宁夏东部风沙区沙化草地土壤水分和植被的空间特征

土壤水分作为土壤-植被-大气连续体的关键因子，对沙化草地的演化过程具有重要作用。为探讨宁夏东部风沙区沙化草地土壤水分、物种丰富度指数及植被盖度的空间变异及其相互关系，以哈巴湖自然保护区沙化草地为对象，采用样线法自潜在沙化草地至重度沙化草地进行植被调查和土壤取样，通过经典统计学和地统计学分析，得出以下结果：0—100 m各土层土壤水分含量、植被盖度和物种丰富度指数的分布范围分别为0.82%—28.22%、41.00%—93.00%和0.82—2.80,变异系数范围为0.20—0.48,均属于中等变异。各土层土壤水分和物种丰富度指数表现为中等的空间自相关性，植被盖度则表现为强烈的空间自相关性。Kriging插值结果表明，0—100 cm各土层土壤水分和植被盖度的空间插值图呈条带状和斑块状的梯度变化，物种丰富度呈斑块分布，自潜在沙化草地至重度沙化草地，表现为逐渐降低的趋势。相关分析表明，植被盖度与0—40 cm各土层土壤水分呈显著正相关，与40—100 cm各土层土壤水分呈极显著正相关。宁夏东部风沙区沙化草地土壤水分含量总体较低，由于结构因素和随机因素的共同作用，随草地沙化程度的加重，表现为...

Spatial characteristics of soil moisture and vegetation in desertification grassland in eastern Ningxia sand-wind area, China

Soil moisture is of crucial importance for hydrological, biological and biogeochemical processes, especially in arid and semiarid regions where water is the main factor limiting vegetation survival and economic development. In order to explore the spatial variability and their relationship with soil moisture, Margalef richness index and vegetation coverage of the desertified grassland in eastern Ningxia sand-wind area, three 3.6 km parallel transects were laid out from the potential desertified grassland to the severe desertified grassland with 500 m interval between the two adjacent transects. Along each transect, quadrats were established at 200 m intervals for the vegetation investigation and soil sampling. Soil samples were collected at the following depths:0-10, 10-20, 20-30, 30-40, 40-50, 50-60, 60-70, 70-80, 80-90, and 90-100 cm. The soil moisture, Margalef richness index and vegetation coverage were measured and their spatial distributions and interrelationships were analyzed by combining of the classical and geostatistical methods. The results showed that the vegetation coverage, species richness and the contents of soil moisture at each soil layer from 0-100 cm ranged from 41.00%-93.00%, 0.82-2.80, and 0.82%-28.22%, respectively, and the variation coefficient ranged from 0.20 to 0.48, all of which belonged to moderate variability. The optimal models of the soil moisture at 0-10 cm layer and Margalef richness index were Spherical and Exponential models, respectively. The Gaussian models are applicable to the soil moisture of each layer at 10-100 cm depth. The determination coefficients ranged from 0.593 to 0.941. The nugget coefficient for the soil moisture in each layer and Margalef richness index were 26.31%-41.86%, which means the spatial heterogeneity caused by structural factors and random factors plays a major role in the soil moisture in each layer and Margalef richness index. The nugget coefficients of vegetation coverage was 2.50%. The nugget coefficients of vegetation coverage were low, which means the spatial heterogeneity caused by structural factors. The range of vegetation coverage, the Margalef richness index, and the soil moisture content of each soil layer ranged from 1453 m to 8110 m, indicating that the ecological process played a role on a large scale with good continuity. Kriging-interpolated maps showed that the soil moisture in each soil layer and vegetation coverage of the study area appeared as stripe and patchy gradient changes. With the aggravating of grassland desertification, the soil moisture of each soil layer, the Margalef richness index and the vegetation coverage decreased gradually. The Margalef richness index presented an obvious patchy pattern, with high-value areas appearing in the transitional area between the potential desertification grassland and the light desertification grassland, the light desertification grassland and the moderate desertification grassland. The values of the soil moisture in each soil layer in the west changed more gently than those in the east of the study plot. The vegetation coverage was significantly related to the soil moisture contents in each layer at 0-40 cm soil depth, and was extremely significantly related to those at the soil depth of 40-100 cm. There was a significantly positive correlation between soil moisture and Margalef richness index in each soil layer at 0-50 cm depth. It was found that the soil moisture contents of each soil layer in the 0-100 cm layer was relatively low in eastern Ningxia sand-wind area. Due to effects of structural factors and random factors, with the degree of grassland desertification increased, the soil moisture contents manifested as a locally increased patch pattern in the process of gradually decreasing gradient changes. Under the influence of soil moisture, the vegetation parameters showed similar spatial distribution pattern to the soil water content. The results of this paper can provide a theoretical basis for the quantitative measurement of the evolution process of grassland desertification and the ecological environment protection and construction of grasslands in arid and sandy areas.