陕西省土壤有机质含量及其与影响因素的关系

目的]分析陕西省土壤有机质空间分布特征及其影响因素,并揭示土壤有机质与地形、植被类型、气候和土壤其他属性的关系,为该区土壤碳汇(碳源)功能变化研究提供科学基础。方法]通过采集陕西省12个样区不同植被类型和地形条件下的85个表层土壤样品,并利用SPSS 16.0中的K-means聚类和Canoco 4.5软件中的冗余(RDA)方法进行分析。结果]土壤有机质浓度在2~6级之间;并表现为由南至北,由西至东大致呈降低趋势;在各样区,最大值是最小值的1.89~14.84倍;同一样区不同样地土壤有机质含量等级不同;各影响因素中,除经度和无霜期的影响不显著外,其他各环境因子的影响均显著,退耕年限和植被类型的影响最大,坡度和坡向的影响程度较低,且交互影响作用明显。结论]除农地转变为果园外,农地退耕能够显著提高土壤有机质含量,并随着恢复年限的延长,有机质含量增加日益显著,生态系统逐渐由碳源转变为碳汇。

Content of Soil Organic Matter and Its Relationships with Influencing Factors in Shaanxi Province

Objective] The spatial distribution and influencing factors of soil organic matter in Shaanxi Province were analyzed to reveal the relationships between soil organic matter and the influencing factors as topography, vegetation types, climate and other soil properties, to provide scientific basis for the study of soil carbon sink(carbon source) function change in this area.Methods] Eighty-five top-soil samples were collected from 12 regional sites with different vegetation types and topographic conditions. Methods K-means clustering analysis and redundancy analysis(RDA) were used by SPSS 16.0 and Canoco 4.5.Results] The soil organic matter concentration belonged to 2~6 levels, spatially having a decrease trend from the south to the north, and from the west to the east of province wide. The maximum value was 1.89~14.84 times of the minimum one. The contents of soil organic matter at different sample sites from a same region was not at similar level. Except for longitude and frost-free period, the content of organic matter was significantly affected by several environmental factors. Among which, years of vegetation restoration and vegetation types were the greatest influencing factors, slope gradient and aspect also have their influences and have obvious interaction effect.Conclusion] Significant increase in soil organic matter content was found when farmland was transformed to other lands but orchard. The increase was more obvious with the increase of farmland converted ages, whereby it made reverted farmland shifted from carbon source to carbon sink.