干旱区典型绿洲土壤有机质含量分布特征及其影响因素

摘要

A field survey was carried out of the Weigan-Kuqa River Delta Oasis in South Xinjiang, collecting a total of 156 samples of topsoil(0~20 cm)and subsoil(20~40 cm)at 78 sampling sites laid out in the light of land use for analysis of soil organic matter(SOM)content and pH and their distributions, and variations of SOM in the topsoil and subsoil layers as affected by crop type,land use and soil pH. Results show that SOM varied in the range of 3.7~24.1 g kg-1 in content,and averaged 11.0±4.2 g kg-1 in the topsoil layer(0~20 cm),and in the range of 2.7~12.9 g kg-1,and 7.0±2.2 g kg-1;in the sub-subsoil layer(20~40 cm). The topsoil layer was much higher than the subsoil layer no matter in mean of SOM contents or standard deviation in soils under different types of crop and patterns of land use,with a variation coefficient being 20%~50%. Obviously the variation was at a moderate level. Variance analysis and stepwise regression analysis shows that the factors affecting SOM content also varied in effect. The integrated effect of the three factors,crop,land use and pH,could explain 45.1% of the variation of SOM content in the topsoil layer and 43.7% of that in the subsoil layer. Comprehensive analysis shows that crop type is the most important factor affecting SOM content in the study area.%以新疆南部的渭干河–库车河流域三角洲绿洲为对象,按照土地利用方式布设78个采样点,分别采集表层(0~20 cm)和亚表层(20~40 cm)土样共156份,分析土壤有机质(SOM)含量和土壤酸碱度(pH)分布特征,并讨论在作物类型、土地利用方式和土壤pH因素的影响下,表层和亚表层SOM含量的差异性.结果表明:表层SOM含量范围为3.7~24.1 g kg-1,平均含量为11.0±4.2 g kg-1;亚表层SOM含量较低,为2.7~12.9 g kg-1,平均含量为7.0±2.2 g kg-1.表层中作物类型和土地利用方式的SOM均值、标准差均高于亚表层,二者的变异系数在20%~50%之间,属中等变异.方差分析和逐步回归分析表明,各因素对SOM含量的变异性影响存在较大差异.作物类型、土地利用方式和土壤pH三种影响因素对研究区表层和亚表层的SOM变异综合解释能力分别为45.1%和43.7%,综合分析得出各因素中作物类型因素对研究区SOM含量影响最大.