黄土丘陵区土壤水分空间分布与环境因子的关系

摘要

为揭示黄土丘陵区土壤水分空间分布规律及其与环境因子的关系,在延河流域,运用自然间隔法划分样区和布设样点,通过定位观测和样品采集,采用统计分析和冗余分析(RDA)方法,研究土壤水分空间分布规律及其与环境因子的关系.结果表明:不同样区土壤水分均值以万花山最高,镰刀湾最低,土壤水分由南向北逐渐降低,可将其划分为4大水分梯度即14.64％、12.36％、10.32％和8.76％;除高桥、县南沟和招安镇3个样区的土壤水分随着土层加深呈现增加的趋势,其他样区呈现先增后减的趋势;土壤水分空间分布具有明显的环境梯度特征.流域东南部土壤水分由年均温度主导,西南部由年均降雨主导,北部由年均蒸散主导;年均蒸散和年均降雨是流域土壤水分的主控因子,地形和土地利用对土壤水分的影响在流域尺度上不明显.环境因子的综合作用形成流域土壤水分的空间生态梯度.研究对进一步认识黄土丘陵区土壤水分空间格局及其与环境因子的关系具有重要作用,该结果可为黄土丘陵区水土保持植被规划提供理论依据.%[Background] Soil moisture content is one of the key factors affecting various ecosystem processes,especially for semi-arid and arid areas.At present,few researches are focused on the spatial distribution of soil moisture content and its relationships with multi-environmental factors in large scale,which is of significance in planning ecological vegetation in soil and water conservation.In this study,we aimed to investigate the spatial distribution of soil moisture content in the loess hilly region and further analyze its relationships with other environmental factors.[Methods] The study was carried out in Yanhe watershed,north of the Loess Plateau.Ten sample areas were chosen by using nature separation method.We investigated the characteristics of soil moisture and 8 environmental factors (annual average rain,annual average evapotranspiration,annual average temperature,elevation,aspect,slope,slope position,and landuse) at each sample area.Firstly,we analyzed the distribution of soil moisture in different sample areas based on sampling analysis and statistical analysis.Then,the redundancy analysis (RDA) was used to determine the key factors leading to these differences.[Results] Soil moisture content in Wanhuashan was significantly higher than that in other sample areas (P ＜ 0.05).While,the lowest soil moisture content was observed in Liandaowan (P ＜ O.05).Moreover,the Yanhe watershed can be divided into four water gradients by moisture content of 14.64％,12.36％,10.32％,and 8.76％,which was in decreasing trend from south to north.Soil moisture content of Gaoqiao,Xiannangou and Zhaoanzhen increased with soil depth,while soil moisture content of the other seven sample areas increased at first and then decreased.Significant environmental gradient were observed in the spatial distribution of soil moisture content.All sampling sites were plotted out 3 groups by RDA.The dominant factor of soil moisture content in the southeastern,southwestern and northern Yanhe watershed were annual average temperature,annual average rain and annual average evapotranspiration,respectively.Redundancy analysis showed that annual average evapotranspiration and annual average rain were the dominant factors influencing soil moisture content spatial distribution pattern in the whole watershed region.Topography and landuse had no significant effect on soil moisture content distribution in the Yanhe watershed.[Conclusions] The comprehensive effect of environmental factors led to the spatial gradient of soil moisture content.These results are essential in explaining the spatial distribution of soil moisture content and its relationships with environmental factors in the loess hilly region.This study provides a theoretical basis for vegetation restoring and reconstructing in the Loess Plateau.