The role of edge contrast and forest structure in edge influence: vegetation and microclimate at edges in the Brazilian cerrado
The effect of the adjacent non-forested environment on the forest near the edge, edge influence (EI), is an important impact in fragmented landscapes and is believed to vary with factors such as forest structure and edge contrast. In order to improve our understanding of the factors governing the variability in EI, we studied microclimate and vegetation at cerrado edges surrounded by variable land uses in southeastern Brazil, a system with both forest and savanna fragments. We determined the significance, magnitude and distance of EI on microclimate, vegetation structure and grass biomass which we measured along five transects perpendicular to fourteen edges in forest or savanna next to different land uses. We introduce a quantitative measure of edge contrast that considers land uses at different distances from the same edge (e.g., a firebreak between a forest edge and a plantation) and verified whether edge contrast is correlated with EI in this system. Notwithstanding the large variation in EI among variables and study sites, there were some similarities in the patterns of EI between forest and savanna edges. Edge contrast was successfully quantified by our measure but was only correlated with EI on moisture and grass biomass. Our results point to the high variability in EI within a region. Our quantitative measure of edge contrast may be useful in explaining variability in EI. However, much unexplained variation remains in the highly fragmented cerrado system which is affected by EI in both forest and savanna fragments.
KeywordsEdge effects Exotic grasses Moisture Savanna Temperature Vegetation height
We thank R. Xavier, E. Recco, C. Zanelli, A. Viscardi, F. Oliveira and others for extensive help with the fieldwork; A. Viscardi for aid in analyzing canopy closure; M. Batalha, A. Peret, M. Bichuette, A. Melo, V. Pivello, A. Braga, I. Paneczko, F. Tiberio, as well as the editor and two anonymous reviewers for valuable comments on previous versions of this manuscript; C. Zanelli for the drawing in Fig. 2; the Forestry Institute of São Paulo State, the Municipal Botanical Garden of Bauru and to the owner of Farm América for permissions and logistic support; and FAPESP—São Paulo State Research Foundation for financial support provided to PD (MSc Grant 2008/07772-0).
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