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Conclusions:Landscapes dominated by woody vegetation had significantly more patches, smaller patches and patch core areas, more total edge, and higher patch diversity than landscapes dominated by anthropogenic cover types. Results indicate that expanding juniper is exacerbating the fragmentation process initiated by previous human activityThresholds/Learnings:
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Synopsis: Reviews information on grassland bird habitat requirements including a focus on the importance of grassland cover, size of contiguous patches, and other landscape factors. Some species require large blocks of unbroken grassland habitat for nesting. In general, where large blocks of undisturbed grassland occur, grassland birds are able to fulfill most of their requirements during the nesting season. For many bird species, these habitats provide winter and migration cover as well. The more grassland available in an area, particularly in large unbroken blocks, the greater the number of area-sensitive grassland birds the area is able to support. Pastures and crop fields also often provide attractive cover...
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Synopsis: Researchers measured the effects of grassland amount and fragmentation on upland and wetland songbird and duck densities and nest success across 16 landscapes in southern Alberta. By comparing these landscape-level effects with local-scale responses, including distance to various edges and vegetation characteristics, the study demonstrated that few species were in fact influenced by grassland amount or fragmentation. In contrast, distance to edge and local vegetation characteristics had significant effects on densities and nest success of many species. Landscape level effects were much less apparent when local characteristics were included in the models. Therefore, researchers concluded that local habitat...
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Synopsis: Recensuses of 54 Wisconsin prairie remnants showed that 8 to 60 percent of the original plant species were lost from individual remnants over a 32- to 52-year period. The pattern of species loss was consistent with the proposed effects of fire suppression caused by landscape fragmentation. Short, small-seeded, or nitrogen-fixing plants showed the heaviest losses, as did species growing in the wettest, most productive environments. The interruption of landscape-scale processes (such as wildfire) by fragmentation is an often overlooked mechanism that may be eroding biodiversity in many habitats around the world. Conclusions: Fragmentation may interrupt landscape-scale processes, such as fire, that are key...
Conclusions:Forest clearcutting differentialy affects birds of different ages. There is a threshold distance between reserves below which birds do not mind crossing clear cuts, making corridors more important as clearcut area and distance between forest reserves expandsThresholds/Learnings:
Conclusions:Results indicated that system and species-specific considerations are important when assessing the potential outcome of habitat loss and fragmentation on regional biotaThresholds/Learnings:
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Conclusions: Grizzly bears avoid high volume roads (25,000 vehicles/day). High quality habitat determines movement decisions relative to roads. Grizzly bears will cross high volume roads to access high-quality habitat. Grizzly bears use areas close to roads more than expected, in particular low-volume roads (10,000 vehicles/day). Prevent loss of habitat connectivity with the following mitigation: maintain high-quality habitat adjacent to roads, install continuous highway fencing and create wildlife passages. Thresholds/Learnings: Synopsis: The study examined the relationships among grizzly bears, their habitats and roads in Banff National Park, a protected area characterized by a major transportation corridor. This...
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Conclusions: The negative effects of patch size and isolation on species may not occur until the landscape consists of less than 10% suitable habitat for birds, and 30% suitable habitat for mammals. Thresholds/Learnings: The negative effects of patch size and isolation on species may not occur until the landscape consists of less than 10% suitable habitat for birds, and 30% suitable habitat for mammals. Synopsis: This study involved a review of studies on birds and mammals in habitat patches in landscapes with different proportions of suitable habitat. The findings demonstrate that there exists a threshold in proportion of suitable habitat in the landscape, above which fragmentation becomes pure habitat loss....
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Synopsis: This study examines the influence of landscape fragmentation on trophic cascades in southern California. Results indicate that, as habitat fragmentation negatively affects the persistence of coyote populations, the abundance of smaller meso-predators increase, resulting in higher mortality rates in scrub-breeding birds. Fragment size was a strong indicator of coyote abundance, and coyote abundance was a strong indicator of bird diversity, as coyotes kept down the number of meso-predators that prey on birds. The positive effect of fragment area and the negative effect of fragment age were the strongest determinants of bird diversity in this system. Conclusions: Fragment size correlates with coyote abundance,...
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Conclusions: At small spatial scales, where extirpation risks are high, landscape fragmentation will likely have long-term negative consequences on the genetic variation of individual assemblages of coastal cutthroat trout. Thresholds/Learnings: Synopsis: This study aimed to determine if coastal cutthroat trout were genetically structured within streams and to assess the effects of habitat fragmentation on coastal cutthroat trout genetic variation. Habitat fragmented by roads and other human disturbances acted as dispersal barriers, which strongly influenced coastal cutthroat trout genetic structure, diversity, and differentiation. At range-wide spatial scales, fragmentation potentially contributes to coastal cutthroat...
Synopsis: This book provides important foundational concepts in landscape ecology, with a particular focus on the effects of land use and landscape fragmentation. Building on Forman’s patterns of landscape change, the book cites the McIntyre and Hobbs model of landscape change, which suggests that landscape modification often increases through time. Four broad classes of landscape condition can therefore be identified along a continuum of increasing human landscape modification: intact, variegated, fragmented, and relictual (figure 3). Similarly to Forman’s model, these classes represented correspond to different spatial patterns in the landscape. Therefore, as the extent of human land use increases, the amount...
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Conclusions: The nature of the surrounding matrix contributes significantly to the degree of patch isolation; matrix modification may improve habitat connectivity and genetic distribution in fragmented landscapes. Thresholds/Learnings: Synopsis: This study challenges traditional assumptions about the uniform nature of the matrix, and the reliance on distance alone as an indicator of patch isolation, by testing whether the type of inter-patch matrix contributes significantly to patch isolation in butterfly populations. The author tracked the movement of six butterfly species between patches of meadow habitat through two natural matrix types (conifer forest and willow thicket). All taxa of butterflies studied responded...
Synopsis: This study aimed to independently examine the effects of varying amounts and configurations of habitat at a landscape scale, with particular attention to critical persistence thresholds. A discrete reaction-diffusion model was used to estimate long-term equilibrium population persistence of a hypothetical species in a patchy landscape. When examined over a broad range of habitat amount and arrangements, population size was largely determined by the proportion of habitat (amount) in a landscape. However, when habitat coverage dropped below 30-50%, population response deviated, coinciding with a persistence threshold. Species persistence declined rapidly at this threshold range (50% for low degrees of aggregation,...
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Synopsis: This study summarized results of a comparative 15N-tracer study from a wide variety of sites throughout the United States, to derive general principles related to headwater streams and nitrogen dynamics. Standardized protocols were applied in 12 headwater streams representing a wide diversity of biomes throughout the United States. These sites were part of the Lotic Intersite Nitrogen eXperiment (LINX). The most rapid uptake and transformation of inorganic nitrogen occurred in the smallest streams. Ammonium entering these streams was removed within a few tens to hundreds of meters, primarily through assimilation by microorganisms, sorption to sediments, and nitrification. Nitrate was also removed from...
Conclusions:Habitat fragmentation results in demographic changes in plant populations associated wtih increased extinction risk.Thresholds/Learnings:Trillium populations in forest remnants within 65m of forest clear-cut edges have almost no recruitment of young plants
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Synopsis: A simulation model, modified from percolation theory, was empirically tested to determine if population distribution patterns correlated with different landscape patterns, for different species across a landscape. Using two grasshopper species in a short-grass prairie of north-central Colorado, the experiment found that the threshold for population aggregation (random to clumped distribution) was differentially affected by dispersal ranges and habitat specialization for habitat generalists and habitat specialists, respectively. Habitat generalists aggregated differentially depending on dispersal abilities. Generalist species with good dispersal abilities aggregated when <35% of the landscape consisted...
Synopsis: This book addresses issues of landscape fragmentation and ecology emanating from the construction and use of roads. The text highlights ecosystem implications of this type of linear disturbance in relation to the following topics: · Roads, vehicles, and transportation planning · Vegetation and roadsides · Wildlife populations and collision mortality · Water, sediment, and chemical flows · Aquatic ecosystems · Wind, noise, and atmospheric effects · Road networks and landscape fragmentation Conclusions: Book addresses issues of landscape fragmentation and ecology emanating from the construction and use of roads. The text highlights ecosystem implications...
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Synopsis: This study attempts to build a forest fragmentation database for the conterminous United States by utilizing high-resolution NLCD data, roads, and a series of fragmentation indices that quantify forest landscape patterns. The paper outlines a methodology for assessing forest fragmentation and provides a comprehensive data set to be used as a base for further investigation at smaller scales. Conclusions: A forest fragmentation database for the conterminous United States was built to quantify forest landscape patterns nationwide. The paper outlines a methodology for assessing forest fragmentation and provides a comprehensive data set to be used as a base for further investigation at smaller scales. Thresholds/Learnings:...
Conclusions:Influx of woody vegetation associated with fragmentation correlates with decline in grassland bird speciesThresholds/Learnings:When native grassland cover dropped below 60% at one site, and 30-40% at another site, the arrangement or habitat patches became more important to the survival of populations than habitat amount alone
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Conclusions: Marten capture rates were negatively correlated with increasing proximity of open areas and increasing extent of high-contrast edges. Forested landscapes were unsuitable for martens when the average nearest-neighbor distance between open, non-forested patches was <100m. Thresholds/Learnings: Synopsis: This study aimed to determine whether American marten abundance changed with incremental increases in habitat fragmentation caused by the combined effects of natural openings and timber clearcuts. Researchers evaluated differences in marten capture rates in 18 study sites with different levels of fragmentation. Martens appeared to respond negatively to low levels of habitat fragmentation, even with remaining...
map background search result map search result map The influence of forest fragmentation and landscape pattern on American martens. The matrix matters: effective isolation in fragmented landscapes. Influences of barriers to movement on within-watershed genetic variation of coastal cutthroat trout Forest fragmentation of the coterminous United States: assessing forest intactness through road density and spatial characteristics. Critical thresholds in species responses to landscape structure. Grassland Birds Relationships among grizzly bears, highways, and habitat in Banff-Bow Valley, Alberta, Canada. Effects of habitat fragmentation on birds and mammals in landscapes with different proportions of suitable habitat: a review. Ecological determinants of species loss in remnant prairies. Mesopredator release and avifaunal extinctions in a fragmented system. Control of Nitrogen Export from Watersheds by Headwater Streams A multi-scale analysis of avian response to habitat amount and fragmentation in the Canadian dry mixed-grass prairie. Influences of barriers to movement on within-watershed genetic variation of coastal cutthroat trout The matrix matters: effective isolation in fragmented landscapes. Relationships among grizzly bears, highways, and habitat in Banff-Bow Valley, Alberta, Canada. A multi-scale analysis of avian response to habitat amount and fragmentation in the Canadian dry mixed-grass prairie. Ecological determinants of species loss in remnant prairies. Critical thresholds in species responses to landscape structure. Mesopredator release and avifaunal extinctions in a fragmented system. Forest fragmentation of the coterminous United States: assessing forest intactness through road density and spatial characteristics. Control of Nitrogen Export from Watersheds by Headwater Streams Grassland Birds Effects of habitat fragmentation on birds and mammals in landscapes with different proportions of suitable habitat: a review.