1990-2013年洋河流域土地利用景观格局的粒度效应

Spatial Grain Size Effect on Land Use Pattern Changes Within the Yanghe Watershed in 1990-2013

为测度景观格局指数在时空上随粒度变化的特征,总结相同景观在不同粒度下的景观特征差异,基于1990、2000、2013年洋河流域的土地利用数据,在斑块类型与景观水平上选择景观格局指数,利用GIS技术和Fragstats软件,在20~400 m粒度范围内探讨流域不同时期景观格局指数的粒度效应,并对景观格局指数进行敏感度与函数拟合分析。结果表明:在斑块类型水平上,随粒度增大,1990—2013年洋河流域6种土地利用类型的归一化形状指数(NLSI)、聚合指数(AI)、聚集度指数(CLUMPY)均呈二次多项式函数减小,耕地、林地、城乡建设用地的斑块密度(PD)呈二次多项式函数减小,未利用土地的PD呈线性函数减小;对粒度响应最敏感的景观格局指数是水域的有效粒度面积(MESH)与城乡建设用地的NLSI,受粒度影响最大的土地利用类型是水域;2013年洋河流域未利用土地的AI、CLUMPY、MESH与平均形状指数(SHAPE_MN)皆小于1990、2000年,但其NSLI值却高于1990、2000年,城乡建设用地的这些景观格局指数的年间差异与未利用土地相反;2013年洋河流域未利用土地和城乡建设用地的PD值均高于1990、2000年。在景观水平上,洋河流域的PD与LSI对粒度响应最敏感,景观丰度(PR)不随粒度变化而变化,但是香农多样性(SHDI)、香农均匀度(SHEI)、形状变异系数(SHAPE_CV)随粒度变化而变化复杂。在景观水平上,1990—2013年洋河流域的SHAPE_MN、平均分维数(FRAC_MN)、AI、蔓延度(CONTAG)、PD、景观形状指数(LSI)与凝聚度(COHESION)随粒度变化的曲线较接近。洋河流域的景观指数具有明显的粒度效应,不同时期的景观格局指数对粒度变化的响应不同,景观类型对空间粒度变化的响应也有所不同,本研究可为流域景观格局变化研究提供参考。

To measure landscape pattern metrics traits with changes of grain of landscape traits in different grain sizes, based on data of land use within 2000 and 2013, landscape pattern metrics were chosen at the levels of class sizes, and summarize differences the Yanghe Watershed in 1990, and landscape, and the effects ofgrain sizes in the range of 20 to 400 m on landscape pattern metrics were analyzed, using Information System （GIS） and Fragstats software. The functions for landscape pattern metrics and grain sizes were fitted and the variation coefficients of landscape pattern metrics were determined. The results showed that the normalized landscape shape index （NLS1）, the aggregation index （A/）, and the clumpiness （CLUMPY） for all land-use types at the class level within the Yanghe Watershed in 1990-2013 decreased with increasing of grain sizes and were well fitted by the quadratic polynomial-functions. Similarly, changes of patch density （PD） with grain sizes for farmland, woodland and rural-urban construction land were well fitted by quadratic polynomial functions and those for unused land were well fitted by a negatively linear function. Moreover, among all the landscape pattern metrics, the effective mesh size （MESH） and the normalized landscape shape index （NLS1） were the most sensitive to the changes of grain sizes for water area and rural-urban construction land, respectively. Among all the land-use types within the Yanghe watershed, the water area was the most sensitive to the changes of grain sizes. The A1, CLUMPY, MESH and the mean shape index （SHAPE MN） for unused land in 2013 were smaller than those in 1990 and 2000, while the NLSI for unused land in 2013 was higher than those in 1990 and 2000. Besides, the yearly differences of the AL CLUMPY, MESH, NLSI for the rural-urban construction land in 1990-2013 were completely contrary to those for the unused land. The PD for unused land and rural-urban construction land in 2013 was higher than those in 1990 and 2000. At the landscape level, among all landscape metrics, the PD and LS1 were the most sensitive to the changes of grain sizes. The patch richness （PR） did not change with the grain sizes. Changes of the Shannon diversity index （SHD1）, the Shannon evenness index （SHE1） and the shape coefficient of variation index （SHAPE_CV） with the grain sizes were complex. Changes of the mean fraetal dimension index （FRAC_MN）, the SHAPE_MN, the AL the contagion （CONTAG）, the PD, the landscape shape index （LS1） and the cohesion （COHESION） with grain sizes in 2013 were similar to those in 1990 and 2000. The paper concludes that significant scale effects exist in most landscape pattern metrics in the Yanghe Watershed landscape, in addition, different responses to the changing grain size occur with different landscape metrics, and various land use types. The present study could improve the understanding of the changes of landscape pattern at the scale of watershed in the future.