Landscape Compositional Heterogeneity Research Articles

Effects of compositional heterogeneity and spatial autocorrelation on richness and diversity in simulated landscapes.

Landscape structure plays a key role in mediating a variety of ecological processes affecting biodiversity patterns; however, its precise effects and the mechanisms underpinning them remain unclear. While the effects of landscape structure have been extensively investigated both empirically and theoretically from a metapopulation perspective, the effects of spatial structure at the landscape scale remain poorly explored from a metacommunity perspective. Here, we attempt to address this gap using a spatially explicit, individual-based metacommunity model to explore the effects of landscape compositional heterogeneity and per se spatial configuration on diversity at the landscape and patch levels via their influence on long-term community assembly processes. Our model simulates communities composed of species of annual, asexual organisms living, reproducing, dispersing, and competing within grid-based, fractal landscapes that vary in their magnitude of spatial environmental heterogeneity and in their degree of spatial environmental autocorrelation. Communities are additionally subject to temporal environmental fluctuations and external immigration, allowing for turnover in community composition. We found that compositional heterogeneity and spatial autocorrelation had differing effects on richness, diversity, and the landscape and patch scales. Landscape-level diversity was driven by community dissimilarity at the patch level and increased with greater heterogeneity, while landscape richness was largely the result of the short-term accumulation of immigrants and decreased with greater compositional heterogeneity. Both richness and diversity decreased in variance with greater compositional heterogeneity, indicating a reduction in community turnover over time. Patch-level richness and diversity patterns appeared to be driven by overall landscape richness and local mass effects, resulting in maximum patch-level richness and diversity at moderate levels of compositional heterogeneity and high spatial autocorrelation.

Crop diversity and within field multi-species interactions mediate herbivore abundances in cotton fields

Insect herbivore abundances in agricultural fields partly depend on surrounding landscape compositional heterogeneity (e.g., landscape complexity). Landscape complexity can directly (e.g., dilution of host crops) and indirectly (promoting herbivore biocontrol) regulate herbivores in agricultural fields. While much is known about direct (e.g., resource concentration) and indirect effects (i.e., promoting biocontrol) of landscape complexity on herbivore populations, more work is needed to study whether landscape complexity can regulate herbivore populations by mediating within field multi-species interactions among herbivores and their shared natural enemies. During 2019 and 2020, we estimated Bemisia tabaci and Aphis gossypii abundances, their dominant predators (coccinellids, spiders, Orius spp., and Geocoris spp.), and their interaction (using molecular analysis) in 38 cotton fields along a gradient of landscape diversity across Georgia, USA. Within cotton fields, we assessed the effect of predator abundances, their frequency of feeding on herbivores, and the correlation between herbivore abundances (B. tabaci and A. gossypii) on the B. tabaci and A. gossypii abundance. At the landscape scale, crop diversity and different cover types influenced the abundance of B. tabaci and A. gossypii within cotton fields. We found a complex interaction among pests at the field scale, with higher aphid abundance correlated with decreased whitefly abundance. Our results support crop diversification for improving suppression of generalist pests in cotton landscapes through promoting biocontrol and diluting host crop area. Our result further suggests that the landscape complexity effect on whiteflies can indirectly mediate aphid abundance in cotton fields, indicating the importance of within field species interactions.

Biodiversity in landscape mosaics: The roles of local land use and the surrounding landscape on dung beetle assemblages

Abstract Biotic communities in heterogeneous agricultural landscapes can be shaped by both the land use of local patches and the structure of surrounding landscapes. However, studies usually focus on one or the other factor, limiting our ability to propose management guidelines for the conservation of biodiversity in human‐modified landscapes. We used a site‐landscape design and multi‐model inference to assess the effects of land use, landscape structure, and their interactions, on dung beetle assemblages in agricultural landscapes in the Brazilian Cerrado, a biodiversity hotspot. We captured dung beetles in five dominant land uses (savanna, forest, eucalypt, cattle pasture and soybean) and estimated species density, abundance of large and small beetles, and functional richness and dispersion. We measured four landscape structure predictors (savanna cover, forest cover, landscape compositional heterogeneity, and matrix harshness) in circular landscapes around sampling plots. All response variables were affected by land use and by at least one landscape predictor. Relationships between landscape predictors and dung beetle responses were as expected (positive for forest and savanna covers and negative for matrix harshness), except landscape compositional heterogeneity, which had unexpected negative effects. More importantly, land use and landscape predictors interacted in two cases: higher forest cover and lower matrix harshness were related to higher species density and large‐beetle abundance, respectively, but this was mainly observed in eucalypt. Synthesis and applications: To better guide the conservation of mobile organisms in anthropogenic habitat mosaics, we need to consider both landscape characteristics and the land use of local patches. Using this approach, we are able to make some recommendations for the conservation of dung beetles in agricultural landscapes in Cerrado, including the following: (i) ensure, through protection and/or restoration, that natural vegetation patches (even small ones) are interspersed in the agricultural matrix, to increase functional diversity in all land uses and taxonomic diversity in tree plantations, (ii) place eucalypt plantations near forest patches to increase the abundance of sensitive species (forest‐specialists, and some large species); (iii) replace some patches of pasture or soybean with tree plantations, to increase the amount of supplementary habitat for sensitive species.

Avifaunal feeding guilds’ response to landscape compositional heterogeneity and their drivers in forest mosaic, Uttarakhand, India

AbstractThe positive association between landscape compositional heterogeneity and avian species richness is widely accepted, however, birds of different feeding guilds are expected to respond differently because of diverse resource utilisation patterns and ecological tolerance. In the present study, we assessed the response of avian species and avifaunal feeding guilds to landscape compositional heterogeneity and factors associated with their richness. Bird richness and landscape variables, edge density, landscape diversity, and area of land cover types were evaluated at 30 sampling sites in the Terai-Arc landscape of Uttarakhand, India. Univariate regression was performed to investigate the response of birds and various feeding guilds to landscape compositional heterogeneity. Average weighted models of most parsimonious generalised linear regression models (<Δ 2AICc) were developed for various feeding guilds to identify significant predictors of species richness. The richness of overall birds and most feeding guilds, except piscivores and frugivores, responded positively to landscape compositional heterogeneity at variable spatial scales. The scale of effect was largest for carnivore (1.5 km), followed by granivore (1 km), insectivore (0.75 km), and frugi-insectivore, nectarivore, and omnivore (0.5 km). Overall bird species richness was positively associated with landscape diversity, teak plantation, and Sal-mixed forest. The average-weighted models identified edge density and dry riverine forest for frugi-insectivore, barren land and water body for the carnivore, teak plantation, Sal-mixed forest and dry-riverine forest for insectivore, edge density, human habitation/agriculture, teak plantation, barren land and scrubland for granivore, human habitation/agriculture for omnivore and waterbodies for piscivore and frugivore guilds as the significant drivers of species richness. The study concludes that the response to landscape compositional heterogeneity differs among feeding guilds and varies with the spatial scale of analysis. The results of our study are expected to serve as a reference for future studies, exploring the landscape relationship to the avian community in similar environmental conditions.

Landscape structure and local variables affect plant community diversity and structure in a Brazilian agricultural landscape

AbstractThe biodiversity in agricultural landscapes depends on land‐use types, natural elements, and farming intensity. The Brazilian Cerrado is a biodiversity hotspot, however, the native vegetation loss rates have increased in the last years, leading several plant species to extinction risk. Here, we analyze the effects of local (soil fertility and litter amount) and landscape variables (patch shape, habitat amount, compositional heterogeneity, matrix dominance and connectivity) on alpha species richness and diversity, and basal area of different Cerrado vegetation types (savanna, forested savanna, and forest) using linear models and Akaike information criterion. We calculated landscape metrics at different spatial scales for 49 sampling sites in intensive farming landscapes. Woody plant diversity and richness were positively related to soil fertility and landscape compositional heterogeneity at 1500 m spatial scale. Plant richness was negatively related to the patch shape of remnants at 1000 m spatial scale. The effects of litter amount to explain the basal area varied between vegetation types. We found a positive effect in savanna and forested savanna and a negative effect in forest areas. Our findings suggest that the increase of monocultures lead to a decline on plant diversity in the studied landscapes. Also, local variables and the diversity of vegetation types need to be considered to design restoration actions in Cerrado. Sustainable intensification and biodiversity‐friendly production systems may be alternatives to increase compositional heterogeneity, thus favoring plant diversity in Cerrado farming landscapes.Abstract in Portuguese is available with online material.

Organic management and landscape heterogeneity combine to sustain multifunctional bird communities in European vineyards

Abstract Conserving functionally diverse bird communities in European farmland is becoming critical, with no exception for regions of wine production. Management intensification combined with the loss of semi‐natural habitats in wine‐growing landscapes has led to a long‐term decline not only in birds of conservation concern but also in once common insectivores and seed eaters. These declines are expected not only to threaten key ecological services provided by vineyard birds, such as pest or weed control, but also their cultural significance. We analysed how organic management and landscape heterogeneity affected taxonomic and functional diversity of 334 bird communities from 12 regions of the three main wine‐producing European countries (France, Italy and Spain). We further modelled the responses of community‐level metrics measuring mean habitat specialization and bird song attractiveness to humans, as well as cumulative abundances of functional insectivores, seed and grape eaters to account for individual avian functions. We found that organic viticulture enhanced bird functional diversity and individual functions, but that its positive effect partially depended on grass cover management in the inter‐rows and landscape heterogeneity. Woodland cover and landscape compositional heterogeneity increased both taxonomic and functional diversity of bird communities, as well as functional insectivory. Landscape configurational heterogeneity also increased functional diversity and mean song attractiveness of bird communities. Overall, both bird diversity and functions were enhanced by higher landscape heterogeneity, especially in organic vineyards. However, mean habitat specialization decreased with woodland cover and configurational heterogeneity, meaning that open habitat specialists preferred more even landscapes with high vineyard cover. Synthesis and applications. Our study highlights the benefits of combining organic management and partial grass cover at the field level and promoting interfaces between vineyards and semi‐natural habitats at the landscape level to sustain multifunctional bird communities in wine‐producing European countries.

Landscape context but not management strategies affects the diversity of native and exotic semi-natural vegetation in Mediterranean agroecosystems of Central Chile

Current knowledge on the effects of farming type and landscape heterogeneity on plant diversity is biased towards temperate ecosystems in Europe and North America, while there is a paucity of information for the Mediterranean agroecosystems. In particular, the Mediterranean region of Central Chile concentrates most of the country's population and have experienced the greatest agricultural changes leading to the replacement of native vegetation remnants by monocultures and livestock ranching. This study aims to analyse the effects of farming type (organic versus conventional) and landscape heterogeneity (composition and configuration), in addition with local habitat type, on semi-natural vegetation. We addressed these effects considering both native and exotic herbs at 14 fruit farms and landscape metrics at three spatial scales (0.5, 1 and 2 km). In total, we recorded 32 native and 103 exotic plant taxa. Farming type and local habitat type did not influence the diversity of native and exotic herbs. We showed that increasing landscape compositional heterogeneity (i.e. percentage of grasslands, of woody elements) increased alpha and beta diversity of native herbs at the scale of 0.5 km and 2 km. Gamma diversity of native plants responded negatively to decreasing landscape configurational heterogeneity (i.e. largest patch index) at the scale of 0.5 km. Exotic specis did not respond to landscape context. Our findings suggest that semi-natural elements in the surrounding landscape of fruit farms particularly benefited native plant species. Therefore, agri-environment schemes designed to preserve native biodiversity in Mediterranean agroecosystems must promote landscape heterogeneity through the conservation of semi-natural elements at multiple spatial scales.

The effects of agricultural landscape composition and heterogeneity on bird diversity and community structure in the Chengdu Plain, China

Farmland is one of the most important ecosystems in the world, providing foods and habitats for humans as well as many wild animals. However, biodiversity in farmlands has been substantially impacted by the intensification of agriculture and changes in landscape. Increasing either the area of natural and semi-natural habitat or the proportion of biodiversity-friendly crops could potentially mitigate the decline of biodiversity, but at the same time they would affect the agricultural economic output and were not widely applied. To date, some studies have focused on whether crops or cropland heterogeneity has a positive impact on biodiversity, but the results were inconsistent and it is difficult to summarize the relationship between farmland heterogeneity and farmland biodiversity in general. Meanwhile, few papers have studied the differences in bird diversity among small-scale agriculture in China. We conducted a year-long field survey on the Chengdu Plain to explore the relationships of landscape composition and the heterogeneity of cropland and non-cropland with bird diversity and community structure across different seasons. Using generalized linear models (GLM) and generalized least squares (GLS) for data analysis, our results showed that bird diversity is positively correlated with natural woodlands but negatively correlated with commercial forests. Both crop and non-crop landscape compositional heterogeneity affect bird diversity and community structure, especially during the non-breeding season, as many high-altitude birds come down to the farmland for foraging. Both bird diversity and community structure are influenced by cropland configurational heterogeneity, but seldomly influenced by non-cropland configurational heterogeneity. We propose to maintain the area of natural habitat and increase the area of mixed commercial forests by replacing monocultures. Diversified crop and non-crop types with a reasonable layout could conserve farmland biodiversity and maintain the stability of local ecosystems. More research on landscape heterogeneity in small-scale agriculture is needed to provide better understanding of the relationship between the agricultural landscape and bird diversity.

Effects of landscape heterogeneity and breeding habitat diversity on rice frog abundance and body condition in agricultural landscapes of Yangtze River Delta, China.

Amphibians play a key role in structuring biological assemblages of agricultural landscapes, but they are threatened by global agricultural intensification. Landscape structure is an important variable influencing biodiversity in agricultural landscapes. However, in the Yangtze River Delta, where a "farmland-orchard-fishpond" agricultural pattern is common, the effects of landscape construction on anuran populations are unclear. In this study, we examined the effects of agricultural landscape parameters on the abundance and body condition of the rice frog (Fejervarya multistriata), which is a dominant anuran species in farmland in China. Employing a visual encounter method, we surveyed rice frog abundance for 3 years across 20 agricultural landscapes. We also calculated the body condition index (BCI) of 188 male frog individuals from these agricultural landscapes. Landscape variables, comprising landscape compositional heterogeneity (using the Shannon diversity index of all land cover types except buildings and roads), landscape configurational heterogeneity (using landscape edge density), breeding habitat diversity (using the number of 5 waterbody types available as breeding habitats), and areas of forest were also measured for each 1-km radius landscape. We found that the amount of forest in each agricultural landscape had a significant positive relationship with rice frog abundance, and breeding habitat diversity was positively related to the BCI of male rice frogs. However, body condition was negatively impacted by landscape configurational heterogeneity. Our results suggested the importance of nonagricultural habitats in agricultural landscapes, such as waterbodies and forest, to benefit rice frog population persistence.

Consequences of Spatial Heterogeneity of Forest Landscape on Ecosystem Water Conservation Service in the Yi River Watershed in Central China

Forest landscapes, especially their spatial heterogeneity, play a key role in sustaining the ecosystem water conservation service in a watershed. However, this domain has not been fully investigated. This study uses the Yi River watershed in central China as the study site. We calculated the water conservation amounts of different forests through the water balance method and quantified the landscape spatial heterogeneity of forests using landscape metrics. Then we ran correlation analysis to find the correlating relationship between the landscape spatial heterogeneity of forests and the ecosystem water conservation service. We finally applied a redundancy analysis to explore the respective influencing strength of the landscape compositional heterogeneity and configurational heterogeneity of forests on the water conservation service. Results indicate that: (1) The area proportion of different forests has a significant impact on the spatial distribution of the water conservation service. When mixed forest is dominant and its area proportion is much greater than that of other forests, the generation of the water conservation service can be best enhanced; (2) Changes of the landscape compositional heterogeneity and configurational heterogeneity of forests can affect the water conservation service to different degrees. In particular, the landscape spatial heterogeneity of mixed forest has the greatest impact on this ecosystem service; (3) The landscape configurational heterogeneity of deciduous broad-leaved forest and mixed forest has a greater impact on the water conservation service than the landscape compositional heterogeneity, whereas that of evergreen needle-leaved forest has the opposite effect. In general, appropriately adjusting the combination and configuration of different forests in a watershed can effectively promote the generation of the ecosystem water conservation service. This study provides a scientific basis for future forest management with a view to improving the landscape sustainability of forests.

Bee communities in forestry production landscapes: interactive effects of local-level management and landscape context

Land-use change is a key driver of pollinator declines worldwide. Plantation forests are a major land use worldwide and are likely to expand substantially in the near term, especially with projected cellulosic biofuel production. But little is known about the potential local and landscape-scale impacts of plantation forestry on bees, the most important group of pollinators worldwide. We studied the effects of local management, landscape context, and their interaction on bee abundance and species richness in the southeastern US, in pine plantations and other nearby land uses. We sampled bee communities using aerial netting and pan trapping in 85 sites over 3 years. We found that both landscape composition and configuration are important factors for bee diversity and abundance at the landscape scale, though interestingly many landscape factors showed contrasting directional responses for diversity versus abundance. Removing the four most common species, all in the genus Lasioglossum (and which comprised ~ 45% of all specimens) largely harmonized the results between diversity and abundance. In addition, we found several interactions between local management and landscape factors, all consistent with the idea that compositional heterogeneity and configurational complexity are more important for bee communities in poorer-quality local habitat. Our results underscore the importance of considering (1) both landscape configuration and composition in analyses, and (2) interactions between local management and landscape factors. The interactions in particular highlight the need to maintain landscape compositional heterogeneity and configurational complexity, particularly in heavily managed landscapes.

Dung beetle richness decreases with increasing landscape structural heterogeneity in an African savanna‐agricultural mosaic

Abstract The landscape heterogeneity hypothesis posits that increasing variance of land cover types in agricultural landscapes will increase landscape level biodiversity. This hypothesis, however, does not detail which component of landscape structural heterogeneity, compositional (the type and amount) or configurational (the shape and arrangement) has the greatest influence on biodiversity and at what spatial scale(s). We investigated how dung beetle (Scarabaeidae) alpha‐diversity responded to landscape structural heterogeneity at a variety of spatial scales in an agricultural mosaic‐landscape in north‐eastern Swaziland. We also compared the effect of these components to the effect of variation in the amounts of major land‐cover types in the landscape and plot level vegetation structure. We used pitfall traps to sample the dung beetle community along a gradient of heterogeneity and used linear mixed effects models to compare the effect of each component on dung beetle richness and Shannon diversity at four separate spatial scales (i.e. 1‐,1.5‐, 2‐ & 3‐km). Land‐cover diversity and number of patches represented compositional and configurational landscape heterogeneity respectively. Landscape compositional heterogeneity was negatively correlated with dung beetle richness at the 1.5‐km and 2‐km spatial scales. The percentage savanna in the landscape was positively correlated with dung beetle richness at the 3‐km and 2‐km scales. Landscape level heterogeneity may enhance diversity of some taxonomic groups, but this was not the case for dung beetles in a southern African savanna. The best way to maintain their diversity is to create or maintain large continuous blocks of savanna while limiting intensive agriculture.

Effects of peat swamp logging and agricultural expansion on species richness of native mammals in Peninsular Malaysia

The biodiversity inhabiting tropical peat swamp forests in Southeast Asia is currently threatened by commercial logging and agricultural expansion. The occurrence of mammals in such forests is often poorly known and the factors influencing their occurrence in these ecosystems have rarely been quantified. We aim to determine the key habitat and landscape drivers of mammal species richness in fragmented peat swamp reserves. We conducted camera trap surveys in the North Selangor Peat Swamp Forest (NSPSF), the last remaining area of peat swamp forest on the west coast of Peninsular Malaysia. We also measured vegetation structure and landscape metrics to investigate the relationship between these factors and mammal richness. We recorded a total of 16 mammal species from 45 sampling sites using camera traps located in peat swamp forest reserves. Mammal species richness increased with the abundance of large trees and distance away from roads. Species richness decreased significantly with canopy cover and height, the abundance of fallen trees, the abundance of forest palms and saplings, distance away from rivers, and a measure of landscape compositional heterogeneity. Our findings underscore the high conservation value of logged peat swamp forests and the urgent need to halt further deforestation. We recommend: (1) protecting riparian habitat; (2) avoiding further forest conversion particularly areas supporting large trees into oil palm plantations; and (3) limiting road development within and around the NSPSF.

Landscape heterogeneity at multiple spatial scales enhances spider species richness in an agricultural landscape

AbstractLandscape supplementation, which enhances densities of organisms by combination of different landscape elements, is likely common in heterogeneous landscapes, but its prevalence and effects on species richness have been little explored. Using grassland‐dwelling spiders in an agricultural landscape, we postulated that richness and abundances of major constituent species are both highest in intermediate mixtures of forests and paddy fields, and that this effect derives from multi‐scale landscape heterogeneity. We collected spiders in 35 grasslands in an agricultural landscape in Japan and determined how species richness and abundances of major species related to local and landscape factors across different spatial scales. We used a generalized linear model to fit data, created all possible combinations of variables at 15 spatial scales, and then explored the best models using Akaike's information criterion. Species richness showed a hump‐shaped pattern in relation to surrounding forest cover, and the spatial scale determining this relationship was a 300–500‐m radius around the study sites. Local variables were of minor importance for species richness. Abundances of major species also exhibited a hump‐shaped pattern when plotted against forest cover. Thus, a combination of paddy fields and forests is important for enhancement of grassland spider species richness and abundance, suggesting habitat supplementation. The effective spatial scales determining abundances varied, ranging from 200 to >1000 m, probably representing different dispersal abilities. Landscape compositional heterogeneity at multiple spatial scales may be thus crucial for the maintenance of species diversity.