Global-Scale Patterns of Forest Fragmentation

Riitters, Kurt H.; Wickham, James D.; O’Neill, Robert V.; Jones, Bruce D.; Smith, Elizabeth

doi:10.5751/es-00209-040203

Cited by 307 publications

(238 citation statements)

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“…Human activities can drastically alter the age of forest stands and the degree of fragmentation (Radeloff et al 2005), potentially creating feedback loops that may enhance or diminish the effects of wind disturbance. Forested landscapes are becoming increasingly homogeneous and fragmented throughout the northern Great Lakes region (Radeloff et al 2005, Schulte et al 2007) and other regions across the globe (Riitters et al 2000). If increased disturbance frequency associated with forest edge and older stands can preferentially modify species composition, structure, demography, and ecosystem processes, then anthropogenically induced increases in forest edge and stand age (via selectively protecting reserves of old stands) may be accentuating the effects of wind disturbance.…”

Section: Discussionmentioning

confidence: 99%

Ecological importance of intermediate windstorms rivals large, infrequent disturbances in the northern Great Lakes

et al. 2011

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Abstract. Exogenous disturbances are critical agents of change in temperate forests capable of damaging trees and influencing forest structure, composition, demography, and ecosystem processes. Forest disturbances of intermediate magnitude and intensity receive relatively sparse attention, particularly at landscape scales, despite influencing most forests at least once per generation. Contextualizing the spatial extent and heterogeneity of such damage is of paramount importance to increasing our understanding of forested ecosystems. We investigated patterns of intermediate wind disturbance across a forested landscape in the northern Great Lakes, USA. A vegetation change tracker (VCT) algorithm was utilized for processing near-biennial Landsat data stacks ) spanning forests sustaining damage from four recent windstorms. VCT predominantly maps stand-clearing disturbance and regrowth patterns, which were used to identify forest boundaries, young stands, and disturbance patterns across space and time. To map wind damage severity, we compared satellite-derived normalized difference vegetation index (NDVI) values calculated from pre-and post-storm Landsat imagery. A geographic information system (GIS) was used to derive wind damage predictor variables from VCT, digital terrain, soils/landform, land cover, and storm tracking data. Hierarchical and random forests regressions were applied to rank the relative importance of predictor variables in influencing wind damage.A conservative estimate of aggregate damage from the intermediate windstorms (extrapolated to ;150,000 ha, ;25,500 severe) rivaled individual large, infrequent disturbances in the region. Damage patterns were relatively congruent among storms and became more spatially heterogeneous with increasing disturbance intensity. Proximity to forest-nonforest edge, stand age, and soils/landform were consistently important damage predictors. The spatial extent and distribution of the first two damage predictors are extremely sensitive to anthropogenic modifications of forested landscapes, the most important disturbance agent in the northern Great Lakes. This provides circumstantial evidence suggesting anthropogenic activities are augmenting and/or diminishing the ecological effects of the natural wind disturbance regime. Natural disturbances of intermediate size and intensity are significant agents of change in this region, and likely in other regions, deserving more attention from ecologists and biogeographers.

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Section: Discussionmentioning

confidence: 99%

Ecological importance of intermediate windstorms rivals large, infrequent disturbances in the northern Great Lakes

et al. 2011

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“…A large number of metrics and indices have been developed to characterize landscape composition and configuration based on categorical map patterns ͑e.g., McGarigal and Marks 1995;McGarigal et al 2002͒. These metrics are used to analyze landscape structure for a wide variety of applications, including quantifying landscape change over time ͑O'Neill et al 1997͒ and relating structure to ecosystem ͑Wickham et al 2000͒, population and metapopulation processes ͑Kareiva and Wennergren 1995; Fahrig 2002͒. Arguably the major application of landscape structure metrics has been assessing effects of habitat loss and fragmentation on landscape connectivity ͑e.g., Fahrig and Merriam 1985;With et al 1997;Fahrig 1998;Fahrig and Jonsen 1998;Wickham et al 1999;Riitters et al 2000͒. Fragmentation is a complex phenomenon that can be seen both as a consequence of habitat loss and as a process in and of itself ͑McGarigal and McComb 1995͒. The process of fragmentation of a continuous matrix habitat begins with reduction in habitat area and an increase in proportion of edge-influenced habitat.…”

Section: Introductionmentioning

confidence: 99%

Behavior of class-level landscape metrics across gradients of class aggregation and area

2004

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Habitat loss and fragmentation processes strongly affect biodiversity conservation in landscapes undergoing anthropogenic land use changes. Many attempts have been made to use landscape structure metrics to quantify the independent and joint effects of these processes. Unfortunately, ecological interpretation of those metrics has been plagued by lack of thorough understanding of their theoretical behavior. We explored behavior of 50 metrics in neutral landscapes across a 21-step gradient in aggregation and a 19-step gradient in area using a full factorial design with 100 replicates of each of the 399 combinations of the two factors to assess how well metrics reflected changes in landscape structure. Metric values from real landscapes were used to determine the extent of neutral landscape space that is represented in real landscapes. We grouped metrics into three major behavioral classes: strongly related to focal class area ͑nϭ15͒, strongly related to aggregation ͑nϭ7͒, and jointly responding to area and aggregation ͑nϭ28͒. Metrics strongly related to class area exhibited a variety of distinct behaviors, and many of these metrics have unique interpretations that make each of them particularly useful in certain applications. Metrics strongly related to aggregation, independent of class area, are particularly useful in assessing effects of fragmentation. Moreover, metrics in this group exhibited a range of specific behaviors, highlighting subtle but different aspects of landscape aggregation even though we controlled only one aspect of aggregation. The non-linear behavior exhibited by many metrics renders interpretation difficult and use of linear analytical techniques inappropriate under many circumstances. Ultimately, comprehensive characterization of landscapes undergoing habitat loss and fragmentation will require using several metrics distributed across behavioral groups.

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“…Entre las principales acciones destaca proteger los árboles remanentes, cuidar los patrones de pastizales, manejar el fuego y reducir el impacto de las actividades humanas, específica-mente el de la explotación de madera, de los asentamientos, del trazo de carreteras y del uso de agroquímicos (Fitzimmons, 2003;Lapin, 2003;Gibbs, 2001;Fahrig, 2001;Verboom et al, 2001;Ford et al, 2001;Riitters et al, 2000;Lindenmayer et al, 1999;Wigley y Roberts, 1997y Ehrlich, 1996. En este sentido apunta la elección de fragmentos prioritarios para la conservación de los ecosistemas vegetales de la subcuenca del río Pilón, en los que inicialmente se sugiere implementar estrategias de manejo forestal que tiendan a un uso más racional de este valioso recurso (Tabla 5).…”

Section: Discussionunclassified

“…A escala global, los bosques son en realidad fragmentos y bordes (Riitters et al, 2000). Latinoamérica ha perdido la tercera parte de superficie boscosa en el periodo 1850-1985(Houghton et al, 1991.…”

Section: Introductionunclassified

Fragmentación forestal en la subcuenca del río Pilón: diagnóstico y prioridades

Némiga

Garza

Jurado

2016

MYB

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RESUMENLa subcuenca del río Pilón es importante por la captación de agua para la agricultura comercial y por la conservación de la riqueza biológica del estado de Nuevo León. Sin embargo, se desconoce la magnitud de la fragmentación de sus bosques y matorrales, y no se han identificado los fragmentos remanentes prioritarios para conservar. Por lo tanto, este estudio evalúa la fragmentación de sus comunidades vegetales usando el tamaño del fragmento y la relación entre el perímetro y el área del fragmento (P/A) como indicadores de tamaño y forma, así como la distancia al vecino más próximo y el índice de intersección y yuxtaposición como indicadores de conectividad. Estos se calcularon en mapas generados mediante interpretación de imágenes de satélite Landsat de 1974 y 2000 (clasificación supervisada y estratificada). Los resultados muestran cambios estadísticamente significativos en el tamaño y forma de los fragmentos de todas las comunidades evaluadas, así como en su conectividad. Las comunidades más afectadas por la fragmentación en su forma y tamaño son el bosque de oyamel y de encino, así como el huizachal, el matorral submontano y el bosque de pino. En su conectividad, la fragmentación afecta sobre todo a los matorrales tipo tamaulipeco, submontano y desértico, así como los huizachales. En este estudio se evalúan los fragmentos prioritarios a conservar, considerando sus funciones como zonas de amortiguamiento y de estabilización de laderas, mediante la aplicación de criterios en un sistema de información geográfica. Al respecto se recomienda conservar 347 fragmentos para amortiguamiento y 210 fragmentos para estabilización de laderas.PALABRAS CLAVE: Conservación de recursos naturales, fragmentación forestal, Nuevo León, SIG, río Pilón. ABSTRACTThe watershed of the Pilón River is important for its water capture for commercial agriculture and for the conservation of the biological diversity of Nuevo Leon state. However, the magnitude of the forest and shrub fragmentation has not been determined, and the remaining fragments of higher conservation priority have not been identified. This study evaluates the vegetation fragmentation, using the fragment size and the relation between the perimeter and the fragment area (P/A) as indicators of size and shape, as well as the distance to the nearest neighbor and the intersection index and juxtaposition as connectivity indicators. These indicators were calculated in maps generated through satellite images Landsat of 1974 and 2000 interpretation (classification supervised and stratified). The results show statistically significant changes in the size and shape of fragments as well as in connectivity for all plant communities evaluated. The communities more affected by fragmentation in their size and shape were Abies and Oak forests, as well as the huizachal (Acacia scrub), piedmont scrub and

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Global-Scale Patterns of Forest Fragmentation

Abstract: Abstract•

Cited by 307 publications

References 22 publications

Ecological importance of intermediate windstorms rivals large, infrequent disturbances in the northern Great Lakes

Ecological importance of intermediate windstorms rivals large, infrequent disturbances in the northern Great Lakes

Behavior of class-level landscape metrics across gradients of class aggregation and area

Fragmentación forestal en la subcuenca del río Pilón: diagnóstico y prioridades

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