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沿368~591 mm降水量梯度选取7个调查地点、共63个调查样点,在每个样点选择恢复年限相近的林地、草地和农地,调查表层(0~30 cm)土壤有机碳的分布特征,分析气候、土层深度和土地利用类型等因素对土壤有机碳分布的影响.结果表明:在黄土丘陵区368~591 mm的降水量范围内,表层土壤有机碳含量表现为草地(8.70 g·kg~(-1))>林地(7.88 g·kg~(-1))>农地(7.73 g·kg~(-1)),土壤有机碳密度表现为草地(20.28 kg·m~(-2))>农地(19.34 kg·m~(-2))>林地(17.14 kg·m~(-2)).林地、草地、农地的土壤有机碳含量无显著差异,综合3种土地利用类型的数据分析表明,不同降雨梯度下土壤有机碳含量差异显著(P<0.001),土壤有机碳含量(r=0.838,P<0.001)与年均降水量间存在显著线性正相关关系;由北向南(以最北端鄂尔多斯为起点),土壤有机碳含量沿着368~591 mm的年均降水量梯度的递增速率为0.04 g·kg~(-1)·mm~(-1),土壤有机碳密度的递增速率为0.08 kg·m~-2)·mm~(-1).年均降水量、土壤黏粒含量、林下枯落物蓄积量和农作物根系密度可较好地模拟表层土壤有机碳分布.
A total of 63 surveyed plots were selected along the precipitation gradient of 368-591 mm, and the woodland, grassland and agricultural land with similar recovery ages were selected at each sampling site. Soil organic carbon Distribution characteristics and the effects of climate, soil depth and land use types on the distribution of soil organic carbon were analyzed.The results showed that in the range of 368-591 mm precipitation in the Loess Hilly region, (kg · kg -1), forestland (7.88 g · kg -1) and farmland (7.73 g · kg -1), the soil organic carbon density was in the range of 20.28 kg · m ~ (-2))> agricultural land (19.34 kg · m -2)> forest land (17.14 kg · m -2). There was no significant difference in soil organic carbon content between forest land, grassland and farmland, Data analysis of land use types showed that soil organic carbon content was significantly different (P <0.001) under different rainfall gradients, and there was a significant linear positive correlation between soil organic carbon content (r = 0.838, P <0.001) and annual precipitation ; From north to south (starting from the northernmost Ordos), the increment rate of soil organic carbon content along the 368-591 mm annual precipitation gradient was 0.04 g · kg -1 · mm -1, Soil organic carbon The rate of increase of soil water content was 0.08 kg · m -2 · mm -1 .The average annual precipitation, soil clay content, litter volume and crop root density could well simulate the surface soil organic Carbon distribution.