祁连山地甘肃臭草斑块土壤水分与植被盖度空间格局

Spatial patterns of soil moisture and vegetation coverage in Melica przewalskyi patches in degraded alpine grassland of Qilian Mountains,Northwest China

土壤水分是植被格局形成和演变的主要因素,土壤水分的空间异质性对于认识干旱区草原植物对环境的响应机制具有重要意义,而在较小尺度上,植被状况是土壤水分空间异质性的主要驱动因子。利用地统计学方法,研究了祁连山北坡甘肃臭草单优种群斑块浅层剖面(0～30cm)土壤水分与植被盖度的空间异质性及其关系。结果表明:甘肃臭草斑块浅层剖面土壤水分和植被盖度均符合正态分布,各层土壤水分均存在高度的空间异质性,其中,80.93%～87.34%的空间异质性是由空间自相关引起的,植被盖度主要体现在4.09～6.91m的尺度上,而由1m以下尺度随机因素引起的空间异质性占12.66%～19.07%;甘肃臭草在斑块尺度上各层土壤水分的空间结构表现出明显的圈层结构和斑块状分布的特点,土壤水分高低值斑块呈镶嵌分布且具有较强的空间异质性;甘肃臭草通过生理整合影响并在一定程度上改变了小尺度上土壤水分的分布格局,从而实现了对土壤水分资源最大限度的利用,提高了种群在干旱生境中的适应能力和竞争力。

Soil moisture is the key factor in the fbrmation and evolution ot vegetation pattern, lne spatial heterogeneity of soil moisture has an important significance in understanding the response mechanisms of plants in arid grasslands to environment. Meanwhile, at small scales, vegetation condition is the important driving factor to the spatial heterogeneity of soil moisture. By the meth- ods of geo-statistics, this paper studied the spatial variability of surface soil （0-30 cm） moisture content and vegetation coverage as well as their relationship in the Melica przewalskyi-dominant patches in degraded grassland on the northern slope of Qilian Mountains, Northwest China. In the M. przewalskyi-dominant patches, both the surface soil moisture content and the vegetation coverage were in line with normal distribution. In different layers at 0-30 cm depth, soil mois- ture content had a high degree of spatial heterogeneity, and 80.93% -87.34% of the heterogene- ity was caused by spatial autocorrelation. The spatial autocorrelation in vegetation coverage was found within the distance from 4.09-6.91 m, whereas the spatial heterogeneity of vegetation cov- erage caused by stochastic factors at 〈1 m scale accounted for 12.66%-19.07%. The spatial heterogeneity of soil moisture content in M. przewalskyi-dominant patches showed an obviously layered and patchy structure, and the high and low moisture values had a mosaic distribution. Through physiological integration, M. przewalskyi affected, and in definite extent, altered the spatial distribution of soil moisture at small scales, and thus, achieved the maximum utilization of soil water resource, and improved the adaptability and competitiveness of M. przewalskyi popula- tions in arid habitats.