【摘要】 盐碱土碳循环在缓解气候变化的贡献与作用等方面受到广泛关注,土地利用是影响干旱区土壤碳动态的主要要素,认识其对土壤碳的影响过程,有助于评估盐碱土的碳汇作用。本研究以三工河流域绿洲为对象,通过野外定点采样结合室内分析,探讨了土地利用对土壤无机碳(SIC)的影响。结果表明:整个研究区SIC含量均值为4.81 g·kg-1,其中人工林地和耕地的SIC均值低于4.61 g·kg-1,超过30%耕地与人工林地样点集中分布在小于4 g·kg-1的区域,而其他土地利用类型均高于5 g·kg-1,其70%以上的样点集中分布在大于4 g·kg-1区域,由于人为活动的影响,自然景观SIC含量明显高于灌溉景观;流域中上部SIC含量明显低于流域下部(P<0.05),随地貌单元变化,SIC含量呈现为冲洪积扇中上部<冲洪积平原上部<冲洪积平原下部<地下水溢出带;土壤SIC储量为盐碱地<灌木林地<草地<人工林地<耕地,其中,盐碱地SIC储量最小(仅1.17 kg·m-2),耕地SIC储量最大(1.44 kg·m-2)。表层土壤SIC储量受区域土地利用作用影响明显,灌溉景观土壤SIC储量高于自然景观;方差、多元线性和逐步回归分析表明,各因素对SIC含量变化影响明显,其程度大小为地貌单元>土地利用类型>电导率>作物类型。更多还原

【Abstract】 Soil carbon( C) cycling in alkaline-saline soils has received great attention in recent years because of its potential role in climate change mitigation in arid regions,and it is sensitive to land use change. Understanding its impacts on soil carbon can help accurately assess carbon sink in saline-alkaline soil. Here,we quantified the effects of different land use types on the spatial distributions of soil inorganic C at a typical watershed in the arid region of northwest China.Soil samples were collected from the oasis in the Sangong River Basin,which covered different land use types,such as grassland,saline-alkali land,shrub land,planted land,as well as different types of croplands. The mean inorganic C content of the entire study area was 4. 81 g ·kg-1. The mean value in cropland and planted forest was lower than 4. 61 g · kg-1,with more than 30% soil samples was concentrated in lower than 4 g·kg-1. The value from other land use types was higher than 5 g·kg-1,with more than 70% soil samples was concentrated in higher than 4 g·kg-1. For all land use types,the mean value of inorganic C content was higher in natural landscape than that in irrigated landscape. The inorganic C content was obviously lower in alluvial-proluvial delta than in alluvial plain( P<0.05),and the soil inorganic C content in different geomorphology zones were in the following order: middle-upper alluvial-proluvial delta <upper alluvial plain<lower alluvial plain<groundwater overflowing zone. The order of soil inorganic carbon density was: saline-alkali land < shrub land < grassland < planted forest < cropland,with the minimum of soil inorganic C storage( 1.17 kg·m-2) in saline-alkali land and the maximum of soil inorganic C storage( 1.44 kg·m-2) in cropland. Land use had a significant effect on the density of soil inorganic C at 0-20 cm layer. Soil inorganic C density in irrigated landscapes was higher than that in natural landscapes. The results of variance analysis, multiple linear regression,and stepwise regression showed that many factors had significant impacts on soil inorganic C content,with their relative contribution to the variation of SIC content following the order: geomorphology zone>land use type>electrical conductivity>crop type.更多还原