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M. Deconchat et al. 2010. Identification and characterization of forest edge segments for mapping edge diversity
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Identification and characterization of forest edge segments for
mapping edge diversity in rural landscapes.
Marc Deconchat, Audrey Alignier, Philippe Espy & Sylvie Ladet
UMR1201, Dynafor, INRA, INPT, F-31326 Castanet tolosan, France
Abstract
Forest edges are key components of rural landscapes and they influence major ecological
processes. There is a variability of forest edges, according to their physiognomy, orientation,
history and topography, but few methods are available to identify automatically these different
types of edges and to map them at a large scale. We propose to identify edge segments based on
morphological subdivision of forest boundaries. These segments can be mapped and
characterized by other spatial data. A procedure based on Arcgis tools, applied on the output
from GUIDOS tools, is used to identify edge segments. We provide examples of edge segments
descriptors obtained from a digital elevation model and from a landcover map. Results showed
the feasibility of the automatic mapping of edge variability over a large scale. It opens new
perspectives for the analysis of landscape dynamics and their effects on biodiversity.
Keywords: Forest edge, GIS, edge segment, morphology
1. Introduction
Forest edges are key components of rural landscapes by their influence on major ecological
processes important for biodiversity conservation (Murcia, 1995). A better understanding and
measurement of the extent and of the variability of edge effects in rural landscapes is required
by land managers to base their decisions on accurate estimations.
Forest edge influence on both microenvironmental conditions and vegetation depends on edge
type (Alignier & Deconchat, 2010). There is a variability of forest edges, according to their
physiognomy, orientation, history and topography, but few methods are available to identify
automatically these different types of edges and to map them at a large scale. Essen et al (2006)
proposed a method based on aerial photography interpretation with a systematic sampling of
edges by a square grid. This method suffers from the difficulty to be applied on very large areas,
the bias associated to the size of the sampling grid and the impossibility to produce a synthetic
map of edge diversity. GUIDOS is a GIS tool developed for the European Union in order to
measure and map habitat fragmentation (Vogt et al., 2007). In this method, edges are defined as
the contour of large tracks of forest, they can be mapped but there is no evaluation of their
diversity. Fragstat (McGarigal et al., 2002) is a set of GIS tools aiming at measuring
fragmentation by patch metrics. It includes several outputs describing edge characteristics, but
with few possibilities to take into account their diversity. Zeng & Wu (2005) introduced the
concept of edge segment as the basic component for computing edge-based metrics to describe
landscape fragmentation. This approach open up new perspective and define the basis for a
systematic and coherent method to map edge diversity in rural landscape.
The aim of the presentation is to introduce the details of a GIS method to identify and
characterize edge segments in landscape, defined from morphological subdivision of forest
boundaries, in the same general framework proposed by GUIDOS. This method, called
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.