Spatial Heterogeneity Of Resources Research Articles

From Barter to Market: an Agent-Based Model of Prehistoric Market Development

AbstractDespite interest in preindustrial markets, archaeological discussions have largely been limited to proposing methods to determine the presence or absence of market exchange in ancient societies. While these contributions are important, methodological limitations have prevented theoretical considerations of the emergence and evolution of marketplaces and market exchange in prehistory. We propose that agent-based modeling provides a window to explore physical conditions and agent behaviors that facilitate the emergence of customary exchange locations and how such locations may evolve into socially embedded institutions. The model we designed suggests that simple bartering rules among agents can generate concentrated locations of exchange and that spatial heterogeneity of resources is the most important factor in facilitating the emergence of such locales. Furthermore, partner-search behaviors and exchange of information play a key role in the institutionalization of the marketplace. The results of our simulation suggest that marketplaces can develop, even with the absence of formalized currency or central planning, as a consequence of collective strategies taken up by agents to reduce exchange partner-search costs and make transactions more frequent and predictable. The model also suggests that, once established as a social institution, marketplaces may become highly conservative and resistant to change. As such, it is inferred that bottom-up and/or top-down interventions may have often been required to establish new marketplaces or relocate marketplaces to incorporate new resources, resolve supply–demand imbalances, or minimize rising economic costs that arise as a result of social, political, and economic change.

Complexity, humility and action: a current perspective on monarchs in western North America.

Recent studies have continued to shed light on the ecology of monarch butterflies (Danaus plexippus) in western North America. These studies have documented a declining overwintering population over several decades, punctuated by unexpected variability in recent years. Understanding this variability will require grappling with the spatial and temporal heterogeneity of resources and risks presented to western monarchs throughout their annual life cycle. Recent changes in the western monarch population further illustrate how interacting global change drivers can create complex causes and consequences in this system. The complexity of this system should inspire humility. However, even recognizing the limits of our current understanding, there is enough scientific common ground to take some conservation actions now.

Unraveling a paradox of habitat relationships: scale-dependent drivers of temporal occupancy-abundance relationships in a cooperatively breeding bird

ContextSpatial occupancy and local abundance of species often positively covary, but the mechanisms driving this widespread relationship are poorly understood. Resource dynamics and habitat changes have been suggested as potential drivers, but long-term studies relating them to abundance and occupancy are rare. In this 34-year study of acorn woodpeckers (Melanerpes formicivorus), a cooperatively breeding species, we observed a paradoxical response to changes in habitat composition: despite a reduction in the availability of high-quality breeding habitat, the population increased considerably.ObjectivesWe investigated the role of annual variation in food availability and long-term changes in habitat composition as predictors of population dynamics.MethodsUsing model selection, we contrasted competing hypotheses on the effects of changing resource availability on occupancy and social group size across three spatial scales: territory, neighborhood, and landscape.ResultsThe increase in abundance was largely determined by the formation of new social groups, driven by a landscape-level expansion of canopy cover and its interaction with neighborhood-level acorn abundance, indicative of long-term increases in overall acorn productivity. Group size increased with neighborhood acorn crop two years earlier but groups were smaller in territories with more canopy cover.ConclusionsOur results indicate that scale-dependent processes can result in paradoxical relationships in systems with spatial and temporal resource heterogeneity. Moreover, the findings support the role of resources in driving changes in abundance and occupancy at a landscape scale, suggesting that colonization of marginal habitat drives the positive occupancy-abundance relationship in this cooperatively breeding species.

A surface water mapping framework combining optical and radar remote sensing and its application in China

Satellite remote sensing provides an efficient pathway to map inland surface water extent across different spatial and temporal scales. However, how to monitor the surface water distribution and its spatiotemporal variability via combining optical and radar remote sensing datasets still faces substantial challenges. In this study, we propose a Seamless Surface Water Mapping Framework (SSWMF) which synergizes both optical (MODIS, Landsat 8, Sentinel-2) and SAR (Sentinel-1) imageries. The validity of SSWMF was first proved over the middle and lower reaches of the Yangtze River of China with abundant lake resources, showing an overall accuracy of 90.72%, and the results indicate that SSWMF can provide surface water map with higher spatial and temporal continuity compared to the Joint Research Centre Global Surface Water dataset. Multi-source validation showed that the SSWMF-derived surface water maps can well capture the temporal fluctuation and spatial heterogeneity of water resources over China, with an overall accuracy of 92.39%. Overall, our results suggest that the proposed water mapping framework is promising and is readily applicable to large-scale water resource management and drought/flood monitoring.

Architectural plasticity in response to population density in Abutilon theophrasti (Malvaceae)

AbstractAn increase in population density may result in the spatial and temporal heterogeneity of resources at scales smaller than an individual, inducing different modular responses at different positions of a plant, or architectural plasticity. To better understand how plants respond to density via architectural plasticity, we conducted a field experiment on an annual species, Abutilon theophrasti. Plants were subjected to three densities and harvested at 50 and 70 days, when each individual plant was separated into different layers vertically from bottom to top with an inter‐layer distance of 10 or 20 cm, before we measured a series of traits per layer and analyzed variations in them among layers, densities, and stages. Increased density reduced variation of traits among layers and had different effects on different layers of modular traits: it increased stem mass in the third to fifth layers (L3–L5) and increased stem diameter in the top layer, leading to an increase in stem density in lower layers and a decrease in stem density in the top layer. In addition, there was an increase in petiole length and mass, lamina size, and leaf number in upper layers, while they decreased in lower layers. Results suggested trade‐offs between upper and lower layers in stem density and leaf traits for plants in a dense population, which were important for keeping most leaves at higher positions to acquire light resources, while saving energy, in concert with the effort of extra stem elongation and the complex plasticity in branch traits.

Spatial autocorrelation and heterogeneity of fish resources in the Xijiang River, Pearl River Basin, China

The Xijiang River, China, is a hotspot for fish biodiversity. Using hydroacoustic data collected from March to June 2016, the spatial autocorrelation and heterogeneity of fish resources were determined using geostatistical methods. We analysed the skewness, kurtosis and coefficient of variation for fish density along the river and also examined the spatial autocorrelation of these data using Moran’s I statistic. Fish density was low in most of the survey areas. Moran’s I values were all positive (z>1.96, p≤0.01), which indicates significant spatial autocorrelation; however, the degree of spatial aggregation varied among months. Hotspot analysis revealed strong local spatial autocorrelation and varying “hot” and “cold spots” in different months. The spatial heterogeneity and directional variation of fish densities were assessed using geostatistical methods and the best-fitting semivariogram was an exponential model. Spatial autocorrelation accounted for 56-75% of the variation in the model, which indicates that fish distribution in the Xijiang River has a clear spatial structure. The results show the applicability of acoustic methods to study the spatial autocorrelation and heterogeneity of fish resources in rivers and provide a reference for the management of fish stocks. Keywords: Fish resources; Hydroacoustic technology; Spatial autocorrelation; Variation characteristics; Xijiang River

Rapid redistribution and long-term aggregation of mulch residues by earthworms (Lumbricus terrestris)

There has been minimal study of how ecosystem engineering anecic earthworms such as Lumbricus terrestris L. may influence the distribution of mulch amendments across the soil surface by collecting residues into middens. The two primary research objectives of this study were: (1) to determine how rapidly earthworms change the surface distribution of mulch following amendment, and (2) to produce a more spatially explicit map of earthworm aggregation of mulch. This study used a microcosm experiment to assess the immediate, short-term impacts of earthworms on recently added mulch at a small scale, and an opportunistic field study of the longer-term impacts of earthworms on the distribution of corn ‘stubble’ mulch in a former agricultural field. In the microcosm experiment, earthworms rapidly redistributed mulch within the first week post amendment, decreasing initial ground cover (15-29% decrease). Over the subsequent five weeks, initial cover continued to decrease (20-45% decrease) as mulch was spread thinly onto adjacent, initially bare soil (49-69% increase). Higher mulch amendment mitigated losses in initial cover. In the field study, earthworms aggregated mulch across the soil surface, collecting 40% of the woody corn residues into 17% of the total area in regularly distributed middens. These results demonstrate the potential for L. terrestris to alter the distribution of mulch rapidly in the first several days and weeks following application and in the longer term over several years, increasing the spatial heterogeneity of soil resources. This physical redistribution has only been minimally investigated and may help inform models of earthworm impacts on various ecological processes and improve soil amendment and residue management in earthworm-occupied soils.

Operational planning of WEF infrastructure: quantifying the value of information sharing and cooperation in the Eastern Nile basin

Integrating the planning of a multi-reservoir system in nexus with agricultural and electricity infrastructure could alleviate security concerns for these resources in regions where demand is growing while water and land scarcity are exacerbated by climate change and anthropogenic pressures. This study focuses on the benefits of resource integration and cooperation in the Eastern Nile basin. To overcome common limitations of equilibrium and soft-linked partial equilibrium models (e.g. high levels of spatial aggregation, non-insightful cooperation scenarios and a lack of heterogeneity), we propose a regional hard-linked WEF-nexus model that explicitly represents resource connectivity networks for water and electricity, and describes heterogeneity in resource availability, production potentials and physical constraints. Using a non-linear operational process, we optimise reservoir operations, water allocations, cropping patterns, electricity mixes and trade quantities on a monthly time-step over multiple years in a receding horizon fashion to maximize economic benefits for each country and regionally. This iterative implementation allows the modelling of operational changes as feedback against exogenous climate disturbances and enables information exchange between upstream-downstream countries. Thus, we describe four different levels of transboundary cooperation with their corresponding constraints and policy objectives. Compared to the reference scenario of unilateral planning, our results indicate an increase in regional economic returns for scenarios in which river flow information is shared between countries (+9%), river flow and trade information are shared (+10%) and WEF resources are coordinated regionally (+15%). These increased returns successively come from an increase in the effectiveness of agricultural water consumption, especially in Sudan, a change in trade patterns for agricultural products and a shift in cropping patterns. These findings underscore the importance of adequate representations of spatial and temporal heterogeneity of resources and their connectivity, as well as the need for a more diverse set of collaboration scenarios to facilitate planning in transboundary river systems.

Fertile islands lead to more conspicuous spatial heterogeneity of bacteria than soil physicochemical properties in a desert ecosystem

The “fertile islands” resulting from discrete plants are important for the structure and function of dryland ecosystems. To understand the spatial heterogeneity of soil biotic and abiotic resources as a result of fertile islands in deserts, soil bacterial and physicochemical profiles were measured at four soil depths (0–10 cm, 10–20 cm, 20–40 cm, and 40–60 cm) in three soil patches (under mid-canopies, at the edge of canopy cover, and in bare soil) around legumes (Hedysarum scoparium shrubs) and non-legumes (Artemisia ordosica shrubs). Unexpectedly, the patches of the two plants showed similar soil abiotic and biotic patterns. Copiotrophs and potential decomposers were enriched under mid-canopies, with more phylogenetically clustered bacterial communities, and co-occurrence networks with lower connectivity and higher modularity than in bare soil. In bare soil, oligotrophs and potential nitrate reducers were enriched. Soil properties showed less conspicuous spatial heterogeneity than bacterial communities. The only soil physicochemical properties enriched under mid-canopies were soil organic matter, dissolved organic carbon, and nitrate; their enrichment was significantly related to bacterial communities. This study elucidates the spatial patterns of soil properties and their relationships, which are observed in fertile islands of desert ecosystems, and provides further insights into the mechanisms of soil nutrient redistribution.

Spatial heterogeneity in resources alters selective dynamics in Drosophila melanogaster.

Environmental features can alter the behaviors and phenotypes of organisms, influencing the dynamics of natural and sexual selection. Experimental environmental manipulation, particularly when conducted in experiments where the dynamics of the purging of deleterious alleles are compared, has demonstrated both direct and indirect effects on the strength and direction of selection. However, many of these studies are conducted with fairly simplistic environments, where it is not always clear how or why particular forms of spatial heterogeneity influence behavior or selection. Using Drosophila melanogaster, we tested three different spatial environments designed to determine if spatial constraint of critical resources influences the efficiency of natural and sexual selection. We conducted two allele purging experiments to (1) assess effects of these spatial treatments on selective dynamics of six recessive mutations, and (2) determine how these dynamics changed when sexual selection was relaxed and spatial area reduced for two of the mutants. Allele purging dynamics depended on spatial environment, however the patterns of purging rates between the environments differed across distinct deleterious mutations. We also tested two of the mutant alleles, and demonstrate sexual selection increased the purging rate.

Understory plant diversity under variable overstory cover in Mediterranean forests at different spatial scales

Mediterranean forest ecosystems are of high conservation value and therefore increasingly managed to restore and promote their natural biodiversity and complexity. The present study aimed to assess plant species diversity of East-Mediterranean conifer forests as affected by overstory cover manipulation at multiple spatial scales. Understanding this interaction in water-limited forest ecosystems is particularly challenging as overstory-understory relations involve both water and light constrains. The experiment was conducted in a mature (40y) planted Pinus halepensis forest in the Jerusalem Mountains of Israel. Understory plant community structure was monitored for five years in sixteen experimental plots (0.5 ha) representing a range of overstory cover levels (leaf area index-LAI = 0–4 m2m−2) created by tree thinning. Light and water availability in the forest understory were monitored using fisheye camera (irradiance), predawn leaf water potential (PLWP) of dominant species and soil water content (SWC) measurements. Plant diversity was measured at increasing spatial scales (grain sizes, 0.01–400 m2), using hierarchical nested sampling. Irradiance and SWC increased with decreasing LAI while PLWP was not affected. Stand-level understory richness (α diversity) increased linearly with decreasing LAI, indicating a consistent, positive resource availability-diversity relationship. The results pointed towards strong dependency of species richness on light availability as compared to its dependency on water availability that was less definite. Understory species composition varied across LAI levels (β diversity at the forest level) indicating species turnover, mainly between annual herbs benefiting from reduced overstory cover vs. woody species benefiting from higher cover. The relationships between overstory cover and understory richness and composition were rank-invariant across grain sizes. These relationships were stronger at the larger (10, 100, 400 m2) compared to the smaller (0.01, 0.1, 1 m2) grain sizes. The 10-m2 grain-size, corresponding to the crown projection area of individual trees, showed the strongest relationship. Observed patterns of overstory cover–understory richness suggest that resource availability, rather than spatial resource heterogeneity, was the main factor shaping understory diversity. Furthermore, grain-size effects on this relationship support “environmental filtering” rather than “resource density” as the main mechanism through which reduced overstory cover promoted understory diversity.'Synthesis and applications’: Our findings demonstrate the importance of overstory cover as a key factor determining plant diversity in water-limited East-Mediterranean forests. We highlight the important role of spatial heterogeneity of overstory cover at both the stand (intra-plot) and forest (inter-plot) scales and support dynamic variable thinning as a management strategy to enhance forest biodiversity and complexity.

Spatiotemporal investigation of the interactive coercing relationship between urbanization and ecosystem services in arid northwestern China

AbstractRapid urbanization has negative effects on ecosystem structure, function, and balance, leading to the loss of ecosystem services (ES) and posing a threat to regional sustainable development. However, the complex interactive coercing relationship between urbanization and ES is not yet fully understood, especially in arid Northwestern China. In this study, we constructed an evaluative framework for urbanization and ES using land cover/land use data and socioeconomic data from 1990 to 2018. We used global and local autocorrelation models to reveal the spatiotemporal interaction between urbanization and ES. The results revealed that the urbanization index increased from 0.06 in 1990 to 0.16 in 2018 in Xinjiang, and urbanization was significantly negatively correlated with ES. With the acceleration of urbanization, the ecosystem services value (ESV) has decreased 2,698.74 × 109 Yuan from 1990 to 2018 (6.62 Yuan = 1 .00 US$). Due to geographical advantages, resource conditions, and land use changes, the spatial relationship of urbanization and ES has obvious heterogeneity. High–low correlation areas are mainly concentrated in the Northern Tianshan Mountain Economic Zone, whereas low–high correlation areas are concentrated in the Kashgar and Hotan Oases in southern Xinjiang. Based on regional geographical conditions and the spatial heterogeneity of resources, diversified ecological, social, and economic balance models should be considered to promote future sustainable urban planning and development.

Resource islands of Salix cupularis facilitating seedling emergence of the companion herbs in the restoration process of desertified alpine meadow, the Tibetan Plateau

Salix cupularis is a common shrub for ecological restoration of the desertified alpine meadow on the Tibetan Plateau. However, the effect of S. cupularis on spatial heterogeneity of soil resources (i.e., resource islands effect) has not been systematically evaluated, and the influence of shrub patches on the rehabilitation of understory herbs has also been unknown. In this study, we randomly selected S. cupularis individuals in the early restoration stage of desertified alpine meadow, where the three native forages (Elymus nutans, Elymus sibiricus and Festuca sinensis) were sown at different microsites around S. cupularis to explore the effects of S. cupularis on soil resources and emergence rates of the native forages. The results showed that S. cupularis significantly increased SWC (soil water content), C (carbon) and N (nitrogen) nutrients (p < 0.01) and enzyme activities (p < 0.05) under canopy compared with the bare land, and the improvement performed better in the topsoil (0–5 cm) than in the subtop-soil (5–15 cm). Moreover, the soil properties were affected significantly by microsites around S. cupularis, resulting in regular changes of SWC, nutrients and enzyme activities in different microsites (Shrub center > Middle of canopy radius > Bare land). In addition, there are significant regression relationships between emergence rates and enriching soil water, C and N nutrients, so the emergence rates of native forages under canopy may be improved significantly with the enriched soil resources, especially for E. nutans. As a result, S. cupularis is a suitable pioneer shrub for the vegetation restoration of desertified alpine meadow on the Tibetan Plateau, because it could not only shape the enrichment of soil resources under canopy, but also facilitate emergence of companion forages in the process of vegetation restoration.

Compost spatial heterogeneity promotes evolutionary diversification of a bacterium.

Spatial resource heterogeneity is expected to be a key driver for the evolution of diversity. However, direct empirical support for this prediction is limited to studies carried out in simplified laboratory environments. Here, we investigate how altering spatial heterogeneity of potting compost—by the addition of water and mixing—affects the evolutionary diversification of a bacterial species, Pseudomonas fluorescens, that is naturally found in the environment. There was a greater propensity of resource specialists to evolve in the unmanipulated compost, while more generalist phenotypes dominated the compost–water mix. Genomic data were consistent with these phenotypic findings. Competition experiments strongly suggest these results are due to diversifying selection as a result of resource heterogeneity, as opposed to other covariables. Overall, our findings corroborate theoretical and in vitro findings, but in semi‐natural, more realistic conditions.

Changes in seasonal and diurnal precipitation types during summer over the upper reaches of the Yangtze River Basin in the middle twenty-first century (2020–2050) as projected by RegCM4 forced by two CMIP5 global climate models

Changes in summer and diurnal precipitation in the upper reaches of the Yangtze River Basin (UYRB) in the middle of the twenty-first century were estimated by RegCM4 with a resolution of 50 km under two representative concentration pathway scenarios. ERA-Interim, CSIRO-MK3.6.0 and MPI-ESM-MR were used as the initial and lateral boundary conditions, and two observation data sets (CN05.1 and CRU) were used to evaluate the precipitation performance. RegCM4 captured the spatial characteristics of summer precipitation in the UYRB during the reference period. Compared with the two observational data sets, the three groups of downscaling results underestimated the precipitation in the eastern part of the basin by 20% and overestimated that in the west by more than 80%. In the middle of the twenty-first century, the total precipitation (TPR) in the UYRB varied significantly from east to west. The multiyear average TPR in the eastern plains was projected to significantly decrease, while it significantly increased in the western mountains. As a major contributor to the TPR in the UYRB, convective precipitation (CPR) differed between the eastern and western regions, especially at night. The TPR changes in the east (decrease) and west (increase) were projected to be strongest in the afternoon. The probability of high-intensity precipitation in the central and western areas will increase, implying a potential increase in the risk of flooding in these areas. The diametric changes in the TPR between the east and west may further exacerbate the spatial heterogeneity of water resources, resulting in large impacts to surface hydrological processes. The spatial variations in precipitation were mainly due to the variation in precipitation mechanisms between the western mountainous area and the eastern basin, while the changes in water vapour transport and atmospheric stability also played a role.

A Non-local Cross-Diffusion Model of Population Dynamics I: Emergent Spatial and Spatiotemporal Patterns.

We extend a spatially non-local cross-diffusion model of aggregation between multiple species with directed motion toward resource gradients to include many species and more general kinds of dispersal. We first consider diffusive instabilities, determining that for directed motion along fecundity gradients, the model permits the Turing instability leading to colony formation and persistence provided there are three or more interacting species. We also prove that such patterning is not possible in the model under the Turing mechanism for two species under directed motion along fecundity gradients, confirming earlier findings in the literature. However, when the directed motion is not along fecundity gradients, for instance, if foraging or migration is sub-optimal relative to fecundity gradients, we find that very different colony structures can emerge. This generalization also permits colony formation for two interacting species. In the advection-dominated case, aggregation patterns are more broad and global in nature, due to the inherent non-local nature of the advection which permits directed motion over greater distances, whereas in the diffusion-dominated case, more highly localized patterns and colonies develop, owing to the localized nature of random diffusion. We also consider the interplay between Turing patterning and spatial heterogeneity in resources. We find that for small spatial variations, there will be a combination of Turing patterns and patterning due to spatial forcing from the resources, whereas for large resource variations, spatial or spatiotemporal patterning can be modified greatly from what is predicted on homogeneous domains. For each of these emergent behaviors, we outline the theoretical mechanism leading to colony formation and then provide numerical simulations to illustrate the results. We also discuss implications this model has for studies of directed motion in different ecological settings.

Stable isotope ratios of emergent adult aquatic insects can be used as indicators of water pollution in the hyporheic food web

Bio-assessment protocols for the subsurface domain of river channels (i.e. hyporheic zone) are scarce despite of the known importance of its ecological function in river ecosystems. The larvae of the Alloperla ishikariana Plecoptera species inhabit the hyporheic zone. Therefore, we examined whether emergent adult A. ishikariana could serve as proxy indicators of the effects of pollution in the hyporheic food web. The study site comprised a 15-km stretch of a gravel bed river in Hokkaido, Japan, from which all invertebrates were collected from the riverbed at a depth of 30–50 cm, and emergent A. ishikariana adults were sampled in riparian zones. Water quality changed gradually along the river owing to the effects of a wastewater treatment plant and surrounding land uses. Nitrogen and carbon stable isotope ratios (SIRs) of epilithic biofilms, hyporheic particulate organic matter (POM), benthic POM, and invertebrates were used to determine the major basal carbon sources, the effects of water pollution on the hyporheic zone, and the trophic positions of dominant invertebrates. Generalized linear (mixed) models were used for statistical testing and modeling. Amphipoda and the larvae of A. ishikariana were considered as top predators and secondary consumers in the hyporheic food web, respectively. The observed similarity in water quality between the hyporheic and surface water suggested a large degree of hydrological exchange between the two zones, and resulted in positive increases in the nitrogen SIRs of hyporheic invertebrates, including A. ishikariana larvae, in proportion to nitrate levels in the surface water. The nitrogen SIRs of A. ishikariana adults were significantly correlated with the nitrogen SIRs of their larvae within the same location (adjusted R2 = 0.78), indicating that emerged adults can provide information on the longitudinal variability of the effects of synthetic nitrogen. In contrast, the carbon SIRs of adults did not predict those of their larvae, possibly reflecting the diverse feeding habitats of larvae. Overall, we demonstrated that adult aquatic insects emerging from the hyporheic zone can be used as indirect indicators of pollution-associated nutrient assimilation as well as the spatial heterogeneity of dietary carbon resources in hyporheic food web.

Human enamel 87Sr/86Sr evidence of migration and land use patterns at Tell Brak, a Late Chalcolithic urban centre in NE Syria

During the Late Chalcolithic 3/4 (c. 3900–3200 BCE), Tell Brak in NE Syria became a large urban centre with central administration, craft specialization and a settlement size of at least 130 ha. 87Sr/86Sr values in enamel of 34 human individuals from Tell Brak representing four temporal subsets were measured and compared against the local background to understand the pattern of migrations and origin of food consumed by inhabitants of the city. The rate of migration from areas with different 87Sr/86Sr background values was constantly low, and there is no evidence of long-distance mobility. Decrease of average 87Sr/86Sr values with time was paralleled by their higher dispersal. Finally, in the last subset representing the end of first urbanization period data are again less variable. All this indicates a rise in spatial heterogeneity of resources to feed the growing population of the expanding city, which was likely caused by a gradual extension of land used for food production.

Impacts of shrub introduction on soil properties and implications for dryland revegetation

The intensive introduction of shrubs to drylands can alter species composition and affect a series of biotic and abiotic processes. This topic has attracted increasing attention by researchers. To assess the response of soil properties to vegetation succession in arid regions of China, we measured the soil water content (SWC) to a depth of 5-m and determined soil properties of surface (0–5 cm) and subsurface (20–25 cm) layers in areas of natural grasses (NGs) and planted shrubs (PSs). The patch size of Caragana korshinskii shrubs resulted in different soil water storage losses (small shrub patch: 206.67 ± 35.58 mm; medium shrub patch: 416.88 ± 35.12 mm; large shrub patch: 588.63 ± 72.00 mm; degraded shrub patch: 740.54 ± 17.00 mm). Shrub cover showed an initial increase but then decreased as shrubs extracted soil water from the deep soil layers (>1 m). The species richness index in the PSs decreased with increasing shrub patch sizes. Surface soil organic carbon (SOC), extractable nitrogen (NH4+-N and NO3−-N), and available phosphorous contents and saturated soil hydraulic conductivity (Ks) in the PSs were all significantly (p < 0.05) lower than those in NGs. Soil particles in the range of 0.002–0.2 mm explained 28.0% and 47.3% of the total variability of these surface indices under NGs and PSs, respectively. The differences in SOC, NH4+-N, NO3−-N, Ks, and field capacity between the surface and subsurface layers declined significantly (p < 0.05). The introduction of shrubs affected the plant community by increasing the spatial heterogeneity of soil resources (e.g. water and nutrient contents). Therefore, the strong feedback between SWC and vegetation succession should be carefully considered when revegetating drylands. The evaluation of regional soil property responses to vegetation succession aids in a better understanding of soil water–vegetation feedback and provides important implications for future revegetation in arid regions.

Mathematical analysis of a spatio‐temporal model for the population ecology of anopheles mosquito

We propose a novel model for the population dynamics of mosquitoes by considering the dispersal states of female mosquitoes of oviposition's cycle and spatial variations. From the modeling perspective, a general functional form of eggs oviposition rate is used including the Malthusian, the Verhlust‐Pearl logistic, the Hassell, and the Maynard‐Smith‐Slatkin functions. From the theoretical and numerical perspectives, the study is done in two steps using the more realistic birth Maynard‐Smith‐Slatkin function. First, we consider an ordinary differential equations model and show that the mosquito‐free equilibrium (MFE) is globally asymptotically stable, whenever the basic offspring number is less than unity. Using a fluctuation argument, we prove that the unique mosquito‐persistent equilibrium (MPE) is globally attractive, whenever exceeds the unity. Moreover, the temporal model undergoes a Hopf bifurcation in the absence of density‐dependent mortality in the aquatic stage of mosquitoes. Second, the temporal model is extended into an advection‐reaction‐diffusion model in order to account for the movement of mosquitoes and their spatial source of heterogeneity. We establish the uniform persistence and the existence of at least one positive steady state whenever the spatial basic offspring number is greater than unity. Finally, for the case study of malaria vector agent (Anopheles mosquito), we construct a nonstandard finite difference scheme that is dynamically consistent with the features of the continuous model to illustrate our results, including the spatial heterogeneity of mosquito resources.