西鄂尔多斯高原干旱荒漠灌木群落空间分布格局及其竞争关系分析

Analysis of spatial pattern and competition relationship of shrub community in arid desert of Western Ordos Plateau

对西鄂尔多斯高原干旱荒漠中的四合木（Tetraena mongolica Maxim.）、霸王（Sarcozygium xanthoxylon Bunge）、白刺（Nitraria tangutorum Bobr.）和红砂〔Reaumuria songarica（Pall.） Maxim.〕优势群落（样方面积50 m×50 m）进行调查,并按土壤中根系分布深度（0-30、30-60、60-90和大于90 cm）将4种灌木分为4个灌木组,运用单变量函数g（t）、标记相关函数markcorr（t）和双变量函数g12（t）对4个灌木组内灌木的空间分布格局及竞争关系进行了研究。g（t）函数和markcorr（t）函数分析结果显示,4个灌木组内的灌木在0-25 m尺度上几乎都呈显著的随机分布,只有根系分布深度在地下0-30 cm的灌木在小于1 m的尺度上呈现均匀分布;除根系分布深度大于90 cm的灌木的标记在12-13 m尺度上呈现较显著的负相关关系外,在0-25 m尺度上每个灌木组间的标记都不相关,表明根系分布深度相似的灌木间无显著的排斥关系,灌木个体的大小不受周围灌木的影响。g12（t）函数分析结果显示,除根系分布深度为0-30与30-60 cm、30-60与60-90 cm的灌木组间分别在某一中小尺度上（3.0-3.5 m、小于1.5 m和7.0-7.5 m）呈现显著的正相关关系外,在0-25 m尺度内根系分布深度相邻的各灌木组间几乎无显著的相关关系,表明根系分布深度不同的灌木间并不互相影响。研究结果表明,在西鄂尔多斯高原干旱荒漠灌木群落中,具有不同生态学特性的灌木分别占据各自的土壤层,呈现出对土壤水分和养分的分层利用,不存在对资源的竞争。

The dominant shrub community（quadrat area 50 m×50 m）of Tetraena mongolica Maxim.,Sarcozygium xanthoxylon Bunge,Nitraria tangutorum Bobr.and Reaumuria songarica（Pall.） Maxim.in arid desert of Western Ordos Plateau was investigated,and four shrubs were divided into four shrub groups according to the root distribution depth（0-30,30-60,60-90 and 90 cm） in soil.Using functions of univariate g（t）,markcorr（t） and bivariate g12（t）,the spatial pattern and competition relationship among shrubs in four shrub groups were researched.The analysis results of g（t） and markcorr（t） functions show that the spatial pattern of shrubs in all four shrub groups almost is significant random distribution in 0-25 m scale,only that of shrubs with root distribution depth of 0-30 cm is uniform distribution in small scale（〈1 m）.Except mark of the shrubs with root distribution depth more than 90 cm appearing more significantly negative correlation in 12-13 m scale,all marks among different shrub groups have no correlation in 0-25 m scale,which means that there is no obvious rejection among shrubs with similar root distribution depth,and individual size of shrubs is not affected by other shrub individuals around them.The analysis result of g12（t） function shows that except correlations between the shrub groups with root distribution depth of 0-30 and 30-60 cm and between those of 30-60 and 60-90 cm being significant in some meso-or small scales（3.0-3.5 m,〈1.5 m and 7.0-7.5 m）,almost there are no significant interactions between any two shrub groups with contiguous root distribution depth in 0-25 m scale,which means the shrub individuals with different root distribution depths have no influence on each other.It is suggested that shrubs possessing different ecological characters occupy respective soil layers and stratify to use water and nutrient in soil,and have no competition to resources with each other in arid desert of Western Ordos Plateau.