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1.
Eelgrass (Zostera marina) is an important feature of coastal ecosystems in Atlantic Canada, providing a suite of valuable ecosystem services. These services, and its sensitivity to stressors, have prompted efforts to characterize the spatial and temporal dynamics of eelgrass landscapes in order to facilitate management and monitoring of coastal ecosystem health. Current methods for broad-scale mapping of eelgrass rely on aerial remote sensing and may not be appropriate in certain types of landscapes, particularly in turbid waters and areas lacking distinct boundaries. This study takes a novel approach to the quantification and analysis of seagrass landscape structure at multiple spatial scales using acoustic data and local spatial statistics. Data from a single-beam acoustic survey in Richibucto, New Brunswick, Canada were analyzed with geostatistical techniques and the Getis-Ord G i * local spatial statistic in order to detect statistically significant zones of high and low cover in an estuarine seagrass bed. Results showed distinct and significant patterns in seagrass cover at multiple spatial scales within a region of apparently continuous spatial cover. Boundaries between areas of high and low cover were also detected. This study demonstrates how acoustic data and local spatial statistics can be used to quantify landscape pattern and to further the application of landscape techniques in the marine environment.  相似文献   

2.
To verify that the stabilized sand dunes of Doñana, southwest Spain, are hierarchically nested, vegetation was sampled along topographic gradients at three spatial scales and Split Moving Window Boundary Analysis was applied to identify vegetation boundaries and ecotones. At small scale, only one window width was used, while for boundaries detection at upper scales the information from five windows was pooled. Environmental factors controlling plant composition were studied along topographic gradients, and diversity was estimated within the boundaries. According to several theoretical frameworks, I discuss the types of boundaries produced at different scales. Lower level boundaries are characterized by transitory gradients linked to local exchanges; intermediate boundaries are symmetric and very stable over the time; the large scale boundary is asymmetric with strong inherent abiotic constraints reinforced by strong biotic feedbacks. In spite of a similar plant composition, a plant community, the mixed shrub, works as an ecocline or an ecotone depending on the spatial scale considered. A certain parallelism exists between shrub composition along dune slopes and dune generations; however, processes at upper scale constraint plant composition at lower scale resulting in different mature formations.  相似文献   

3.
Understanding what features of the landscape affect species distribution is critical to effectively implement conservation strategies. This study investigates how a boundary analysis framework can be used to characterize the spatial association between boundaries (i.e., spatial locations of high rates of change) in bird species?? distributions and landscape features at the regional scale. The study area covers 92,000?km2 in southern Ontario (Canada) and extends from the Great Lakes-St. Lawrence biome to the southern Canadian Shield biome. Landcover composition was derived from Ontario Land Cover data (1991?C1998; 7 types) and elevation data were derived from the Canada3D digital elevation model. Bird distributions were estimated using indicator kriging based on point counts obtained from the Ontario Breeding Bird Atlas data (2001?C2005; 60 species). Boundaries were delineated for both data types using a 10?×?10?km cell resolution. Spatial boundary overlap statistics were used to quantify the spatial relationship between landscape features and bird boundaries and tested using a randomization procedure. There was significant positive association and spatial overlap between delineated landscape feature boundaries and bird boundaries. The number of spatially overlapping cells between the two boundary types was 67 out of 164 (41?%) and 76?% of cells were within 11.42?km of each other. These results were statistically significant (P?<?0.001) and suggest a strong spatial relationship between high rates of change in landscape features and bird species?? distributions at the regional scale. A boundary analysis framework could be used to identify boundary shifts in response to climate change and anticipate changes in species distributions.  相似文献   

4.
Human activities and natural disturbances create spatial heterogeneity within forested landscapes, leading to both sharp and gradual boundaries in vegetation and abiotic attributes, such as rocks. Those boundaries may affect the detailed delineation of avian territories (independently of their general location), but their role is largely unknown. We tested, using a spatial analysis approach, whether spatial heterogeneity of vegetation and abiotic attributes were associated with territory boundaries of ten black-throated blue warblers (Dendroica caerulescens) and 14 ovenbirds (Seiurus aurocapillus). The study was conducted during summer 1999 in a mature deciduous forest near Québec City, Canada. Singing males were mapped from repeated surveys at 756 points, 25 m apart, on a 49 ha grid. Spatial heterogeneity was obtained from 27 attributes measured at each point. Boundaries of bird territories, vegetation, and abiotic attributes were delineated using the lattice-wombling boundary detection algorithm. The spatial association between territory and microhabitat boundaries was computed using the spatial overlap statistics. There was significant spatial overlap between territory boundaries and those of 15 and 17 attributes for black-throated blue warbler and ovenbird, respectively. The attributes most strongly associated with territory boundaries were conifer seedling cover, grass and total vegetation cover between 0-2 m high for black-throated blue warbler and fern cover, vegetation-covered rocks and shrub diversity for ovenbird. Complementary to this, a redundancy analysis (RDA) was used to compare attributes associated with the general occurrence of males to those whose boundaries were associated specifically with territory boundaries. Most attributes whose boundaries were associated with territory boundaries did not correspond to resource attributes, i.e., those where birds were detected most frequently. We conclude that soft boundaries associated with spatial heterogeneity may help shape forest bird territories by providing landmarks not necessarily related to resources used within territories.  相似文献   

5.
Scale dependency of insect assemblages in response to landscape pattern   总被引:5,自引:0,他引:5  
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6.
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   

7.
Coastal vegetation of South Florida typically comprises salinity-tolerant mangroves bordering salinity-intolerant hardwood hammocks and fresh water marshes. Two primary ecological factors appear to influence the maintenance of mangrove/hammock ecotones against changes that might occur due to disturbances. One of these is a gradient in one or more environmental factors. The other is the action of positive feedback mechanisms, in which each vegetation community influences its local environment to favor itself, reinforcing the boundary between communities. The relative contributions of these two factors, however, can be hard to discern. A spatially explicit individual-based model of vegetation, coupled with a model of soil hydrology and salinity dynamics is presented here to simulate mangrove/hammock ecotones in the coastal margin habitats of South Florida. The model simulation results indicate that an environmental gradient of salinity, caused by tidal flux, is the key factor separating vegetation communities, while positive feedback involving the different interaction of each vegetation type with the vadose zone salinity increases the sharpness of boundaries, and maintains the ecological resilience of mangrove/hammock ecotones against small disturbances. Investigation of effects of precipitation on positive feedback indicates that the dry season, with its low precipitation, is the period of strongest positive feedback.  相似文献   

8.
Human modification of landscapes overlying natural environmental heterogeneity is resulting in an increase in the numbers and types of ecological patches and their intervening boundaries. In this paper, we describe an operational framework for understanding and predicting dynamics of these biotic transitions for a range of environmental conditions across multiple spatial scales. We define biotic transitions as the boundary and the neighboring states, a more general definition than typically denoted by the terms boundary, ecotone, edge or gradient. We use concepts of patch dynamics to understand the structural properties of biotic transitions and to predict changes in boundaries through time and across space. We develop testable hypotheses, and illustrate the utility of our approach with examples from arid and semiarid ecosystems. Our framework provides new insights and predictions as to how landscapes may respond to future changes in climate and other environmental drivers.  相似文献   

9.
Projections of indicators of forest ecosystem goods and services (EGS) based on process-based landscape models are critical for adapting forest management to climate change. However, the scarcity of fine-grained, spatially explicit forest data means that initializing these models is both a challenge and a source of uncertainty. To test how different initialization approaches influence the simulation of forest dynamics and EGS indicators we initialized the forest landscape model LandClim with fine resolution empirical data, coarse empirical data, and simulation-derived data, and evaluated the results at three spatial scales (stand, management area and landscape). Simulations were performed for a spruce (Picea abies) dominated landscape in the Black Forest, Germany, under current climate and a climate change scenario. We found that long-term (>150 years) projections are robust to initialization uncertainty. In contrast, shorter-term projections are sensitive to initialization uncertainty, with sensitivity increasing when EGS are assessed at smaller spatial scales, and when the EGS indicators depend on the spatial distribution of individual species. EGS dynamics are strongly influenced by interactions between the density, species composition, and age structure of initialized forests and simulated forest management. If EGS dynamics are strongly influenced by climate change, such as when climate change induces mortality in drought-sensitive species, some of the initialization uncertainty can be masked. We advocate for initializing landscape models with fine-grained data in applications that focus on spatial management problems in heterogeneous landscapes, and stress that the scale of analysis must be in accordance with the accuracy that is warranted by the initialization data.  相似文献   

10.
Grazing by large herbivores is a major determinant of vegetation dynamics in many semi-natural ecosystems, including ghe replacement of heather moorland by rough grassland in the British uplands. Herbivore foraging is influenced by vegetation patterns and, in turn, their grazing drives vegetation dynamics. Although vegetation impacts are local, spatially heterogeneous local impacts can have different conseqences as would the same impact distributed uniformly. We constructed a simulation model of the spatial effects of grazing by sheep on the vegetation dynamics of heather moorland, a vegetation community of international conservation importance in the UK. The model comprised three sub-models to predict (1) annual average heather utilisation, (2) spatial variation in heather utilisation (higher near the edge of grass patches) and (3) competition between heather and grass. Here we compare the predicted heather utilisation and vegetation dynamics of the spatial model, relative to those of a non-spatial model. The spatial model resulted in a reduced loss of heather cover for a given sheep stocking rate. The model demonstrtaes how spatial interactions between large herbivores and their forage drive vegetation dynamics, leading to changes in community structure and composition. Indeed, omitting spatial effects in grazing models may lead to inaccurate predictions. We have shown that ecosystem modelling, based around an iterative dialogue between developers and experienced researchers, has the potential to make a substantial contribution towards the conservation and management of vulnerable landscapes. Combining modelling with experimental studies will facilitate progress towards understanding long-term vegetation/herbivore dynamics.  相似文献   

11.
Responses of mammals to habitat edges: an overview   总被引:10,自引:0,他引:10  
Life generates discontinuites (boundaries) in the distribution of matter and energy. One class of these constitutes the edges between habitat-types; these are fundamental structures in landscape functioning, and hence are of central importance in conservation biology. The symposium on which this series of papers is based focused on the responses of mammals to habitat edges. A diversity of views are represented, and a variety of edge related behaviors illustrated. A survey of general ecology texts dating back to 1933 demonstrates a decline of interest in ecotones and edge effects extending into the 1980's but showing a resurgence of interest in the 1990's. Habitat edges are defined operationally with respect to particular focal species leading to a number of important corollary features. The variety of phenomena subsumed under edge effects is emphasized, and an initial attempt at classification is proposed based primarily on the presence or absence of emergent properties in edge response behaviors (matrix vs. ecotonal effects). This scheme provides for clear null hypotheses needed to distinguish the two types, enlightens mechanistic explanations of edge effects, and encourages predictions about the results of untested management schemes or other novel situations. The use and design of landscape corridors are tied to edge related behaviors. A functional and general definition of corridors is urged, so that their effectiveness can be judged with respect to specified attributes rather than to a general collection of things that might be termed corridors. Linear habitat patches are specifically excluded from the definition. Studies on small mammals have contributed to our understanding of the potential role of corridors in metapopulation dynamics. Fine versus coarse grained perceptions of environment by different species will generate ecotonal edge effects such as spillover predation. In general, the effects on landscape processes of various species operating on different spatial scales seems a fruitful direction for future research.  相似文献   

12.
Palmer  S. C. F.  Gordon  I. J.  Hester  A. J.  Pakeman  R. J. 《Landscape Ecology》2004,19(8):817-827
Grazing by large herbivores is a major determinant of vegetation dynamics in many semi-natural ecosystems, including the replacement of heather moorland by rough grassland in the British uplands. Herbivore foraging is influenced by vegetation patterns and, in turn, their grazing drives vegetation dynamics. Although vegetation impacts are local, spatially heterogeneous local impacts can have different consequences as would the same impacts distributed uniformly. We constructed a simulation model of the spatial effects of grazing by sheep on the vegetation dynamics of heather moorland, a vegetation community of international conservation importance in the UK. The model comprised three sub-models to predict (1) annual average heather utilisation, (2) spatial variation in heather utilisation (higher near the edge of grass patches) and (3) competition between heather and grass. Here we compare the predicted heather utilisation and vegetation dynamics of the spatial model, relative to those of a non-spatial model. The spatial model resulted in a reduced loss of heather cover for a given sheep stocking rate. The model demonstrates how spatial interactions between large herbivores and their forage drive vegetation dynamics, leading to changes in community structure and composition. Indeed, omitting spatial effects in grazing models may lead to inaccurate predictions. We have shown that ecosystem modelling, based around an iterative dialogue between developers and experienced researchers, has the potential to make a substantial contribution towards the conservation and management of vulnerable landscapes. Combining modelling with experimental studies will facilitate progress towards understanding long-term vegetation/herbivore dynamics.  相似文献   

13.
Grazing by large herbivores is a major determinant of vegetation dynamics in many semi-natural ecosystems, including the replacement of heather moorland by rough grassland in the British uplands. Herbivore foraging is influenced by vegetation patterns and, in turn, their grazing drives vegetation dynamics. Although vegetation impacts are local, spatially heterogeneous local impacts can have different consequences as would the same impacts distributed uniformly. We constructed a simulation model of the spatial effects of grazing by sheep on the vegetation dynamics of heather moorland, a vegetation community of international conservation importance in the UK. The model comprised three sub-models to predict (1) annual average heather utilisation, (2) spatial variation in heather utilisation (higher near the edge of grass patches) and (3) competition between heather and grass. Here we compare the predicted heather utilisation and vegetation dynamics of the spatial model, relative to those of a non-spatial model. The spatial model resulted in a reduced loss of heather cover for a given sheep stocking rate. The model demonstrates how spatial interactions between large herbivores and their forage drive vegetation dynamics, leading to changes in community structure and composition. Indeed, omitting spatial effects in grazing models may lead to inaccurate predictions. We have shown that ecosystem modelling, based around an iterative dialogue between developers and experienced researchers, has the potential to make a substantial contribution towards the conservation and management of vulnerable landscapes. Combining modelling with experimental studies will facilitate progress towards understanding long-term vegetation/herbivore dynamics.  相似文献   

14.

Context

Arid rangelands have been severely degraded over the past century. Multi-temporal remote sensing techniques are ideally suited to detect significant changes in ecosystem state; however, considerable uncertainty exists regarding the effects of changing image resolution on their ability to detect ecologically meaningful change from satellite time-series.

Objectives

(1) Assess the effects of image resolution in detecting landscape spatial heterogeneity. (2) Compare and evaluate the efficacy of coarse (MODIS) and moderate (Landsat) resolution satellite time-series for detecting ecosystem change.

Methods

Using long-term (~12 year) vegetation monitoring data from grassland and shrubland sites in southern New Mexico, USA, we evaluated the effects of changing image support using MODIS (250-m) and Landsat (30-m) time-series in modeling and detecting significant changes in vegetation using time-series decomposition techniques.

Results

Within our study ecosystem, landscape-scale (>20-m) spatial heterogeneity was low, resulting in a similar ability to detect vegetation changes across both satellite sensors and levels of spatial image support. While both Landsat and MODIS imagery were effective in modeling temporal dynamics in vegetation structure and composition, MODIS was more strongly correlated to biomass due to its cleaner (i.e., fewer artifacts/data gaps) 16-day temporal signal.

Conclusions

The optimization of spatial/temporal scale is critical in ensuring adequate detection of change. While the results presented in this study are likely specific to arid shrub-grassland ecosystems, the approach presented here is generally applicable. Future analysis is needed in other ecosystems to assess how scaling relationships will change under different vegetation communities that range in their degree of landscape heterogeneity.
  相似文献   

15.
Zhang  Minghua  Geng  Shu  Ustin  Susan L. 《Landscape Ecology》1998,13(1):37-54
Quantitative agricultural landscape indices are useful to describe functional relationships among climatic conditions, groundwater dynamics, soil properties and agricultural land use for mathematical models. We applied methods of regression statistics, variance component estimation and a Geographical Information System (GIS) to construct indices describing crops and soils and to establish functional relationships among these variables. This paper describes the development of indices and the partitioning of the spatial and temporal variation in groundwater models using the data from Tulare County, California, which was selected as the study area. Indices of ground surface elevation, total crop water demand, soil water infiltration rate, and soil production index explain 91% of the variation in average spring groundwater level. After relating spatial patterns of groundwater use to indices of crop and soil properties, we found that mean groundwater use is positively related to total crop water demand and soil water infiltration rate while the variation in groundwater use was negatively correlated with the crop water demand and soil water infiltration rate and positively related to soil water holding capacity. The spatial variation in groundwater use was largely influenced by crops and soil types while the temporal variation was not. We also found that groundwater use increased exponentially with decreasing annual precipitation for most townships. Based on these associations, groundwater use in each township can be forecast from relative precipitation under current methods of agricultural production. Although groundwater table depth is strongly affected by topography, the statistically significant indices observed in the model clearly show that agricultural land use influences groundwater table depth. These simple relationships can be used by agronomists to make water management decisions and to design alternative cropping systems to sustain agricultural production during periods of surface water shortages.  相似文献   

16.
Context

Seagrasses are submerged marine plants that have been declining globally at increasing rates. Natural resource managers rely on monitoring programs to detect and understand changes in these ecosystems. Technological advancements are allowing for the development of patch-level seagrass maps, which can be used to explore seagrass meadow spatial patterns.

Objectives

Our research questions involved comparing lacunarity, a measure of landscape configuration, for seagrass to assess cross-site differences in areal coverage and spatial patterns through time. We also discussed how lacunarity could help natural resource managers with monitoring program development and restoration decisions and evaluation.

Methods

We assessed lacunarity of seagrass meadows for various box sizes (0.0001 ha to 400.4 ha) around Cat Island and Ship Island, Mississippi (USA). For Cat Island, we used seagrass data from 2011 to 2014. For Ship Island, we used seagrass data for seven dates between 1963 and 2014.

Results

Cat Island, which had more continuous seagrass meadows, had lower lacunarity (i.e., denser coverage) compared to Ship Island, which had patchier seagrass beds. For Ship Island, we found a signal of disturbance and path toward recovery from Hurricane Camille in 1969. Finally, we highlighted how lacunarity curves could be used as one of multiple considerations for designing monitoring programs, which are commonly used for seagrass monitoring.

Conclusions

Lacunarity can help quantify spatial pattern dynamics, but more importantly, it can assist with natural resource management by defining fragmentation and potential scales for monitoring. This approach could be applied to other environments, especially other coastal ecosystems.

  相似文献   

17.
Gillson  Lindsey 《Landscape Ecology》2004,19(8):883-894
The Hierarchical Patch Dynamics Paradigm provides a conceptual framework for linking pattern, process and scale in ecosystems, but there have been few attempts to test this theory because most ecological studies focus on only one spatial scale, or are limited in their temporal scope. Here I use palaeoecological techniques (analysis of fossil pollen and stable carbon isotopes) to compare vegetation heterogeneity in an east African savanna at three spatial scales, over hundreds of years. The data show that patterns of vegetation change are different at the three spatial scales of observation, and suggest that different ecological processes dominate tree abundance at micro, local and landscape scales. Interactions between plants, disturbance (e.g., by fire and herbivores), climate and soil type may influence tree density at differing spatial and temporal scales. This hierarchical explanation of savanna vegetation dynamics could inform future biodiversity conservation and management in savannas. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

18.
The Hierarchical Patch Dynamics Paradigm provides a conceptual framework for linking pattern, process and scale in ecosystems, but there have been few attempts to test this theory because most ecological studies focus on only one spatial scale, or are limited in their temporal scope. Here I use palaeoecological techniques (analysis of fossil pollen and stable carbon isotopes) to compare vegetation heterogeneity in an east African savanna at three spatial scales, over hundreds of years. The data show that patterns of vegetation change are different at the three spatial scales of observation, and suggest that different ecological processes dominate tree abundance at micro, local and landscape scales. Interactions between plants, disturbance (e.g., by fire and herbivores), climate and soil type may influence tree density at differing spatial and temporal scales. This hierarchical explanation of savanna vegetation dynamics could inform future biodiversity conservation and management in savannas. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

19.
Understanding the drivers and mechanisms of the dynamics in grassland productivity is prerequisite for studying effective resource institutions and policies that can be used to govern grassland resources sustainably. We present a diagnostic analysis of the major drivers of the dynamics in grassland net primary productivity (NPP) across ecological zones on the Mongolian Plateau. We estimated a spatial panel data model for NPP (1986–2009) as a function of climatic and socioeconomic variables. Static and dynamic spatial panel models were estimated in each of the sub-regions, which were classified based on rural livelihoods and ecological models of grassland dynamics, to identify the major drivers of NPP dynamics. The statistical modeling results indicated that the major drivers of NPP dynamics vary across the six sub-regions. Grain output was the major predictor of NPP dynamics in the farming and farming-grazing zones of Inner Mongolia. Precipitation and livestock populations both had significantly positive relationships with NPP in the two grazing zones of Inner Mongolia. However, in Mongolia, livestock populations was the only significant predictor of NPP in the grazing zone with relatively stable climate, and precipitation was the only significant predictor of NPP in the grazing zone with highly variable climate. Human land-use activities and livestock management behaviors and the bidirectional causal relationships between livestock populations and NPP could explain the positive relationships between livestock population and grassland NPP. The heterogeneous drivers of NPP dynamics across space indicated the necessity of diverse resource polices and institutions for sustainable governance of grassland resources.  相似文献   

20.
Responses of species to landscape modifications are generally documented through their distribution at a given time along an intensity gradient of land transformation. By focusing on patterns, we are limited to infer ecological processes occurring within a system and its response to environmental disturbances which can further change over time. Using diachronic datasets at the scale of France, we analyzed the spatial responses of the black-billed magpie, which has recently colonized cities, to landscape urbanization. This study applied recently developed statistical approaches incorporating detection uncertainty of the magpie, based on the capture-recapture statistical framework. We tested whether, and how, extinction and colonization mechanisms influenced variations of magpie occupancy from 2001 to 2005. In addition, we assessed the importance of the recent urbanization of the French countryside in determining population dynamics. Overall, our analysis proved that the proportion of urban areas and recent urbanization in France led to an increase in the probability of magpie occupancy. Unexpectedly, the species is concomitantly disappearing from the countryside, leading to a rapid change in the distribution of the species. This study stressed the importance of incorporating detection uncertainty in inference process about spatial dynamics. Overall, we show how useful it is to account for the dynamic evolution of the landscape in ecological studies.  相似文献   

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