区域土地覆被景观特征的幅度效应及其变异规律

尺度是空间地理现象普遍存在的问题，由于尺度本身的复杂性以及人们认知的局限性，对于尺度问题的讨论仍然有待深入，因此，尺度问题仍然是当前生态学、地理学研究中的热点问题。尺度又包括粒度和幅度两种类型。本文基于2005年广州市的TM遥感影像解译土地覆被类型图，剪裁最大矩形区域景观类型图，沿对角线分别形成不同方向的一系列幅度大小的景观类型图，研究土地覆被景观特征的幅度效应及变异规律。结果表明：景观特征指数的幅度效应及指数之间的差异是明显的，随幅度由小到大，幅度效应减小或趋于平缓，幅度400（144km²）是研究区域景观特征的“临界阈”幅度；景观特征指数的幅度效应及指数之间差异还存在方向性，如PD在NE—SW方向的变化较其它方向大；景观特征指数对幅度效应的程度各异，相对于整体景观而言，指数PD和SHDI在各方向的变幅都较大，而指数FRAC_MN和SHAPE_MN则随幅度的变化只有很小的效应。

The Extent Response of Landscape Characteristics to Regional Land-Cover and Its Variation

Based on the remote sensing image TM of full Guangzhou in 2005,the landscape map of land cover was interpreted.In the map a maximal square region was set in the middle part of Guangzhou.Along each diagonal at two directions,4 series of different extent landscape maps were created.Landscape indices on these maps were analyzed.The results showed there were obvious responses to extent varying for all landscape indices,and the ranges of index response varied from strong to weak with extent increasing.The extent 400(144km~2) is a special sensitive extent which means threshold extent in the study region.Under different extents,the variations of these indices relied on directions where the series landscape maps were created.In the direction of NE-SW,index PD varied strongly. For index SHDI,just in direction NW-SE the index fluctuated lightly and the values of index in other three directions fluctuated greatly.The variations of index SHDI in different direction were focused on 100 to 400 of extent,and the variation was light after extent 400.So extent 400 was defined as the threshold extent of this index.For indices FRAC_-MN and SHAPE_-MN the variations had been different under different extents in the same direction SE-NW.The index varied from high to low greatly when extent changed from 100 to 200,and it varied from low to high greatly when extent changed from extent 200 to 400.For the two indices the threshold extents were obvious too.For index CONTAG,great fluctuations occurred in two directions SE-NW and SW-NE,and at other directions the index fluctuations were small.For this index at all directions the threshold extent was extent 300.All of these characteristics of these indices could be revealed by coefficients of index variation.In relative variation,the results showed that index PD was the biggest,and the greatest fluctuation direction was in NE-SW.Comparing other indices,the relative fluctuations of index SHDI and CONTAG were the second and the third respectively.The smallest relative variation was the index FRAC_-MN.For index PD,in direction SE-NW,its relative variation was very small,and it was even smaller than that in the center.Considering absolute variation of these indices,the absolute variations of indices PD and SHDI were big,and the most variation was appeared in SE-NW for index SHDI.The threshold extent 400 is a range of 144km~2,and this area is equal to the area of one town.In District of Huadu and Baiyun,the average area of 28 towns is 143km~2.