科尔沁沙地景观格局特征分析

SPATIAL ANALYSIS OF PATTERN OF SANDY LANDSCAPESIN KERQIN,INNER MONGOLIA

用修改分维数、分维数和景观多样性指数方法，对科尔沁沙地不同沙漠化土地景观空间格局进行了研究。结果表明，在所划分的人工固沙区、围封保护区和流动沙丘区三种沙地景观类型中，人工固沙区景观空间格局最复杂，修改分维数Ｄｍ为１．５４７６；其次为围封保护区Ｄｍ为１．４９７５；流动沙丘景观格局最简单Ｄｍ为１．４２０５。在沙漠化发展过程中（从保护区景观到流沙区景观）Ｄｍ减少，景观格局趋向简单；在沙漠化逆转过程中（从流沙区景观到人工固沙区景观）Ｄｍ增大，景观格局趋向复杂。在不同的景观类型中，斑块格局因受不同的作用过程影响变化规律各异。在人工固沙区，由于人工固沙措施为主的作用过程的影响，斑块类型从固定沙丘（ａ）、半固定沙丘（ｂ）、半流动沙丘（ｃ）到流动沙丘（ｄ），格局多样性逐渐趋向复杂（Ｄ和Ｄｍ依次增加）；在围封保护区，由于受季节性放牧、樵采和植被自然恢复等过程的多重作用影响，斑块类型ａ和ｄ的空间结构最为复杂，斑块修改分维数分别为１．４６６３和１．４４３５。此外，从本项研究所用的三种格局分析方法的结果来看，修改分维数Ｄｍ比分维数Ｄ和景观多样性指数Ｈ能更好地描述景观和斑块的空间格局。

We use fractal dimension(D),modified fractal dimension(Dm),landscape diversity index(H)to analyze the spatial pattern in relation to ecological processes of sandy landscapes in Kerqin,Inner Mongolia.Our results show that among three types of sandy landscapes,the artificial fixed sanddune region exhibited the most complex spatial pattern(Dm=15476),the fenced sanddune area was less complex(Dm=14975),and the flowing sanddune region was least complex(Dm=14205).This suggests that during desertification(i.e.,from a fixed or fenced sanddune to a flowing sanddune landscape),Dm decreased,and the spatial pattern of landscapes tended to be simper.On the contrary,Dm seemed to increase progressively during the recovery process of desertified lands(i.e.,from flowing sanddunes to artificial fixed sanddunes),and thus landscape pattern became more complex.For different landscapetypes,the spatial pattern of patches was affected by various factors and processes,which changed variably.In the artificial fixed sanddune region,the complexity of individual patches increased from the fixe(type a),semifixed(type b),semiflowing(type c), to flowing sanddune(type d)patch type due to human activities(both D and Dm increase progressively).In the fenced region,however,the fixed and flowing patch types were the highest in spatial complexity(Dm was 14663 and 14435 for type a and type d,respectively).The results of this study suggest that modified fractal dimension is superior to fractal dimension and diversity index in describing landscape diversity at both the individual patch and landscape levels.