干旱半干旱区农田土壤碳垂直剖面分布特征研究

以中国干旱半干旱区农田土壤为研究对象,通过收集自然农田和长期定位站点(178个剖面,0~100 cm土层)农田土壤碳的数据并对其进行整合,分析了农田土壤有机碳和无机碳含量的垂直剖面分布特征及其影响因素。结果表明,随土层深度增加,农田土壤有机碳呈下降趋势,表层含量高于底层;不同地区农田土壤无机碳含量变化趋势不一,随土壤深度增加整体呈现升高的趋势,但是也有一些地区呈现下降趋势。土壤剖面深度为100 cm的农田土壤有机碳和无机碳密度平均值分别为8.33和15.83 kg m-2,农田土壤无机碳储量大约是土壤有机碳的2倍。土壤深度为0~30 cm的有机碳占100 cm总有机碳含量的45%,无机碳仅占100 cm总无机碳含量的29%;土壤无机碳主要集中在30~100 cm土层,占100 cm总无机碳含量的71%,远高于有机碳在此土层占100 cm总有机碳含量的百分比(55%)。综合自然农田和长期定位站点农田土壤碳的数据,土壤容重与土壤p H是影响农田土壤有机碳和无机碳分布特征的重要因素:自然农田土壤有机碳与土壤p H(R2=0.61,p0.01)和土壤容重(R2=0.64,p0.01)呈显著负相关;长期定位站点土壤无机碳与土壤p H(R2=0.56,p0.01)和土壤容重(R2=0.63,p0.01)呈显著正相关。中国干旱半干旱区农田土壤有机碳和无机碳的分布特征与影响因素,将为陆地生态系统碳储量估算提供数据基础与理论支撑。

Profile Distribution of Soil Inorganic and Organic Carbon in Farmland in Arid and Semi-Arid Areas of China

Objective]The objective of this study was to investigate distribution of soil inorganic (SIC)and soil organic carbon(SOC)in farmland in the arid and semi-arid areas of China,and analyze factors influencing SIC and SOC stocks.Method]Data of SOC and SIC contents in farmland were collected from some articles published after 2000 and some unpublished sources,involving 178 soil profiles(0~100 cm in depth)located in natural farmlands and long-term field stations. Linear regression analyses of the data were performed to evaluate relationships of SIC and SOC with soil physical properties(i.e. pH,and bulk density)with Sigmaplot(version 12.5)and ArcMAP(version 10.1).Result]Results show that SOC content decreased with soil depth. However,vertical distribution of SIC content varied from field to field. In general,SIC content increased with soil depth in natural farmlands,but decreased in the fields of the long-term experiment stations,which indicates that climate condition(i.e. annual precipitation)and soil properties might be the factors influencing vertical distribution of SIC. On average,the SOC and SIC of these soil profiles was 8.33 and 15.83 kg m-2,respectively,in density. SOC was mainly accumulated in topsoil (0~30 cm),whereas SIC in subsoil(30~100 cm). The SOC in topsoil accounted for 45% of the total in profile 100 cm in depth,whereas SIC in subsoil accounted for 71% of the total. Soil bulk density and soil pH were important factors influencing SOC and SIC stocks. Significantly negative correlations of SOC density with soil pH(R2 = 0.61,p< 0.01)and soil bulk density(R2 = 0.64,p< 0.01)were found in this study,while profoundly positive relationships of SIC density with soil pH(R2 = 0.56,p< 0.01)and soil bulk density (R2 = 0.63,p< 0.01)were.Conclusion] The study on profile distribution and total SOC and SICstocks in farmlands in the arid and semi-arid areas of China may provide some basic data and theoretical support to carbon budgeting in inland terrestrial ecosystems.