Whole‐landscape modelling of compositional turnover in aquatic invertebrates informs conservation gap analysis: An example from south‐western Australia

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Sediment deposition from eroding peatlands alters headwater invertebrate biodiversity

Land use and climate change are driving widespread modifications to the biodiverse and functionally unique headwaters of rivers. In temperate and boreal regions, many headwaters drain peatlands where land management and climate change can cause significant soil erosion and peat deposition in rivers. However, effects of peat deposition in river ecosystems remain poorly understood. We provide two lines of evidence—derived from sediment deposition gradients in experimental mesocosms (0–7.5 g/m²) and headwaters (0.82–9.67 g/m²)—for the adverse impact of peat deposition on invertebrate community biodiversity. We found a consistent negative effect of sediment deposition across both the experiment and survey; at the community level, decreases in density (1956 to 56 individuals per m² in headwaters; mean 823 ± 129 (SE) to 288 ± 115 individuals per m² in mesocosms) and richness (mean 12 ± 1 to 6 ± 2 taxa in mesocosms) were observed. Sedimentation increased beta diversity amongst experimental replicates and headwaters, reflecting increasing stochasticity amongst tolerant groups in sedimented habitats. With increasing sedimentation, the density of the most common species, Leuctra inermis, declined from 290 ± 60 to 70 ± 30 individuals/m² on average in mesocosms and >800 individuals/m² to 0 in the field survey. Traits analysis of mesocosm assemblages suggested biodiversity loss was driven by decreasing abundance of invertebrates with trait combinations sensitive to sedimentation (longer life cycles, active aquatic dispersal of larvae, fixed aquatic eggs, shredding feeding habit). Functional diversity metrics reinforced the idea of more stochastic community assembly under higher sedimentation rates. While mesocosm assemblages showed some compositional differences to surveyed headwaters, ecological responses were consistent across these spatial scales. Our results suggest short‐term, small‐scale stressor experiments can inform understanding of “real‐world” peatland river ecosystems. As climate change and land‐use change are expected to enhance peatland erosion, significant alterations to invertebrate biodiversity can be expected where these eroded soils are deposited in rivers.     

Benthic macroinvertebrate biodiversity improved with irrigation ponds linked to a rice paddy field

Traditionally, many irrigation ponds supplied water to paddy fields, but most of these ponds have disappeared through improvements in irrigation systems. The aim of this study was to assess the ecological functions (especially biodiversity conservation) of irrigation ponds by using benthic macroinvertebrates that inhabit paddy fields. This study was conducted in Hwaseong‐si, Yesan‐gun, Hongseong‐gun, Uljin‐gun and Damyang‐gun, Korea. Benthic macroinvertebrates were collected using a quadrat sampler from August to September for three years (2010–2012) in paddy fields with and without an irrigation pond. In the comparisons between two paddy field types (paddy fields with and without an irrigation pond) for species richness and densities of benthic macroinvertebrates, the species richness and densities were higher in the paddy fields with a pond than in the paddy fields without a pond (P < 0.001). Biodiversity enhancement effect degree (BEED) of the irrigation pond showed positive values in all survey regions. There were no significant differences among the survey regions. BEED showed positive values in all taxonomic groups (excluding Crustacea) and were not significantly different among taxonomic groups. The BEED values for non‐insects, passive dispersers, were relatively higher than for insects, active dispersers. The results indicate that BEED is related to the dispersal abilities of each taxonomic group and an irrigation pond increases biodiversity in a paddy field in all regions. Therefore, the irrigation pond is one method that can be immediately applied in paddy fields in order to improve the biodiversity of agricultural ecosystems.     

Effects of advance and retreat of agricultural landscapes on Rana japonica and R. ornativentris

Paddy fields are essential habitats for frogs. We evaluated the impacts of both farmland consolidation including agricultural road improvement and farmland abandonment on the two Rana species using a model incorporating spatial autocorrelation. A sampling unit consists of several paddy fields that share a ditch and are isolated from other blocks by roads or other land covers. We surveyed 619 blocks in an area of about 1000 km² from the plain to the mountains of Toyota City in central Japan. Among them, 124 blocks included at least a flooded paddy field where frogs could lay eggs. R. ornativentris and R. japonica bred in 50 and 25 blocks, respectively. We constructed models to explain the presence/absence of two species by GLM (non-spatial model) and hierarchical Bayesian model with INLA (spatial model) that includes spatial autocorrelation as a random effect. Explanatory variables of the local scale were the altitude, location of the paddy field (yatsuda (valley bottom paddy fields) or non-yatsuda), farmland consolidated or not consolidated, and under cultivation or abandoned. Those of the landscape scale were areas of forest and paddy fields, and road density in 14 circles with different radius from 50 to 2000 m. Both species’ distribution had significant spatial autocorrelation. The spatial model had a higher discriminative ability than the non-spatial model. Farmland consolidation and the forest area in the 400 m radius had a positive effect on R. ornativentris. Altitude and road density in the 50 m radius had negative effects, cultivation had a positive effect, and farmland consolidation and yatsuda had no or negative effects on R. japonica. R. ornativentris was threatened by farmland abandonment, but the urbanization and/or farmland consolidation threatened R. japonica.

     

Can hydrologic management practices of rice fields contribute to macroinvertebrate conservation in southern Brazil wetlands?

The expansion of rice fields is one of the main human activities responsible for the decline of natural wetlands throughout the world. However, rice fields have been recognized as having considerable potential value for many aquatic species. In this sense, an important question from the point of view of biodiversity conservation is the adequacy of these agricultural wetlands as an integrated managed landscape that contributes to maintain a rich biodiversity. The two main questions of this study were: (1) Do richness, density, and composition of macroinvertebrates differ in rice fields with different management practices (flooded and dry)?; and, (2) Do richness, density and composition of macroinvertebrates change in rice fields over the rice cultivating phases? Six collections were carried out in six rice fields with different management practices after cultivation (three dry and three flooded during the fallow phase). The macroinvertebrates were sampled using a corer (7.5-cm diameter) inserted 10 cm into the substratum of the rice fields. We recorded 6,425 macroinvertebrates, comprising 71 macroinvertebrate taxa. Macroinvertebrate richness and density varied over the rice cultivating cycle. The different management practices adopted after cultivation did not influence the macroinvertebrate richness and density; however, they influenced composition. Thus, the mosaic created by the variation of flooded and dry rice fields would provide the setting for a greater number of taxa within the agricultural landscape. The difference in taxa composition between flooded and dry rice fields is an interesting result in terms of biodiversity conservation. Rice producers could maintain part of their agricultural land flooded during the fallow phase. These management practices adopted could be an important strategy for biodiversity conservation in areas where the natural wetlands were converted into rice fields.     

Biogeography and conservation of aquatic fauna in spring-fed tropical canyons of the southern Sonoran Desert,Mexico

In arid regions, spring-fed habitats are frequently the only year-round source of surface water and are essential habitats for aquatic organisms and primary water sources for terrestrial animals and human settlements. While these habitats have been relatively well-studied in some regions, those of the southern Sonoran Desert have received little attention. In 2008 and 2009, we documented the biodiversity of aquatic animals at 19 sites across three arid mountain ranges in Sonora, Mexico, characterized macrohabitat types, examined seasonal variation in aquatic invertebrate communities, and explored the effects of an exotic fish (tilapia) on native communities. We documented >220 aquatic animal species, including several new species and range extensions for others. Macrohabitat type (oasis, tinaja, riffle, and seep) was more important than geographic location in structuring aquatic invertebrate communities at the scale of our study area (~9,000 km²). We found little evidence of predictable seasonal variation in invertebrate communities, despite dramatic hurricane-induced flooding. Aquatic vertebrates were not diverse across the study region (4 amphibian species and 2 species each of fishes and reptiles), but were often locally abundant. Presence of non-native tilapia at one site was associated with reduced abundances of native leopard frogs and reduced richness and density of native aquatic invertebrates. The most pressing aquatic habitat conservation concerns in the region, as in other deserts, are groundwater withdrawal, unmanaged recreational visitation, and the introduction of exotic species. Spring-fed habitats around the world have been called hotspots of freshwater biodiversity, and those of the Sonoran Desert are no exception.     

Plantation forests and biodiversity: oxymoron or opportunity?

Losses of natural and semi-natural forests, mostly to agriculture, are a significant concern for biodiversity. Against this trend, the area of intensively managed plantation forests increases, and there is much debate about the implications for biodiversity. We provide a comprehensive review of the function of plantation forests as habitat compared with other land cover, examine the effects on biodiversity at the landscape scale, and synthesise context-specific effects of plantation forestry on biodiversity. Natural forests are usually more suitable as habitat for a wider range of native forest species than plantation forests but there is abundant evidence that plantation forests can provide valuable habitat, even for some threatened and endangered species, and may contribute to the conservation of biodiversity by various mechanisms. In landscapes where forest is the natural land cover, plantation forests may represent a low-contrast matrix, and afforestation of agricultural land can assist conservation by providing complementary forest habitat, buffering edge effects, and increasing connectivity. In contrast, conversion of natural forests and afforestation of natural non-forest land is detrimental. However, regional deforestation pressure for agricultural development may render plantation forestry a ‘lesser evil’ if forest managers protect indigenous vegetation remnants. We provide numerous context-specific examples and case studies to assist impact assessments of plantation forestry, and we offer a range of management recommendations. This paper also serves as an introduction and background paper to this special issue on the effects of plantation forests on biodiversity.

Environmental correlates of plant and invertebrate species richness in ponds

Ponds (lentic water bodies <2 ha) constitute a considerable biodiversity resource. Understanding the environmental factors that underlie this diversity is important in protecting and managing the habitat. We surveyed 425 ponds for biological and physical characteristics with 78 of those also surveyed for chemical characteristics. A total of 277 invertebrate species and 265 plant species were found. Species richness varied between 2 and 99 (mean 27.2 ± 0.6 SE) for invertebrates and 1 and 58 (mean 20.8 ± 0.4 SE) for plants. Generalised additive models were used to investigate variables that correlate with the species richness of plants and invertebrates, with additional models to investigate insect, Coleoptera, Odonata, Hemiptera, Trichoptera and Mollusca species richness. Models performed reasonably well for invertebrates in general (R ² = 30.3%) but varied between lower-order invertebrate taxa (12.7–34.7%). Ponds with lower levels of shading and no history of drying contained higher numbers of species of plants and all invertebrate groups. Aquatic plant coverage positively correlated with species richness in all invertebrate groups apart from Trichoptera and the presence of fish was associated with high invertebrate species richness in all groups apart from Coleoptera. The addition of chemistry variables suggested non-linear relationships between oxygen demand and phosphate concentration and higher-order richness. We demonstrate that the composition of biological communities varies along with their species richness and that less diverse ponds are more variable compared to more diverse ponds. Variables positively correlated with richness of one taxon may be negatively correlated with that of another, making comprehensive management recommendations difficult. Promoting a high landscape-level pond biodiversity will involve the management of a high diversity of pond types within that landscape.     

Balance between climate change mitigation benefits and land use impacts of bioenergy: conservation implications for European birds

Both climate change and habitat modification exert serious pressure on biodiversity. Although climate change mitigation has been identified as an important strategy for biodiversity conservation, bioenergy remains a controversial mitigation action due to its potential negative ecological and socio-economic impacts which arise through habitat modification by land use change. While the debate continues, the separate or simultaneous impacts of both climate change and bioenergy on biodiversity have not yet been compared. We assess projected range shifts of 156 European bird species by 2050 under two alternative climate change trajectories: a baseline scenario, where the global mean temperature increases by 4 °C by the end of the century, and a 2 degrees scenario, where global concerted effort limits the temperature increase to below 2 °C. For the latter scenario, we also quantify the pressure exerted by increased cultivation of energy biomass as modelled by IMAGE2.4, an integrated land use model. The global bioenergy use in this scenario is in the lower end of the range of previously estimated sustainable potential. Under the assumptions of these scenarios, we find that the magnitude of range shifts due to climate change is far greater than the impact of land conversion to woody bioenergy plantations within the European Union, and that mitigation of climate change reduces the exposure experienced by species. However, we identified potential for local conservation conflict between priority areas for conservation and bioenergy production. These conflicts must be addressed by strict bioenergy sustainability criteria that acknowledge biodiversity conservation needs beyond existing protected areas and apply also to biomass imported from outside the European Union.     

Noncrop features and heterogeneity mediate overwintering bird diversity in agricultural landscapes of southwest China

Farmland birds are of conservation concerns around the world. In China, conservation management has focused primarily on natural habitats, whereas little attention has been given to agricultural landscapes. Although agricultural land use is intensive in China, environmental heterogeneity can be highly variable in some regions due to variations in crop and noncrop elements within a landscape. We examined how noncrop heterogeneity, crop heterogeneity, and noncrop features (noncrop vegetation and water body such as open water) influenced species richness and abundance of all birds as well as three functional groups (woodland species, agricultural land species, and agricultural wetland species) in the paddy‐dominated landscapes of Erhai water basin situated in northwest Yunnan, China. Birds, crop, and noncrop vegetation surveys in twenty 1 km × 1 km landscape plots were conducted during the winter season (from 2014 to 2015). The results revealed that bird community compositions were best explained by amounts of noncrop vegetation and compositional heterogeneity of noncrop habitat (Shannon–Wiener index). Both variables also had a positive effect on richness and abundance of woodland species. Richness of agricultural wetland species increased with increasing areas of water bodies within the landscape plot. Richness of total species was also greater in the landscapes characterized by larger areas of water bodies, high proportion of noncrop vegetation, high compositional heterogeneity of noncrop habitat, or small field patches (high crop configurational heterogeneity). Crop compositional heterogeneity did not show significant effects neither on the whole community (all birds) nor on any of the three functional groups considered. These findings suggest that total bird diversity and some functional groups, especially woodland species, would benefit from increases in the proportion of noncrop features such as woody vegetation and water bodies as well as compositional heterogeneity of noncrop features within landscape.     

Biodiversity conservation in cocoa production landscapes: an overview

Cocoa agroforests that retain a floristically diverse and structurally complex shade canopy have the potential to harbour significant levels of biodiversity, yet few studies have documented the plant and animal species occurring within these systems or within landscapes dominated by cocoa production. In this special issue, we bring together nine studies from Latin America, Africa and Asia that document the contribution of cocoa agroforestry systems to biodiversity conservation, and explore how the design, management and location of these systems within the broader landscape influence their value as habitats, resources and biological corridors. Tree diversity within the cocoa production systems is variable, depending on management, cultural differences, location and farm history, among other factors. Animal diversity is typically highest in those cocoa agroforests that have high plant diversity, structurally complex canopies, and abundant surrounding forest cover. In general, both plant and animal diversity within cocoa agroforests is greater than those of other agricultural land uses, but lower than in the original forest habitat. There are several emerging threats to biodiversity conservation within cocoa production landscapes, including the loss of remaining forest cover, the simplification of cocoa shade canopies and the conversion of cocoa agroforestry systems to other agricultural land uses with lower biodiversity value. To counter these threats and conserve biodiversity over the long-term, land management should focus on conserving native forest habitat within cocoa production landscapes, maintaining or restoring floristically diverse and structurally complex shade canopies within cocoa agroforests, and retaining other types of on-farm tree cover to enhance landscape connectivity and habitat availability.     

Integrating biodiversity conservation into land consolidation in hilly areas – A case study in southwest China

Based on the analysis of land consolidation engineering effects on biodiversity conservation in hilly areas, this study considers integrating biodiversity conservation into traditional land consolidation projects and integration biodiversity conservation measures into land consolidation engineering from the overall planning, land leveling engineering, farmland water conservancy engineering, roads and landscape construction engineering respectively. It aims to conserve biodiversity and improve eco-environment and arable land quality for increase yields of crops by integration biodiversity conservation ideas and measures into land consolidation activities in advance.     

A comparison of the catchment sizes of rivers,streams, ponds,ditches and lakes: implications for protecting aquatic biodiversity in an agricultural landscape

In this study we compared the biodiversity of five waterbody types (ditches, lakes, ponds, rivers and streams) within an agricultural study area in lowland England to assess their relative contribution to the plant and macroinvertebrate species richness and rarity of the region. We used a Geographical Information System (GIS) to compare the catchment areas and landuse composition for each of these waterbody types to assess the feasibility of deintensifying land to levels identified in the literature as acceptable for aquatic biota. Ponds supported the highest number of species and had the highest index of species rarity across the study area. Catchment areas associated with the different waterbody types differed significantly, with rivers having the largest average catchment sizes and ponds the smallest. The important contribution made to regional aquatic biodiversity by small waterbodies and in particular ponds, combined with their characteristically small catchment areas, means that they are amongst the most valuable, and potentially amongst the easiest, of waterbody types to protect. Given the limited area of land that may be available for the protection of aquatic biodiversity in agricultural landscapes, the deintensification of such small catchments (which can be termed microcatchments) could be an important addition to the measures used to protect aquatic biodiversity, enabling ‘pockets’ of high aquatic biodiversity to occur within working agricultural landscapes. Guest editors: R. Céréghino, J. Biggs, B. Oertli & S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

Future land use effects on the connectivity of protected area networks in southeastern Spain

Land-use change is a major driver of the global biodiversity crisis, mainly via the fragmentation and loss of natural habitat. Although land-use changes will accelerate to meet humankind's growing demand for agricultural products, conservation planning rarely considers future land uses and how they may affect the connectivity of ecological networks. Here, we integrate land-use models with landscape fragmentation and connectivity analyses, to assess the effects of past and future land-use changes on the connectivity of protected area networks for a highly dynamic region in southeast Spain. Our results show a continued geographical polarisation of land use, with agricultural intensification and urban development in the coastal areas, and the abandonment of traditional land use in the mountains (e.g., 1100 km² of natural vegetation are projected to be lost in coastal areas whereas 32 km² of natural vegetation would recover in interior areas from 1991 to 2015). As a result, coastal protected areas will experience increasing isolation. The connectivity analyses reveal that the two protected area networks in place in the study area, the European “Natura 2000” and the Andalusian “RENPA” networks, include many landscape connectors. However, we identify two areas that currently lack protection but contain several important patches for maintaining the region's habitat connectivity: the northwestern and the southwestern slopes of the Sierra Cabrera and Bédar protected area. Our results highlight the importance of considering future land-use trajectories in conservation planning to maintain connectivity at the regional scale, and to improve the resilience of conservation networks.     

Forest fragmentation in China and its effect on biodiversity

Land‐use change is fragmenting natural ecosystems, with major consequences for biodiversity. This paper reviews fragmentation trends – historical and current – in China, the fourth largest country on Earth, and explores its consequences. Remote sensing makes it possible to track land‐use change at a global scale and monitor fragmentation of dwindling natural landscapes. Yet few studies have linked fragmentation mapped remotely with impacts on biodiversity within human‐modified landscapes. Recent reforestation programs have caused substantial increases in forest cover but have not stopped fragmentation, because the new forests are mostly monocultures that further fragment China's remnant old‐growth lowland forests that harbour the highest levels of biodiversity. Fragmentation – and associated biodiversity declines – is unevenly distributed in China's forests, being most problematic where agricultural expansion is occurring in the southwest and northeast, serious in the densely populated eastern regions where urbanisation and transport infrastructure are modifying landscapes, but less of a problem in other regions. Analyses of temporal trends show that the drivers of forest fragmentation are shifting from mainly agricultural expansion to urbanisation and infrastructure development. Most of China's old‐growth forests persist in small, isolated fragments from which many native species have disappeared, on land unsuitable for human utilisation. Fragmentation throughout China is likely to have major consequences on biodiversity conservation, but few studies have considered these large‐scale processes at the national level. Our review fills this research gap and puts forward a systematic perspective relevant to China and beyond.     

Does habitat heterogeneity influence taxonomic richness and abundance? A case study from a terrestrial protected area in Abu Dhabi,United Arab Emirates

Biodiversity is under enormous pressure from multiple threats including climate change, land use change, habitat alterations and hunting pressure. One way to ease this pressure on biodiversity and to mitigate the effects of above-mentioned threats, is to establish protected areas. Importance of protected increases many folds in regions that are considered as biodiversity poor regions i.e. deserts. Protected areas have long been a major pillar of biodiversity conservation strategies; the Houbara Protected Area (HPA) is one of the 13 terrestrial protected areas in Abu Dhabi Emirate officially declared in 2017. However, no information regarding the status of biodiversity in the HPA has been communicated to the research fraternity. During the present study, surveys were conducted to fill this gap. The survey area was divided in to 50 grids of 5 × 5 km² and monitoring surveys were undertaken from January to December 2016. A total of 14 bi-monthly to monthly surveys were conducted within HPA and 196 species of different taxonomical groups were recorded. A year-long survey yielded highly diversified fauna and flora from 19 different habitat types (H) 1.32, (E) 2.28, Shannon Diversity Index). We looked at the influence of habitat breadth and temperature on the species richness and abundance, results shows that in desert setup heterogeneity of habitat is not an important factor in maintaining the biodiversity as total number of individuals as well as species were similar in the grids that have different number of habitat types (df = 34.3, t = -0.472, P = 0.640). However, we did find a positive impact of mean monthly temperature on species richness (df = 154, t = 2.53, P = 0.012). Our study highlights the importance of temperature in driving species abundance and richness in protected area. Abundance and species richness are similar in protected areas indicating that protection is allowing species to explore the heterogenous habitats. Overall, we can conclude that protection is beneficial for species.     

Forest mammal roadkills as related to habitat connectivity in protected areas

Fragmentation of wildlife habitat by road development is a major threat to biodiversity. Hence, conservation and enhancement of habitat connectivity in roaded landscapes are crucial for effectively maintaining long-term persistence of ecological processes, such as gene flow and migration. Using multivariate statistical techniques combined with graph theoretical methods, we investigated the influence of road-crossing habitat connectivity and road-related features on roadkill abundance of forest mammals in protected areas of South Korea. Because species have different dispersal abilities and thus connectivity would differ between them, we explored three different groups of road-killed mammals, categorized as small, intermediate, and large ones. We found that in all three mammal groups, roadkills are increased on roads that intersect high-connectivity routes. Furthermore, the effect of habitat connectivity on roadkill abundance was scale-dependent. The roadkill abundances of small, intermediate, and large mammals were related with connectivity measured at scales ranging between 100 and 300 m, between 5 and 7 km, and between 10 and 25 km, respectively. Our finding with regard to scale-dependency highlights the importance of maintaining movement and connectivity across roads at multiple scales based on the dispersal potential of different species when planning conservation strategies for forest mammalian roadkill mitigation.     

Restoration of Biodiversity and Ecosystem Services on Agricultural Land

Cultivation and cropping are major causes of destruction and degradation of natural ecosystems throughout the world. We face the challenge of maintaining provisioning services while conserving or enhancing other ecosystem services and biodiversity in agricultural landscapes. There is a range of possibilities within two types of intervention, namely “land sharing” and “land separation”; the former advocates the enhancement of the farmed environment, but the latter a separation between land designated for farming versus conservation. Land sharing may involve biodiversity-based agricultural practices, learning from traditional farming, changing from conventional to organic agriculture and from “simple” crops and pastures to agro-forestry systems, and restoring or creating specific elements to benefit wildlife and particular services without decreasing agricultural production. Land separation in the farmland context involves restoring or creating non-farmland habitat at the expense of field-level agricultural production—for example, woodland on arable land. Restoration by land sharing has the potential to enhance agricultural production, other ecosystem services and biodiversity at both the field and landscape scale; however, restoration by land separation would provide these benefits only at the landscape scale. Although recent debate has contrasted these approaches, we suggest they should be used in combination to maximize benefits. Furthermore, we suggest “woodland islets”, an intermediate approach between land abandonment and farmland afforestation, for ecological restoration in extensive agricultural landscapes. This approach allows reconciliation of farmland production, conservation of values linked to cultural landscapes, enhancement of biodiversity, and provision of a range of ecosystem services. Beyond academic research, restoration projects within agricultural landscapes are essential if we want to halt environmental degradation and biodiversity loss.     

Past and present disturbances influence biodiversity value of subtropical grassland ecological networks

The effect of transforming natural habitat to commercial land uses can be mitigated by implementing ecological networks (ENs) in production landscapes. However, EN ability to conserve biodiversity is potentially influenced by past and present disturbances, and spatial configuration of habitat patches. Here, we investigated how plant assemblages of a subtropical EN in a timber production landscape in South Africa respond to disturbance history (i.e. natural vs. recovering after removal of Pinus spp.), mowing in firebreaks (i.e. 30 m wide grassy strips intended to stop spread of fires in plantations), and three design parameters: corridor width, distance to protected area boundary, and context i.e. proportion eucalypt compartments within 500 m radius. Reference sites were in the adjacent iSimangaliso Wetland Park, a protected area (PA). Past disturbances and the current practice of mowing in firebreaks significantly influenced plant species composition, but not plant species richness. Plant dominance was greatest in mowed firebreaks, but similar between natural and recovering grassland. None of the design variables affected plant species richness, or composition. However, dominance was significantly and negatively correlated with corridor width, and positively correlated with context. Hence, sites are ordered in terms of their biodiversity value from greatest to lowest: natural areas > recovering areas > firebreaks. Based on these results, natural grassland in wide, well-connected corridors should have greatest conservation priority. We recommend that past disturbances, and current management practices should be taken into account and integrated into the design of future ENs. Such an approach is necessary for effective biodiversity conservation in production landscapes.     

基于景观连接度的土地整理生态效应评价

近年来,土地整理区的生物多样性保护和景观功能的维持受到广泛关注。本文选取贵州省道真县洛龙镇国家重点土地整理项目区,运用基于结构与功能相结合景观连接度模型(综合连接度(IIC)和连接度概率(PC)),计算了500、1000、2000、3000和4000m种群迁移扩散距离阈值情景下,土地整理前后各生境斑块对景观连接度的重要程度,识别重要斑块变化范围,从功能角度评价整理后的生态效应。结果表明:连接度指数能较好地识别土地整理前后各生境斑块的重要类别及其改变;其中,巨型斑块所占面积最大,分别占总面积的57.0%和57.2%;小型斑块数目整理前后分别占斑块总数的48.0%和48.9%;空间上,斑块的重要性分布也产生一定的变化。整理后生境斑块的连通性较整理前也有所下降,IIC和PC平均值分别为0.434和0.680,且随着距离阈值的增大,连接度逐渐增大。巨型斑块对生境斑块景观连通性的相对重要值最大,中型斑块和大型斑块次之,小型斑块最低。研究表明,土地整理过程中,大面积生境斑块和"踏脚石"斑块对维持土地整理生态效益具有重要作用。