Grain effects of landscape in forest-grassland ecotone by county extent

Forest-grassland ecotone is sensitive, complex and diverse. Hulun Buir forest-grassland ecotone is an important ecological barrier in northern China. Study of landscape grain effect and identification of appropriate grain size are essential to establish ecological security. Analysis of grain effect, grain sensitivity, and appropriate grain in Evenk Autonomous Banner, a county in Hulun Buir forest-grassland ecotone, was performed. Variation curve of landscape index was classified into three types. Type Ⅰ declined with coursing of grain. Type Ⅱ increased with coursing of grain. Type Ⅲ waved with coursing of grain. The most appropriate grain size in was found to be 200 m. Sensitivity of landscape index was significantly different. Low sensitivity landscape index contained TA, PAFRAC, AWMPFP, SHDI, SHEI and COHESION, high sensitivity index contained MPI, MNN, MPS and IJI. The former had priority in landscape analysis, the latter index considered grain effect. The time curve of landscape index in different grain indicated that grain effect influence was more important than time change. The importance of grain effect is proved in this study. Choice of index is also given.