A structural equation modeling approach for formalizing and evaluating ecological integrity in terrestrial ecosystems

Ecological integrity is a functional property that integrates habitat functions and species information for maintaining key ecological interactions in predator-prey systems. As a functional property, ecological integrity can be modeled as a latent concept from observable spatial attributes that measure the ecosystem's capacity to provide suitable habitat conditions for apex predators. Ecological integrity is a tri-dimensional concept that stems from “stable”, “concurrent” and “intact” conditions. A theoretical framework and a methodology is presented here for modeling ecological integrity from observable attributes (as GIS layers) to obtain a spatial representation of the integrity condition. From a theoretical framework, the ecological integrity concept is obtained with a structural equation modeling approach, where several other latent variables are obtained for characterizing a hierarchical network of spatial information. Later on, these observable attributes, and several latent modeled variables are translated into sources of geographic information that can be used to monitor changes in the natural remnant areas due to human impacts. When examining the direct, indirect and total effects of habitat loss and fragmentation on ecological integrity, spatial intactness (e.g., the amount of remnant habitat and connectivity) and stability (resistance in the interaction network and mobile links) are the attributes more affected by the pathway effects. The balance of the formative parameters obtained for the model supports the idea that ecosystems that have a high degree of integrity should maintain a high level of stability, self-organization and naturalness. These attributes are achieved when spatial habitat intactness and species interactions are maintained.     

挠力河流域平原区湿地景观完整性评价

探讨一种景观完整性评价方法对湿地管理和保护非常重要.利用遥感和GIS技术,选择10个指标构建景观完整性指数,对挠力河流域平原区开展景观完整性评价.结果显示,1950年挠力河流域洪泛平原中的湿地景观完整性远好于2005年;人类活动影响越强的区域湿地景观完整性越差;2005年仅河岸带湿地景观比其它区域具有较好的景观完整性.由于景观完整性指数包涵了必要的景观结构和功能完整性特征信息,对评价景观尺度生态完整性,诊断生态受损区域,保护、恢复和管理湿地具有重要作用.     

Sequential movement into coastal habitats and high spatial overlap of predator and prey suggest high predation pressure in protected areas

In theory, predators should attempt to match the distribution of their prey, and prey to avoid areas of high predation risk. However, there is a scarcity of empirical knowledge on predator and prey spatial use when both are moving freely in their natural environment. In the current study, we use information collated on a predators’ diet, its population structure, as well as predator and prey relative abundance, and track the movements of predator and prey simultaneously to compare habitat use and evaluate predation pressure. The study was conducted in elasmobranch protected areas of coastal Tasmania, Australia. The species considered were the broadnose sevengill shark Notorynchus cepedianus, the apex predator in the area, and five chondrichthyan prey species. Notorynchus cepedianus and its prey show similar seasonality in the use of these coastal areas: more abundant in warmer months and absent in winter. Predator and prey also showed high spatial overlap and similar habitat use patterns. These similar movement patterns of predator and prey combined with the additional ecological information (diet, population structure of predator, relative abundance of predator and prey) suggests that N. cepedianus move into coastal areas to exploit seasonally abundant prey. Also, while in protected areas, chondrichthyans are subjected to high predation pressure. Overall, results illustrate the value of simultaneously recording and integrating multiple types of information to explore predator–prey relationships and predation pressure.     

Habitat preferences of sympatric sandgrouse during the breeding season in Spain: a multi-scale approach

Predictive species’ distribution models may answer ecological questions about habitat selection, co-occurrence of species and competition between them. We studied the habitat preferences and segregation of two sympatric species of declining sandgrouse, the black-bellied sandgrouse (Pterocles orientalis) and the pin-tailed sandgrouse (Pterocles alchata), during the breeding season. We developed predictive models that related sandgrouse presence to environmental variables at three different spatial levels: large geographical, landscape and microhabitat scales. At the large geographical scale, differences between sandgrouse distributions, in the Iberian Peninsula, seem to be explained mainly in terms of bioclimatology: pin-tailed sandgrouse appear to be a more thermophilous species and occupy warmer sites usually located in flatter areas. At the landscape spatial level, in those areas that exhibit environmental conditions allowing for both species’ co-existence at a large geographical scale, black-bellied sandgrouse appear to be more tolerant to environmental variation than pin-tailed sandgrouse. At the microhabitat level, however, differences between species could be related to different flocking behaviour as a consequence of different sensitivities to vegetation structure and predators. Thus, the observed spatial distribution patterns are the result of different ecological factors that operate at different spatial levels. Conservation guidelines for these species should therefore consider their habitat preferences at large geographical, landscape and microhabitat scales.     

An indicator system to assess ecological integrity of managed forests

Ecological integrity of managed forests includes the ability of an ecosystem to support a community of organisms with a similar species composition and functional organization as found in nearby natural systems. We developed an indicator system for ecological integrity based on simulated natural disturbance and indicator species to test if forest condition and habitat in managed forests are similar to that found or expected in natural systems. We then applied the method in an area of the boreal forest (Ontario, Canada) where the objective of Ontario's strategic forest management planning approach is, in part, to conserve ecological integrity through the emulation of the natural disturbance process. Forest condition controls the supply of habitat to support the diversity of native organisms, and historically in boreal forests the natural disturbance process drove forest condition. We selected indicators of forest condition (landscape pattern and compositional mosaic) and habitat function (occupancy rates for a broad range of forest birds), and applied our assessment system to test whether indicators of forest condition and habitat function reflect outcomes expected if natural disturbance processes were successfully emulated. We collected occupancy data in natural and managed forest disturbance types using autonomous acoustic recorders, applied occupancy/detection modeling to estimate corrected occupancy rates (ψ), and then tested for differences in ψ between disturbance types. Some indicators of forest condition were within the range expected under natural disturbance, but we found relatively less old conifer, more young deciduous and greater edge density in managed forests relative to forests of natural disturbance origin. Most species (11 of 14) occurred with equal ψ in habitat originating from the two disturbance types. Brown creeper (Certhia americana), bay-breasted warbler (Mniotilta varia) and red-eyed vireo (Vireo olivaceus) differed between disturbance types. Brown creeper uses older conifer and occurred at lower rates in managed forest, while red-eyed vireo uses a range of deciduous forest ages, and occurred at higher rates in managed forest. Differences in quantity and/or quality of specific habitat types likely explain the responses. The results suggest what directional changes in the forest pattern and compositional mosaic would improve ecological similarity with natural systems, but also indicate what further research is required. We believe this approach to assessing ecological integrity can be adapted to study the effectiveness of conservation management strategies in other systems, and will contribute to adaptive management approaches and evidence-based policy development.     

Ecological traps and species distribution models: a challenge for prioritizing areas of conservation importance

Species distribution models analyse how species use different types of habitats. Their spatial predictions are often used to prioritize areas for conservation. Individuals may, however, prefer settling in habitat types of low quality compared to other available habitats. This ecological trap phenomenon is usually studied in a small number of habitat patches and consequences at the landscape level are largely unknown. It is therefore often unclear whether the spatial pattern of habitat use is aligned with the behavioural decisions made by the individuals during habitat selection or reflects actual variation in the quality of different habitat types. As species distribution models analyse the pattern of occurrence in different habitats, there is a conservation interest in examining what their predictions mean in terms of habitat quality when ecological traps are operating. Previous work in Belgium showed that red-backed shrikes Lanius collurio are more attracted to newly available clear-cut habitat in plantation forests than to the traditionally used farmland habitat. We developed models with shrike distribution data and compared their predictions with spatial variation in shrike reproductive performance used as a proxy for habitat quality. Models accurately predicted shrike distribution and identified the preferred clear-cut patches as the most frequently used habitat, but reproductive performance was lower in clear-cut areas than in farmland. With human-induced rapid environmental changes, organisms may indeed be attracted to low-quality habitats and occupy them at high densities. Consequently, the predictions of statistical models based on occurrence records may not align with variation in significant population parameters for the maintenance of the species. When species expand their range to novel habitats, such models are useful to document the spatial distribution of the organisms, but data on population growth rates are worth collecting before using model predictions to guide the spatial prioritization of conservation actions.     

Landscape structure and management regime as indicators of calcareous grassland habitat condition and species diversity

This study investigates the importance of spatial landscape characteristics and habitat management on the condition of calcareous grassland in the North Down Natural Area, Kent UK. We used a digitised map of the study area containing shapefiles of all the habitats including 82 patches of calcareous grassland together with management information for each patch and data on the presence and abundance of a range of calcareous grassland indicator plant species. We defined habitat condition by presence of indicator species and used classification trees to generate models with rules for predicting habitat condition from the landscape spatial characteristics and management information. We also applied the same method to investigate the factors affecting presence or diversity of three ecological groups of positive indicator species and dominance of a negative indicator species. All the models except one showed good classification accuracy and high kappa statistic. Favourable habitat condition was predicted by presence of different types of grazing management, presence of woodland around patches of calcareous grassland and shape complexity. These results indicate that calcareous grassland in favourable condition is management-dependent but also located in less intensively managed landscapes. Unfavourable habitat condition was predicted by threat factors such as lack of management and high incidence of arable or improved grassland around patches of calcareous grassland, indicating nutrient enrichment and habitat degradation. Some of these factors also predicted high diversity of the different ecological species groups. The value of this method for predicting habitat condition and species diversity from baseline ecological data for conservation monitoring at the landscape level is emphasised.     

农田景观格局对害虫天敌生态控害功能的调控作用

如何提升农田景观的生态服务功能是当前景观生态学和害虫防治学的前沿研究热点.基于区域农田景观格局可显著调节植物-植食性昆虫-天敌之间相互关系的理论基础,本文系统概括总结了农田景观格局及其变化对农田重要天敌多样性与生态控害功能的影响.从不同天敌类群的角度,分析了农田景观格局对捕食性天敌、寄生性天敌、有益微生物及其生态控害功能的调控作用.同时,对优化农田景观作物布局、采取合理的植被生境管理策略进行了展望.本文可为应用植被生境管理提升农田景观中天敌的生态系统服务功能提供参考,进一步促进区域生态农业响应"化学农药减量施用"的战略目标提供理论支撑.     

Landscape transformation alters functional diversity in coastal seascapes

The ecological impacts of landscape modification and urbanisation have transformed the composition of plant and animal assemblages, and altered the condition of ecosystems globally. Landscape transformation influences the spatial distribution of species and ecological functions by selecting for generalist species with wide ecological niches, which can adapt to opportunities in highly-modified environments. These effects of landscape modification can shape functional diversity on land, but it is not clear whether they have similar functional consequences in the sea. We used estuaries as a model system to test how landscape transformation alters functional diversity in coastal seascapes, and measured how variation in level of urbanisation, catchment modification and habitat loss influenced fish diversity across thirty-nine estuaries in eastern Australia. Fish were surveyed with baited remote underwater video stations and functional diversity was indexed with three metrics that describe variation in the functional traits and niche space of assemblages. The extent of landscape transformation in the catchment of each estuary was associated with variation in the functional diversity of estuarine fish assemblages. These effects were, however, not what we expected as functional diversity was highest in modified estuaries that supported a large area of both urban and grazing land in their catchments, were bordered by a small area of natural terrestrial vegetation and that contained a moderate area of mangroves. Zoobenthivores and omnivores dominated assemblages in highly-modified estuaries, and piscivorous fishes were common in natural waterways. Our results demonstrate, that the modification and urbanisation of ecosystems on land can alter functional diversity in the sea. Intense landscape transformation appears to select for abundant generalists with wide trophic niches, and against species with specialised diets, and we suggest that these changes might have fundamental consequences for ecosystem functioning in estuaries, and other highly modified seascapes.     

Landscape-scale impacts of transportation infrastructure on spatial dynamics of two vulnerable ungulate species in Ghamishloo Wildlife Refuge,Iran

Development of roads through protected areas can have deleterious effects on natural habitats containing species of conservation concern. During the past decades road construction has affected many former remote areas and led to fragmentation and isolation of wildlife populations. The present study focuses on the ecological impacts of Isfahan's West Freeway, which passes through Ghamishloo Wildlife Refuge; an IUCN category IV protected area, in Isfahan Province. The two key affected species, both classified as vulnerable by IUCN, the goitered gazelle (Gazella subgutturosa subgutturosa) and the wild sheep (Ovis orientalis isphahanica) were subject to impact analyses. We used habitat evaluation procedure (HEP) as a habitat-based impact assessment methodology which considers habitat quality and quantity. Habitat quality was measured as habitat suitability index (HSI) for each species. By literature review and field observations, five variables defining habitat suitability were identified and suitability maps for both species generated. Habitat units (HUs) were derived from multiplying the HSI for each species by the habitat area before and after freeway construction. The results showed that due to the construction of the freeway, about 14% of the HUs for goitered gazelle and about 9% of the HUs for wild sheep were lost. In addition, for quantifying landscape pattern change due to freeway construction, various landscape metrics were calculated for the species distribution polygons for two times before and after freeway construction. Results obtained through quantifying landscape metrics showed that mean nearest neighbor (MNN) and number of patches (NP) metrics increased. On the other hand, CONTAG metric decreased in both goitered gazelle and wild sheep distribution polygons, demonstrating the negative effect of freeway on these species distribution polygons integrity. According to the results of this study, mitigation and compensation activities should be considered in Ghamishloo Wildlife Refuge. Our study demonstrated that HEP method combined with quantifying landscape metrics might provide a powerful tool for assessing ecological impact of technical infrastructures on populations of far-ranging species of conservation concern.     

Forest cover and level of protection influence the island-wide distribution of an apex carnivore and umbrella species,the Sri Lankan leopard (<Emphasis Type="Italic">Panthera pardus kotiya</Emphasis>)

Apex predators fulfil potentially vital ecological roles. Typically wide-ranging and charismatic, they can also be useful surrogates for biodiversity preservation, making their targeted conservation imperative. The Sri Lankan leopard (Panthera pardus kotiya), an endangered, endemic sub-species, is the island’s apex predator. Of potential keystone importance, this carnivore also fulfills “umbrella” and “flagship” criterion and is of high ecological and existence value. Apex predator conservation requires identifying factors underlying distribution, so we used multi-scale maximum entropy modelling with sampling bias correction to investigate a broad suite of relevant ecological, climatic and anthropogenic factors in order to identify potentially suitable leopard habitat. Presence locations were determined from 15 years of surveys, observations and verified reports. The best bias correction procedure and scale were uncertain, so we employed a novel method of using information from all models across analyses to determine top models and identify influential variables. Leopard presence was most strongly linked to the landscape proportion encompassed by Protected Areas strictly limiting human presence, with more porous Protected Areas less influential. All three forest composition and configuration metrics investigated (area weighted mean patch size, patch density and forest connectivity) were influential, with increased patch size and higher connectivity predicting better habitat suitability for leopards. Habitat suitability was also better where cropland extent and urban patch size were small. In summary, ground-level protection and natural forest extent and connectivity are of profound importance to Sri Lankan leopard distribution and are key factors in ensuring the ecological integrity of the island’s faunal assemblages.     

Relationships between patterns of habitat cover and the historical distribution of the Marsh Tit,Willow Tit and Lesser Spotted Woodpecker in Britain

Spatial analysis of remotely-sensed land cover data in conjunction with species distribution atlases can reveal large-scale relationships between animal taxa and their habitats. We investigated the historical distribution patterns of three declining woodland birds, the Marsh Tit (Poecile palustris), Willow Tit (Poecile montana) and Lesser Spotted Woodpecker (Dendrocopos minor), in relation to a parsimonious landscape metric for describing habitat availability in Britain. Bird distributions were derived from two field-based atlas surveys, conducted in 1968–1972 and 1988–1991, and used to classify areas of the landscape for each species as retained, lost or gained between atlas periods, or unoccupied in both. We used remotely-sensed land cover data from 1990 to compare percentage habitat cover between landscape areas classified by bird occupation, and regional summary data from national woodland inventories to investigate changes in habitat cover and bird distributions. Percentage habitat cover was a sufficient landscape metric to explain the distribution pattern of all three bird species; habitat cover was greatest in areas where each species was retained between atlas surveys, significantly less in areas from which species were lost, and least in areas that remained unoccupied. Reductions in Marsh Tit distribution were less in regions that showed greater increases in habitat cover, but there was no such relationship for other species. Results indicated that spatial studies could be used to infer aspects of the spatial ecology of species where field data is lacking: by comparing distribution patterns with the relatively well-studied Marsh Tit, we found support for the assumption that the Lesser Spotted Woodpecker occupies very large territories in Britain, and provided evidence that the spatial habitat requirements of the Marsh Tit could be used as a proxy for the data-poor Willow Tit. The results showed that the habitat cover required to retain each species in the landscape had increased over time, illustrating how spatial studies can be used to identify priorities for further research and suggest conservation measures for declining species, and these are discussed.     

The landscape of fear as an emergent property of heterogeneity: Contrasting patterns of predation risk in grassland ecosystems

The likelihood of encountering a predator influences prey behavior and spatial distribution such that non‐consumptive effects can outweigh the influence of direct predation. Prey species are thought to filter information on perceived predator encounter rates in physical landscapes into a landscape of fear defined by spatially explicit heterogeneity in predation risk. The presence of multiple predators using different hunting strategies further complicates navigation through a landscape of fear and potentially exposes prey to greater risk of predation. The juxtaposition of land cover types likely influences overlap in occurrence of different predators, suggesting that attributes of a landscape of fear result from complexity in the physical landscape. Woody encroachment in grasslands furnishes an example of increasing complexity with the potential to influence predator distributions. We examined the role of vegetation structure on the distribution of two avian predators, Red‐tailed Hawk (Buteo jamaicensis) and Northern Harrier (Circus cyaneus), and the vulnerability of a frequent prey species of those predators, Northern Bobwhite (Colinus virginianus). We mapped occurrences of the raptors and kill locations of Northern Bobwhite to examine spatial vulnerability patterns in relation to landscape complexity. We use an offset model to examine spatially explicit habitat use patterns of these predators in the Southern Great Plains of the United States, and monitored vulnerability patterns of their prey species based on kill locations collected during radio telemetry monitoring. Both predator density and predation‐specific mortality of Northern Bobwhite increased with vegetation complexity generated by fine‐scale interspersion of grassland and woodland. Predation pressure was lower in more homogeneous landscapes where overlap of the two predators was less frequent. Predator overlap created areas of high risk for Northern Bobwhite amounting to 32% of the land area where landscape complexity was high and 7% where complexity was lower. Our study emphasizes the need to evaluate the role of landscape structure on predation dynamics and reveals another threat from woody encroachment in grasslands.     

An overview on the role of Hexanchiformes in marine ecosystems: biology, ecology and conservation status of a primitive order of modern sharks

The large size, high trophic level and wide distribution of Hexanchiformes (cow and frilled sharks) should position this order as important apex predators in coastal and deep-water ecosystems. This review synthesizes available information on Hexanchiformes, including information not yet published, with the purpose of evaluating their conservation status and assessing their ecological roles in the dynamics of marine ecosystems. Comprising six species, this group has a wide global distribution, with members occurring from shallow coastal areas to depths of c. 2500 m. The limited information available on their reproductive biology suggests that they could be vulnerable to overexploitation (e.g. small litter sizes for most species and suspected long gestation periods). Most of the fishing pressure exerted on Hexanchiformes is in the form of commercial by-catch or recreational fishing. Comprehensive stock and impact assessments are unavailable for most species in most regions due to limited information on life history and catch and abundance time series. When hexanchiform species have been commercially harvested, however, they have been unable to sustain targeted fisheries for long periods. The potentially high vulnerability to intense fishing pressure warrants a conservative exploitation of this order until thorough quantitative assessments are conducted. At least some species have been shown to be significant apex predators in the systems they inhabit. Should Hexanchiformes be removed from coastal and deep-water systems, the lack of sympatric shark species that share the same resources suggests no other species would be capable of fulfilling their apex predator role in the short term. This has potential ecosystem consequences such as meso-predator release or trophic cascades. This review proposes some hypotheses on the ecology of Hexanchiformes and their role in ecosystem dynamics, highlighting the areas where critical information is required to stimulate research directions.     

Assessing species traits and landscape relationships of the mammalian carnivore community in a neotropical biological corridor

Mammalian carnivores play an important role in regulating food webs and ecosystems. While many carnivore populations are facing various threats such as habitat loss and fragmentation, poaching, and illegal trade, others have adapted to human-dominated landscapes. Information about Neotropical carnivore communities in particular is limited, especially in disturbed landscapes. We conducted a camera trap survey at 38 sites across the San Juan–La Selva Biological Corridor in Costa Rica to assess occupancy and detection probabilities of the carnivore community. We developed hypotheses within a likelihood-based framework in order to determine the landscape features and species traits (diet and size) that influenced their occupancy. We detected nine of the 13 native carnivores predicted to occur in the corridor. When modeled separately, each species responded to land cover changes differently, suggesting no strong community-wide predictors of occupancy. We then modeled three separate guilds within the carnivore community: omnivorous mesopredators, obligate carnivorous mesopredators, and apex predators. These community guild models revealed a negative relationship between omnivorous mesopredators and increasing forest and tree plantation cover, suggesting omnivores utilize forest fragments and edge habitats in agricultural landscapes. Obligate carnivorous mesopredator models did not reveal any strong habitat relationships, but landscape effects tended to contradict our a priori predictions. Apex predators were positively associated with increasing forest and tree plantation cover, protected areas, and increasing distances to villages. Alarmingly, apex predators and obligate carnivorous mesopredators were generally rare within the biological corridor. A lack of top-down control alone might result in heightened occupancy for all mesopredators, but because the community is dominated by omnivorous species, bottom-up release from human-induced land cover changes and resource provision may better explain their high occupancy.     

Spatial segregation of sympatric marten and fishers: the influence of landscapes and species‐scapes

Co‐occurring species are rarely considered as a factor influencing habitat selection. However, niche theory predicts that sharing resources, predators, and other interspecific interactions can limit the environmental conditions under which a species may exist. How does the spatial distribution of one species affect that of another within shared landscapes? We tested whether sympatric marten Martes americana and fishers M. pennanti in a mountain landscape in Alberta, Canada exhibit local‐scale spatial segregation, beyond differential habitat selection. We modelled marten and fisher distribution in relation to remotely‐sensed habitat data and species co‐occurrence, using generalized linear models and information‐theoretic model selection. Marten and fishers selected different habitat types and showed different responses to habitat fragmentation. Even after accounting for these differences, the absence of one species significantly explained the occurrence of the other. We conclude that the spatial distribution of marten and fishers influences habitat selection by each other at landscape scales, and hypothesize that this pattern may result from competition in a spatially heterogeneous environment. Species‐habitat models that consider only resources may fail to capture key predictors of species’ occurrence. Reliable prediction and inference requires that ecologists expand from landscapes to also include species‐scapes: a spatial plane of species interactions that combines with resources to drive species’ distributions.     

Effects of Culling on Mesopredator Population Dynamics

Anthropogenic changes in land use and the extirpation of apex predators have facilitated explosive growth of mesopredator populations. Consequently, many species have been subjected to extensive control throughout portions of their range due to their integral role as generalist predators and reservoirs of zoonotic disease. Yet, few studies have monitored the effects of landscape composition or configuration on the demographic or behavioral response of mesopredators to population manipulation. During 2007 we removed 382 raccoons (Procyon lotor) from 30 forest patches throughout a fragmented agricultural ecosystem to test hypotheses regarding the effects of habitat isolation on population recovery and role of range expansion and dispersal in patch colonization of mesopredators in heterogeneous landscapes. Patches were allowed to recolonize naturally and demographic restructuring of patches was monitored from 2008–2010 using mark-recapture. An additional 25 control patches were monitored as a baseline measure of demography. After 3 years only 40% of experimental patches had returned to pre-removal densities. This stagnant recovery was driven by low colonization rates of females, resulting in little to no within-patch recruitment. Colonizing raccoons were predominantly young males, suggesting that dispersal, rather than range expansion, was the primary mechanism driving population recovery. Contrary to our prediction, neither landscape connectivity nor measured local habitat attributes influenced colonization rates, likely due to the high dispersal capability of raccoons and limited role of range expansion in patch colonization. Although culling is commonly used to control local populations of many mesopredators, we demonstrate that such practices create severe disruptions in population demography that may be counterproductive to disease management in fragmented landscapes due to an influx of dispersing males into depopulated areas. However, given the slow repopulation rates observed in our study, localized depopulation may be effective at reducing negative ecological impacts of mesopredators in fragmented landscapes at limited spatial and temporal scales.     

生境质量对城镇化的时空响应——以长春市为例

生境质量是评价区域生态安全的重要指标,掌握其对城镇化发展的时空响应,有利于新型城镇化的深入推行。本研究基于土地利用数据,在综合利用空间分析及生态模型分析基础上,从网格尺度对长春市景观格局、生境质量及其样带进行时空特征分析,并进一步探讨生境质量在城镇化发展过程中的响应状况。结果表明: 长春市景观斑块密度、边缘密度及Shannon多样性指数低值多分布在西部平原地带,聚合度指数高值区则在市域东部及南部呈现片状格局。2000—2015年,长春市生境质量呈退化趋势且空间异质性显著,大致呈现出“东高西低”分布态势,建设用地扩张及交通基础设施建设对区域生境质量退化起到主导作用;不同样带内生境质量变化存在显著差异性,水域整体变化相对较小,而山脉、城市扩张及交通的变化频度及幅度处于较高水平。坡度及高程等自然因素基本塑造了长春市生境质量整体分布格局,而人口密度、国内生产总值、夜间灯光指数等城镇化要素与生境质量总体呈负相关关系。为缓解城镇化带来的生态压力、促进生境质量的回升,本研究提出防止大黑山脉林区滥砍乱伐、以生态手段修复生境退化地区,提升城镇建成区土地利用效率、促进城镇“精明增长”,设定丘陵地带耕地红线、加强生态基础设施建设等差异化发展策略。     

Land use changes affect distributional patterns of desert birds in the Baja California peninsula, Mexico

Reliable plans for desert bird conservation will depend on accurate prediction of habitat change effects on their distribution and abundance patterns. Predictive models can help highlight relationships between human‐related and other environmental variables and the presence of desert bird species. Presence/absence of 30 desert bird species of Baja California peninsula was modelled on the basis of explanatory variables taken from the field, maps, and digital imagery. Generalized linear models were fit to each bird species using both variables representing human activity and other environmental factors as predictors that might influence distribution. Probability of species presence was used as a habitat suitability index to evaluate the effect of human activity when the model contained a significant human activity variable. No differences were found in bird species richness between natural sites and those transformed by agriculture or urbanization. Of 59 bird species recorded in surveys, 34% were positively or negatively associated with human‐transformed habitats. Fourteen species seem to benefit from transformation of natural vegetation by agriculture or urbanization, while six were negatively affected. Sensitivity analyses of final models indicated all were robust. Results suggest that the occurrence of a large percentage of bird species inhabiting scrub habitats is sensitive to human habitat transformation. This finding has important conservation implications at regional scale as fragmentation and conversion of desert ecosystems into agricultural and urban areas affect the distribution of species that are highly selective for scrub habitat. Land use and anthropogenic activities seem to change ecological patterns at large spatial scales, but other factors could drive species richness distribution too (i.e. individual species response, species–energy relationships). The spatial modelling approach at regional scale used in this study can be useful for designing natural resource management plans in the Sonoran desert scrub.