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Research Article

Landscape attributes drive complex spatial microclimate configuration of Brazilian Atlantic forest fragments [ 389-402 ]

Severino R.R. Pinto, Gabriel Mendes, André M.M. Santos, Mateus Dantas, Marcelo Tabarelli and Felipe P. L. Melo

Abstract
Habitat fragmentation imposes profound impacts on the tropical forest microclimate, but the microclimatic configuration of isolated forest patches and its implications for biodiversity persistence and habitat management are not clear. In this study we assessed a set of 10 aged (> 80 years) fragments (3.0 – 3,500 ha in size) of the Atlantic forest to examine to what extent fragment microclimatic attributes are correlated with distance to the nearest edge as frequently proposed in the literature. We used 129 sampling points and took a total of 516 measures of air temperature and humidity, vapor pressure deficit and light incidence to characterize the microclimate of forest fragments in terms of their relative deviation from the surrounding matrix. Fragments as a whole presented strong internal variation and strongly differed from the microclimate exhibited by the open matrix of sugar-cane fields. Distance to nearest edge, percentage of forest cover around the measurement point, percentage of edge-affected area, and geographical orientation of the nearest edge all proved to have minor effects on the microclimate of forest fragments. Conversely, we identified percentage of forest cover and fragment area as the most significant explanatory variables driving their microclimatic configuration: as forest cover increases at landscape scale, forest microclimate deviates less from the open matrix (a forest-mediated matrix buffering). Our results suggest that microclimatic conditions are spatially complex, as they do not correlate with the distance to the nearest forest edges; rather, they are driven by a forest-mediated buffering of the surrounding matrix that minimizes heat and humidity exchanges between forest and non-forest habitats, thus shaping the microclimatic signature of isolated forest fragments.


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    English: Unfortunately tropical forests are still vanishing around the world and former large tracts of natural habitats are being converted into archipelagoes of isolated forest fragments, this is forest fragmentation. After fragmentation, exchanges of heat and moisture occur between forest and non-forest area so that forest understory near the border of the fragment begins to get warmer and drier, altering thus the microclimate of the forest and affecting inhabiting life, in most of cases negatively. In a fragmented landscape, forest remnants strongly vary in shape and size and all these features may affect forest microclimate. Our study investigated how deep these changes penetrate into the forest fragment and whether the distance to nearest edges is a good predictor of changes in microclimate of forest fragments. The study site was the hyper-fragmented Atlantic forest of northeastern Brazil, one of the most threatened portions of diverse Tropical forests in the world. Our results suggest that microclimate of forest remnants is governed by landscapes factors such as isolation rather than distance to nearest edges (i.e. forest fragment boundary). These findings contrast with previous knowledge that assumed that the microclimate of forest fragments is mainly driven by distance to the forest boundaries (edges). We demonstrate that changes in microclimate of fragmented forests are complex and influenced by landscape configuration as a whole. Therefore, important implications for landscape management and biodiversity conservation can be drawn from our results that suggest that the “edge vs. core area” paradigm is a misleading approach. Protecting large areas and preventing further fragmentation are key recommendations to avoid ecological deterioration of fragmented landscapes.

    Español: Desafortunadamente las selvas del mundo están desapareciendo rápidamente por la actividad humana y en muchos casos grandes extensiones de selva son transformadas a archipiélagos de fragmentos de selva. Después de la fragmentación, existe un intercambio de calor y humedad ante al fragmento de selva y el área deforestada, de modo que la orilla del fragmento empieza a calentarse y a resecarse mas, alterando así el microclima del fragmento y afectando la vida en su interior, en la mayoría de los casos de modo negativo. En los paisaje fragmentados, las selvas remanentes varían mucho en su tamaño y forma y estos rasgos influyen el microclima en su interior. Con esto en mente, estudiamos que tan profunda es la penetración de estos efectos en fragmentos de selva y si la distancia al borde es un buen predictor de cambios en el microclima en el interior de estos. El estudio lo hicimos en la región altamente fragmentada de la selva Atlántica de Brasil, una de las regiones más amenazadas y diversas del mundo. Nuestros datos sugieren que el microclima de los remanentes de selva parece estar gobernado por factores del paisaje como el aislamiento del fragmento, más que por factores del fragmento como la distancia del centro de este al borde más cercano. Así, es claro que la configuración del paisaje es determinante de los cambios microclimaticos en los fragmentos, por lo que debemos alejarnos del paradigma que enfatiza la relación “borde vs área central” del fragmento y trabajar con la configuración del paisaje a nivel de conservación.

    Portugués: Infelizmente as florestas tropicais continuam sofrendo com o desmatamento que cria arquipélagos de floresta em meio a zonas não florestadas, a isso chamamos fragmentação florestal. Após a fragmentação, começam a ocorrer trocas de calor e umidade entre a floresta e a matriz não florestada de modo que o interior da floresta se torna mais seco e quente em zonas mais próximas à borda do fragmento, afetando a vida que aí habita, quase sempre negativamente. Numa paisagem fragmentada, os remanescentes florestais variam enormemente em tamanho e forma e esses fatores podem afetar enormemente o microclima da floresta remanescente. O presente estudo foi feito numa paisagem hiper- fragmentada da floresta Atlântica do Nordeste do Brasil, uma das porções mais ameaçadas de floresta tropical do mundo. Nossos resultados sugerem que o microclima da floresta fragmentada é majoritariamente influenciado por atributos de paisagem como o isolamento em vez de distância à borda (i.e. fronteira entre floresta e matriz). Esses resultados contrastam com o conhecimento previamente estabelecido que assumia que o microclima dos fragmentos de floresta era influenciado basicamente pela proximidade à borda. Nós demonstramos que as mudanças no microclima de fragmentos isolados são complexas e influenciadas pela configuração da paisagem como um todo. Portanto, podemos tirar importantes implicações para a conservação da biodiversidade e manejo de paisagens já que nossos resultados mostraram que o paradigma “borda vs. núcleo” constitui uma abordagem limitada. Porteger grandes áreas de e prevenir futuro aumento da fragmentação são recomendações chave para evitar a deterioração ecológica de paisagens fragmentadas.
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   Tropical Conservation Science is an open-access e-journal that publishes research relating to conservation of tropical forests and other tropical ecosystems.

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