岩溶山地土壤有机碳的分布特征及表层土壤有机碳的影响因素分析——以重庆市北碚区为例

Distribution and impact factor of soil organic carbon on topsoil in karst mountain:A case study of Beibei District of Chongqing

通过野外采样调查分析,运用地统计学方法,分析了北碚区土壤有机碳(SOC)的分布特征和表层土壤有机碳的影响因素。结果表明:空间上,从表土层到底土层SOC含量依次降低,且差异显著,降幅依次为35.02%和47.12%;时间上,与1984年第二次土壤普查相比,从表土层到底土层土壤有机碳的含量呈增加趋势,增加幅度分别为:4.36%,31.92%和14.74%。对表层土壤有机碳的影响因素进行了分析,发现SOC含量随着土壤中全氮、碱解氮、黏粒含量的增加而增加;含有碎屑岩的碳酸盐岩比纯碳酸盐岩形成的土壤有机碳含量高;随着海拔的升高SOC含量增大,表现为:山顶(21.94g/kg)>平坝(19.53g/kg)>槽谷(15.60g/kg)>山腰(13.40g/kg);不同土地利用方式下的SOC含量高低顺序为:林地(26.16g/kg)>草坡(21.95g/kg)>菜地(16.75g/kg)>果园(15.31g/kg)>耕地(12.85g/kg)。传统的耕作方式容易造成SOC损失,建议在岩溶山地通过退耕还林还草、坡改梯、增施有机肥增加土壤有机碳;推广应用免耕、少耕、秸秆还田等耕作措施,增加农田土壤固碳能力。

Beibei district lies in the northeast of Chongqing and covers an area of 753 km2 with subtropical humid monsoon climate,parallel low hill landform and calcareous soil and yellow soil.Besides Devonian and Tertiary strata,all strata would be found in this district.Carbonate rock layers are mainly composed of the Jialingjia ng group and the Feixianguan group of Triassic and the Maokou group of Permian in the area.In order to provide theoretical basis for soil improvement and land use,the distribution and impact factor of soil organic carbon （SOC） on topsoil are analyzed by means of geo-statistics on the basis of field investigation and lab analysis in the paper.The results show that,spatially,the content of SOC decreases remarkably from the surface layer to the bottom layer with the decreasing range being 35.02 ％ and 47.12 ％ respectively; temporarily,compared with the second soil survey conducted in 1984,the SOC content of surface,central and bottom layerall has an increasing tendency as well,with increasing range being 4.36 ％,31.92 ％ and 14.74 ％ respectively.The results of influence factor analysis show that the SOC content increases with the increase of the total nitrogen,alkaline hydrolysis nitrogen and clay particle in the soil.The SOC content in the soil that formed by carbonate rocks with clastic rocks is higher than that formed by pure carbonate rocks.The SOC increases with altitude as follows,mountain top （21.94 g/kg） ＞ flat dam （19.53 g/kg） ＞ trough valley （15.60 g/kg） ＞mountainside （13.40 g/kg）.With respect to land use,the SOC content displays as woodland （26.16 g/kg） ＞ grassy slope （21.95 g/kg）＞ vegetable plot （16.75 g/kg） ＞ orchard （15.31 g/ kg） ＞ cultivated land （12.85 g/kg）.Traditional tillage method is easy to lead loss of SOC.It is suggest that to increase SOC by return farmland to forests or grassland,terracing and applying more organic fertilizer in karst mountain; to strengthen carbon sequestration capacity of the farmland by no-tillage,straw returning and so on.