不同母质发育旱地土壤反硝化功能差异及其关键影响因素

Denitrification Characteristics of Dryland Soils Derived from Different Parent Materials

农田土壤反硝化作用强度具有较高的空间异质性,不同类型土壤反硝化作用活性的影响机制可能存在差异。本研究通过大规模样带调查,系统采集了3种不同母质发育的旱地农田土壤,对比分析了土壤反硝化能力的差异及其与土壤环境因子的关系。结果发现:土壤反硝化势在3个类型土壤间有显著差异,其中河流冲积物发育的潮土(AS)反硝化势(以单位时间单位质量土壤的N2O释放量表示)显著高于其他两个类型土壤22.22~579.09μg/(kg·h),平均高达213.34μg/(kg·h),黑土(BS)的反硝化势平均为136.38μg/(kg·h),略高于第四纪红色黏土发育的红壤(QRCS)(96.17μg/(kg·h)),但两者无显著差异。相关性分析表明,土壤pH与反硝化势极显著正相关,说明在本研究所测定的土壤性质中,pH可能是影响不同类型土壤反硝化势差异的关键因素,另外,有机质含量对3个类型土壤反硝化势也有一定影响。同一母质发育的土壤,反硝化能力在不同采样地点也存在差异,而且调控不同类型土壤内部反硝化势的关键土壤环境因素不尽相同,其中对第四纪红色黏土发育的红壤、潮土和黑土影响最为显著的因素分别为土壤有机质、pH和黏粒含量。

Denitrification actively takes place in dryland soils due to drastic increase of anthropogenic application of nitrogen fertilizer.Many studies have demonstrated that soil properties strongly influence the heterogeneity of denitrifying capacity in dryland soils,and the relationship between denitrification and soil properties of different soil types differentiate in some degree.However,most studies were restricted to small-scale spatial denitrifying activity and were difficult to uncover the variation of denitrifying capacity of different soils.Soil denitrifying enzyme activities(DEA)and physicochemical properties were studied over 90 sites in dryland soils derived from three different parent materials,including red soil derived from quaternary red clays(QRCS),alluvial soil derived from river deposits(AS),and black soil(BS).The results showed that DEAs were significantly different in the three tested soils.DEA in AS was ranged from N2O 22.22 to 579.09μg/(kg·h)with an average of N2O 213.34μg/(kg·h),significantly higher than those of other two soils.The average DEA in BS was N2O 139.68μg/(kg·h),higher but not significantly than that of QRCS with an average DEA of N2O 98.53μg/(kg·h).Correlation analysis based on all soil samples showed that DEA significantly positively correlated with pH,indicating that pH might be the key factor of DEA.Furthermore,soil organic matter(SOM)also influenced DEA.Soil DEAs and their influential factors were different in different sampling sites even with the same parent material.SOM,pH or clay content was the dominant factor for DEAs of QRCS,AS and BS,respectively.This study suggests that DEAs are different in different soil types,hence soil type should be considered when adopting measures to decrease nitrogen loss through denitrification.