Spatial and temporal distribution characteristics of soil moisture in the non-freezing period under the bare land and vegetation cover in the Mu Us desert
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摘要:
在水资源短缺的沙地生态系统中,土壤水分是植被恢复和水资源管理的主要控制因子,正确认识沙地土壤水分的分布特征及时空变化规律是促进沙地水资源可持续发展的基础。以毛乌素沙地为研究区,利用原位试验观测、经典统计学分析和聚类分析相结合的方法,揭示了有无植被覆盖下的土壤剖面水分时空变化特征,探讨了植物生长对土壤水分布的影响。结果表明:在2016年非冻结期内,地下水水位埋深较浅时,裸地与植被覆盖情况下土壤平均含水率均随土壤深度的增加而增大,可将0~350 cm土层划分为气候影响层、过渡层与地下水影响层。裸地剖面平均含水率为23.59%,变异系数为4.24%,属于弱变异,剖面含水率在观测期间明显上升,并在8月中旬强降雨时上升速率达到最大;植被覆盖下土壤剖面平均含水率为17.74%,变异系数为15.61%,属于中等变异,剖面含水率在观测期间显著下降,在8月沙柳发育成熟后剖面含水率下降最快。在垂向深度上,植被对土壤剖面含水率的影响近似呈高斯曲线变化,对过渡层含水率的影响最大,占总影响的50%以上,对气候影响层与地下水影响层的影响相对较小,且随着植物生长,气候影响层受到的相对影响逐渐减弱,地下水影响层受到的相对影响逐渐增强。研究成果可为半干旱区毛乌素沙地合理的水资源调控以及沙地生态系统的稳定发展提供参考依据。
Abstract:In the sandy land ecosystem with water shortage, soil moisture is the main controlling factor for vegetation restoration and water resources management. Therefore, a correct understanding of the distribution characteristics and spatial-temporal variation of soil moisture in the sandy land is the basis for promoting the sustainable development of sandy land water resources. The Mu Us desert is taken as the study area, in-situ experimental observations, classical statistical analysis and hierarchical clustering analysis methods are used to reveal the spatial and temporal changes of soil profile moisture with or without vegetation cover, and the effect of plant growth on soil water distribution are discussed in this paper. The results show that in the non-freezing period of 2016, when the groundwater depth was relatively shallow, the average soil moisture content increased with the increasing soil depth under the bare land and vegetation coverage. The soil layer of 0−350 cm thick can be divided into the climate-influencing layer, transition layer and groundwater-influencing layer. The average moisture content of the bare soil profile is 23.59%, and the coefficient of variation is 4.25%, which belongs to weak variation. The profile moisture content increased significantly during the observation period, and the rate of increase reached the maximum when the heavy rainfall event occurred in mid-August. The average moisture content of the soil profile under the vegetation cover is 17.74%, and the coefficient of variation is 15.61%, which is a medium variation. The water content of the profile dropped significantly during the observation period, and it dropeds the fastest in August after the Salix matures. At the vertical depth, the influence of vegetation on the soil profile moisture content approximates a Gaussian curve, and has the greatest influence on the moisture content of the transition layer, accounting for more than 50% of the total influence. The impact on climate-influencing layer and groundwater-influencing layer is relatively small. As plants grow, the relative influence on the climate-influencing layer gradually weakens, and the relative influence on the groundwater-influencing layer gradually increases. The research results can provide references for the rational regulation of water resources in the semi-arid Mu Us Sandy Land and the stable development of the sandy land ecosystem.
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Key words:
- soil moisture /
- spatial and temporal distribution /
- bare land /
- vegetation cover /
- Mu Us desert
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表 1 均质风积沙的物理参数
Table 1. Physical parameters of the homogeneous aeolian sand measured in the laboratory
土壤容重
/(g·cm−3)残余含水率
/(cm3·cm−3)饱和含水率
/(cm3·cm−3)渗透系数
/(m·d−1)1.45±0.005 0.014±0.002 0.31±0.009 6.2±0.6 表 2 裸地和沙柳地不同土层土壤含水率和变异系数
Table 2. Soil moisture content and coefficient of variationin different soil layers in the bare land and Salix land
土地类型 土层/cm 平均值/% 标准差SD/% 变异系数CV/% 裸地 0~80 11.65 1.05 9.01 80~170 19.97 3.77 18.88 170~350 30.71 0.21 0.68 0~350 23.59 1.00 4.24 沙柳地 0~150 10.55 1.21 11.47 150~250 18.43 6.36 34.51 250~350 27.82 3.28 11.79 0~350 17.74 2.77 15.61 表 3 沙柳不同生长阶段各土层的土壤水分差量占比
Table 3. Δθ proportions of each soil layer at different growth stages of Salix
/% 土层 发芽期 生长期 成熟期 枯萎期 休眠期 0~150 cm 36.71 42.53 30.28 22.37 19.93 150~250 cm 56.23 53.40 58.29 56.00 55.55 250~350 cm 7.06 4.07 11.43 21.63 24.52 -
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