塔里木河下游河水漫溢后胡杨幼苗分布格局初探

采用最近邻体法,将Clark-Evans指数作为度量胡杨幼苗分布格局的指标,并用标准正态分布检验实际CE指数值偏离1的显著性,分析塔里木河下游河水漫溢后胡杨幼苗的分布格局。结果表明:(1)在3m×3m的样方尺度上,河水漫溢后0～1年和1～2年的胡杨幼苗呈聚集分布,漫溢后2～3年的胡杨幼苗呈均匀分布,漫溢后4～5年和5～7年的胡杨幼苗呈随机分布。(2)在3m×3m的样方尺度上,随着胡杨幼苗年龄的增长,胡杨幼苗的空间分布格局由聚集分布转变为均匀分布,最终呈现为随机分布的格局。(3)在2m×2m至10m×10m的样方尺度上,漫溢后5～7年的胡杨幼苗空间分布格局均表现为随机分布。(4)标准正态分布检验结果显示,各个尺度上胡杨幼苗的CE值与理论值1之间的偏离均不显著,说明随着尺度的增大,胡杨幼苗的空间分布格局并没有发生显著变化,始终呈现出随机分布的格局。

Distribution Pattern of Seedlings of Populus euphratica after River Overflowing in the Lower Reaches of Tarim River

In order to analyzing the distribution patterns of Populus euphratica seedlings after river overflowing,Clark-Evans index was calculated for measuring the distribution patterns by using the nearest neighbor analysis method and tested the deviation of actual CE index from the 1 by using the standard normal distribution.The results indicated that:(1)In the quadrats of 3 m×3 m,seedlings of P.euphratica presented aggregated distribution after river overflowing for 0~1 year and 1~2 year,uniform distribution after river overflowing for 2~3 year,and random distribution after river overflowing for 4~5 year and 5~7 year.(2)With the increase of P.euphratica’s age,the special distribution pattern of P.euphratica seedlings changed from aggregated distribution to uniform distribution and to random distribution finally in the quadrats of 3 m×3 m.(3)In the various sizes of quadrats of 2 m×2 m to 10 m×10 m,seedlings of P.euphratica presented random distribution after river overflowing for different years.And the test value of standard normal distribution show that the deviation of CE value of P.euphratica seedlings from 1 in the various sizes of quadrats were not significant.As the scale increase,the spatial distribution pattern of P.euphratica seedlings had no significant change,and they always presented random distribution pattern.