黑河流域荒漠绿洲过渡带两种优势植物种群空间格局特征

Spatial pattern of two dominant shrub populations at transitional zone between oasis and desert of Heihe River Basin

应用地统计学的原理和方法 ,对降水量 1 1 7 1mm、降水量和潜在蒸发量比值为 0 0 5的荒漠绿洲过渡带斑块状植被优势植物泡泡刺、红砂种群的密度、盖度以及泡泡刺沙堆体积和高度的空间格局进行了研究 .结果表明 ,泡泡刺和红砂种群平均盖度分别为 1 5 6± 2 34%和 0 2 3± 0 2 2 % ;密度分别为 1 5± 1 8丛·1 0 0m-2 和 2 3± 2 1株·1 0 0m-2 泡泡刺灌丛沙堆是稳定戈壁下垫面受风沙流干扰形成的一种景观 ,灌丛高度和体积都比较小 ,平均值分别为 0 1 8± 0 1 5m和 0 1 0± 0 1 8m3 泡泡刺种群在样地内靠近绿洲和浅山区有几条明显的分布带 ,而红砂分布相对均匀 .用半方差函数分析表明 ,两种种群密度和盖度的块金值与基台值之比都比较小 ,介于 0 0 8～ 0 1 2之间 ,说明在总空间异质性中随机因素所起的作用很小 ,占 8%～ 1 2 % .两种种群盖度和密度的变程相近 ,基本在 34m以内 ,其中随机因素引起的异质性对应的尺度在 1 0m以下 ,而结构性因素引起的异质性对应的尺度为 1 0～ 34m .泡泡刺和红砂种群盖度和密度的空间异质性均具有各向同性和各向异性特征 ,其中红砂种群的各向同性的范围略大于泡泡刺种群 .

Based on the field investigation in a 500 m×500 m plot and applying geo statistical theory and methods,this paper described the spatial pattern of the coverage,density,height and volume of two shrub populations Nitraria sphaerocarpa and Reaumuria soongorica at the transitional zone between oasis and desert of Heihe River Basin.The average coverage of the two populations was 1.56±2.34% and 0.23±0.22%,and their average density was 1.5±1.8 clump·100 m -2 and 2.3±2.1 individual·100 m -2 ,respectively.The height of N. sphaerocarpa was 0.18±0.15 m,and its volume 0.10±0.18 m 3. N. sphaerocarpa population exhibited strip distribution pattern,while R. soongorica population showed uniform distribution pattern.The nugget (c 0) /sill (c 0+c) ratio of the semivariogram of the two populations was 0.08～0.12,which indicates that the random variance of spatial heterogeneity occupied 8%～12%.In semivariogram model,the range value (A 0) of the coverage and density was 14.7 and 33.9 m for N. sphaerocarpa,and 25.2 m and 24.9 m for R. soongorica ,respectively.As a whole,the random spatial heterogeneity existed at the scale of 10m,and autocorrelated spatial heterogeneity existed at the scale of 34 m.The spatial heterogeneity of the coverage and density of the two dominant populations showed both isotropy and anisotropy,and the isotropy scope of R.soongorica population was larger than that of N.sphaerocarpa .The spatial pattern of N. sphaerocarpa population was controlled by two factors.The first was precipitation and surface runoff,and the second was oasisofication and desertification.