National assessment of the evolution of forest fragmentation in Mexico

摘要

This paper presents assessments of the fragmentation of the temperate and tropical forests in Mexico at the national level for two dates 1993 and 2002.The study was based on land use and vegetation cover data sets scale 1:250,000.Two broad forest types(Temperate Forests and Tropical Forests) and five more specific forest types(Broadleaf Forests,and Coniferous Forests;Tropical Dry Deciduous Forests,Tropical Sub-evergreen Forests,and Tropical Evergreen Forests) were defined to conduct the analyses.FragStats 3.3 was used to estimate nine metrics of the spatial pattern of the forests for each forest type and date considered.The results indicate that the land cover transitions that have occurred between 1993 and 2002 have resulted in more isolated forest patches with simpler shapes in both the Temperate and Tropical Forests.The remaining Tropical Forest patches have become smaller and more numerous.In contrast,the remaining Temperate Forest patches are fewer and on average larger.Of the more specific forest types defined in this study,the Broadleaf Forests have the highest indicators of fragmentation.However these forests are usually embedded or adjacent to Coniferous Forests.Of more concern for conservation purposes are the high values of fragmentation metrics found for the Tropical Evergreen Forests and Tropical Dry Deciduous Forests,because these forest types are usually surrounded by non-forest land covers or anthropogenic land uses.