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Tourism development can stimulate regional economic growth and improve living standards in economically underdeveloped regions. However, rapid tourism expansion may also negatively affect regional sustainability, particularly in eco‐fragile areas. As a representative arid and semiarid region, Northwestern China provides a valuable case for analyzing the coupling coordination relationship within the tourism–economy–ecology (TEE) system. This analysis is crucial for promoting sustainable tourism development in eco‐fragile areas. This paper utilizes the entropy weight method, coupling coordination degree (CCD), and obstacle degree models to assess the development level, coupling status, and related obstacles within the TEE system across the five northwestern provinces from 2011 to 2022. The results show the following. (1) While the northwest region has made significant strides in environmental management, most provinces have low comprehensive development status in tourism and economic subsystems, which lag behind the ecological system's development. (2) The CCD level in each province improved continuously from 2011 to 2022. Provinces with lower coupling coordination in 2011 had higher improvement rates in the later period. (3) The obstacles to coordinated development shifted over time, ranging from low foreign exchange earnings from tourism and low international tourist arrivals in 2011 to low forest management areas in 2019 and a significant decline in foreign exchange earnings from tourism in 2022. (4) The impact of COVID‐19 on the coordinated development of the TEE system has been relatively manageable. While most provinces in the northwest continue to see steady ecological improvement, the challenges of lagging tourism development and insufficient economic growth momentum remain significant. Based on this analysis, this paper offers four policy recommendations to support the sustainable development of arid and semiarid regions in Northwestern China. These recommendations provide valuable insights for achieving high‐quality economic development in other eco‐fragile areas. [ABSTRACT FROM AUTHOR]

Remote sensingmonitoring of regional ecological quality has advanced significantly with the rapid developments of remote sensing technology. At present, remote sensing ecological index (RSEI) has been widely used in ecological status monitoring. However, RSEI was proposed for urban environments, and the rationality and accuracy of its applicability to desert-dominated arid region ecosystems need to be demonstrated. Therefore, in this study, we incorporated desertification monitoring index (DMI) and salinity monitoring index (SMI) to RSEI and developed the modified remote sensing ecological index (MRSEI) for arid regions. Moreover, we analyzed the stability of MRSEI in ecological status monitoring for arid regions. The MRSEI was then used to evaluate the ecological quality of Inner Mongolia from 2000 to 2020 and exploring its causes. The results show that (1) Although the evaluation results of RSEI and MRSEI are more consistent in areas with high ecological status grades, the MRSEI results are more cautious and reliable in extreme conditions (e.g., desertification, salinization) than the RSEI. (2) Approximately 87.66% of ecological quality have improved or remain stable from 2000 to 2020, but the remaining areas (accounting for 12.34% of the whole area) are still under degraded conditions. This demonstrates that although local governments have made some progress in ecological conservation, the areas that are fluctuating or degraded still require protection or management. (3) In Inner Mongolia, the ecological quality which drove by precipitation (P) & temperature (T) accounting for 26.67% of the study area, population density (D) and GDP per capita (G) affected 13.23% of regional ecological quality. Overall, this research is crucial for evaluating spatial and temporal changes in arid region ecology and establishing conservation strategies. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "A 5-and a-half-year-experiment shows precipitation thresholds in litter decomposition and nutrient dynamics in arid and semi-arid regions." The original article was published online on November 27, 2023, with Open Access under a Creative Commons Attribution 4.0 International License. However, the authors later decided to cancel Open Access, and the copyright of the article changed on December 7, 2023, to © The Author(s), under exclusive license to Springer-Verlag GmbH Germany, part of Springer Nature 2023 with all rights reserved. The publisher, Springer Nature, remains neutral regarding jurisdictional claims and institutional affiliations. The authors of the article are Hao Qu, Eduardo Medina-Roldán, Shaokun Wang, Xujun Ma, Xinyuan Wang, Xia Tang, and Liangxu Liu. [Extracted from the article]

Megafauna play important roles in the biosphere, yet little is known about how they shape dryland ecosystems. We report on an overlooked form of ecosystem engineering by donkeys and horses. In the deserts of North America, digging of ≤2-meter wells to groundwater by feral equids increased the density of water features, reduced distances between waters, and, at times, provided the only water present. Vertebrate richness and activity were higher at equid wells than at adjacent dry sites, and, by mimicking flood disturbance, equid wells became nurseries for riparian trees. Our results suggest that equids, even those that are introduced or feral, are able to buffer water availability, which may increase resilience to ongoing human-caused aridification. [ABSTRACT FROM AUTHOR]

The article presents a study report on the nature of aridity dynamics in semi-arid agro climatic zone of eastern Rajasthan for a definite period, 1985-2015. Topics include that semi-arid and sub-humid regions are Ajmer, and Jaipur; and the enhancement of temperature and evapotranspiration has effected aridity and climatic parameters.

Dryland (semiarid and arid) ecosystems are responsible for most of the interannual variation in atmospheric CO2 concentrations and contain a considerable fraction of the globe's soil carbon (C) stock. Despite their important contribution to the global land C sink, we have a poor mechanistic understanding of the processes that drive C cycling patterns in drylands. In this study in eastern Utah, we examined the natural variation of soil C pools and fluxes along semiorthogonal gradients of climate and soil texture in order to determine the pertinent environmental controls on soil C cycling dynamics. Our study revealed a high degree of collinearity among C stocks and fluxes, which were related to climate, vegetation, and soil clay content. Soil C pools were positively correlated with both soil clay content and precipitation, which in turn was linked to aboveground plant biomass. By contrast, enzyme activities were negatively associated with temperature. We observed a strong decoupling of C pools and fluxes (for example, total C, DOC, microbial biomass C, and respiration) from the enzyme activities involved in organic matter decomposition. Overall, our findings indicate that the within- and between-site variation of soil C pools across diverse dryland ecosystems was strongly linked to both climate and edaphic characteristics, but the high degree of local variability within sites could challenge interpretations of environmental controls at broader scales. [ABSTRACT FROM AUTHOR]

The decline of soil organic carbon (SOC) has aggravated salinity-related problems in semi-arid irrigation areas of the Awash river basin, Ethiopia. This study aimed at evaluating the performance of potential remediation crops on saline soil and their effectiveness for remediating soil salinity and improving pH, SOC, bulk density (BD) and hydraulic conductivity (HyCo). Rhodes grass (RHG), alfalfa (ALF), sudangrass (SUG) and blue panicgrass (Retz) (BPG) were grown in saline (3-13.9 dS/m) field plots. The crop biomass was incorporated into the soil immediately before flowering. The results show that at high soil salinity levels, BPG and SUG grew well, with the harvesting frequency of BPG being much higher than for SUG. Conversely, the growth of ALF and RHG was strongly inhibited by high soil salinity. Significant (P < 0.05) reduction of soil salinity levels (-3.2 dS/m) and related ionic concentrations, an increase of SOC (0.8% to 1.6%) and improvement of BD and HyCo were observed in BPG plots. The fast-growing nature of BPG in the hot climate of the experimental area resulted in harvests every three weeks and promoted the incorporation of high amounts of biomass to the soil and efficient soil salinity remediation. At moderately saline conditions, ALF also showed a great potential for salinity reclamation (-1.8 dS/m) and SOC accumulation. The cultivation of fast-growing annual crops proved an efficient and low-cost strategy for soil salinity mitigation and the reclamation of salinity-associated soil degradation in irrigation agriculture in Ethiopia. [ABSTRACT FROM AUTHOR]

Desertification is a major environmental problem in arid and semiarid regions. Tree plantation has been commonly employed to foster the recovery of degraded areas. However, this technique is costly, and their outcomes are often uncertain. Therefore, we evaluated an alternative method for the restoration of degraded semiarid steppes that involved the construction of branch piles to attract frugivores as potential seed‐dispersing birds, promoting seed rain, and fostering the formation of woody patches. We measured the success of branch piles in terms of the number of bird visits and seed input compared to naturally occurring shrub patches. Generally, frugivorous birds visited branch piles less frequently than shrub patches. Yet, branch piles accumulated seeds of patch‐forming shrub species. Seed rain was higher under patches of the dominant shrub Rhamnus lycioides than under branch piles. In contrast, woody patches and branch piles did not differ in seed input of the less abundant Pistacia lentiscus shrub. Our study demonstrates that branch piles are used by frugivorous birds and accumulate seeds of patch‐forming shrubs. Branch piles may be a suitable method to promote the expansion of bird‐dispersed plant species and restore semiarid wooded steppes. However, their efficiency largely depends on pile persistence and economic cost. [ABSTRACT FROM AUTHOR]

Highlights • NDVI thresholds corresponding to bare soil were determined using field information. • Bare soil was mapped over the period of 2000–2016 in the Northeast of Brazil. • A degradation index based on the recent land use history is proposed. • The proposed index was used to characterize degradation trends in the study area. Abstract Information about changes in land use and land cover is useful to address issues related to drylands management, as well as to support decision-making related to the sustainable use of soils. Since drylands are frequently affected by accelerated soil erosion, land degradation and desertification associated with vegetation cover losses, constant monitoring of land use and land cover changes are required. However, land use and land cover maps are often not available, making it difficult to monitor degradation. Therefore, in this work, we developed an efficient mapping method to monitor bare soil areas, which are indicative of land degradation in the case of the Northeast of Brazil, using Normalized Difference Vegetation Index images. The proposed methodology was field calibrated and applied to the region using 17-year (2000–2016) NDVI maps, with a spatial resolution of 250 m. Based on bare soil mapping, we estimated the degree of degradation using an index calculated from the persistence and frequency of bare soil during the study period. The results indicated that the degraded areas increased in the period of the study, mainly in areas of pasture and Caatinga. This expansion has been accelerated due to the severe drought that affected the region since 2011. [ABSTRACT FROM AUTHOR]

Abstract Biological invasions can induce trajectories of changes that make ecosystems fragile and less reliable in providing services and goods. Here we set out to assess the economic value of dry land ecosystem services affected by the invasive tree Prosopis, which was originally introduced in Africa and elsewhere for providing firewood, animal fodder and other services to rural people. Based on choice experiment method, we estimated the economic values of dry land ecosystem services affected by Prosopis in the heavily invaded Afar region, Ethiopia and Baringo County, Kenya. Including labor and cash contributions as payment attributes, a random parameters logit model was employed for analyzing households' preferences for the affected ecosystem services. We found that, despite the services provided by Prosopis, households from both regions were willing to pay for its management primarily driven by biodiversity and water. WTP was on average higher in Afar (USD 50.42/year) than in Baringo (USD 37.74/year), which may be because the ecosystems in Afar were less degraded prior to the invasion by Prosopis than in Baringo and that charcoal production in Afar is officially prohibited. Our results indicate that the costs imposed by the deliberately introduced Prosopis outweigh its benefits in both Afar and Baringo. Highlights • Using choice experimental data, ecosystem services economic valuation of Prosopis invasion was conducted. • Households from Afar were willing to contribute USD 50.42 per annual for Prosopis invasion management options that will improve biodiversity, water availability, seasonal mobility and tourism flow. • Households from Baringo were willing to contribute USD 37.74 per annual for Prosopis management option(s) that will improve biodiversity and water availability. • In both areas, microclimate regulation was acknowledged as a current ecosystem service by Prosopis. [ABSTRACT FROM AUTHOR]

Coprinellus phaeoxanthus A.R.Gomes & Wartchow is described as a new species and is characterised by cordiform basidiospores similar to those of the recently described Coprinellus arenicola. However, it differs in the presence of voluminous pleurocystidia in the velar elements, which are shorter than in Coprinellus arenicola , and in the lack of clamp connections. In addition, exsiccatae of a Brazilian collection identified as ' Coprinus xerophilus ' are analysed, and because of the star-shaped velar patch on the pileus and the non-volvate stipe base, it is considered to be the same as Coprinus calyptratus , representing a new record from South America. [ABSTRACT FROM AUTHOR]

For more than 75 years, scientists and educators in New Mexico have provided programs that translate research on dryland ecosystems into broader scientific understanding for the public. Kindergarten through twelfth grade (K–12) students and teachers became a primary audience for these programs in the 1990s. Our team from the Jornada Long-Term Ecological Research Program, the US Department of Agriculture Agricultural Research Service Jornada Experimental Range, and the nonprofit Asombro Institute for Science Education navigated changes in K–12 science education to educate more than 200,000 students. The goal of this article is to describe our program's responses to six education trends in order to provide experience-based guidance to others designing and delivering K–12 programs in a shifting science education landscape. We expect our experience will be relevant to others who are trying to scale their outreach programs to larger, more diverse communities while maintaining alignment with changing trends in education at local, state, and federal levels. [ABSTRACT FROM AUTHOR]

The arid and semi-arid (ASA) region of Asia occupies a large area in the middle latitudes of the Northern Hemisphere, of which the main body is the ASA region of Central and East Asia (CEA). In this region, the climate is fragile and the environment is sensitive. The eastern part of the ASA region of CEA is located in the marginal zone of the East Asian monsoon and is jointly influenced by westerly circulation and the monsoon system, while in the western part of the ASA of CEA, the climate is mainly controlled by westerly circulation. To understand and predict the climate over this region, it is necessary to investigate the influence of general circulation on the climate system over the ASA region of CEA. In this paper, recent progress in understanding the relationship between the general circulation and climate change over the ASA region is systematically reviewed. Previous studies have demonstrated that atmospheric circulation represents a significant factor in climate change over the ASA region of CEA. In the years with a strong East Asian summer monsoon, the water vapor flux increases and precipitation is abundant in the southeastern part of Northwest China. The opposite situation occurs in years when the East Asian summer monsoon is weak. With the weakening of the East Asian summer monsoon, the climate tends to dry over the semi-arid region located in the monsoon marginal zone. Recently, owing to the strengthening of the South Asian monsoon, more water vapor has been transported to the ASA region of Asia. The Plateau summer monsoon intensity and the precipitation in summer exhibit a significant positive correlation in Central Asia but a negative correlation in North China and Mongolia. A significant positive correlation also exists between the westerly index and the temperature over the arid region of CEA. The change in the westerly circulation may be the main factor affecting precipitation over the arid region of Central Asia. [ABSTRACT FROM AUTHOR]

Species losses and additions can disrupt the relationship between resident species and the structure and functioning of ecosystems. Persistent human-trampling, on the other hand, can have similar effects through the disruption of biocrusts on surface soils of semiarid systems, affecting soil stability and fixation of carbon and nitrogen. Here, we tested the interactive and synergistic impacts of the exclusion of native mammalian herbivores and the effects of introduced lagomorphs in a semiarid thorn scrub ecosystem, where soils were subjected to two different trampling intensities (i.e., trampled and non-trampled). We postulated that because of their differential habitat use and fossorial activities, with respect to native small mammals, lagomorphs would have strong negative effects on soil structure, biocrust cover, and biocrust bacterial community structure. Our expectations were that changes in biocrust cover in response to trampling where native mammals were excluded, but exotic lagomorphs were present, will spread their impacts on soil chemical and physical features. To test our hypotheses, we measured changes in soil biogeochemical properties in four experimental plots where lagomorphs (L)/small mammals (SM) were experimentally manipulated to exclude them from the plots (−), or let them be present (+). The experimental combinations monitored were: -L/+SM, -L/-SM, +L/+SM, and +L/-SM. Results showed that human-trampling disturbance interacted with the loss of native small mammals and the presence of non-native lagomorphs to cause large changes on biological (i.e., biocrust cover, bacterial and nifH genes abundance), physical (i.e., soil moisture and soil stability) and chemical (i.e., TC and TN) soil features. The relative impacts of trampling disturbance on biological and physicochemical features were strongly influenced by the presence of non-native lagomorphs. For example, larger decreases in biocrust cover and bacterial abundance were observed in treatments without lagomorphs (-L/+SM; -L/-SM). In turn, losses of biocrust cover, in addition to trampling, determined decreases in soil stability in all treatments. These results suggest that non-native lagomorphs surpass the effects of the loss of native small mammals in reducing soil quality and productivity. Therefore, human-trampling has the potential to convert low disturbed soils, as those observed in non-trampled soils in treatments -L/+SM, -L/-SM into poor soils with low biocrusts cover and concomitant low stability, as observed in +L/+SM; +L/-SM treatments. These findings agree with previous observations that different components of global change act in synergic ways in fragile, water-limited environments. Because biological invasions and soil surface disturbance are becoming widespread in dryland regions globally, understanding the long-term consequences of these interactions is essential. [ABSTRACT FROM AUTHOR]

Grazing removes a plant’s aboveground vegetative and reproductive tissues and can modify the soil seed bank, potentially impacting the restoration of preferred species. Knowledge about aboveground vegetation and species composition of soil seed bank and the processes that contribute to vegetation recovery on and surrounding watering points subjected to grazing is lacking. Successful restoration strategies hinge on addressing these knowledge gaps. We assessed the effects of livestock grazing on aboveground vegetation and soil seed bank characteristics along a river bank and surrounding areas subject to different grazing intensities and draw implications for restoration. Plots (50 × 50 m) were established along five transects representing differing levels of grazing intensity. Soil samples were taken from three layers within each plot to determine soil properties and species composition of soil seed bank using the seedling emergence method. Heavy grazing resulted in the disappearance of perennial grasses, a reduction in species diversity and a decrease in soil nutrients with increased soil depth. Overall, the similarity between the extant aboveground vegetation and flora within the soil seed bank was low. The soil seed bank was dominated by herbaceous species and two woody species, suggesting that many woody species are not accumulating in the soil. With increasing soil depth, the seed density and richness declined. Canonical correspondence analyses (CCAs) showed that emerged seedlings from the soil seed bank were significantly influenced by soil carbon, organic matter, total nitrogen, total potassium and soil cation exchange capacity. This finding suggests that current grazing practices have a negative impact on the vegetation surrounding watering points; hence there is a need for improved grazing management strategies and vegetation restoration in these areas. The soil seed bank alone cannot restore degraded river banks; active transfer of propagules from adjacent undisturbed forest areas is essential. [ABSTRACT FROM AUTHOR]

Abstract: Dryland vegetation is limited by water scarcity, and usually appears in the form of sparsely distributed patches within a heterogeneous unvegetated matrix often covered by biological soil crust. Biocrusts usually act as runoff sources, whereas vegetation acts as sinks, reinfiltrating most of the run‐on from upstream biocrusted areas. Alteration of biocrusts by human disturbances or climate change may exert a strong impact on soil erosion, promoting rill formation, increasing flow connectivity between source areas and reducing run‐on inputs to vegetation, strongly affecting ecosystem functioning. The role of biocrust runoff in vegetation productivity, which to date has not been studied in depth, must therefore be understood to predict the consequences of such changes. In this study, we analysed the response of Machrochloa tenacissima to run‐on exclusion for two years and compared it to the performance of plants of the same species receiving runoff from biocrusted source patches. The results showed that plants receiving run‐on had more photosynthetically active biomass, net C uptake rates and water‐use efficiency than plants under run‐on exclusion. Differences between treatments became wider over time, especially after rainfall, when the differences in water availability were greatest. These results lead to the conclusion that run‐on is a crucial water input for dryland vegetation. Any alteration of unvegetated areas usually covered by biocrust may have important effects on vegetation productivity similar to those from changes in precipitation pattern, and would result in a new, eco‐hydrological equilibrium of the whole ecosystem. [ABSTRACT FROM AUTHOR]

Background and aim: Biological soil crusts (biocrusts) play numerous crucial roles in drylands, which comprise over 40% of Earth’s terrestrial surface. Among these key contributions is the fixation of atmospheric nitrogen. Yet, relatively little is known about the N2 fixation capabilities of different lichen species that are found in late successional biocrust communities across drylands globally.Methods: In order to improve our species-specific understanding of biocrust lichen N2 fixation, we collected biocrusts dominated by four common species of lichens - Collema spp., Gyalolechia desertorum, Psora decipiens, and Squamarina lentigera - that represent a range of lichen families and morphological types. Nitrogenase activity of the biocrust community dominated by these lichens was evaluated using the acetylene reduction assay. Additionally, biocrust community composition was assessed using the point-intercept method along transects at varied distances from exposed bedrock.Results: As expected, Collema spp.-dominated biocrusts had the highest rates of nitrogenase activity, with rates up to seven times larger than those of the other three target species. Nitrogen concentrations and carbon:nitrogen ratios of lichen tissue differed among lichen species. However, when the composite biocrust profile was assessed (i.e., biocrust tissue, microbial cells, and mineral soil to a 2 cm depth) these among-species differences in total nitrogen disappeared. Community composition changed according to distance from exposed bedrock, with a higher diversity of lichens closer to the bedrock.Conclusion: Multiple drivers, including climate and land use change, affect biocrust community composition and species-specific functional information, even within a group such as late successional biocrusts, could help in forecasting the potential effects of global change on N2 fixation, and consequently, soil fertility in drylands. [ABSTRACT FROM AUTHOR]

Aims: Biological soil crusts (biocrusts) are widespread in many drylands, where plant growth is limited due to water scarcity. One of their most important functions is the stabilization of the topsoil, particularly in regions with sandy soils prone to desertification. Since the mechanisms playing a role in soil stabilization are poorly understood, this study aims to shed light on the connection between crust stability and different cementing agents.Methods: We measured the penetration resistance and the concentrations of different cementing agents of biocrusts in the Israeli Negev Desert. Structural equation modelling was performed to examine the direct and indirect effects of the variables analyzed and identify variables that are best able to explain the observed patterns of penetration resistance.Results: All observed variables showed a high variability within and between sites. Structural equation modelling revealed that the main parameters explaining penetration resistance are the content of fines and the electrical conductivity, while carbonates and organic carbon only have an indirect effect.Conclusions: Our results suggest that adding silt and clay to (natural or induced) biocrusts is very likely to produce stronger, more stable crusts, which will be more effective in combating desertification and improve their ability to survive trampling by livestock. [ABSTRACT FROM AUTHOR]

To successfully restore drylands, where the scarcity of water is one of the main limiting factors for plant survival, water inputs should be enhanced as much as possible. A specific type of water harvesting that concentrates runoff generated in bare areas upslope (runoff source areas) in a planting area downslope (runoff sink area) is an effective technique that, unlike traditional restoration, does not entail much over-cost. The objective of this study was to analyze the effectiveness of terrain modification techniques, aimed at water harvesting, on a degraded hillslope at a quarry restoration site in an arid area (Almeria, southeast Spain). Two different terrain modifications, to harvest surface runoff and increase soil water retention, were applied at two different hillslope sectors: a) micro-catchments were constructed on the upper section of the hillslope, where the slope gradient was high and b) narrow terracing was done in the middle part of the hillslope, which was characterized by moderate slope gradients. An additional sector, not subjected to terrain modification treatment, was used as a control, and was set in the lower part of the hillslope where the slope gradient was the lowest. A similar planting system was adopted for all experimental treatments; planting was done in 12 fertility island patches. Within each patch 12 different autochthonous plant species were planted in a staggered pattern with 80 cm separation. All plant species, which were from a nursery, were planted within a 1 L container made from organic fibers and containing compost from plant residues enriched with zeolites. To determine the microtopographical modifications required in the analysis of the optimal water harvesting strategy, a digital elevation model, with 0.2 m spatial resolution, was created from the data generated using a terrestrial laser scanner. Runoff flow direction and contribution areas, as well as a set of topographical attributes strongly related to the terrain water retention capacity (wetness index, slope gradient, aspect, USLE LSF factor, etc.), were calculated. Results indicated that micro-catchments had the highest plant survival rates and vegetation coverage values because they were the terrain treatment areas with the largest capacity to retain run-on from contributing areas. The areas without terrain modification (control areas) showed the highest plant mortality. [ABSTRACT FROM AUTHOR]

Arid and semi-arid ecosystems (aridlands) cover a third of Earth's terrestrial surface and contain organisms that are sensitive to low level atmospheric pollutants. Atmospheric nitrogen (N) inputs to aridlands are likely to cause changes in plant community composition, fire frequency, and carbon cycling and storage. However, few studies have documented long-term rates of atmospheric N inputs in aridlands because dry deposition is technically difficult to quantify, and extensive sampling is needed to capture fluxes with spatially and temporally heterogeneous rainfall patterns. Here, we quantified long-term spatial and temporal patterns of inorganic N deposition in protected aridland ecosystems across an extensive urban-rural gradient using multiple sampling methods. We compared long-term rates of N deposition from ion-exchange resin (IER) collectors (bulk and throughfall, 2006–2015), wet-dry bucket collectors (2006–2015), and dry deposition from the inferential method using passive samplers (2010–2012). From mixed approaches with IER collectors and inferential methods, we determined that 7.2 ± 0.4 kgNha −1 y −1 is deposited to protected Sonoran Desert within metropolitan Phoenix, Arizona and 6.1 ± 0.3 kgNha −1 y −1 in nearby desert ecosystems. Regional scale models overestimated deposition rates for our sampling period by 60% and misidentified hot spots of deposition across the airshed. By contrast, the easy-deployment IER throughfall collectors showed minimal spatial variation across the urban-rural gradient and underestimated deposition fluxes by 54%, largely because of underestimated dry deposition in throughfall. However, seasonal sampling of the IER collectors over 10 years allowed us to capture significant seasonal variation in N deposition and the importance of precipitation timing. These results, derived from the longest, spatially and temporally explicit dataset in drylands, highlight the need for long-term, mixed methods to estimate atmospheric nutrient enrichment to aridlands in a rapidly changing world. [ABSTRACT FROM AUTHOR]

Context: Biodiversity is modulated by the spatial structure of the landscape. Thus, landscape metrics can be useful indicators of biota integrity and vulnerability, helping in conservation and management decisions.Objective: We performed the first quantitative analysis of the spatial structure of the Caatinga drylands. We estimated the habitat amount and the fragmentation pattern of this region using a multi-scale perspective.Methods: Using the Brazilian official database of native remnants, we calculated the number and percentage of remaining fragments per size class and we describe how habitat amount changes along the landscape. By simulating different dispersal capacities, we estimated the functional connectivity among remnants. We also calculated the cumulative core area as a function of different edge effect widths.Results: Caatinga is subdivided into 47,100 fragments. Although 91% of them are smaller than 500 ha, 720 fragments are larger than 10,000 ha, corresponding to 78% of the remaining vegetation. Potentially, 95% of the vegetation is accessible to species that can cross 1000 m of matrix. With one kilometer of edge effect, the core area is reduced to a quarter of the remaining vegetation. The habitat amount analyzes reinforced the regional differences in the spatial distribution of the remnants.Conclusions: Caatinga remains well connected for species with moderate and high dispersal capacities. However much of its remaining area is vulnerable to anthropogenic disturbances. Expansion of the protected area network and effective natural resource management to avoid overexploitation of the remnants are key strategies for maintaining the Caatinga biodiversity and its services. [ABSTRACT FROM AUTHOR]

The role of secondary circulations has recently been studied in the context of well-defined surface heterogeneity in a semiarid ecosystem where it was found that energy balance closure over a desert-forest system and the structure of the boundary layer was impacted by advection and flux divergence. As a part of the CliFF ("Climate feedbacks and benefits of semi-arid forests", a collaboration between KIT, Germany, and the Weizmann Institute, Israel) campaign, we studied the boundary layer dynamics and turbulent transport of energy corresponding to this effect in Yatir Forest situated in the Negev Desert in Israel. The forest surrounded by small shrubs presents a distinct feature of surface heterogeneity, allowing us to study the differences between their interactions with the atmosphere above by conducting measurements with two eddy covariance (EC) stations and two Doppler lidars. As expected, the turbulence intensity and vertical fluxes of momentum and sensible heat are found to be higher above the forest compared to the shrubland. Turbulent statistics indicative of nonlocal motions are also found to differ over the forest and shrubland and also display a strong diurnal cycle. The production of turbulent kinetic energy (TKE) over the forest is strongly mechanical, while buoyancy effects generate most of the TKE over the shrubland. Overall TKE production is much higher above the forest compared to the shrubland. The forest is also found to be more efficient in dissipating TKE. The TKE budget appears to be balanced on average both for the forest and shrubland, although the imbalance of the TKE budget, which includes the role of TKE transport, is found to be quite different in terms of diurnal cycles for the forest and shrubland. The difference in turbulent quantities and the relationships between the components of TKE budget are used to infer the characteristics of the turbulent transport of energy between the desert and the forest. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the reproduction of the Whiptail lizard Aspidoscelis tigris maximus from the arid tropical region of the Cape Region of Baja California Sur, Mexico. The study involved sampling of Aspidoscelis from herpetology collections, abdominal incision and left testis removal from ovaries, and analysis of yolk deposition. Information on the breeding of the lizard is also given.

Purpose: The objective of this work was to identify hyperaccumulator plants and evaluate their capacity on copper mine tailings in the Antofagasta Region (Chile), considered one of the most arid in the world.Materials and methods: Two native plant species, Gazania rigens and Pelargonium hortorum, were grown during 11 weeks on mine tailings. The physico-chemical characterization of the mine tailings under study indicated that the substrate required conditioning to support a phytoremediation system. In this respect, organic and inorganic amendments and mycorrizhal fungi were added to the substrate. Three treatments were designed to assess the effects of the amendments through an analysis of variance.Results and discussion: Indicators of plant growth and development were measured weekly, and concentrations of Cd, Cu, Fe, Mn, Pb, Al, and Zn in roots of tailing-grown plants and substrate were measured at the end of the experiment.Conclusions: The results were used to determine the bioconcentration factor (BCF), which demonstrated that both species act as excluders of Fe, Mn, Pb, Al, and Zn. In addition, it was found that both species present characteristics of potential accumulators of Cu. [ABSTRACT FROM AUTHOR]

Abstract: Temporal variation in soil nitrogen (N) availability affects growth of grassland communities that differ in their use and reuse of N. In a 7‐year‐long climate change experiment in a semi‐arid grassland, the temporal stability of plant biomass production varied with plant N turnover (reliance on externally acquired N relative to internally recycled N). Species with high N turnover were less stable in time compared to species with low N turnover. In contrast, N turnover at the community level was positively associated with asynchrony in biomass production, which in turn increased community temporal stability. Elevated CO2 and summer irrigation, but not warming, enhanced community N turnover and stability, possibly because treatments promoted greater abundance of species with high N turnover. Our study highlights the importance of plant N turnover for determining the temporal stability of individual species and plant communities affected by climate change. [ABSTRACT FROM AUTHOR]

Accurate classification of plant functional types (PFTs) reduces the uncertainty in global biomass and carbon estimates. Airborne small-footprint waveform lidar data are increasingly used for vegetation classification and above-ground carbon estimates at a range of spatial scales in woody or homogeneous grass and savanna ecosystems. However, a gap remains in understanding how waveform features represent and ultimately can be used to constrain the PFTs in heterogeneous semi-arid ecosystems. This study evaluates lidar waveform features and classification performance of six major PFTs, including shrubs and trees, along with bare ground in the Reynolds Creek Experimental Watershed, Idaho, USA. Waveform lidar data were obtained with the NASA Airborne Snow Observatory (ASO). From these data we derived waveform features at two spatial scales (1 m and 10 m rasters) by applying a Gaussian decomposition and a frequency-domain deconvolution. An ensemble random forest algorithm was used to assess classification performance and to select the most important waveform features. Classification models developed with the 10 m waveform features outperformed those at 1 m (Kappa (κ) = 0.81–0.86 vs. 0.60–0.70, respectively). At 1 m resolution, lidar height features improved the PFT classification accuracy by 10% compared to the analysis without these features. However, at 10 m resolution, the inclusion of lidar derived heights with other waveform features decreased the PFT classification performance by 4%. Pulse width, rise time, percent energy, differential target cross section, and radiometrically calibrated backscatter coefficient were the most important waveform features at both spatial scales. A significant finding is that bare ground was clearly differentiated from shrubs using pulse width. Though the overall accuracy ranges between 0.72 and 0.89 across spatial scales, the two shrub PFTs showed 0.45–0.87 individual classification success at 1 m, while bare ground and tree PFTs showed high (0.72–1.0) classification accuracy at 10 m. We conclude that small-footprint waveform features can be used to characterize the heterogeneous vegetation in this and similar semi-arid ecosystems at high spatial resolution. Furthermore, waveform features such as pulse width can be used to constrain the uncertainty of terrain modeling in environments where vegetation and bare ground lidar returns are close in time and space. The dependency on spatial resolution plays a critical role in classification performance in tree-shrub co-dominant ecosystems. [ABSTRACT FROM AUTHOR]

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Abstract: The cumulative volume and spatial distribution of large wood (LW) along river corridors (channels and floodplains) reflect interactions between rates and volumes of LW recruitment and channel transport capacity through time. Rivers of the semiarid interior western US can have relatively low‐magnitude disturbances associated with annual snowmelt or relatively high‐magnitude disturbances associated with episodic rainfall runoff, especially following wildfires. We use characteristics of LW from 25 river segments in four regions of New Mexico and Colorado to analyze wood loads and spatial patterns of wood distribution in relation to disturbance regime. High‐magnitude disturbances move LW onto floodplains and create longitudinally nonuniform LW distributions with aggregated (closer together than random) LW pieces and abundant LW jams in the floodplain. Sites with low‐magnitude disturbances have a greater proportion of LW in the channel and much of this wood is within segregated (farther apart than random) jams. These results imply that river management, which typically focuses on LW within channels, should focus on floodplain as well as in‐channel LW in rivers with high‐magnitude disturbances. The results also indicate that the proportions of LW loads in channels versus floodplains can differ significantly among rivers with different disturbance regimes that are otherwise similar in terms of forest type or drainage area. This is particularly relevant to mountainous regions with elevation‐related changes in flow and disturbance regime. River management that reintroduces LW to river corridors will be most effective if it incorporates the mobility and spatial distribution of LW. [ABSTRACT FROM AUTHOR]

Global-scale studies suggest that dryland ecosystems dominate an increasing trend in the magnitude and interannual variability of the land CO 2 sink. However, such model-based analyses are poorly constrained by measured CO 2 exchange in open shrublands, which is the most common global land cover type, covering ∼14% of Earth’s surface. Here we evaluate how the amount and seasonal timing of water availability regulate CO 2 exchange between shrublands and the atmosphere. We use eddy covariance data from six US sites across the three warm deserts of North America with observed ranges in annual precipitation of ∼100–400mm, annual temperatures of 13–18°C, and records of 2–8 years (33 site-years in total). The Chihuahuan, Sonoran and Mojave Deserts present gradients in both mean annual precipitation and its seasonal distribution between the wet-winter Mojave Desert and the wet-summer Chihuahuan Desert. We found that due to hydrologic losses during the wettest summers in the Sonoran and Chihuahuan Deserts, evapotranspiration (ET) was a better metric than precipitation of water available to drive dryland CO 2 exchange. In contrast with recent synthesis studies across diverse dryland biomes, we found that NEP could not be directly predicted from ET due to wintertime decoupling of the relationship between ecosystem respiration (R eco ) and gross ecosystem productivity (GEP). Ecosystem water use efficiency (WUE=GEP/ET) did not differ between winter and summer. Carbon use efficiency (CUE=NEP/GEP), however, was greater in winter because R eco returned a smaller fraction of carbon to the atmosphere (23% of GEP) than in summer (77%). Combining the water-carbon relations found here with historical precipitation since 1980, we estimate that lower average winter precipitation during the 21st century reduced the net carbon sink of the three deserts by an average of 6.8TgC yr 1 . Our results highlight that winter precipitation is critical to the annual carbon balance of these warm desert shrublands. [ABSTRACT FROM AUTHOR]

Managing and restoring faunal diversity across large areas requires an understanding of the roles of connectivity and dispersal in driving community patterns. We sought to determine the influence of connectivity, water regime, water source, geographical location, and dispersal traits on patterns of aquatic invertebrate diversity across a continent‐wide arid biome. We compiled data on freshwater invertebrate assemblages from sites spanning the breadth of arid Australia. Univariate analyses (analysis of variance and rarefaction) revealed that alpha and gamma diversity across sites decreased as latitude increased. Multivariate analyses (ordination and analysis of similarity) revealed that community composition had considerable fidelity to geographic regions. Hydrological connectivity was strongly associated with riverine community composition although water rarely flowed (often less than annually). Hydrologically isolated sites (springs and rockholes) supported communities that were markedly dissimilar to hydrologically connected sites, and to each other. We investigated the influence of dispersal on diversity patterns by examining distance decay relationships for each of four dispersal trait groups (obligate aquatic and passive, weak, and strong aerial dispersers) on the basis of geodesic (shortest path) distances between pairs of sites and Mantel tests. We did not detect clear differences between dispersal traits and distance decay relationships at the continental scale, even for the two groups with the lowest dispersal ability (obligate aquatics and passive dispersers). Our results suggest that the loss of hydrological connectivity from water developments in arid lands (for example, the impoundment of intermittent rivers) is likely to affect macroinvertebrates. However, the exact flow mechanisms underlying such changes remain to be determined. [ABSTRACT FROM AUTHOR]

Remotely sensing recent growth, herbivory, or disturbance of herbaceous and woody vegetation in dryland ecosystems requires high spatial resolution and multi-temporal depth. Three dimensional (3D) remote sensing technologies like lidar, and techniques like structure from motion (SfM) photogrammetry, each have strengths and weaknesses at detecting vegetation volume and extent, given the instrument's ground sample distance and ease of acquisition. Yet, a combination of platforms and techniques might provide solutions that overcome the weakness of a single platform. To explore the potential for combining platforms, we compared detection bias amongst two 3D remote sensing techniques (lidar and SfM) using three different platforms [ground-based, small unmanned aerial systems (sUAS), and manned aircraft]. We found aerial lidar to be more accurate for characterizing the bare earth (ground) in dense herbaceous vegetation than either terrestrial lidar or aerial SfM photogrammetry. Conversely, the manned aerial lidar did not detect grass and fine woody vegetation while the terrestrial lidar and high resolution near-distance (ground and sUAS) SfM photogrammetry detected these and were accurate. UAS SfM photogrammetry at lower spatial resolution under-estimated maximum heights in grass and shrubs. UAS and handheld SfM photogrammetry in near-distance high resolution collections had similar accuracy to terrestrial lidar for vegetation, but difficulty at measuring bare earth elevation beneath dense herbaceous cover. Combining point cloud data and derivatives (i.e., meshes and rasters) from two or more platforms allowed for more accurate measurement of herbaceous and woody vegetation (height and canopy cover) than any single technique alone. Availability and costs of manned aircraft lidar collection preclude high frequency repeatability but this is less limiting for terrestrial lidar, sUAS and handheld SfM. The post-processing of SfM photogrammetry data became the limiting factor at larger spatial scale and temporal repetition. Despite the utility of sUAS and handheld SfM for monitoring vegetation phenology and structure, their spatial extents are small relative to manned aircraft. [ABSTRACT FROM AUTHOR]

Belowground microbial nitrogen (N) processes play key roles in regulating terrestrial ecosystem services such as vegetation production, however, our understanding of their responses to climate change remains limited. We determined patterns and controls of five gross N transformation processes along a typical aridity gradient on the Tibetan Plateau. Potential gross N transformation rates responded diversely to the changing aridity. Both mineralization ( M N , average rate: 2.87 mg N kg −1 soil d −1 ) and ammonium immobilization ( I NH4 , 3.35 mg N kg −1 soil d −1 ) declined as aridity increased. Autotrophic nitrification ( O NH4 , 1.72 mg N kg −1 soil d −1 ) exhibited a bell-shaped pattern along the gradient, with an optimum aridity of 0.53 (1- aridity index (AI)). By contrast, rates of nitrate immobilization ( I NO3 , 0.46 mg N kg −1 soil d −1 ) and dissimilatory nitrate reduction to ammonium ( DNRA , 0.10 mg N kg −1 soil d −1 ) did not respond to the changing aridity. These results suggest that predicted increases in aridity will exert different effects on various soil internal N cycling processes, and thus potentially have profound impact on structure and function of dryland ecosystems. [ABSTRACT FROM AUTHOR]

Climate variability and climate extremes are important climatic determinants of plant growth, species distribution and net primary productivity. A comprehensively quantitative analysis of the sensitivity and resilience of ecosystems to climate variability is vital to identify which regions and species are most in danger in response to future climate change. Here, we proposed an empirical approach to assess the relative sensitivity and resilience of ecosystems to short-term climate variability in the Heihe River Basin (HRB) which is the second largest inland river basin in the northern China and contains ecosystems of semi-arid, arid and hyper-arid types. Based on the monthly time series of normalized difference vegetation index (NDVI), land surface temperatures (LST) and the ratio of actual evapotranspiration to potential evapotranspiration (AET/PET) derived from MODIS sensor from 2000 to 2013, we developed a multiple linear regressive and autoregressive model to determine the sensitivity of NDVI anomalies to climate variability indicated by monthly LST anomalies (temperature variability) and monthly AET/PET anomalies (water variability). We included 1 month time lag of NDVI anomalies in order to reflect ecosystem resilience. We found that the sensitivity and resilience to climate variability were different in the upper, middle and lower reaches of the HRB. Temperature variability dominantly controlled vegetation anomalies in the upper reach, but water variability was the dominant climatic factor in the middle and lower reaches. The different responses of semi-arid to hyper-arid ecosystems to climate variability depended much on the distinct climatic conditions and diverse vegetation types. Ecosystems in drier condition tended to show higher sensitivity to water variability, and ecosystems with colder climate were likely to be more sensitive to temperature variability. The most sensitive vegetation type to water variability and temperature variability in the HRB was crop and meadow, respectively. Grass had been proved to have the lowest resilience. Our research on the sensitivity and resilience of semi-arid to hyper-arid ecosystems is helpful for formulating and implementing adaptation and mitigation strategies in response to climate change. [ABSTRACT FROM AUTHOR]

Soil respiration is a dynamic and fundamental process across all terrestrial ecosystems. However, how physical and biogeochemical factors control seasonal variation and annual rates of soil respiration remains poorly understood. A topographical gradient in a semiarid forest was chosen as the study site to assess how both biogeochemical and physical factors control respiration rates. Parameters measured include soil respiration, litterfall, fine root biomass, soil physical and chemical properties, soil bacteria and archaea gene abundance, ectomycorrhizal fungi abundance and richness, and soil carbon isotope signatures. The results showed that increases in soil temperature and moisture exponentially and linearly promoted root activity, driving seasonal variation of total soil respiration. Seasonal variation of heterotrophic respiration was driven by soil moisture in a second-order polynomial pattern. Autotrophic respiration only contributed to 20% of the total soil respiration, and seasonal variation in the soil respiration rate was driven by heterotrophic respiration. Utilizing soil moisture as a scalar, the values of Q 10 and R 10 in different poisons on the slope indicated soil respiration was controlled by interaction of soil temperature and moisture, and a new transformation of the R 10 function inducing soil moisture was proposed. Along the topographical gradient, the long-term average soil temperature and moisture significantly varied from the top to the bottom of a slope. This variation in physical processes induced differences in plant productivity and biomass accumulation, leading to varying organic matter accumulation across the gradient. The topographical position also induced differences in the size of the soil organic matter aggregates, archaea and bacteria gene abundances, and ectomycorrhizal fungi abundance and richness. The aforementioned parameters are interrelated due to their association with the long-term average soil temperature and moisture, and the interrelation of these parameters ultimately affects annual rates of soil respiration. [ABSTRACT FROM AUTHOR]

Restoration islands are concentrated plantings in strategic locations, created to efficiently use resources to achieve restoration goals. These methods have been used effectively in mesic ecosystems, particularly tropical forests, where the goal of island plantings is often to 'nucleate' across a degraded area, providing a seed source for spread outside the planted area. Here, we consider how an island strategy might be used to achieve restoration goals in dryland ecosystems, where limited resources and large areas of degraded land make restoration extremely challenging. In contrast to more productive areas, spread or 'nucleation' from restoration islands in drylands may not occur or occur more slowly than required by most management time frames. Despite this, small-scale, more intensive island plantings may still be useful for achieving short-term goals, such as weed control, fire management, erosion control, and creation of wildlife habitat. Over the long term, island plantings could serve the same nucleation function as in other ecosystems and serve as repositories for genetic diversity within highly fragmented native systems. Here, we highlight the opportunities for using these high-intensity, targeted planting methods in dryland ecosystems, provide the guidelines for establishing islands to achieve short- and long-term restoration goals, and identify the areas where additional research is needed to understand the value of restoration islands in dryland ecosystems. [ABSTRACT FROM AUTHOR]