基于Ripley的K(r)函数和分形维数的梭梭种群空间格局

应用Ripley的K(r)函数和分形维数,研究了古尔班通古特沙漠土质、沙质、盐土和石砾质4种生态类型梭梭在不同发育阶段的分布格局和分形特征.结果表明:沙质、盐土和石砾质生态类型中的梭梭种群呈显著聚集分布,而土质生态类型梭梭种群仅在1～18m范围内呈聚集分布,说明荒漠植物群落通过聚集分布适应其生存的环境;梭梭不同发育阶段的分布格局不同,幼苗和幼树呈聚集分布,成年树呈随机分布.与Ripley的K(r)函数相比,关联维数能反映种群的个体对空间占据能力的强弱,但不能直接反映干旱区种群的个体聚集/非聚集.此外,3种分形维数对样地内梭梭种群个体数量和植株大小较为敏感.

Distribution pattern of Haloxylon ammodendron population based on Ripley's K(r) function and fractal dimension

By using Ripley’s K(r) function and fractal dimension, this paper studied the spatial pattern and fractal characteristics of four ecotypes Haloxylon ammodendron population at different development stages in Gurbantonggut desert. Of the four ecotypes, soil ecotype clumped in 1-18 m scale, while sand, saline soil and gravel ecotypes clumped in all scales, suggesting that desert plant could adapt a habitat via clumping. The spatial pattern of H. ammodendron population differed with its development stage. Seedlings and saplings clumped, while adult trees showed random distribution. Compared with Ripley’s K(r) function, correlation dimension could reflect the ability of spatial occupation, but couldn’t directly reflect the clump or not clump in arid area. Moreover, the dimension was susceptible to the number and size of H. ammodendron.