毛乌素沙区地下水对植被盖度空间格局影响分析

通过在榆溪河流域沿地下水埋深增大方向设置植被调查样带,基于植被盖度、地下水埋深及土壤含水量等数据,利用多元经验模态分解(MEMD)获取植被盖度及其影响因子所表征的空间尺度,结构方程解析植被盖度空间分布的驱动因素,并结合聚类分析划分了植被群落自然恢复演替空间格局状态变化特征。结果表明：(1)MEMD将空间多元数据分解为3个本征模态函数,经希尔伯特转换得到各模态函数相应的空间尺度分别为14,27,38 km;(2)结构方程模型和MEMD分解后的最大表征尺度相关分析表明,地下水埋深与植被盖度在整个样带尺度上呈显著负相关(R²=-0.95,p<0.001);土壤含水量与植被盖度以地下水埋深5 m空间尺度为分界点,<5 m的区域呈显著正相关(路径系数为0.68,p<0.001),>5 m的区域呈显著负相关(路径系数为-0.43,P<0.01);(3)在此基础上,结合系统聚类分类结果将植被盖度划分为核心区(地下水埋深0～3 m)、过渡区(地下水埋深3～4 m)、稳定区(地下水埋深4～5 m)、外围区(地下水埋深5～10 m)及边缘区(地下水埋深1...

Effect of Subsurface Water on Spatial Pattern of Vegetation Coverage in Mu Us Sandy Area

By setting vegetation survey transect along the increasing direction of groundwater table depth (GTD) in Yuxi River basin,and based on the data of vegetation coverage,GTD and soil water content,the spatial scale represented by vegetation coverage and its influencing factors was obtained by Multivariate Empirical Mode Decomposition (MEMD),the driving factors of vegetation coverage spatial distribution were analyzed by structural equation,then the spatial pattern change characteristics of natural restoration and succession of vegetation communities were divided combining cluster analysis.The results showed that:(1) MEMD decomposed the multivariate spatial data into three intrinsic mode functions.After Hilbert''s transformation,the corresponding spatial scales of each modal part were 14,27,and 38 km,respectively.(2) The maximum represent scale correlation analysis of structural equation model and MEMD after decomposition showed that the GTD had a significant negative correlation with vegetation coverage at the whole transect scale (R²=-0.95,p<0.001);taking GTD 5 m as the cut-off point,the correlation between soil moisture content and vegetation coverage was significantly positive in the GTD less than 5 m (Path coefficient is 0.68,p < 0.001),and significantly negative in greater than 5 m (Path coefficient is-0.43,p<0.01).(3) On this basis,combined with the results of systematic clustering classification,vegetation coverage was divided into the core area (GTD 0~3 m),transition area (GTD 3~4 m),stability area (GTD 4~5 m),peripheral area (GTD 5~10 m) sand marginal area (GTD 10~15 m).The results showed that the response of vegetation coverage to subsurface water had multi-scale characteristics in space,which can provide scientific basis for ecological restoration of sandy land and the protection and utilization of groundwater resources.