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Vegetation patterns in arid and semi-arid regions create source–sink systems with vegetated patches capturing the resources produced by inter-patches. Patches and inter-patches are the fundamental hydrological units, and their properties can be scaled up to describe ecohydrological functioning at the hillslope or catchment levels. The objective was to compare ecohydrological properties at the patch level in relation to ground cover and at the vegetation type level using landscape function analysis (LFA). Runoff and sediment production were measured in vegetation types of rosetophilous desert shrubland, microphyllous desert shrubland, and crassicaulescent shrubland. Inter-patches (cover = 12.54% ± 2.35% SE) had the highest runoff rates and sediment production, while medium coverage patches (cover = 43.68% ± 2.37% SE) and dense cover patches (cover = 83.56% ± 2.48% SE) produced less runoff and sediments. Runoff, sediments and landscape organization were similar between vegetation types. High litter and stone fragment cover and low soil bulk density were associated with low runoff and sediment production. The LFA infiltration and stability indices explained 10 and 19% of the variability of infiltration and sediment production, respectively. Our results show that vegetation types function similarly, but the hydrological and erosional responses of patches and inter-patches are fundamental to supporting ecohydrologically-based management and restoration plans. • Hydrological and erosional properties were evaluated in patterned semi-arid landscapes. • Rainfall simulation data were integrated at landscape level to estimate runoff and erosion. • Hydrological responses differed from patches and inter-patches, but not between landscapes. • LFA's soil surface assessment had low relationship with measured infiltration and sediment. • Results may be used for restoration plans with a ecohydrological perspective. [ABSTRACT FROM AUTHOR]

Abstract Exclosures are widely used for rangeland restoration in semiarid woodlands. However, grass recovery could be hampered if degradation exceeded certain thresholds. In this study we assessed four years effects of seasonally grazed exclosures –vs. open rangelands– on understory cover (grasses, low shrubs and litter) and peak standing biomass in three increasing degradation stages –mature forests, secondary forests and shrublands– in semiarid Chaco woodlands. We found that grass cover and biomass increased tenfold in four years in mature and secondary forests but remained virtually null in shrublands. In rested forests, the grass cover increments remained relatively constant regardless the annual rainfall amount, both in the driest year 2013 (531 mm) and the wettest year 2015 (924 mm). Only in an extraordinarily wet year (2015) did grass biomass increased in rested shrublands. In that wet year, low shrubs cover –higher at higher overstory degradation– decreased in all woodlands. Our results suggest that shrublands may constitute a new steady state unable to recover by grazing exclusion itself, but probably by its combination with wet periods. Highlights • Seasonal exclosure promotes grass recovery in mature and secondary forests in semiarid Chaco. • Shrublands appear to be a new steady state limited by water shortage. • El Niño Southern Oscillation events represent a window of opportunity to revert degradation by grazing rest in shrublands. • The more severe the canopy degradation, the higher the low-shrub understory cover. • Aerial cover (<50%) is a good proxy for standing biomass of both grasses (<1900 KgDM ha−1) and low shrubs (<500 KgDM ha−1). [ABSTRACT FROM AUTHOR]

Dryland ecosystems are often characterized by their vegetation patchiness. The Succulent Karoo, a semi-arid region in South Africa is characterised by distinct vegetation patches surrounded by a homogenous vegetation matrix. These patches, locally known as heuweltjies, are naturally developed earthen mounds found throughout the region that contribute significantly to landscape heterogeneity. Arthropods are key for ecological functioning in semi-arid ecosystems. However, few studies have assessed the role that heuweltjies play in maintaining arthropod diversity in the landscape. This study investigates how arthropod abundance, species richness, beta-diversity and composition respond to heuweltjies at multiple spatial scales (biotope and site). Two sampling techniques (pitfall and vacuum sampling) were used to collect epigaeic (ground) and foliage-dwelling arthropods on heuweltjies and in the surrounding matrix, at three different sites in the Succulent Karoo during drought conditions. Heuweltjies had greater epigaeic and foliage alpha-diversity and abundance than the matrix. Additionally, epigaeic and foliage arthropod community composition were dissimilar at both the biotope and site scales. Beta diversity across the three sites was high and driven by species turnover. At the biotope scale, heuweltjie and matrix plots both showed high beta-diversity. This study took place during a prolonged drought with high plant mortality and relatively few foliage arthropods, but patterns in arthropod diversity between heuweltjies and the surrounding matrix were nevertheless still apparent. These results suggest that heuweltjies promote arthropod diversity and heterogeneity in the landscape, playing a vital role as refuges, providing food and nesting resources for various arthropod species. • Heuweltjies promote arthropod diversity and landscape heterogeneity. • Species replacement drives changes in ground arthropod communities whereas nestedness drives changes in foliage arthropods. • Heuweltjies provide refuge for arthropods against unfavourable environmental conditions (drought). [ABSTRACT FROM AUTHOR]

Selecting livestock genetics adapted to arid environments, such as Criollo cattle, is one of several strategies recommended for decreasing the vulnerability to climate change of ranching in the southwestern USA. Our objective was to determine whether desirable foraging traits of Criollo cattle previously documented in the Chihuahuan Desert, held true in two of the most climate-vulnerable ecosystems of the Southwest. We conducted a study at Rancho Corta Madera (RCM) in southern California and Dugout Ranch (DR) in southeast Utah. Twenty mature cows, 10 Raramuri Criollo and 10 Red or Black Angus, were monitored with GPS collars during multiple seasons between 2018 and 2021. Geolocation data were used to compute daily distance traveled (km*d−1), movement velocity (m*min−1), path sinuosity (SI), time spent grazing, resting, or traveling (h*d−1), and area of the pasture explored (ha*d−1) as well as to calculate selection of vegetation cover types (E , Ivlev's Electivity Index) by cows of each breed. The effects of breed, season, year, and pasture on each of these metrics were modeled with repeated measures analyses of variance. At both ranches, statistically detectable differences (P ≤ 0.05) between breeds were observed for most behavior metrics during the dormant season. Conversely, few breed differences were observed during the growing season. Criollo cattle exhibited greater relative preference for a number of shrub dominated vegetation types at both ranches, and similar relative selection of grassland dominated sites compared to Angus counterparts. At both ranches, Criollo cattle exhibited similar or less relative preference for riparian areas vs. Angus counterparts. Breed divergence vs. convergence of foraging behaviors during the dormant vs. growing seasons, previously observed in the Chihuahuan Desert, was documented at both sites. Positive system outcomes associated with foraging traits of Criollo cattle could be expected to occur more broadly across the Southwest. [ABSTRACT FROM AUTHOR]

Dormant seeds in the soil are an important contribution to the regenerative potential of an area. Understanding factors that affect seed bank dynamics in arid regions provides insight into how communities respond to disturbance and environmental change. We characterized seed banks in a Great Basin sagebrush steppe system, using field surveys and seed bank studies to compare 17 sites that differed in above-ground vegetation, fire history, and grazing use. We asked whether shrub cover, ground cover, climate, or disturbance history were predictive of seed densities, diversity, the presence of rare species, and similarity between above- and below-ground communities. Fire frequency and a coarse measure of grazing use were not highly predictive of seed bank dynamics, with the exception that sites that burned <10 years ago had greater above-vs. below-ground similarity. Shrub cover predicted multiple below-ground characteristics: Ericameria nauseosa was associated with increased density of introduced species, Chrysothamus viscidiflorus was associated with increased densities of native annual species, and Artemisia tridentata was associated with increased richness of rare native species. Shrub cover estimates were predictive of seed bank composition, and suggest that areas dominated by A. tridentata would have the greatest restoration potential within their seed banks. [ABSTRACT FROM AUTHOR]

Dryland forests are the areas most threatened by climate change, urbanization and land-use change simultaneously. Ecosystem services provided by Mediterranean dryland forests are have been in steep decline, and are extensively studied in the Mediterranean basin, however considerably less in other areas with Mediterranean climates. Knowledge of these services is necessary for the promotion of their conservation and restoration. Here, we synthesize current knowledge regarding the main ecosystem services provided by Chilean Mediterranean sclerophyllous forests and shrublands (SFSh). This knowledge allows for the valuation of SFSh in order to conserve, restore and study them. We found 158 studies, including technical reports, theses, and scientific literature regarding the social and environmental benefits derived from Chilean SFSh, though many did not use the term "ecosystem services" (ES). We found data on 19 ecosystem services with four or more studies per service. ES studies in Chile increased in number a couple years after Millennium Ecosystem Assessment published its synthesis in 2005. The most frequently reported services were provisioning services, especially medicinal plants and extracts. Despite the advances in knowledge, ecosystem services of SFSh appear to be rarely quantified, most frequently using oversimplified variable indicators. Services related to animal biodiversity, such as pollination and plague control, are poorly known. In recent years social studies of perception and valuation have increased, showing people's high valuation of SFSh. Additional studies are needed especially regarding water regulation and provision, as global warming will significantly reduce water supply in Mediterranean climates. Finally, we reflect on the advances necessary to enhance conservation, restoration and adaptation of ecosystems and their benefits to people, especially considering political, social and scientific factors. [Display omitted] • We found 19 ecosystem services provided by Chilean sclerophyllous forests, in at least 158 works, 54 of which are WoS. • "Medicinal and chemical extracts" is the most studied ecosystem service of the Chilean sclerophyllous forest. • Ecosystem services in productive systems, such as pollination and soil formation, have been studied in recent years. • There is a lack of knowledge regarding the services related to water regulation, animal biodiversity and erosion control. [ABSTRACT FROM AUTHOR]

Fog is an important resource for plant growth in arid communities. However, it is unclear whether small shrubs have an ability to capture fog water. We aimed to test this role and expected that were modulated by plant geometry (e.g., height, volume), as neighbor tree species do. Moreover, if xerophytes are adapted to this water resource, they should follow the temporal fluctuations in atmospheric fog offer, to exhibit a high efficiency in fog harvest, and capturing more fog than rain. Two sites in north-central Chile were worked, where 11–12 species per site were studied. Three funnels connected to bottles were placed beneath each plant, and evaluated monthly to quantify fog dripping. Fog offer was measured with standard fog collectors (SFCs). Several species collected more water than the controls in open spaces, reaching up to 182 mm/yr. A significant correlation of water harvest with plant height and volume was found. Only in the xeric site, water capture correlated significantly with SFC data. The capture efficiency was also the highest in this site. Fog harvest by plants was several times the rainwater input (31–34 mm), highlighting the role of xerophytes in the capture of the more abundant resource supplied by fog. • Xerophytic plants capture more fog than rain falling in fog ecosystems. • Plant fog capture efficiency was higher in xeric than in mesic sites. • The cactus Eulychnia breviflora had an annual efficiency of 73% in fog harvest. • The most efficient species could be used as alternatives to artificial fog catchers. [ABSTRACT FROM AUTHOR]

In temperate drylands, livestock grazing and irrigation agriculture alter biocrust cover and thereby soil nitrogen (N) dynamics. However, the influence of land use on biocrusts and soil N dynamics in tropical drylands is unknown. We evaluated the influence of rainfed agriculture and firewood extraction on biocrust functional groups and soil N dynamics in a tropical dryland. We collected biocrusts in abandoned croplands resulting from rainfed agriculture and mesquite shrublands resulting from firewood extraction to measure the cover of heterocystous cyanobacteria, non-heterocystous cyanobacteria, cyanolichens, and chlorolichens. We also collected soil below biocrusts to evaluate soil N dynamics (total and available N, N transformation rates, microbial biomass N), energy availability (total C), and microbial activity (C mineralization). We evaluated the correlation between biocrust functional group cover and soil N dynamics, and between microbial activity and soil N dynamics. In abandoned croplands, heterocystous cyanobacteria had high cover and were associated to altered soil N dynamics. In mesquite shrublands, cyanolichens had high cover and were associated to unaltered soil N dynamics. In this tropical dryland, both activities have contrasting changes in biocrust functional group cover and soil N dynamics, probably due to differences in energy availability and soil microenvironments for microbial activity under biocrusts. • Heterocystous cyanobacteria had high cover values in abandoned croplands. • H. cyanobacteria had low N availability, transformation, and immobilization. • Cyanolichens had high cover values in mesquite shrublands. • Cyanolichens had high N availability, transformation, and immobilization. • H. cyanobacteria favor soil N losses, while cyanolichens favor soil N conservation. [ABSTRACT FROM AUTHOR]

Shrub encroachment, a common occurrence in drylands over the past 150 years, has the potential to alter the redistribution of soil and soil resources by wind and water. This may affect decomposition via soil-litter mixing (SLM). SLM can accelerate decomposition, but its contributions and relationship with abiotic controls, particularly in the context of shrub encroachment, are unknown. To better understand the spatiotemporal relationships between decomposition and shrub encroachment, we conducted a 24 month decomposition study aimed at understanding how placement of litter on either up or downwind sides of dunes in association dune volume affected litter decomposition. There was little decomposition in the first six months of the experiment, with 97.2% of mass remaining despite high exposure to solar radiation. Decay occurred in synchrony with monsoons and SLM, suggesting precipitation during the monsoon season plays an important role in facilitating both SLM and decomposition. Litter placements across a gradient of shrub volumes had no effect on decomposition rates and SLM, but litter placement on the downwind side of dunes had a positive influence on soil-microbial film development. Ultimately, monsoons rainfall and SLM promoted decomposition across a gradient of shrub encroachment in this dryland ecosystem. [ABSTRACT FROM AUTHOR]

Our objective was to assess whether long-term continuous sheep grazing was associated with the bacterial community of the Patagonian Monte soils. We randomly extracted soil samples from 5 plant-covered patches (PCP) and the nearest inter-canopy areas (IC) at sites with low (L), moderate (M) and heavy (H) grazing intensity. Bacterial communities were evaluated by denaturing gradient gel electrophoresis (DGGE) and dominant bands were sequenced. Dendrograms showed a different association among grazing sites in PCP compared to IC areas. In PCP, M and H sites were clustered and DGGE revealed a high similarity in the bacterial community regardless of grazing intensity. In IC areas, analyses clustered L and M sites. Band sequencing revealed that members of these communities belonged to Sphingobacteria , Solibacteres , Gammaproteobacteria , Betaproteobacteria and Bacilli. S ome of the band sequences related to Nitrosococcus oceani and Nitrosococcus watsonii which are restricted to marine environments and salt lakes. Microcoleus vaginatus and diatom chloroplast-related sequences were mainly detected in IC areas from L and M. Heavy grazing could alter autotrophic bacteria/diatom composition in IC areas possibly due to physical disturbance of biological crusts by trampling, threatening the potential of crust re-formation. Grazing intensity affected soil bacterial communities differently in PCP and IC areas with soil crust, highlighting the importance of improving our understanding of microbial diversity responses to land use. [ABSTRACT FROM AUTHOR]

In arid environments, vegetation is distributed in patches. Herbivory and fires promote changes and seed rain plays a key role in the soil seed bank and the colonization of new spaces. This study focuses on the effect of different land use histories on the spatial and temporal seed rain distribution in Patagonia. We placed traps to capture seed rain of perennial grasses, shrubs and annual forage dicots at five sites with different grazing and fire histories. With grazing and fire seed rain diversity is higher than in absence of disturbances. Functional groups seed rain in vegetation patches did not show differences between sites, but at the interpatch level, grazing increased shrub seed and decreased perennial grass seed in the seed rain. Fire decreased the effects of grazing on shrub seed rain, but did not change its effects on perennial grasses. Shrub species showed a minimum abundance in the seed rain in the undisturbed site. Our results suggest that changes described for vegetative attributes are reflected in the seed rain, and this could reinforce the patch-interpatch pattern; fire did not reduce the grazing effects because it decreased the seed rain of the preferred grasses and increased the less preferred ones. [ABSTRACT FROM AUTHOR]

The Daurian hedgehog ( Mesechinus dauuricus ) inhabits eastern Mongolia and adjacent areas of Asia. Previous research indicated that Daurian hedgehogs occupy larger home ranges than other hedgehog species and exhibit broad habitat selection for shrublands and rocky areas. However, few details about fine-scale habitat use exist. We investigated vegetation and topographic characteristics in areas used by two male and two female Daurian hedgehogs fitted with radio transmitters from June to September 2011. We recorded movement paths by continuously tracking each hedgehog during 10 nighttime periods (4–9 h) and used radio-tracking data to develop random alternative paths. We evaluated fine-scale habitat selection based on 1475 individual locations collected along five actual paths and five randomly-generated alternatives per animal. Hedgehog movement paths averaged 3.38 km (±0.39 SE, range = 0.25–12.23 km). Comparisons between actual and random paths indicated that hedgehogs selected topographically level terrain and areas with shrubs, specifically wild apricot ( Amygdalus pedunculata ). Hedgehogs probably foraged around wild apricot because it supports higher densities of insects important to their diets, and use of level areas may reduce the energetic costs of foraging. Our results provide evidence of non-random fine-scale habitat selection by Daurian hedgehogs. [ABSTRACT FROM AUTHOR]

Arid shrublands are spatially heterogeneous environments composed of shrubs patches surrounded by a matrix of bare soil. In this biome, bare soils harbor fewer protist species than soils covered by shrubs because they represent low quality habitats for most of them. Furthermore, protist species composition in bare soils often represents a subset of that found in soils covered by shrubs. This pattern suggests that the variability in protist species composition is the result of a non-random mechanism. I performed a nested analysis to test the hypothesis that the source–sink dynamics is shaping the spatial distribution of soil testate amoebae (a polyphyletic group of protists) in an arid shrubland of northern Chile. I found that assemblages of soil testate amoebae are significantly nested in this biome. The species-poor assemblages inhabiting bare soils are thus, only a subset of species-rich assemblages located in vegetated soils. This nested pattern may be the result of a colonization–extinction tradeoff characterized by species-poor bare soils acting as ‘sinks’ maintained by the permanent colonization of individuals coming from species-rich vegetated soils acting as ‘sources’. Thus, the source–sink dynamics represents a valid conceptual framework to explain the spatial patterns of soil protists distribution in arid shrublands. [ABSTRACT FROM AUTHOR]

Desert mule deer (Odocoileus hemionus eremicus) populations throughout the arid Southwestern USA and Mexico have declined; hence, it is important to identify habitats that provide for their requirements to inform habitat management. We used resource-area-dependence analysis (RADA), which relates home range size to composition of home ranges, to determine habitats most associated with decreasing home range sizes (i.e., increasing quality) for adult male and female mule deer in the San Andres Mountains (SAM) of south-central New Mexico, USA. Pinyon-juniper woodland and oak-mountain mahogany shrubland were the habitats most associated with home range quality for both lactating and dry females, likely because they provided the highest quantity and diversity of browse and the best cover attributes of habitat types in the SAM. Grama grassland was the only habitat associated with male home range size; despite the lack of cover, grama grassland provided more forbs than other habitats in the SAM, and males are less tied to cover than females. Management actions that increase diversity and retard successional status of woodlands and shrublands while retaining cover could increase habitat quality for female mule deer. Actions that favor forbs and increase cover in grasslands would similarly increase habitat quality for males. • RADA relates home range size and habitat quality without masking among habitat types. • Quality of female ranges was associated with pinyon-juniper and oak-mountain mahogany. • Quality of male home ranges was associated with grama grasslands. • Female mule deer balanced food and cover needs; males emphasized food over cover. [ABSTRACT FROM AUTHOR]

Abstract: We studied the impacts of nitrogen (N) deposition and precipitation gradients on soil chemistry and functioning of calcareous soils from semiarid Mediterranean shrublands. Under greenhouse conditions, N fertilization at 0, 10, 20 and 50 kg N ha−1 yr−1 and low water increased inorganic N. The concentration of extractable cations was higher under low water due to reduced leaching, whereas soil carbon (C) to N ratio was affected by the interaction of N fertilization and water supply, suggesting the role of rainfall in the response of soil C and N storage capacity to N deposition. Soil phosphatase activity increased with N as a consequence of an induced N to phosphorus imbalance, whereas N-fixation was down-regulated by N fertilization, a response attributed to high levels of nitrate. Net N mineralization and nitrification were also reduced by N fertilization. Under field conditions, N availability was positively related to the N deposition gradient (3.98–6.05 kg N ha−1 yr−1). Nutrient availability was primarily and positively related to rainfall and temperature, although N deposition contributed to an overall cation depletion. Finally, we suggest the importance of conducting additional studies on the effects of N deposition and climate change on calcareous soils in Mediterranean ecosystems. [Copyright &y& Elsevier]

Abstract: In many parts of the world the boundaries between grassland and shrubland biomes have changed substantially over the course of the last century. Many are projected to shift further from being grass-dominated to shrub-dominated by 2050 under global climate change and land use change projections. This paper used long-term surveys and repeat photography to assess vegetation change at the shrubland-grassland ecotone in semi-arid, South Africa. Changes in several climate variables as well as in the cover of grasses and dwarf shrubs over three time periods (1962, 1989 and 2009) were investigated at eight localities within a broad 500 km ecotone between the Grassland and Nama-karoo biomes. Results showed that for most sites grass cover has increased and that dwarf shrub cover has decreased over time. This contradicts earlier views which warned against the expansion of dwarf shrublands in response to over-grazing as well as more recent views which suggest that more mesic biomes in the Karoo Midlands will contract in response to climate-induced aridification. The decline in stocking densities and more conservation-friendly land management practices together with an increase in large wet events in the Nama-karoo biome may have contributed to the increase in grass cover. [Copyright &y& Elsevier]

Abstract: While numerous studies focus on heterogeneity created by living plants and animal diggings in arid lands, little information exists on the pattern and role of heterogeneity created by large woody debris. We studied soil nutrient content, volumetric water content, and vegetation associated with the presence of logs in sites subject to different grazing intensity in a chenopod shrubland of South Australia. Soil volumetric water content was lower close to logs, and the soil there dried faster after rains. Organic carbon was higher, but available phosphorus was lower in soil associated with logs. We documented greater seedling emergence, species richness and diversity, and greater annual plant biomass next to logs. Our results were similar in the sites with high and low grazing pressure, the latter having higher numbers of seeds and species in the germinable soil seed bank. Logs in this system create patches that differ in properties from other patches in the system (i.e. those created by perennial plants, depressions, or diggings). Logs constitute a unique microenvironment which affects the plant community structure and may enhance the diversity of the system, and should be considered in management schemes. [Copyright &y& Elsevier]

Abstract: In this article we evaluate the potential use of Cladonia foliacea tissue N content, C:N ratio, and phosphomonoesterase (PME) activity as biomarkers of N deposition by means of a field experiment. In order to do this, we continuously added NH4NO3 to a semi-arid shrubland at four rates: 0, 10, 20 and 50 kg N ha−1 yr−1 starting in October 2007. Tissue N content and C:N ratios, considered as N stress indicators, significantly increased and decreased, respectively, after 1.5 years. The response found suggests N saturation above 20 kg N ha−1 yr−1. After 2.5 years, extracellular PME activity increased with 20 kg N ha−1 yr−1 and this was attributed to an induced nutritional (N to P) imbalance. Above this threshold, PME significantly decreased as a consequence of the physiological stress caused by extra N. Effects on PME were dependent on the soil properties (pH and Ca and Mg availability) experienced by C. foliacea. PME response suggests a critical load of ∼26.4 kg N ha−1 yr−1 (20 kg N ha−1 yr−1 + background) for this lichen. Further tissue chemistry and PME evaluations in C. foliacea and soil surveys conducted along wide N deposition gradients will confirm the potential use of this species as a biomonitor of N pollution and the importance of soil properties on its ability to respond to atmospheric reactive N. [Copyright &y& Elsevier]

Abstract: In the Central High Plateau of Mexico, perennial nopal (Opuntia spp.) orchards are used by several native rodent species. The effect of orchard aging on habitat heterogeneity and rodent assemblages are not known. I surveyed rodent community abundance, species richness, diversity and composition, and habitat heterogeneity (hab-H) in 3 nopal orchards—6 months (O1), 2 years (O2), and 12 years (O3) old—and 1 natural nopalera (NN). Hab-H increased with orchard age, and a unique rodent assemblage was associated with each nopal orchard. Grassland rodents dominated O1 and O2. The shrubby habitat of O3 supported a complex suite of rodents that included grassland and shrubland species, and the NN supported a rodent assemblage that was dominated by shrubland species. In O3, aging of the orchard had led to a hab-H and establishment of a rodent assemblage resembling that of NN. Similar ecological relationships are expected in other nopal orchards of the region. In view of my data, regional conservation efforts should take advantage of the mosaic of differently-aged nopal orchards, because they offer suitable conditions for different species of native rodents, particularly given that some of these species occupy natural habitats that are currently highly fragmented. [Copyright &y& Elsevier]

Abstract: Vegetation and small features of ground cover are known to affect erosion, but the areal extent of small features is rarely studied because they are difficult to estimate for large areas. We studied the variation in components of cover, with 67 sites representing the regional variation of vegetation and topography, in northwestern México. Surface-level cover, mostly by litter and gravel, was skewed to higher values than canopy cover, and only about one third of inter-plant points had bare soil. However, litter mass was not closely related to the spatial measure of ground cover. Drip height for intercepted precipitation was always <0.5 m and most obstructions were branches, not leaves. Soil roughness increased with slope gradient, suggesting it resulted from erosion. Neither land form (elevation, exposure and slope) nor species associations were strong factors in determining cover. However, the height of the vegetation was a good predictor of surface cover, drip height and canopy cover. Applied to erosion with the RUSLE model, this ground study estimated cover was better by more than an order of magnitude compared to a remote perception index. The dynamics of cover at surface level in arid and semi-arid shrublands warrants more attention. [Copyright &y& Elsevier]

Abstract: Present-day Sahelian vegetation in a highly anthropized semi-arid region is assessed from local to regional scales, through the joint analysis of MODIS LAI (1km2 and 8-day resolutions), daily rainfall, morphopedological and land cover datasets covering the period 2000–2008. The study area is located in northwest Senegal and consists of the “Niayes” and the northwestern “Peanut Basin” eco-regions, characterized by market gardening and rain-fed cultivated crops, respectively. The objectives are i) to analyse at pixel scale LAI time series and their relation to vegetation and soil types, ii) the estimation of phenological metrics (start of season SOS, end of season EOS, growing season length GSL) and their inter-annual variability, iii) to recognize the vegetation responses to rainfall trends (mean annual precipitation, MAP; frequency of rainy events, K; combination of MAP and K, called F). Pixel-scale analyses show that LAI time series 1) describe the actual phenology (agreeing with ground-truth AGHRYMET data), and thus can be used as a proxy for Sahelian vegetation dynamics, 2) are strongly dependent on soil types. Median maps of SOS and EOS suggest an increase of the GSL from Saint-Louis to Dakar, in agreement with both the North-South rainfall gradient and the intensification of agricultural practices around Dakar. Significant correlations (R: 0.64) between annual variation coefficient of LAI and MAP for both herbaceous crops and natural vegetation are highlighted; this correlation is reinforced (R: 0.7) using the rainfall distribution factors K and F. Rainfall thresholds allowing the SOS can be defined for each type of vegetation. These thresholds are estimated at 0–5mm, 20mm and 40mm for natural herbs, herbaceous crops and shrublands, respectively. If previous works revealed the close link between the MAP and the SOS, our results highlight that LAI dynamics are also controlled by rainfall distribution during the Monsoon season. In this study, climatic indicators are proposed for estimating vegetation dynamics and monitoring SOS. Coupling Earth Observation data, such as MODIS LAI, with rainfall data, vegetation and soil information is found to be a reliable method for vegetation monitoring and for assessing the impact of human pressure on vegetation degradation. [Copyright &y& Elsevier]

Abstract: We studied the effects of afforestation on soil respiration (R s) in an arid shrubland in northern Chile. We sampled R s monthly for three years in two adjacent plots, one left as control in natural condition, and one afforested with Acacia saligna. Sampling occurred 3–6 years after afforestation. Soil temperature (T s) was a good predictor of R s on certain periods of the year, although we could not relate this to specific levels of soil moisture (θ). Seasonal R s variation related more to θ than to T s, which could be explained by extremely low annual precipitation (138mm), concentrated during winter months. The correlation between T s and R s was higher when measured under plants compared to bare ground. The afforested site had in average 17% lower annual R s (p =0.06) than the control site. During some months of the third year of measurements, the afforested site showed greater R s than the control, suggesting that in the near future, R s might be higher for the afforested site than for the natural condition, depending on the effect that trees may have on soil carbon stability, temperature and hydrological conditions. [Copyright &y& Elsevier]

Abstract: Shrub encroachment is the advance of woody plants over grasslands. For some shrub species this process is favoured by fire and high precipitation. In northwestern Patagonia spring precipitation is related with the El Niño Southern Oscillation (ENSO). Over the past years, ENSO has shown an increase in both amplitude and frequency. Our study focuses on the population dynamics of the shrub Fabiana imbricata Ruiz & Pav. (Solanaceae) using stochastic models which involve different fire frequencies and variations in spring precipitation. Our results indicate that F. imbricata''s population grows at a wide range of fire frequencies, reaching its maximum every 6–10 years. The elasticity analysis show that, as fire frequency diminishes, population growth rate depends almost exclusively on adult survival, recruitment events are rare and the presence of seedlings or juveniles is seldom observed. In this case, the landscape would be formed by mature F. imbricata shrublands, and population persistence would depend on adult survival, seed production and their accumulation in the soil bank. However, in the case of very high fire frequencies, more recurrent recruitment pulses would be observed, with a landscape dominated by young shrublands composed of individuals of different ages and reproductive status. [Copyright &y& Elsevier]

Abstract: Southern Californian chaparral and coastal sage scrub (CSS) shrublands are exposed to high-levels of dry-atmospheric nitrogen (N) deposition. A field experiment was conducted over a 6-year period to assess the effects of cumulative, dry-season N inputs on soil and vegetation carbon (C) and nitrogen (N). We hypothesized that plots exposed to exogenous N should exhibit signs of N enrichment once a cumulative N exposure threshold was reached and the N immobilization capacity was exceeded. Using mass-balance we found that chaparral and CSS have the capacity to immobilize 6.2 and 11.9gNm−2 y−1, respectively. Soil extractable N increased significantly after 7–10g/m2 of cumulative N exposure, resulting in a simultaneous increase in the N concentration and a decline in the C:N ratio of shrub tissue. Similar results were observed for the surface litter pool and litter production but at a higher cumulative N exposure. While we cannot tease out the potential for lagged responses to affect our estimate of the cumulative N threshold, these results indicate that the C and N cycling of semi-arid shrublands is significantly altered once the ecosystem N uptake capacity is exceeded. [Copyright &y& Elsevier]

Abstract: Wildfires can cause severe impacts on the terrestrial ecosystems depending on their frequency and behavior. We studied the environmental factors influencing the spatial and temporal distribution of fires, their size and duration in the central semiarid Argentina. We identified fires using MODIS satellite data and we analyzed their association with climate and land cover/use patterns. Spatial and temporal fire patterns varied between eastern, central and western regions according to the presence of agriculture, shrublands and water deficits, respectively. The frequency and behavior of fires also varied temporally with water conditions. Years with low effective precipitations were characterized by an important hotspot density and fire number, as well as the months preceded by two months with low effective precipitation (r 2: 0.42; p < 0.0001). We observed a spatial delay of fires in a northeast–southwest sense, related to the delay of the spring beginning (r 2: 0.7594; p < 0.0001). The mean fire sizes and duration varied significantly among vegetation types (F: 10.76, p < 0.0001 and F: 3.703, p < 0.01). Fires were bigger in shrublands and longer in shrublands or forests regarding agricultural areas or degraded areas (F: 16.0, p < 0.0001). The results obtained would be useful to prevent/control fires and to preserve natural resources and human communities. [Copyright &y& Elsevier]

Abstract: Information on shrubland biomass across wide semi-arid regions is of limited availability. A new model is presented that estimates shrubland biomass based on biomass-pattern-precipitation relationships. The model uses a pattern parameterization that represents the effect of the shrub patches’ spatial arrangement on their water use efficiency. Shrubland biomass productivity is then estimated by modulating rainfall availability along climatic gradients by this Pattern Water Use Efficiency. Preliminary assessment of the new model was achieved by comparing its results with biomass as extracted from high-resolution imagery based on allometric equations. This assessment utilized ten high-resolution images acquired from an ultralight aircraft flying at low altitude over sites between the Northern Negev (100 mm annual rainfall) in the south and Avisur Highland in the north (500 mm annual rainfall). [Copyright &y& Elsevier]

Abstract: Changes in plant community structure and composition of the Mojave Desert in response to greater fire intensity and extent are likely to have strong bottom-up effects on the biological community. The objective of this study was to determine how expansive fire in Mojave Desert impacts small mammal communities across seasons. We sampled small mammals in paired burned (4–5 years post-fire) and unburned areas of Beaver Dam Wash in southwestern Utah. Fire reduced total abundance of small mammals, and species richness and species diversity of the small mammal community. Merriam’s kangaroo rat (Dipodomys merriami) responded positively to fire (15% greater in burned areas). Long-tailed pocket mouse (Chaetodipus formosus) and canyon mouse (Peromyscus crinitus) were 91% and 98% less abundant in burned versus unburned areas. The positive response of Merriam’s kangaroo rat to fire is most likely correlated with their preference for open foraging microhabitat while other species captured prefer greater and more diverse cover. Because the small mammal community has been dramatically affected by fire, it is likely that top-down control of vegetation structure will be dominated by Merriam’s kangaroo rat in burned areas, which may promote more open habitat by limiting the growth of annual and perennial grasses. [Copyright &y& Elsevier]

Abstract: The tension between pyrophytic hummock grasslands and fire-sensitive mulga shrubland is a major ecological theme in central Australia. On a sandplain on the edge of the Tanami Desert, grassland and shrubland are juxtaposed with abrupt boundaries that cut across a subtle environmental gradient. We compare woody plant diversity among vegetation types and explore correlates of the distribution of woody plant species. Alpha diversity in grassland and shrubland was almost identical, but plot-level species richness was greater in grassland. Gamma (landscape) diversity was scarcely greater than alpha diversity. Few long-lived plants, and not even the dominant hummock grass and shrub, were exclusively associated with one vegetation type, but most common species were aligned with elements – soil texture, fire frequency and the extent of physical soil crusting – that characterise the environmental gradient between vegetation types. Most species were resprouters and there was no tendency for obligate seeders or facultative resprouters to be associated with the less fire-prone shrubland. Our data are consistent with the suggestion that hummock grasslands and mulga shrubland are alternative stable states maintained by fire-soil feedback loops and possibly also by competitive exclusion of pyrophytic species by Acacia aneura. [Copyright &y& Elsevier]

Abstract: In the highlands of northern Ethiopia, degraded hillslopes are closed for grazing and agriculture for environmental rehabilitation. In order to assess the effect of these exclosures on water balances, a correct assessment of evapotranspiration is needed. A common method for calculating evapotranspiration employs the reference evapotranspiration in combination with a crop coefficient. However, for natural vegetation, these crop coefficients are not readily available. Therefore, the objective of this study was to derive crop coefficients for semiarid natural vegetation using two different approaches. The crop coefficients were assessed with the dual crop coefficient approach as outlined in the FAO Irrigation and Drainage Paper n°56 and compared with crop coefficients derived from a simple soil water balance. A good agreement between both methods was found. The mid-season crop coefficients ranged from 0.50 to 0.85 for open vegetation with small shrubs and from 0.85 to 0.95 for well developed shrubland. Vegetation with a closed tree canopy was characterized by a mid-season crop coefficient between 0.95 and 1.1. Additionally, a significant logarithmic relation between vegetative soil cover and crop coefficient was found. Using this relation, crop coefficients can be easily derived for semiarid shrub savannahs in similar environments and used for the calculation of evapotranspiration. [Copyright &y& Elsevier]

Abstract: Grazing is a dominant determinant of aboveground net primary production (ANPP) and composition of plant communities. However, ANPP can be maintained following grazing due to compensatory growth, the level of which might depend on additional environmental factors, such as precipitation and edaphic conditions. Several studies have shown that along large-scale regional gradients, community-level compensatory ability is positively correlated with ANPP and soil resource availability. However, community-level responses to grazing are also expected to be affected by local-scale heterogeneity in ANPP, particularly under low primary productivity typical to arid environments. Here, we studied the effect of local-scale variations in ANPP on the compensatory growth of an annual community in a semi-arid region. For two consecutive years, ANPP was evaluated following shoot damage in sites with different primary productivity. The results demonstrated that annual ANPP varied significantly among sites and among plots within sites; however, compensatory ability was negatively correlated with annual ANPP, with overcompensation in the least productive patches and under-compensation in the most productive patches. This pattern contradicts the positive correlation between ANPP and compensatory ability commonly found along large-scale productivity ecoclines, suggesting that the effects of ANPP on compensatory ability might be scale-dependent. [ABSTRACT FROM AUTHOR]

Abstract: Studies of plant-frugivore interactions are important for identifying the roles that biotic seed vectors play in seed dispersal, and ultimately plant recruitment. In a subandean shrubland of central Chile, 50% of total flora (14 species) has fleshy fruits dispersed by birds. We examined two aspects of frugivore-plant interaction in this system: the structure of the seed-dispersal network, to predict the effect of hypothetical frugivore species loss for seed dispersal and disperser effectiveness, by analyzing whether birds contribute equally to the removal of seeds from different shrub species. We show that the seed-dispersal network is highly and significantly nested, resulting in a core of interactions among generalist vertebrates and plant species. A reduction in the populations of the three main avian generalists, Turdus falcklandii, Mimus thenca and Elaenia albiceps, would disrupt seed dispersal and natural regeneration for most woody species. Monte Carlo simulations showed that the network was robust to the random loss of frugivorous species but highly sensitive to the loss of generalist species first. Mist-net sampling of birds corroborated that most fruit removal was effected by E. albiceps and T. falcklandii, highlighting the importance of frugivore species identity on seed dispersal for the maintenance of Mediterranean shrublands. [ABSTRACT FROM AUTHOR]

Abstract: The potential role of two species of pack rats (Neotoma albigula and Neotoma micropus) as keystone ecological engineers was examined by estimating the species diversity of invertebrates living in the nest middens, and nitrogen mineralization rates in soils associated with the middens. Although pack-rat middens in tarbush (Flourensia cernua) shrublands were smaller than those in creostebush (Larrea tridentata) shrublands, they housed a higher abundance and diversity of arthropods. The Neotoma spp. middens were an important microhabitat for crickets (Gryllus sp.), wolf spiders (Lycosa spp.), and lycid beetle larvae (Lycidae) in all of the shrub habitats. There were five arthropod taxa that occupied all middens in the creosote-bush shrubland, and 12 arthropod taxa that occupied all middens in the tarbush shrubland. Soils associated with pack-rat middens had significantly higher soil organic-matter content than reference soils. Nitrogen mineralization was significantly higher in soils associated with pack-rat middens than in reference soils. Neotoma spp. create habitats with moderate microclimates that are essential for several invertebrates, thus contributing to maintenance of biodiversity. The effects of middens on soil organic matter and nitrogen mineralization create nutrient-rich patches. Neotoma spp. affect biodiversity and critical ecosystem processes, thus supporting the designation of keystone ecological engineers. [Copyright &y& Elsevier]

Abstract: Desertification, the conversion of arid grasslands to shrublands due to overgrazing and drought, is occurring on over a quarter of the land on earth. Conceptual models of desertification predict desertified shrublands are in a stable state, and grass recovery is unlikely. These models hypothesize that as grass is lost, feedback loops involving low soil nutrients or insufficient water infiltration rates prevent the return of perennial grasses to desertified sites. However, these models cannot account for recent reports of reversals of desertification following long-term livestock removal. Here, we analyzed soil nutrients and water infiltration at a desertified site where native perennial grasses are recovering inside a 49-year livestock exclosure. We found higher water infiltration and soil nutrients inside the exclosure. We postulate that in the absence of livestock there is a slow release from compaction that, over decades, results in an increase in water infiltration and a concomitant decrease in erosion, which promotes nutrient accumulation in the soil. Our data support key desertification model assumptions: increased nutrients and infiltration are associated with reversal of desertification. This suggests that given sufficient time and removal of livestock, soil properties at some desertified sites can improve sufficiently to support the re-establishment of perennial grasses. [Copyright &y& Elsevier]

Abstract: Precipitation variability and shrub encroachment in response to global environmental change are likely to affect both richness and aboveground net primary production (ANPP) of annual plants in arid and semi-arid ecosystems in the northern Chihuahuan Desert, especially given the grazing history and desertification potential of this aridland region. Using a nine-year dataset (1999–2007), we examined the spatial and temporal variation in annual plant communities in grass- and shrub-dominated vegetation, and evaluated the relationships between species richness and ANPP with seasonal and annual precipitation and soil moisture. We found that species richness and ANPP varied among seasons and between years in both grass- and shrub-dominated areas. Cryptantha crassisepala, Plantago patagonica, and Phacelia integrifolia were the most common species found in both communities in both seasons, and Chamaesyce serrula, C. serpyllifolia, and Kallstroemia parviflora were more common in summer only. We found that species richness in summer was significantly correlated with summer precipitation and summer soil moisture in both communities, but summer ANPP was significantly correlated with summer precipitation and soil moisture only in shrubland. However, richness and ANPP of winter annuals were significantly correlated with winter precipitation and winter soil moisture in shrubland and grassland. Our results demonstrate that temporal variation in rainfall can be as important as annual total amounts for plant performance, and that response to temporal dynamics varies among species but not between grass- and shrub-dominated communities. We conclude that desert annuals provide a highly dynamic system for understanding the processes that influence plant species composition and abundance, and that desert annual systems will likely be highly impacted by shrub encroachment along with increases in precipitation variability as a consequence of anthropogenic climate change. [Copyright &y& Elsevier]

Abstract: High levels of atmospheric nitrogen (N) deposition to southern California chaparral shrublands may interact with fire to affect biomass production and plant species composition during secondary succession. To determine the potential interactions between postfire recovery and N deposition we compared rates of aboveground net primary production (ANPP), shrub growth, and the relative abundance of Adenostoma fasciculatum, other sub-dominant shrubs, and herbaceous species of three chaparral stands exposed to different levels of atmospheric N deposition over the first 3 years of post-fire succession. Our data suggest that rates of ANPP (gdwm−2 month−1) and aboveground N storage (gNm−2 month−1) for these chaparral stands were not related to N deposition even though sites exposed to high levels of N deposition had significantly higher rates of shrub growth (gdwplant−1 month−1) and N uptake (gNplant−1 month−1). However, high-N stands were composed of larger shrubs with a lower density, and this trade-off between shrub size and density may explain the low correlation between N deposition and post-fire ANPP. Differences in relative plant species abundance between sites were significantly correlated with N deposition exposure, where stands exposed to high N deposition had a lower relative abundance of A. fasciculatum and a higher relative abundance of other shrub and herbaceous species. While many factors can affect rates and patterns of post-fire recovery, these results suggest that chronic exposure to N deposition may significantly alter plant growth and species composition in successional chaparral stands. [Copyright &y& Elsevier]

Abstract: Our study was focused on the effect of abandonment on above-ground biomass and net primary productivity (ANPP) in a Montado in Southern Portugal. The Montado has a long history of human management and control of invasion by shrubs is achieved by clearing, ploughing and grazing. When these cease, it is invaded by Mediterranean matorral species. We hypothesized that the change in life form dominance would affect both biomass and productivity, but while the total biomass was expected to increase, the effects on ANPP were less clear. We tested our hypothesis by determining above-ground biomass and ANPP along a gradient of decreasing land use intensity, ranging from extensive grazing to 20 years of abandonment. Above-ground biomass increased with abandonment, which was related with the increase in shrub cover. In addition, we found a decrease in herbaceous ANPP that was more than compensated by an increase in shrub ANPP in plots abandoned for longer time, resulting in a significant increase in total ANPP. This increase was strongly related with the increase in the cover of Cistus ladanifer, a pioneer species that colonises degraded areas and forms one of the first stages of succession of woody communities. [Copyright &y& Elsevier]

To estimate the effect of browsing on the mountain range of the Sierra de San Francisco, Mexico, we assessed browse species richness and canopy cover and the relative abundance of goats (large flocks), cattle, sheep, and equids (small herds) across 2700 m from pens used to milk goats in 1 lowland and 2 upland mesas, which differ in the sarcocaulescent shrublands that inhabit there. Also, we evaluated the relation between browse species preference by domestic herbivores and their canopy cover. Small ruminants (mainly goats), not cattle and equids, had a greater relative abundance near milking pens and, even more, far from them, which was observed as a ditch-shaped pattern across the distance. Goats did not affect browse species richness across the distance, but they affected the total canopy cover; sites with greater goat relative abundance had less total canopy cover, which was observed as a hump-shaped pattern. Preferred and non-preferred browse species by goats showed increasing and hump pattern across distance. Non-preferred species also showed decreasing and U-shaped patterns. Thus, goats have created trends in browse species canopy cover, stressing the hump pattern in the total canopy cover in lowland and upland sarcocaulescent shrublands. [Display omitted] • Lowland and upland shrublands have a similar total canopy cover of browse species. • Goat abundance showed a ditch-shaped pattern throughout 2700 m from milking pens. • Goats have caused a hump-shaped pattern in the total canopy cover of browse species. • Canopy covers of browse species showed hump, increasing, and decreasing patterns. • Goat abundance pattern likely has disturbed species composition in rangeland. [ABSTRACT FROM AUTHOR]

The Chihuahuan Desert has been overgrazed by livestock ranching since the 16th century. This has changed the structure and dynamics of the ecosystem, and native species have developed physiological adaptations to survive these vegetation changes. We evaluated the changes in packed cell volume (PCV) and plasma protein of Dipodomys merriami , Merriam's kangaroo rats, inhabiting shrubland and grassland areas at Mapimí Biosphere Reserve, Chihuahuan Desert, Mexico. We captured 57 individuals from two vegetation types in March–April for two years. We found higher kangaroo rat packed cell volume in grassland than shrubland. However, the plasma protein/packed cell volume ratios were not significantly different between rats from both vegetation types, suggesting that an increase in PCV is a consequence of dehydration. Monitoring the packed cell volume can be a useful and rapid screening tool to assess responses to changes in habitat degradation in arid areas. • Assessment of packed cell volume and plasma protein of Merriam's kangaroo rats to evaluate changes in vegetal cover. • Higher packed cell volume of kangaroo rats from grassland than shrubland rats. • The packed cell volume increases in the same intensity as plasma protein in kangaroo rats suggesting a dehydration effect. • Monitoring packed cell volume can be a tool to assess responses to changes in habitat degradation in arid areas. [ABSTRACT FROM AUTHOR]

Abstract: Fire and atmospheric N deposition have the capacity to alter the N and C cycling and storage of semi-arid shrublands. Thus, we measured the pre- and post-fire soil and tissue C and N dynamics of three southern California chaparral stands exposed to varying levels of N deposition. Total soil N was positively correlated with N deposition exposure before and after fire, indicating that fire did little to alter patterns of soil N enrichment from atmospheric N deposition. Fire caused a significant increase in soil extractable N, and this increase was positively correlated with N deposition indicating that fire enhanced soil N availability more at sites exposed to high N deposition. Fire also caused the tissue N concentration of regenerating Adenostoma fasciculatum (chamise) shrubs to be significantly correlated with N deposition; however, the correlation was negative during the first year of fire recovery (r 2=0.62) and positive during the second (r 2=0.94) indicating complex and transient dynamics in shrub growth and N concentration. Overall, our results suggest that periodic fire in chaparral may not reduce the potential for N enrichment that develops over decades of N deposition and have important implications for the propensity of these semi-arid shrublands to become “N-saturated”. [Copyright &y& Elsevier]

Abstract: Patches of fire-sensitive, closed-canopy Acacia aneura shrubland occur within a matrix of highly flammable Triodia grasslands in central Australia (<400mm mean annual precipitation). We used digitised repeat aerial photography to chart the dynamics of these mosaics over 52 years (1950–2002). During this period, traditional Aboriginal fire management had largely ceased. The spatial extent of A. aneura shrubland patches varied over the 52-year study period but the aggregated change was small (an increase of 3.1% from 1950 to 2002, with the largest excursion a 13.1% decrease between 1950 and 1983). This change was restricted to within 50m of boundaries between the shrublands and grasslands. Statistical modelling for the period for which landscape fire activity was available (1980–2002) showed that the dynamism of the boundaries was associated with burning. Fire effects on boundaries were mediated by the size of A. aneura patches, with small patches most likely to contract, explaining the dynamic spatial arrangement of small patches in the landscape. We conclude that a series of reinforcing fire, soil and vegetation feedbacks maintain the mosaic of shrubland patches. However these feedbacks might eventually be overwhelmed by large and sustained changes to fire regimes, leading to the landscape-wide dominance of Triodia grasslands. [Copyright &y& Elsevier]

Abstract: Semi-arid shrublands of southern California, including chaparral and coastal sage, are found in widely varying elevation and microclimatic regimes and are subjected to disturbance such as fire and atmospheric N deposition that have the capacity to alter soil and litter C and N storage. Here we present a case study where soil and litter C and N were measured over 19 months in post-fire chaparral and mature coastal sage stands to assess whether differences in soil and litter C and N between these diverse shrublands could be attributed to differences in elevation, stand age, rainfall, and/or estimated N deposition exposure. Our results indicate that atmospheric N deposition exposure, either alone or in conjunction with other environmental variables (elevation, rainfall, and/or stand age), was the most frequent predictor of the spatial pattern in the soil and litter N and C variables observed. These results are consistent with those reported for high-elevation coniferous forests arrayed along an N deposition gradient in southern California, suggesting that N deposition may affect the soil N and C storage of semiarid shrublands and woodlands in a qualitatively similar manner. [Copyright &y& Elsevier]

Abstract: Most semi-arid and arid regions around the world have lost a major part of their original vegetation. Restoration of once shrublands and woodlands is often challenged by low seedling establishment success due to water stress and herbivory. In some regions, increased rainfall during El Niño Southern Oscillation (ENSO) events can significantly stimulate plant recruitment. However, recruitment seems to be strongly modulated by herbivore pressure. Also, seedling establishment in arid ecosystems can be facilitated by adult trees and shrubs whose canopies contribute to improve seedling water relations. We performed a field experiment to test the role of small mammalian herbivores and shade availability during simulated rainy ENSO conditions on the growth and survival of Prosopis chilensis saplings in semi-arid Chile. When mammalian herbivores were absent, sapling survival increased from 25% under simulated strong ENSO rain to 60% under very strong rainy events. This positive effect of increased water availability was over-ruled by strong herbivory of mainly introduced European rabbits (Oryctolagus cuniculus) and hares (Lepus europaeus). Most saplings died when herbivores were present. Shade availability did not significantly improve plant growth and survival. Our results support the hypothesis that rainy years such as those associated to ENSO events could improve the possibilities for successful tree reforestation in semi-arid ecosystems when combined with a reduction in herbivore pressure. [Copyright &y& Elsevier]

Abstract: Grasslands dominated by Stipa tenacissima are important ecosystems in the arid and semiarid climates of western Mediterranean, where they have originated by degradation of open dry forests and shrublands. At present, although the level of exploitation in these ecosystems is very low, succession processes seem to have stopped. In this study, we explore the role of microsite and post-dispersal seed predation on the seedling emergence of two species from advanced successional stages (Rhamnus lycioides, Quercus coccifera), three species from degraded stages (Cistus clusii, Helianthemum violaceum, Anthyllis terniflora), and of the dominant species (Stipa tenacissima). Seeds of these species were sown in plots divided into two microsites: (i) under tussocks of S. tenacissima and (ii) in the bare soil between tussocks. Soil moisture was significantly higher in the tussock microsites. The interaction observed between microsite and time, reflected the slower drying process under tussocks. Seed predation was in general high and differed significantly between species but not between microsites. Q. coccifera was especially affected by predation. The only germination detected in gap areas was that of H. violaceum. The results pointed to a direct facilitative effect of tussock grass on the germination in R. lycioides (20.4±8.0%) and S. tenacissima (41.3±5.7%) while the corresponding figures for bare ground were 0%. These results suggest that the recovery of potential vegetation in this ecosystem is not possible or, at least, is very slow because the residual shrub patches do not generate a sufficient number of seeds able to disperse to favorable germination microsites. S. tenacissima may act as facilitator of seedling recruitment if there is a supply of diaspores. [Copyright &y& Elsevier]

Abstract: Fire has been historically infrequent in the Mojave Desert, and its increased prevalence caused by the invasion of non-native annual grasses is a major concern for land managers there. The most dramatic changes have occurred in middle elevation shrublands dominated by creosotebush (Larrea tridentata), Joshua tree (Yucca brevifolia), and/or blackbrush (Coleogyne ramossissima), where most of the fires occurred between 1980 and 2004. This zone is more susceptible than other areas of the Mojave Desert to increased fire size following years of high rainfall. Increases in fire size are likely related to the flush of non-native annual grasses, Bromus rubens in particular, that produces continuous fuelbeds following years of high rainfall. This dynamic also has occurred to some degree at lower elevations, but the background cover of native perennial fuels there is already very low, muting the effects of the ephemeral fuels. At elevations above the middle elevation shrublands, fire size does not vary with rainfall, indicating that native woody fuels dictate fire regimes. These results suggest that an invasive plant/fire regime cycle is currently establishing in the middle and possibly the low elevation shrublands of the Mojave Desert, but not at higher elevations. [Copyright &y& Elsevier]

Abstract: General models of degradation suggest soil and nutrients are lost and conversion of rainfall into primary productivity is diminished when rangeland is degraded. These models are supported by studies on non-resilient landscapes, where loss of primary productivity also translated into loss of secondary productivity, but have not been tested on resilient landscapes. Elsewhere we showed that loss of chenopod shrubs from a landscape characterized as resilient was associated with declines in plant productivity and efficiency of conversion of rainfall into plant mass. To explore whether these differences in primary productivity translated into differences in secondary productivity, we grazed sheep at five rates of stocking for 10 years on 2000ha of this landscape. The experiment was necessarily replicated in time not space (i.e. pseudo-replicated), which limits confident extrapolation of results to other landscapes. Productivity of sheep at all except highest rates of stocking varied little between sites where shrubs were abundant or scarce. From an animal production point of view, greater rates of stocking were unsustainable through dry years on the degraded site, but animal performance was generally unaffected on the non-degraded site, where shrubs were abundant. While these results provide evidence of economic penalties associated with degrading a resilient landscape, important ecological penalties were only partially explored. [Copyright &y& Elsevier]

Gross precipitation, throughfall, and stemflow were measured in a representative matorral subinerme study plot within a small montane basin of the Sierra Madre Oriental throughout three wet season periods. Data analysis suggests that of the 394.8 mm of cumulative gross precipitation generated by 25 sampled events, throughfall, stemflow, and canopy interception loss fluxes were 329.0±7.7 mm (83.3±1.9%), 33.5±7.6 mm (8.5±1.9%), and 32.3±10.8 mm (8.2±2.7%), respectively. Stemflow from four woody plant stems was found to be moderately correlated (r=0.54) with the product of gross precipitation multiplied by stem basal area, while the season-long Herwitz (Earth Surf. Process. Landforms 11 (1986) 401) funneling ratios for these stems averaged 21.1. The relatively large concentrations of water delivered to the bases of these plants suggest that stemflow generation may be a means of surviving drought conditions. The importance of and possible factors influencing during-event evaporation from the saturated matorral subinerme canopy, as well as recommendations for future canopy water flux studies in this plant community, are discussed. [Copyright &y& Elsevier]

This research describes the effects on the soil mite fauna of two sheep-grazing intensities applied to chenopod shrublands in both good and poor conditions. Soil was sampled from within and between bluebush (Maireana polypterygia) accretion mounds, 9 and 18 months following a 10-year grazing trial. There were major differences in the mite assemblages associated with the grazing treatments. Heavily grazed sites had reduced abundances of most mite species and substantially reduced diversity. In this ecosystem, soil accretion mounds below bluebush are important sites of acarine diversity and abundance. Of a total of 75 species, 49% were found only in this habitat. The decline of mite assemblages associated with vegetation degradation and mound decay mirrors declining soil properties, which have been described for these sites. These soils have particularly high species richness, with broad similarities in mite composition (at family and generic levels) with similar environments elsewhere in the world, continuing the trends found by other researchers. [Copyright &y& Elsevier]

A hypothesis for understanding the stability of northern Chihuahuan Desert landscapes is that the distribution of soil resources changes from spatially homogeneous in arid grasslands to spatially heterogeneous in invading shrublands. Since radioactive fallout 137Cesium (137Cs) was deposited uniformly across the landscape during the 1950s and 1960s and was quickly adsorbed to soil particles, any redistribution of 137Cs across the landscape would be due to soil redistribution or instability at either plant-interspaces or on a landscape scale. The concentration of 137Cs in soils collected from different vegetation communities (black grama grass, tarbush, tobosa grass, and mesquite) at the USDA-ARS Jornada Experimental Range in the Northern Chihuahuan Desert in New Mexico was determined. At the black grama grass and tobosa grass sites, 137Cs was uniformly distributed at the plant interspace scale. At the mesquite sites, 137Cs was concentrated in the dune area under mesquite shrubs with little to no 137Cs in the interdune areas. 137Cs data support the hypothesis that significant soil redistribution has occurred at dune sites created by invading mesquite. In the arid grassland-shrub sites with black grama grass, tobosa grass, and tarbush the 137Cs data support the hypothesis of spatially homogeneous distribution of soil resources. High concentrations of 137Cs in the biological soil crusts (0–5 mm) at the tarbush sites indicate that biological soil crusts can contribute to the stability of these sites. [Copyright &y& Elsevier]

Haloxylon ammodendron is a shrubby perennial distributed in many sandy and saline areas of deserts of Northwest China. It is an important economic plant used for sand fixation, pasture and fuel. Seed germination is the critical stage for species survival. The optimal temperature for germination is 10°C and germination was the lowest at 30°C in light and darkness. The higher the salinity of NaCl, the lower the percentage of germination, but after exposure to higher salinity, the seed recovery percentage is higher.The seed viability of about 10 months can be extended by cold or ultra dry storage at seed moisture content below 5%. [Copyright &y& Elsevier]

The Waite–Nicolson rangeland management method for semi-arid chenopod shrublands predicts that smaller paddocks with medium to moderate stocking rates help to preserve the native vegetation. Vegetation cover around waterpoints in three small paddocks (<2000 ha) from Middleback Station, South Australia was studied using multivariate analysis. Data from quadrats sampled along radiating transects were tested for correlations with a number of site features and grazing history factors. Two significant associations were detected: quadrats with an abundance of Rhagodia parabolica and less palatable species such as Maireana pyramidata, and Atriplex stipitata were correlated positively with proximity to water points, paddock age and stocking rate, and negatively with paddock size. In contrast, quadrats with species such as Rhagodia ulicina and the more palatable M. sedifolia were correlated with increasing distance from the water points and paddock size, but negatively with age and stocking rates. Transect direction was not correlated with either group. Twelve of the 20 species examined, including the important forage species A. vesicaria, also were not correlated with those paddock and grazing features included here. These results suggest that the distribution of some chenopod shrub species in fenced paddocks is still possibly affected by a combination of these factors in the long term by grazing at densities of 6 ha sheep−1 and that the method, although maintaining the fodder species, may not be preserving biodiversity at these grazing levels, although further study is needed. [Copyright &y& Elsevier]