sand prevails. In order to understand this thermal anomaly and its scientific significance in the arid environmental ecosystem development, a series of intensive research activities have been conducted in the past several years, including remote sensing analysis and meteorological modeling. In the paper, we present part of the series studies on the issue: the ground temperature measurement and emissivity determination. The region is mainly composed of four basic surface patterns: biogenic crust, bare sand, vegetation and playa (physical crust). Our hypothesis to occurrence of the thermal anomaly is that it is the direct result of the different surface composition structures and ground emissivities on both sides. Results from our ground temperature measurements during 1997–1998 validate the hypothesis of a significant LST difference existing among the main surface patterns of the region. Biogenic crust covering 72% on the Israeli side and only about 12% on the Egyptian side has an average kinetic surface temperature of above 3°C higher than bare sand. Emissivity of the two most important surface patterns also presents a significant difference. Biogenic crust has an average emissivity ranging from 0.9671 at low temperature to 0.9725 at high temperature. Bare sand occupying above 80% of the surface on the Egyptian side and only about 7% on the Israeli side has an average emissivity between 0.9435 and 0.9543. On the basis of the ground temperature measurements, we use the estimated surface cover percentage to factor the emissivity for a simple simulation of average LST on both sides, which results in an outcome that strongly support the explanation of the thermal anomaly in the border region. Since biogenic crust that covers most surface of the region plays important functions in arid ecosystem development and is common in several deserts such as north Africa and central Australia, our documentation of its surface temperature change and determination of its emissivity, which have not been seen in the literature, will provide valuable scientific basis for other studies on arid environmental ecosystems. [Copyright &y& Elsevier]

Biomass burning is an important ecosystem process in southern Africa, with significant implications for regional and global atmospheric chemistry and biogeochemical cycles. In this paper, representative Landsat path-row scene locations, distributed over southern Africa, were used to quantify the area burned and to understand the coupled role of the timing and the extent of burning on regional emissions. The total area burned and the scar size distribution were found to vary between semi-arid and humid scenes and dry and average rainfall years. Analysis of images from the start and end of the burning season resulted in a modest underestimate of the annual area burned, as compared to using a monthly time-series approach. However, at the regional level the start/end method is likely to yield acceptable annual burned area estimates and total carbon dioxide estimates. On the other hand, combustion factors and emission factors vary sufficiently during the burning season to result in large errors in emission estimates of products of incomplete combustion, when using the start/end method. This study indicates that in southern Africa, the timing in addition to the extent of burning must be considered and that time-series satellite burned area products are needed to quantify pyrogenic emissions accurately. [Copyright &y& Elsevier]