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1.
Context
Habitat loss and habitat fragmentation negatively affect amphibian populations. Roads impact amphibian species through barrier effects and traffic mortality. The landscape variable ‘accessible habitat’ considers the combined effects of habitat loss and roads on populations.Objectives
The aim was to test whether accessible habitat was a better predictor of amphibian species richness than separate measures of road effects and habitat loss. I assessed how accessible habitat and local habitat variables determine species richness and community composition.Methods
Frog and tadpole surveys were conducted at 52 wetlands in a peri-urban area of eastern Australia. Accessible habitat was delineated using a highway. Regressions were used to examine relationships between species richness and eleven landscape and local habitat variables. Redundancy analysis was used to examine relationships between community composition and accessible habitat and local habitat variables.Results
Best-ranked models of species richness included both landscape and local habitat variables. There were positive relationships between species richness and accessible habitat and distance to the highway, and uncertain relationships with proportion cover of native vegetation and road density. There were negative relationships between species richness and concreted wetlands and wetland electrical conductivity. Four species were positively associated with accessible habitat, whereas all species were negatively associated with wetland type.Conclusions
Barrier effects caused by the highway and habitat loss have negatively affected the amphibian community. Local habitat variables had strong relationships with species richness and community composition, highlighting the importance of both availability and quality of habitat for amphibian conservation near major roads.2.
Context
An increasing number of studies have investigated the impact of environmental heterogeneity on faunal assemblages when measured at multiple spatial scales. Few studies, however, have considered how the effects of heterogeneity on fauna vary with the spatial scale at which the response variable is characterised.Objectives
We investigated the relationship between landscape properties in a region characterised by diverse fire mosaics, and the structure and composition of avian assemblages measured at both the site- (1 ha) and landscape-scale (100 ha).Methods
We surveyed birds and calculated spatial landscape properties in sub-tropical woodlands of central Queensland, Australia.Results
Environmental heterogeneity, as measured by topographic complexity, was consistently important for bird species richness and composition. However, the explanatory power of topographic complexity varied depending on the spatial scale and the component of diversity under investigation. We found different correlates of richness within particular foraging guilds depending on the scale at which richness was measured. Extent of long-unburnt habitat (>10 years since fire) was the most important variable for the landscape-scale richness of frugivores, insectivores and canopy feeders, whereas environmental heterogeneity in the surrounding landscape was more important for site-scale richness of these foraging guilds.Conclusions
The response of species richness to landscape characteristics varies among scales, and among components of diversity. Thus, depending on the scale at which a biodiversity conservation goal is conceptualised—maximising richness at a site, or across a landscape—different landscape management approaches may be preferred.3.
Context
The relative importance of habitat area and connectivity for species richness is often unknown. Connectivity effects may be confounded with area effects or they may be of minor importance as posited by the habitat-amount hypothesis.Objectives
We studied effects of habitat area and connectivity of linear landscape elements for plant species richness at plot level. We hypothesized that connectivity of linear landscape elements, assessed by resistance distance, has a positive effect on species richness beyond the effect of area and, further, that the relative importance of connectivity varies among groups of species with different habitat preferences and dispersal syndromes.Methods
We surveyed plant species richness in 50 plots (25 m2) located on open linear landscape elements (field margins, ditches) in eight study areas of 1 km2 in agricultural landscapes of Northwest Germany. We calculated the area of linear landscape elements and assessed their connectivity using resistance distance within circular buffers (500 m) around the plots. Effects of area and connectivity on species richness were modelled with generalised linear mixed models.Results
Species richness did not increase with area. Resistance distance had significant negative effects on total richness and on the richness of typical species of grasslands and wetlands. Regarding dispersal syndromes, resistance distance had negative effects on the richness of species with short-distance, long-distance and aquatic dispersal. The significant effects of resistance distance indicated that species richness increased with connectivity of the network of linear landscape elements.Conclusions
Connectivity is more important for plant species richness in linear landscape elements than area. In particular, the richness of plant species that are dispersal limited and confined to semi-natural habitats benefits from connective networks of linear landscape elements in agricultural landscapes.4.
Elsa Aggemyr Alistair G. Auffret Love Jädergård Sara A. O. Cousins 《Landscape Ecology》2018,33(12):2273-2284
Context
Understanding how landscape patterns affect species diversity is of great importance in the fields of biogeography, landscape ecology and conservation planning, but despite the rapid advance in biodiversity analysis, investigations of spatial effects on biodiversity are still largely focused on species richness.Objectives
We wanted to know if and how species richness and species composition are differentially driven by the spatial measures dominating studies in landscape ecology and biogeography. As both measures require the same limited presence/absence information, it is important to choose an appropriate diversity measure, as differing results could have important consequences for interpreting ecological processes.Methods
We recorded plant occurrences on 112 islands in the Baltic archipelago. Species richness and composition were calculated for each island, and the explanatory power of island area and habitat heterogeneity, distance to mainland and structural connectivity at three different landscape sizes were examined.Results
A total of 354 different plant species were recorded. The influence of landscape variables differed depending on which diversity measure was used. Island area and structural connectivity determined plant species richness, while species composition revealed a more complex pattern, being influenced by island area, habitat heterogeneity and structural connectivity.Conclusions
Although both measures require the same basic input data, species composition can reveal more about the ecological processes affecting plant communities in fragmented landscapes than species richness alone. Therefore, we recommend that species community composition should be used as an additional standard measure of diversity for biogeography, landscape ecology and conservation planning.5.
Habitat fragmentation strongly affects insect species diversity and community composition, but few studies have examined landscape
effects on long term development of insect communities. As mobile consumers, insects should be sensitive to both local plant
community and landscape context. We tested this prediction using sweep-net transects to sample insect communities for 8 years
at an experimentally fragmented old-field site in northeastern Kansas, USA. The site included habitat patches undergoing secondary
succession, surrounded by a low turf matrix. During the first 5 years, plant richness and cover were measured in patches.
Insect species richness, total density, and trophic diversity increased over time on all transects. Cover of woody plants
and perennial forbs increased each year, adding structural complexity to successional patches and potentially contributing
to increased insect diversity. Within years, insect richness was significantly greater on transects through large successional
patches (5000 m2) than on transects through fragmented arrays of 6 medium-sized (total area 1728 m2) or 15 small (480 m2) patches. However, plant cover did not differ among patch types and was uncorrelated with insect richness within years. Insect
richness was strongly correlated with insect density, but trophic and α diversities did not differ among patch types, indicating
that patch insect communities were subsets of a common species pool. We argue that differences in insect richness resulted
from landscape effects on the size of these subsets, not patch succession rates. Greater insect richness on large patches
can be explained as a community-level consequence of population responses to resource concentration. 相似文献
6.
Context
Quantifying variability in landscape-scale surface water connectivity can help improve our understanding of the multiple effects of wetlands on downstream waterways.Objectives
We examined how wetland merging and the coalescence of wetlands with streams varied both spatially (among ecoregions) and interannually (from drought to deluge) across parts of the Prairie Pothole Region.Methods
Wetland extent was derived over a time series (1990–2011) using Landsat imagery. Changes in landscape-scale connectivity, generated by the physical coalescence of wetlands with other surface water features, were quantified by fusing static wetland and stream datasets with Landsat-derived wetland extent maps, and related to multiple wetness indices. The usage of Landsat allows for decadal-scale analysis, but limits the types of surface water connections that can be detected.Results
Wetland extent correlated positively with the merging of wetlands and wetlands with streams. Wetness conditions, as defined by drought indices and runoff, were positively correlated with wetland extent, but less consistently correlated with measures of surface water connectivity. The degree of wetland–wetland merging was found to depend less on total wetland area or density, and more on climate conditions, as well as the threshold for how wetland/upland was defined. In contrast, the merging of wetlands with streams was positively correlated with stream density, and inversely related to wetland density.Conclusions
Characterizing the degree of surface water connectivity within the Prairie Pothole Region in North America requires consideration of (1) climate-driven variation in wetness conditions and (2) within-region variation in wetland and stream spatial arrangements.7.
Wetland and pond hydric vegetation is impacted across the rural, peri-urban, and urban zones by anthropogenic activities such as agricultural production, industrial manufacturing, and urban development. Previous studies have assessed urban and rural wetland vegetation, but have rarely explored the peri-urban zone of development. Therefore, to investigate the impacts of urbanization on hydric vegetation, thirty pond sites (10 rural, 10 peri-urban, and 10 urban) were randomly selected within each of the three zones. The vegetation community at each site was assessed using a quadrat method to compare the vegetation composition. In addition, floristic quality based on the conservatism value of each plant species was used to assess wetland vegetation. Results show plant communities of rural sites differed from both urban and peri-urban sites due partly to urbanization reducing the cover of obligate wetland species. Peri-urban sites contained the highest species richness, due to the increase in introduced plants associated with urbanization. Urban sites contained the lowest species richness, some of which is due to the use of rock riprap surrounding the edges of most sites. The plant conservatism values of vegetation were not different for rural and peri-urban sites, but were significantly lower in urban sites. Information from this study is useful to wetland professionals, environmental managers, and urban planners to predict hydric vegetation responses within peri-urban areas in the Prairie Pothole Region. 相似文献
8.
Birds may use urban parks as shelter and refuge, contributing with numerous ecosystem services upon which humans and other organisms depend on. To safeguard these services, it is important that bird communities of urban environments hold some degree of resilience, which refers to the capacity of a system to absorb disturbances and changes, while maintaining its functions and structures. Here we assessed the resilience of the bird community inhabiting an urban park in the Southeast region of Brazil. We classified birds in feeding guilds and identified discontinuities and aggregations of body masses (i.e., scales) using hierarchical cluster analysis. We then calculated five resilience indices for our urban park and for a preserved continuous forest (reference area): the average richness of functions, diversity of functions, evenness of functions, and redundancy of functions within- and cross-scale. The urban park had less species, lower feeding guild richness, and lower within-scale redundancy than the reference area. However, they had similar proportion of species in each function, diversity of functions, evenness of functions, and cross-scale redundancy. The lower species richness and, consequently, the lack of some species performing some ecological functions may be responsible for the overall lower resilience in the urban park. Our results suggest that the bird community of the urban park is in part resilient, as it maintained many biological functions, indicating some environmental quality despite the high anthropogenic impacts of this area. We believe that urban forest remnants with more complex and diverse vegetation are possibly more likely to maintain higher resilience in the landscape than open field parks or parks with suppressed or altered vegetation. We propose that raising resilience in the urban park would possibly involve increasing vegetation complexity and heterogeneity, which could increase biodiversity in a large scale. 相似文献
9.
The river valley of the French upper Meuse and its floodplain, constitutes a relatively natural ecosystem which still contains many endangered species of high conservation value. For example, several birds (Crex crex, Numenius arquata) as well as plant species (Gratiola officinalis, Inula britannica, Teucrium scordium, Ranunculus lingua and Mentha pulegium) which have declined seriously in France in recent times are found in the upper Meuse floodplain. Phytosociological studies and water level measurements have shown that the floristic diversity is mainly influenced by hydrological fluctuations and agricultural practices. The plant communities are structured along a topographical gradient in the high water bed reflecting the duration of floods and the ground water table depth. Agricultural practices have influenced the vegetation changes by selecting species adapted to particular management practices (e.g., fertiliser use, grazing, cutting regime). The data collected in this study from the upper Meuse as enabled 13 grassland and wetland ecotopes to be defined which are correlated with different environmental factors. Fertiliser use, grazing and reduction in the frequency of the cutting lead to a lower species richness because they encourage competitive species. However, it is also demonstrated, that maximum biodiversity is not always synonymous with high conservation value because some impoverished ecosystems, e.g., sedges and tall forb formations, may contain endangered plant and bird species. Knowledge of the boundaries between the different plant communities enables likely changes in floristic composition after modification of one or more site factors to be forecasted. Such factors include, water table depth and flood frequency, cutting regime, fertiliser use and grazing pressure. Thus, the definition of these ecotopes, corresponding to correlations between water regime, agricultural practice and vegetation composition, could lead to the establishment of guidelines for water and agricultural managements that could be involved in restoration projects. 相似文献
10.
Balázs Deák Orsolya Valkó Péter Török András Kelemen Ádám Bede András István Csathó Béla Tóthmérész 《Landscape Ecology》2018,33(7):1117-1132
Context
Landscape and habitat filters are major drivers of biodiversity of small habitat islands by influencing dispersal and extinction events in plant metapopulations.Objectives
We assessed the effects of landscape and habitat filters on the species richness, abundance and trait composition of grassland specialist and generalist plants in small habitat islands. We studied traits related to functional spatial connectivity (dispersal ability by wind and animals) and temporal connectivity (clonality and seed bank persistence) using model selection.Methods
We sampled herbaceous plants, landscape (local and regional isolation) and habitat filters (inclination, woody encroachment and disturbance) in 82 grassland islands in Hungary.Results
Isolation decreased the abundance of good disperser specialist plants due to the lack of directional vectors transferring seeds between suitable habitat patches. Clonality was an effective strategy, but persistent seed bank did not support the survival of specialist plants in isolated habitats. Generalist plants were unaffected by landscape filters due to their wide habitat breadth and high propagule availability. Clonal specialist plants could cope with increasing woody encroachment due to their high resistance against environmental changes; however, they could not cope with intensive disturbance. Steep slopes providing environmental heterogeneity had an overall positive effect on species richness.Conclusions
Specialist plants were influenced by the interplay of landscape filters influencing their abundance and habitat filters affecting species richness. Landscape filtering by isolation influenced the abundance of specialist plants by regulating seed dispersal. Habitat filters sorted species that could establish and persist at a site by influencing microsite availability and quality.11.
The question of what determines plant community composition is fundamental to the study of plant community ecology. We examined
the relative roles of historical land use, landscape context, and the biophysical environment as determinants of plant community
composition in regenerating citrus groves in north-central Florida. Results were interpreted in light of plant functional
traits. Herbaceous and woody plants responded differently to broad-scale variables; herbs correlated most strongly with surrounding
land cover at a scale of 8 km, while the only significant determinant of woody species distributions was local land use history.
There were significant correlations between herbaceous species and spatial context, habitat isolation, environmental variables,
and historical variables. Partial Mantel tests indicated that each variable provided a unique contribution in explaining some
of the variation in the herbaceous dataset. The correlation between woody plants and local historical variables remained significant
even with other effects corrected for. In the herbaceous community, species composition was linked to functional traits much
as expected from classical theory. While spatial influences in our study system are important for both woody and herbaceous
plants, the primary determinant of plant community composition in regenerating citrus groves is historical land use. Our results
suggest that the fine-scale mechanisms of local competition, tolerance and facilitation invoked by many classical studies
may ultimately be less important than land use history in understanding current plant community composition in regenerating
agricultural areas. 相似文献
12.
Helena Tukiainen Janne Alahuhta Richard Field Terhi Ala-Hulkko Raino Lampinen Jan Hjort 《Landscape Ecology》2017,32(5):1049-1063
Context
‘Conserving Nature’s stage’ has been advanced as an important conservation principle because of known links between biodiversity and abiotic environmental diversity, especially in sensitive high-latitude environments and at the landscape scale. However these links have not been examined across gradients of human impact on the landscape.Objectives
To (1) analyze the relationships between land-use intensity and both landscape-scale biodiversity and geodiversity, and (2) assess the contributions of geodiversity, climate and spatial variables to explaining vascular plant species richness in landscapes of low, moderate and high human impact.Methods
We used generalized additive models (GAMs) to analyze relationships between land-use intensity and both geodiversity (geological, geomorphological and hydrological richness) and plant species richness in 6191 1-km2 grid squares across Finland. We used linear regression-based variation partitioning (VP) to assess contributions of climate, geodiversity and spatial variable groups to accounting for spatial variation in species richness.Results
In GAMs, geodiversity correlated negatively, and plant species richness positively, with land-use intensity. Both relationships were non-linear. In VP, geodiversity best accounted for species richness in areas of moderate to high human impact. These overall contributions were mainly due to variation explained jointly with climate, which dominated the models. Independent geodiversity contributions were highest in pristine environments, but low throughout.Conclusions
Human action increases biodiversity but may reduce geodiversity, at landscape scale in high-latitude environments. Better understanding of the connections between biodiversity and abiotic environment along changing land-use gradients is essential in developing sustainable measures to conserve biodiversity under global change.13.
Context
Complex landscapes with high resource availability can support more diverse natural enemy communities and better natural pest control by providing resources and facilitating organism dispersal. Moreover, in agricultural landscapes, local agroecosystem management can support biodiversity maintenance and pest control by adding resources in less complex landscapes with fewer resources. However, we lack an understanding of how local and landscape factors interact to affect natural enemy communities and their site fidelity to agroecosystems in urban landscapes (i.e., cityscapes).Objective
To better understand how local and landscape factors influence natural enemies in urban agroecosystems, we used urban community gardens as a model system to test if and how local resource manipulation and differences in cityscape quality affect natural enemy (ladybird beetles, parasitoid wasps) communities and their fidelity to urban habitats.Methods
We performed two manipulations. First, we added local floral resources in 6 of 12 gardens situated in different cityscapes to measure differences in natural enemy biodiversity. Second, in those 12 gardens, with and without resource additions, we manipulated populations of a common natural enemy, Hippodamia convergens, to assess fidelity to the gardens.Results
Floral resource additions increased parasitoid abundance and changed community composition, but had little effect on ladybeetle abundance, richness or site fidelity. Rather, ladybeetle fidelity to gardens was lower in gardens in low quality cityscapes with high impervious cover.Conclusions
Cityscape quality influences natural enemies in and fidelity to gardens. Landscape-moderated biodiversity patterns observed in rural landscapes likely differ from urban contexts with implications for pest control.14.
Context
Mosquito-borne diseases in the United States are notorious for their seemingly erratic temporal and spatial outbreak patterns in humans. Identifying linkages between fine-scale phenomenon and macroscale outbreak patterns can improve the understanding of these complex socio–ecological systems.Objectives
Using West Nile virus (WNV) as a model system, we examine whether fine-scale wetland characteristics—wetland size, connectivity, and inundation regime—have an important effect on macroscale human disease outbreak in the northeastern and midwestern United States.Methods
We take a spatially explicit GIS-based approach, derive new macroscale wetland metrics based on fine-scale wetland characteristics, and use county-level annual human WNV incidence data over 11 years to evaluate linkages between the fine and macroscales (1.6 million km2).Results
In regions dominated by the Culex tarsalis WNV vector, U.S. counties with a small average wetland size had more than 100 % higher human WNV incidence than counties with a large average wetland size. In regions dominated by the Cx. pipiens and Cx. restuans vectors, a low proportional area of connected wetland was associated with at least 50 % higher human WNV incidence than a high proportional area of connected wetland. Finally, Cx. tarsalis-dominated counties with a high proportional area of semi-permanent wetland that were experiencing drought conditions had over 300 % higher annual WNV incidence than drought-affected counties with a low proportional area of semi-permanent wetland.Conclusions
Our results suggest that phenomena occurring at the individual wetland scale may aggregate to influence macroscale human WNV outbreak patterns and may be mediated by the interplay of other factors such as vector species-specific traits and climate.15.
Context
The world is becoming increasingly urbanized, with more than half of the global population now living in cities. Understanding the factors impacting natural communities in fragmented landscapes is therefore crucial for predicting how the remaining ecosystems will respond to global change. Ground-active arthropods, which are important in nutrient cycling, are likely sensitive to habitat changes resulting from urbanization.Objectives
We addressed two questions: (1) What is the relative importance of local and landscape factors in shaping ground-active arthropod communities in urban woodlands? (2) How does body size (as a surrogate for dispersal ability) affect sensitivity to landscape-level factors?Methods
In the summers of 2010 and 2011, we sampled ground-active arthropod communities in 19 woodlands in the Chicago metropolitan region using pitfall traps. We also assessed local plant and soil characteristics, as well as landscape-level variables using GIS.Results
Redundancy analyses and variation partitioning revealed that local factors, particularly invasive woody-plant cover and soil nitrate, had the most influence on arthropod communities, explaining 12% of the total variation. Of the landscape-level variables, landscape richness, which is one measure of landscape fragmentation, explained the most variation; however, the shared variance between landscape and local variables was responsible for half (16%) of the total explained variation (32%). Landscape factors alone explained only 4% of variation. No relationship between arthropod body size and landscape variables was observed, but several groups (e.g. ants and ground beetles) were correlated with landscape-level factors.Conclusions
Our research shows that both local and landscape variables are important in influencing ground-active arthropods, but the majority of explained variance is attributed to the covariation between landscape richness, invasive woody-plant cover, and soil nitrate. We therefore conclude that landscape fragmentation is likely affecting the ground-active arthropods through its positive influence on invasive woody plants and soil nitrogen.16.
In semiarid landscapes, the ratio of herbaceous to woody plant biomass is a major determinant of ecosystem properties. This ratio depends to a large extent on the amount and spatial distribution of soil moisture that is available to plants, and these variables, in turn, are determined primarily by climate and land use. Current conceptual models for determining the ratio of herbaceous to woody plant biomass in semiarid plant communities are based either on differences in soil moisture with depth (vertical heterogeneity) from one site to another (Walter's two-layer model) or on differences in soil moisture between canopy and intercanopy patches at the same site (horizontal heterogeneity) that result from disturbances associated with land use (Schlesinger et al.'s model of desertification). We developed a model that unifies these two perspectives by relaxing two assumptions of Walter's two-layer model. First, our model recognizes that soil moisture varies horizontally between canopy and intercanopy patches, not only due to land-use disturbance, a general assumption of the Schlesinger et al. model, but also due to the physical nature of the canopy itself. Second, while retaining the general assumption of Walter that woody plants obtain moisture from deeper soil layers than do herbaceous plants, our model recognizes the existence of two types of woody plants: those that extract a substantial proportion of their moisture from deeper layers and those that extract mainly from shallower layers. By modifying the two-layer hypothesis to include four soil compartments and distinguishing between shallow- and deeper-rooted woody species, our model integrates three key concepts in semiarid ecology: (1) the proportion of woody cover increases as moisture in the deeper soil layers increases (Walter's two-layer hypothesis for coexistence of herbaceous and woody plants); (2) land use practices that cause a reduction in herbaceous vegetation and compaction of intercanopy soils lead to a long-term increase in the proportion of woody plants (Schlesinger et al.'s concept, or more generally, that at a given site multiple variations in the proportions of herbaceous and woody plant biomass are possible); and (3) changes in the ratios of herbaceous to woody plant biomass exhibit complex behavior (changes can happen quickly and are not directly reversible without intensive management). This integration of concepts results because rather than assuming a simple, one-way dependence of plant functional types on soil moisture heterogeneity, our model assumes an interdependence between the two: soil moisture heterogeneity constrains the composition of the plant community, which in turn modifies soil moisture heterogeneity. The four-compartment model that we propose enables, for the first time, an integrated picture of both dimensions of soil moisture heterogeneity – horizontal and vertical – and of the interdependence between soil moisture heterogeneity and the proportions of the plant functional types that make up a given plant community. This unified conceptual model can be applied to provide insight into the individual and the combined effects of climate and land use on semiarid plant communities within the grassland/forest continuum, which vary in the proportions of canopy and intercanopy patches. 相似文献
17.
Context
We address the issue of adapting landscapes for improved insect biodiversity conservation in a changing climate by assessing the importance of additive (main) and synergistic (interaction) effects of land cover and land use with climate.Objectives
We test the hypotheses that ant richness (species and genus), abundance and diversity would vary according to land cover and land use intensity but that these effects would vary according to climate.Methods
We used a 1000 m elevation gradient in eastern Australia (as a proxy for a climate gradient) and sampled ant biodiversity along this gradient from sites with variable land cover and land use.Results
Main effects revealed: higher ant richness (species and genus) and diversity with greater native woody plant canopy cover; and lower species richness with higher cultivation and grazing intensity, bare ground and exotic plant groundcover. Interaction effects revealed: both the positive effects of native plant canopy cover on ant species richness and abundance, and the negative effects of exotic plant groundcover on species richness were greatest at sites with warmer and drier climates.Conclusions
Impacts of climate change on insect biodiversity may be mitigated to some degree through landscape adaptation by increasing woody native vegetation cover and by reducing land use intensity, the cover of exotic vegetation and of bare ground. Evidence of synergistic effects suggests that landscape adaptation may be most effective in areas which are currently warmer and drier, or are projected to become so as a result of climate change.18.
Habitat specificity indices reflect richness (α) and/or distinctiveness (β) components of diversity. The latter may be defined by α and γ (landscape) diversity in two alternative ways: multiplicatively () and additively (). We demonstrate that the original habitat specificity concept of Wagner and Edwards (Landscape Ecol 16:121–131, 2001) consists of three independent components: core habitat specificity (uniqueness of the species composition), patch area and
patch species richness. We describe habitat specificity as a family of indices that may include either area or richness components,
or none or both, and open for use of different types of mean in calculation of core habitat specificity. Core habitat specificity
is a beta diversity measure: the effective number of completely distinct communities in the landscape. Habitat specificity
weighted by species number is a gamma diversity measure: the effective number of species that a patch contributes to landscape
richness. We compared 12 habitat specificity indices by theoretical reasoning and by use of field data (vascular plant species
in SE Norwegian agricultural landscapes). Habitat specificity indices are strongly influenced by weights for patch area and
patch species richness, and the relative contribution of rare vs. common species (type of mean). The relevance of properties
emphasized by each habitat specificity index for evaluation of patches in a biodiversity context is discussed. Core habitat
specificity is emphasized as an ecologically interpretable measure that specifically addresses patch uniqueness while habitat
specificity weighted by species number combines species richness and species composition in ways relevant for conservation
biological assessment.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
Landscape patch shape complexity as an effective measure for plant species richness in rural landscapes 总被引：13，自引：0，他引：13
Moser Dietmar Zechmeister Harald G. Plutzar Christoph Sauberer Norbert Wrbka Thomas Grabherr Georg 《Landscape Ecology》2002,17(7):657-669
The application of landscape patch shape complexity as a predictor ofvascularplant and bryophyte species richness is analysed. Several common complexityindices (shape index, fractal dimension, comparison to the area of the minimumbounding rectangle) are tested for their predictive power for plant speciesrichness. One new robust measure for shape complexity is presented whichovercomes some disadvantages of common complexity measures applied to highresolution analysis of agricultural landscapes based on aerial photographs. Thenew index is based on the number of shape characterising points along apolygons boundary. This new measure shows promising predictive capabilitiesforspecies richness of vascular plants and bryophytes (correlation coefficient:0.85 for vascular plants, 0.74 for bryophytes).This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
20.
Effects of land ownership and landscape-level factors on rare-species richness in natural areas of southern Ontario,Canada 总被引：5，自引：0，他引：5
Lovett-Doust J. Biernacki M. Page R. Chan M. Natgunarajah R. Timis G. 《Landscape Ecology》2003,18(6):621-633
Surprisingly few studies have considered the extent to which the nature of the ownership of land is associated with differences
in biodiversity. We analysed ownership and other landscape-level effects on rare-species richness for both globally- and regionally-rare
biota (including birds, herpetofauna, butterflies, mammals, and plants) in 289 designated natural areas (NAs) in southern
Ontario, Canada. Information about each NA −including area, number of plant communities, ownership status and details of species
diversity were collected from published sources. Length of perimeter of NA, relative isolation, and an estimate of fragmentation
were measured using image analysis and GIS techniques. NAs were in general relatively small, with mean area of 158 ha (median
85 ha, range from 0.9 to 1278 ha) for private NAs; public NAs had mean area of 132 ha (median 16 ha, range from 0.1 to 1481
ha). Mean number of plant communities was 4.6 (median 4, range 1- 13) at private NAs and 3.8 (median 3, range 1-16) at public
NAs. Our results show that, of several landscape-level factors, area had the greatest effects on rare-species richness and
other biotic indices. Effects of area were followed by effects of plant community diversity, however this was itself significantly
affected by area and the extent of perimeter of the NA. Both these factors were followed by effects of ownership of the NA
and by effects of isolation of the NA (represented by minimum distance to nearest NA and by number of NAs in 10 km radius).
Other landscape- level factors did not appear to have overall significant effects. Variation in area accounted for 0.1% to
29% of variation in number of rare species, with lower values for globally-rare, than for regionally-rare taxa. For all biotic
groups, public ownership of NAs was associated with significantly greater rare-species richness compared to private ownership,
even after other factors such as area were controlled. For all globally-rare biota except butterflies, area of NA had greater
effects on rare-species richness than did ownership. Richness of regionally- rare birds was more affected by plant community
diversity than by area of NA. Number of recorded plant communities accounted from 2.1% of variation in number of globally-rare
plant species to as high as 31% of variation in regionally-rare butterflies. The diversity of plant communities was itself
influenced by total site area (accounting for 45% of variation), extent of elongation of the NA, and both external- and interior-
edge perimeters. Public NAs had greatest numbers of rare biota and so should be a significant focus for conservation programs.
Smaller, privately-owned patches of natural area dominate (by number and area) in this densely populated region and their
significance should not be overlooked.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献