南方集体林区森林破碎化模式及趋势遥感刻画——以浙江余杭为例

Remote sensing based characterization of fragmentation patterns and trends of the collective forests in southern China——A case study from Yuhang city of Zhejiang province

利用1984、1994和2005年Landsat TM遥感影像,采用ISODATA算法将浙江余杭区分别划分为105个光谱类别。然后借助1980和1995年的中国土地利用数据、2004—2006年间全球第1个300m分辨率的土地覆盖数据库Globcover以及2005年余杭森林二类调查数据,将105个光谱类重新聚合为森林、非森林及缺失值3类以支持基于森林破碎化模型(非传统森林景观格局指数方式)的森林破碎化分析。结果表明:1984至1994年间该区的森林面积增加,而1994至2005年间森林面积降低。在整个研究期内,森林破碎化程度一直加剧,具体表现为内部森林的份额减少,斑块森林、过渡森林、孔洞森林比重增加。因此应对森林进行科学的调控,减少对该区森林的不合理干扰,制定相应的政策,以消除或减少森林破碎化对整个森林生态系统的潜在威胁。

Quantitative and spatially explicit forest change and fragmentation information is critical for addressing many pressing issues,including global climate change, carbon budgets, and sustainability. In this study, multitemporal TM images in 1984, 1994 and 2005 were used to classify 105 spectral classes respectively by implementing the unsupervised ISODATA algorithm. and the spectral classifications were conversed into the actual land cover classes involving forest, nonforest and missing value based on the local reference data including China’s land use for 1980’s and 1995, as well as the Globcover data for 2004—2006 and forest inventory data for 2005 in this analysis. Built on the aggregated patterns of forest versus nonforest, a forest fragmentation model was employed to extract the forest fragmentation status and trends over this collective forest area. Analysis results showed that forest area increased in the period from1984 to 1994 but it gradually reduced from 1995 to 2005. An accelerated forest fragmentation was observed in the whole study period, which was evidenced by a gradual decreasing share of interior forest accompanied by an increasing trend for perforated forest, patch forest and transitional forest, while with a relative stable status for edge forest and undetermined forest. The findings has implied that the unreasonable anthropogenic disturbances should be prohibited to impose on the existing forests over this region and an informative regulation plan sponsored by the local administrative agencies should be implemented when pursuing a philosophy of sustainable forest management to mitigate even eliminate the potential threats to forest ecosystems and biodiversity.