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1.
The diversity of future landscapes might depend on our ability to predict their potential species richness. The predictability
of patterns of vascular plant species richness in a Finnish agricultural river landscape was studied using generalized linear
modeling, floristic records from fifty-three0.25-km grid squares in the “core” study area, and environmental variables derived
from Landsat TM images and a digital elevation model. We built multiple regression models for the total number of plant species
and the number of rarities, and validated the accuracy of the derived models with a test set of 52 grid squares. We tentatively
extrapolated the models from the core study area to the whole study area of 601 km2 and produced species richness probability maps using GIS techniques. The results suggest that the local ‘hotspots’ of total
flora (grid squares with > 200species) are mainly found in river valleys, where habitat diversity is high and a semi-open
agricultural-forest mosaic occurs. The ‘hotspots’ of rare species (grid squares with > 4 rare species) are also found in river
valleys, in sites where extensive semi-natural grasslands and herb-rich deciduous forests occur on steep slopes. We conclude
that environmental variables derived from satellite images and topographic data can be used as approximate surrogates of plant
species diversity in agricultural landscapes. Modeling of biological diversity based on satellite images and GIS can provide
useful information needed in land use planning. However, due to the potential pitfalls in processing satellite imagery and
model-building procedures, the results of predictive models should be carefully interpreted.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Landscape Ecology - Native pollinators provide an important ecosystem service for many pollination-dependent fruit crops, but require nesting and foraging resources in proximity to target crop... 相似文献
3.
Patch geometry and habitat quality among patches are widely recognized as important factors affecting population dynamics in fragmented landscapes. Little is known, however, about the influence of within-patch habitat quality on population dynamics. In this paper, we investigate the relative importance of patch geometry and within-patch habitat quality in determining population dynamics using a spatially explicit, agent-based model. We simulate two mobile species that differ in their species traits: one resembles a habitat specialist and the other a habitat generalist. Habitat quality varies continuously within habitat patches in space (and time). The results show that spatial variation in within-patch quality, together with patch area, controls population abundance of the habitat specialist. In contrast, the population size of the generalist species depends on patch area and isolation. Temporal variation in within-patch quality is, however, less influential in driving the population resilience of both species. We conclude that specialist species are more sensitive than generalist species to within-patch variation in habitat quality. The patch area-isolation paradigm, developed in metapopulation theory, should incorporate variation in within-patch habitat quality, particularly for habitat specialists. 相似文献
4.
A simple, straightforward, cartographic modelling technique is presented for measuring relations between environmental characteristics and rare species distribution patterns. This approach is corroborated by digitizing rare bird distribution data for Tanzania and statistically analyzing these patterns in relation to geographic and environmental variables. Of the available natural resource data for Africa, only the vegetation and soils data appeared accurate enough to represent regional natural resource distribution patterns. Available data for Tanzania at the regional scale is not currently precise or comprehensive enough to analyze ongoing dynamic ecological processes.Statistical relations, associated with a study quadrangle within Tanzania, are documented for these parameters. Final confirmation of the accuracy of predictions about rare species diversity patterns will ensue from future field observations. When confirmed, this methodology can be used for setting conservation priorities in biologically little known regions of the world. 相似文献
5.
Protection of rare ecosystems requires information on their abundance and spatial distribution, yet mapping rare ecosystems,
particularly those which are fragmented, is a challenge. Use of high spatial resolution satellite imagery is increasing, in
part because it may be well-suited for mapping fine-scale components of landscapes. We classified high spatial resolution
QuickBird imagery of coastal British Columbia, Canada into late seral forest associations. With an emphasis on rare forest
associations, we compared the classification accuracies resulting from contrasting accuracy assessment techniques. We also
evaluated the impact of post-classification image smoothing on the quantity and configuration of rare forest associations
mapped. Less common associations were generally classified with lower accuracies than more abundant associations, however,
accuracies varied depending on the assessment technique used. In particular, ignoring the presence of fine-scale heterogeneity
falsely lowered the estimates of map accuracy by approximately 20%. Smoothing, while generally increasing the accuracies of
rare forest associations, had a large effect on their predicted spatial extent and configuration. Simply due to smoothing,
areal estimates of rare associations differed by as much as 36%, the number of patches decreased by 73% on average, and mean
patch size increased by up to 650%. Our findings indicate that routinely used post-classification and map assessment techniques
can greatly impact the portrayal of rare and fragmented ecosystems. Further research is needed on the specific challenges
of mapping and assessing the accuracy of rare ecosystems in fragmented and heterogeneous landscapes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
6.
Modeling invasive species spread in complex landscapes: the case of potato moth in Ecuador 总被引:1,自引:0,他引:1
Verónica Crespo-Pérez François Rebaudo Jean-François Silvain Olivier Dangles 《Landscape Ecology》2011,26(10):1447-1461
Tropical mountains have a long history of human occupation, and although vulnerable to biological invasions, have received
minimal attention in the literature. Understanding invasive pest dynamics in socio-ecological, agricultural landscapes, like
the tropical Andes, is a challenging but timely issue for ecologists as it may provide developing countries with new tools
to face increasing threats posed by these organisms. In this work, road rehabilitation into a remote valley of the Ecuadorian
Andes constituted a natural experiment to study the spatial propagation of an invasive potato tuber moth into a previously
non-infested agricultural landscape. We used a cellular automaton to model moth spatio-temporal dynamics. Integrating real-world
variables in the model allowed us to examine the relative influence of environmental versus social landscape heterogeneity
on moth propagation. We focused on two types of anthropogenic activities: (1) the presence and spatial distribution of traditional
crop storage structures that modify local microclimate, and (2) long-distance dispersal (LDD) of moths by human-induced transportation.
Data from participatory monitoring of pest invasion into the valley and from a larger-scale field survey on the Ecuadorian
Andes allowed us to validate our model against actual presence/absence records. Our simulations revealed that high density
and a clumped distribution of storage structures had a positive effect on moth invasion by modifying the temperature of the
landscape, and that passive, LDD enhanced moth invasion. Model validation showed that including human influence produced more
precise and realistic simulations. We provide a powerful and widely applicable methodological framework that stresses the
crucial importance of integrating the social landscape to develop accurate invasion models of pest dynamics in complex, agricultural
systems. 相似文献
7.
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
8.
9.
Despite good theoretical knowledge about determinants of plant species richness in mosaic landscapes, validations based on
complete surveys are scarce. We conducted a case study in a highly fragmented, traditional agricultural landscape. In 199
patches of 20 representative multi-patch-plots (MPPs, 1 ha) we recorded a total of 371 plant species. In addition to an additive
partitioning of species diversity at the (a) patch- and (b) MPP-scale, we adopted the recently proposed ‘specificity’ measure
to quantify the contribution of a spatial subunit to landscape species richness (subunit-to-landscape-contribution, SLC).
SLC-values were calculated at both scales with respect to various spatial extents. General regression models were used to
quantify the relative importance of hypothesis-driven determinants for species richness and SLC-values.
At the patch scale, habitat type was the main determinant of species richness, followed by area and elongated shape. For SLC-values,
area was more important than habitat type, and its relevance increased with the extent of the considered landscape. Influences
of elongated shape and vegetation context were minor. Differences between habitat types were pronounced for species richness
and also partly scale-dependent for SLC-values.
Relevant predictors at the MPP-scale were nonlinear habitat richness, the gradient from anthropogenic to seminatural vegetation,
and the proportions of natural vegetation and rare habitats. Linear elements and habitat configuration did not contribute
to species richness and SLC. Results at the MPP-scale were in complete accordance with the predictions of the mosaic concept.
Hence, our study represents its first empirical validation for plant species diversity in mosaic landscapes. 相似文献
10.
Land-bridge islands formed by dam construction are considered to be “experimental” systems for studying the effects of habitat
loss and fragmentation, offering many distinct advantages over terrestrial fragments. The Thousand Island Lake in Southeast
China is one such land-bridge system with more than 1000 islands. Based on a field survey of vascular plant richness on 154
land-bridge islands during 2007–2008, we examined the effects of island and landscape attributes on plant species richness
and patterns of species nestedness. We also examined the different responses of plant functional groups (classified according
to growth form and shade tolerance) to fragmentation. We found that island area explained the greatest amount of variation
in plant species richness. Island area and shape index positively affected species diversity and the degree of nestedness
exhibited by plant communities while the perimeter to area ratio of the islands had a negative effect. Shade-tolerant plants
were the most sensitive species group to habitat fragmentation. Isolation negatively affected the degree of nestedness in
herb and shade-intolerant plants including species with various dispersal abilities in the fragmented landscape. Based on
these results, we concluded that the effects of habitat loss and fragmentation on overall species richness depended mostly
on the degree of habitat loss, but patterns of nestedness were generated from different ecological mechanisms due to species-specific
responses to different characteristics of habitat patches. 相似文献
11.
Mediterranean landscapes are suffering two opposing forces leading to large-scale changes in species distribution: land abandonment
of less productive areas and an increase in wildfire impact. Here, we test the hypothesis that fires occurred in recent decades
drive the pattern of expansion of early-successional, open-habitat bird species by aiding in the process of colonisation of
newly burnt areas. The study was carried out in Catalonia (NE Spain). We selected 44 burnt sites occurring between 2000 and
2005 to model colonisation patterns under different assumptions of potential colonisers’ sources and evaluated the colonisation
estimates with empirical data on six bird species especially collected for this purpose. We first defined three landscape
scenarios serving as surrogates of potential colonisers’ sources: open-habitats created by fire, shrublands and farmlands.
Then, we used a parameter derived from a functional connectivity metric to estimate species colonization dynamics on the selected
sites by each particular scenario. Finally, we evaluated our colonisation estimates with the species occurrence in the studied
locations by using generalized linear mixed models. The occurrence of the focal species on the newly burnt sites was significantly
related to the connectivity patterns described by both the recent fire history and the other open-habitat types generated
by a different type of disturbance. We suggest that land use changes in recent decades have produced a shift in the relative
importance of habitats acting as reservoirs for open-habitat bird species dynamics in Mediterranean areas. Before the middle
of the twentieth century species’ reservoirs were probably constituted by relatively static open habitats (grassland and farmland),
whereas afterwards they likely consist of a shifting mosaic of habitat patches where fire plays a key role as connectivity
provider and largely contributes to the maintenance of species persistence. 相似文献
12.
Habitat loss and fragmentation of natural and semi-natural habitats are considered as major threats to plant species richness.
Recently several studies have pinpointed the need to analyse past landscape patterns to understand effects of fragmentation,
as the response to landscape change may be slow in many organisms, plants in particular. We compared species richness in continuously
grazed and abandoned grasslands in different commonplace rural landscapes in Sweden, and analysed effects of isolation and
area in three time-steps (100 and 50 years ago and today). Old cadastral maps and aerial photographs were used to analyse
past and present landscape patterns in 25 sites. Two plant diversity measures were investigated; total species richness and
species density. During the last 100 years grassland area and connectivity have been reduced by about 90%. Present-day habitat
area was positively related to total species richness in both habitats. There was also a relationship to habitat area 50 years
ago for continuously grazed grasslands. Only present management was related to species density: continuously grazed grasslands
had the highest species density. There were no relationships between grassland connectivity, present or past, and any diversity
measure. We conclude that landscape history is not directly important for present-day plant diversity patterns in ordinary
landscapes, although past grassland management is a prerequisite for the grassland habitats that can be found there today.
It is important that studies are conducted, not only in very diverse landscapes, but also in managed landscapes in order to
assess the effects of fragmentation on species. 相似文献
13.
Dead wood is a critical resource for biodiversity in boreal forests. We analysed the persistence of five model species inhabiting
dead wood. By parameterising a metapopulation model (the incidence function model), the model species were all assigned characteristics
that makes it likely that they have disappeared from some (20%) forest landscapes with a long history of forest management.
In the metapopulation model, a forest stand (5 ha) was regarded as a habitat patch. The amount of habitat in each patch was
obtained from models of dead wood dynamics of Norway spruce in central Sweden. Dead wood generated by altered management over
the entire landscape was found to be less efficient in reducing extinction risks in comparison to the same amount of dead
wood generated by protecting reserves. Because generation of dead wood by altered management is often less expensive than
setting aside reserves, it is difficult to determine which conservation measure is most cost-efficient. In a landscape subjected
to forestry for the first time, it was better to preserve a few large reserves than many small ones. However, in a managed,
highly fragmented forest landscape it was better to set aside many small reserves. The reason for this was that small plots
with high habitat quality could be selected, while large reserves originally contained habitats both of high and low quality,
and the rate of habitat quality increase was low. A strategy for biodiversity conservation in a managed forest landscape should
include information about the history of the landscape, the current amount and spatial distribution of forest habitats, and
the potential for rapid restoration of forest habitats, both on managed and unmanaged forest land. 相似文献
14.
The role of landscape structure in species richness distribution of birds,amphibians, reptiles and lepidopterans in Mediterranean landscapes 总被引:2,自引:2,他引:0
The parameters referring to landscape structure are essential in any evaluation for conservation because of the relationship that exists between the landscape structure and the ecological processes. This paper presents a study of the relationships between landscape structure and species diversity distribution (estimated in terms of richness of birds, amphibians, reptiles and butterflies) in the region of Madrid, Spain. The results show that the response of species richness to landscape heterogeneity varies depending on the group of species considered. For birds and lepidopterans, the most important factor affecting the distribution of richness of species is landscape heterogeneity, while other factors, such as the specific composition of land use, play a secondary role at this scale. On the other hand, richness of amphibians and reptiles is more closely related to the abundance of certain land-use types. The study highlights the importance of heterogeneity in Mediterranean landscapes as a criterion for landscape planning and for definition of management directives in order to maintain biodiversity. 相似文献
15.
Kevin Watts Amy E. Eycott Phillip Handley Duncan Ray Jonathan W. Humphrey Christopher P. Quine 《Landscape Ecology》2010,25(9):1305-1318
The focus of biodiversity conservation is shifting to larger spatial scales in response to habitat fragmentation and the need
to integrate multiple landscape objectives. Conservation strategies increasingly incorporate measures to combat fragmentation
such as ecological networks. These are often based on assessment of landscape structure but such approaches fail to capitalise
on the potential offered by more ecologically robust assessments of landscape function and connectivity. In this paper, we
describe a modelling approach to identifying functional habitat networks and demonstrate its application to a fragmented landscape
where policy initiatives seek to improve conditions for woodland biodiversity including increasing woodland cover. Functional
habitat networks were defined by identifying suitable habitat and by modelling connectivity using least-cost approaches to
account for matrix permeability. Generic focal species (GFS) profiles were developed, in consultation with stakeholders, to
represent species with high and moderate sensitivity to fragmentation. We demonstrated how this form of analysis can be used
to aid the spatial targeting of conservation actions. This ‘targeted’ action scenario was tested for effectiveness against
comparable scenarios, which were based on random and clumped actions within the same landscape. We tested effectiveness using
structural metrics, network-based metrics and a published functional connectivity indicator. Targeting actions within networks
resulted in the highest mean woodland area and highest connectivity indicator value. Our approach provides an assessment of
landscape function by recognising the importance of the landscape matrix. It provides a framework for the targeting and evaluation
of alternative conservation options, offering a pragmatic, ecologically-robust solution to a current need in applied landscape
ecology. 相似文献
16.
David J. Lieske Megan MacIntosh Lee Millet Soren Bondrup-Nielsen J. Bruce Pollard Glen Parsons Nic R. McLellan G. Randy Milton Frances MacKinnon Kevin Connor Lauren K. Banks 《Landscape Ecology》2018,33(1):35-57
Context
This study synthesizes evidence from three separate surveys of American Black Duck and Mallard breeding habitat usage to quantify the effects of agriculture at the landscape scale.Objectives
To assess duck breeding activity in agricultural landscapes within the Canadian maritimes in order to measure the overall impact of agricultural land use, the response to particular agricultural activities, and the influence of landscape configuration.Methods
Models, constructed using a long-term census (SURVEY1), were used to predict habitat selection for two other independent surveys (SURVEY2, SURVEY3). Predictions incorporated information about wetland area and diversity, as well as anthropogenic factors, allowing subsequent analyses to focus on the remaining residual error attributable to agricultural effects.Results
SURVEY2 results demonstrated that the proportion of active agriculture is an important indicator of the severity of human disturbance, yielding threshold estimates of 39% for Mallards and 60% for Black Ducks, with an overall average of 50%. Agricultural conversion beyond these thresholds deterred breeding ducks independently of other factors. SURVEY3 land cover information demonstrated that the presence of cropland intensified this deterrence effect, even at levels as low as 10%. Woodland cover (in excess of 30%) was important for both species, but its configuration was not.Conclusions
In addition to quantifying threshold effects, this study reaffirms that woodland is an important part of the maritime landscape matrix, and contributes positively to habitat diversity in mixed use, moderate intensity agricultural regions. Wetland restoration in agricultural landscapes should monitor and promote less crop-intensive, mixed-use practices.17.
Context
Environmental processes and dispersal are primary determinants of metacommunity dynamics. The relative importance of these effects may vary between species of different abundance classes, given variation in life history traits. Under high disturbance conditions, rare species may be more easily eliminated from their optimal habitats and their distribution may therefore be more heavily dependent upon dispersal from nearby habitat patches than common species.Objectives
We tested if metacommunity dynamics vary between abundance classes in a high disturbance environment.Methods
Standardized butterfly sampling was conducted in the urban parks of Hong Kong. To estimate the strength of environmental processes, we measured an array of environmental variables for all sampled parks. Spatial predictors were generated to estimate the effect of dispersal.Results
For shaping common species compositions, we found environmental processes (and specifically environmental variables including floral density and surrounding woody plant cover) slightly more important than spatial processes. For rare species, only spatial processes were significant while environmental processes were insignificant. Our result contrasts previous studies in natural metacommunities, which have shown that both common and rare species compositions are shaped by environmental processes and similar variables.Conclusions
Our results demonstrate that high disturbance conditions may inhibit rare species establishment and persistence in urban landscapes. Local habitat management may not be sufficient in conserving rare species in urban environments—spatial context and configuration should be considered in planning for biodiversity. We also highlight the utility of community deconstruction analysis in providing insights into rare species metacommunity dynamics.18.
Rune H. Økland Harald Bratli Wenche E. Dramstad Anette Edvardsen Gunnar Engan Wendy Fjellstad Einar Heegaard Oddvar Pedersen Heidi Solstad 《Landscape Ecology》2006,21(7):969-987
Knowledge of variation in vascular plant species richness and species composition in modern agricultural landscapes is important
for appropriate biodiversity management. From species lists for 2201 land-type patches in 16 1-km2 plots five data sets differing in sampling-unit size from patch to plot were prepared. Variation in each data set was partitioned
into seven sources: patch geometry, patch type, geographic location, plot affiliation, habitat diversity, ecological factors,
and land-use intensity. Patch species richness was highly predictable (75% of variance explained) by patch area, within-patch
heterogeneity and patch type. Plot species richness was, however, not predictable by any explanatory variable, most likely
because all studied landscapes contained all main patch types – ploughed land, woodland, grassland and other open land – and
hence had a large core of common species. Patch species composition was explained by variation along major environmental complex
gradients but appeared nested to lower degrees in modern than in traditional agricultural landscapes because species-poor
parts of the landscape do not contain well-defined subsets of the species pool of species-rich parts. Variation in species
composition was scale dependent because the relative importance of specific complex gradients changed with increasing sampling-unit
size, and because the amount of randomness in data sets decreased with increasing sampling-unit size. Our results indicate
that broad landscape structural changes will have consequences for landscape-scale species richness that are hard or impossible
to predict by simple surrogate variables. 相似文献
19.
Landscape Ecology - Theory predicts that species diversity of isolated habitat patches depends on patch size and isolation. However, there are few previous studies of how patch size and isolation... 相似文献
20.
F. M. Caryl A. K. Hahs L. F. Lumsden R. Van der Ree C. Wilson B. A. Wintle 《Landscape Ecology》2014,29(7):1237-1248
Understanding of how species distributions are driven by landscape-level processes has been obscured by null or inconsistent findings from poorly designed studies. We explore how differences in the way potential drivers of species distributions are defined can influence their perceived effects. Specifically, we evaluate how much statistical power is lost when continuous variables are discretised, and how the use of qualitatively defined nominal variables impacts biological interpretation of results. We fitted generalized linear models to dependent variables relating to bat distribution (species richness, diversity, relative abundance of functional groups and individual species) obtained from 36 sites across Melbourne, Australia, and independent variables that were continuous (percentage tree cover, dwelling density), ordinal (dichotomised continuous variables) or nominal (land-use, urban context). We found that models fitted with continuous predictors had better fit and explanatory power than those fitted with ordinal predictors for all response variables. Ordinal models failed to detect statistically significant effects for 4 of the 11 response variables that were successfully modelled with continuous data, suggesting Type II errors had occurred. Models fitted with nominal data explained a comparable amount of variation in some dependent variables as continuous models. However, interpretation of the mechanisms behind responses to nominal categorical levels was obscured because environmental conditions within them were confounded and not homogenous. To gain better understanding from nominal predictors would therefore require further investigation. Our findings show that careful consideration must be given to the choice of environmental variables used for species distribution modelling and how those variables are defined. 相似文献