ANALYSIS OF SPACE-TIME DYNAMICS OF FOREST FRAGMENTS IN THE ALEGRE RIVER SUBWATERSHED, BRAZIL

Knowing the history of forest fragmentation in watersheds helps plan and implement practices based on restoration of degraded forest areas. Structural analysis of forest fragments in the Alegre River subwatershed, State of Espírito Santo, was based on landscape metrics using ArcGIS 10 software with Patch Analyst extension, regarding changes during 1975, 2002, and 2007. Analysis showed an increase of about 7% in the total area of forest cover and emergence of 645 new forest fragments. Numerous patches and a small drainage area resulted in a high perimeter-to-area ratio. Simple geometric shapes predominated in smaller patches (< 1 ha). Larger patches (> 20 ha) were close to each other, with a tendency to decrease proximity metric values. The results show that despite increase in vegetated area, the environmental quality of forest remnants is highly jeopardized.

了解流域森林破碎化的历史，可为退化森林区域修复相关工作的规划与实施提供依据。本研究以巴西圣埃斯皮里图州阿雷格里河子流域的森林斑块为研究对象，借助搭载Patch Analyst扩展模块（Patch Analyst extension）的ArcGIS 10软件，基于景观格局指数（landscape metrics）分析了1975年、2002年与2007年三个时段的景观变化。分析结果显示，研究区森林覆盖总面积增加了约7%，同时新增645个森林斑块。斑块数量较多且汇水面积偏小，导致斑块的周长面积比偏高。面积小于1公顷的小型斑块多以简单几何形状为主。面积大于20公顷的大型斑块彼此间距较近，且邻近度指数呈下降趋势。研究结果表明，尽管研究区植被覆盖面积有所提升，但森林残存斑块的环境质量已受到严重损害。