岷江上游植被生境适应性空间分异格局的间隙度分析

了解岷江上游不同植被生境适宜性类型在整体和局部上的空间分异格局对植被生境管理和修复具有非常重要的意义。基于岷江上游4类植被生境适宜性类型空间分布图借助分形和贝叶斯理论,建立间隙度指数模型和多水平贝叶斯模型,实现定量表征不同植被生境适宜性类型在整体和局部空间上的聚簇和分异程度。结果表明:1)汶川在Ⅰ~Ⅳ类、Ⅲ类和Ⅳ类生境适宜性下的间隙度指数最大,其对应的空间分异尺度为3 000 m(即为30倍网格边长,网格边长为100 m)、2 900 m、2 800 m,而松潘在Ⅰ类和Ⅱ类型下的间隙度指数最大,其空间分异尺度为3 000 m、2 700 m。2)Ⅰ~Ⅳ类、Ⅰ类和Ⅱ类生境适宜性分别在汶川、松潘和理县的间隙度维数最大,空间格局聚簇性较小,进一步证明空间分异尺度较大,而Ⅲ类和Ⅳ类生境适宜性在茂县的间隙度维数最大。岷江上游植被生境空间分异格局的间隙度分析,可以为研究生境空间格局及其生境管理尺寸在整体和局部上的差异提供必备的条件和依据。

LACUNARITY ANALYSIS OF SPATIAL VARIATION PATTERNS OF VEGETATION HABITAT SUITABILITY IN THE UPPER REACHES OF MIN RIVER

The spatial variation patterns of various vegetation habitat suitability categories under global and local scales are main characteristic and symbol for vegetation habitat management and restoration in the upper reaches of Min River. Based on spatial distributions of four class vegetation habitat suitability categories (class one was suitable vegetation habitat whose habitat suitability index was highest, class two was sub-suitable, class three was unsuitable, class four was worst suitable whose habitat suitability index was lowest), in this study we established a lacunarity index and used multilevel bayesian models to quantify spatial cluster and variation of diverse vegetation habitat suitability categories from global (the whole upper reaches of Min River) and local scales (five counties including Heishui County, Li County, Songpan County, Mao County, and Wenchuan County). The detailed results were as following:(1) The maximum lacunarity indices of comprehensive class (Ⅰ~Ⅳ), class three (Ⅲ), and class four (Ⅳ) occurred in the Wenchuan County, the spatial variation scale of above three habitat suitability categories were 3000 m (30 times of grid size, the grid size is 100 m), 2900 m, and 2800 m, respectively. It is attributed to driving factors including the lower elevation, flat topography, higher precipitation and lower evaporation. The class two (Ⅱ) and class three (Ⅲ) appeared in the Songpan County owing to higher altitude, steeper slope, lower precipitation, and higher evaporation. The spatial variation scale of previous two habitat suitability categories were 3000 m and 2800 m, respectively. It was suggested that the habitat management of Wenchuan and Sonpan counties was sensitive to sampling grid size (habitat management unit) because of the spatial variation of different habitat suitability categories represented by topographical, meteorological, soil, and vegetation driving environmental factors. The habitat suitability category of maximum lacunarity index appeared in Heishui County, Li County, Wenchuan County, and whole watershed was class Ⅰ. However, the habitat suitability category of maximum lacunarity index appeared in Mao County, and Songpan County was class Ⅳ. (2) The maximum lacunarity dimensions of Ⅰ~Ⅳ, Ⅰ and Ⅱ occurred in the Wenchuan County, Songpan County and Li County, respectively, which meant their spatial structures were in the discrete state. The maximum lacunarity dimensions of Ⅲ and Ⅳ occurred in Mao County. The county administrative unit had the largest impact on spatial variation and character scale of class Ⅱ and had smallest impact on spatial variation and character scale of class Ⅰ~Ⅳ. The analysis of spatial variation of vegetation habitat suitability could provide the theories for vegetation habitat management in the upper reaches of Min River.