古尔班通古特沙漠南缘固定沙丘上土壤水分与地形-植被因子的关系

土壤水分是干旱和半干旱生态系统格局和过程的主要驱动力,地形-植被因子是小尺度上影响土壤水分的主要因子。以古尔班通古特沙漠南缘北沙窝附近固定沙丘上不同深度的土壤水分(表层0-40 cm、中层40-200 cm、深层200-300 cm和整体0-300 cm)作为研究对象,利用广义线性模型(GLM)、广义加性模型(GAM)和随机森林(RF)模型研究了土壤水分与地形-植被因子之间的关系和变化规律。结果表明:(1)不同深度的土壤水分均呈现一致的单峰分布,不同深度土壤水分的大小顺序为深层>中层>表层,且两两之间具有显著差异。(2)GLM和GAM模型得到的影响不同深度土壤水分的植被和地形因子完全相同,RF模型的精度优于GLM和GAM模型。(3)地形因子海拔、坡度、高差和植被因子灌木多度与其影响的不同深度的土壤水分呈负相关关系,地形因子坡向(规定正东方向为0,顺时针旋转)和植被因子生物量与其影响的土壤水分呈正相关关系。植被因子草本盖度与表层土壤水分呈正相关关系,与中层土壤水分呈负相关关系。研究结果可为研究区制定相应的防风固沙措施以及建立科学合理的植物固沙模式提供理论参考。

Relationship Between Soil Moisture and Topography-vegetation Factors on Fixed Dunes in the Southern Margin of the Gurbantunggut Desert

Soil moisture is the main driving force for the patterns and processes in arid and semi-arid ecosystem, and topography-vegetation factors are the main factors affecting soil moisture on the small-scale. Soil moisture at different depths (0-40 cm in surface layer, 40-200 cm in middle layer, 200-300 cm in deep layer and 0-300 cm in whole) on fixed sand dunes near the northern sand dune in the southern edge of the Gurbantunggut Desert was used as a study object to investigate the relationship and variation patterns between soil moisture and topography-vegetation factors using generalized linear model (GLM), generalized additive model (GAM) and random forest (RF) models. The results showed that: (1) Soil moisture at different depths showed a consistent single-peaked distribution, and the magnitude of soil moisture at different depths was in the order of: deep > middle > surface, and there were significant differences between the two. (2) The vegetation and terrain factors affecting soil moisture at different depths obtained by GLM and GAM models were identical, and the accuracy of the RF model was better than that of GLM and GAM models. (3) Topographic factors elevation, slope, height difference and vegetation factors shrub multiplicity were negatively correlated with soil moisture at different depths under their influence, while topographic factors slope direction (specified as 0 due east, rotated clockwise) and vegetation factor biomass were positively correlated with the soil moisture they affected. The vegetation factor herbaceous cover was positively correlated with surface soil moisture and negatively correlated with mesocosm soil moisture. The results of the study can provide theoretical reference for the formulation of corresponding wind and sand control measures and the establishment of scientific and reasonable vegetation sand fixation model in the study area.