Tropical forest fragmentation: typology and characterization

The analysis and quantification of deforestation and forest degradation require diffuse ecological and spatial concepts such as forest fragmentation and forest/non forest interfaces. Anthropic factors associated with natural geophysical conditions are leading to a wide range of fragmentation patterns: their characterization and measurement represent the objectives of this study. Based on visual concepts, a qualitative approach is undertaken to propose a topology of fragmentation patterns: four types (massive, linear, insular and diffuse) are identified and illustrated in a catalogue with 34 samples selected all over the tropical belt. In a second step, some mathematical indicators, based on the number of forest/non forest pixels interfaces and the number of edge pixels, are developed and tested to quantify forest fragmentation. In the TREES Project, AVHRR classifications have to be ultimately calibrated with TM data by linear regressions between the forest cover percentages. Within and in between regions, the regression parameters present a high variability which is expected to be significantly reduced by stratifying the AVHRR classifications. This study further investigates on the most sensitive fragmentation indices affecting the regression slopes.