澎溪河消落带不同植物类型下土壤无机氮及相关微生物特征

Inorganic nitrogen forms and related biochemical action intensity of soil under Four Typical Plants in the Littoral Zone of Pengxi River

消落带土壤氮素循环因植被群落演替和季节性淹水会影响整个库区水环境安全。选择三峡库区一级支流澎溪河消落带为研究区域,分别在潮土、紫色土和水稻土分布区采集3种自然草本(狗牙根、香附子、苍耳)和1种农作物(玉米)覆盖区土壤,分析了土壤无机氮形态以及氨化、硝化、亚硝化、反硝化功能菌数量和生化作用强度,并分析了氮转化菌数量、生化作用强度以及土壤理化特征之间的关系。研究结果表明:不同植物覆盖对消落带土壤无机氮和氮素生理群微生物及其功能影响显著;狗牙根和香附子覆盖土壤硝化、亚硝化微生物数量与作用强度高于苍耳和玉米,进而土壤硝态氮和亚硝态氮含量表现相同规律;狗牙根与香附子覆盖区土壤反硝化细菌数量与作用强度高于苍耳和玉米,有利于消落带对氮素的拦截转化;消落带植被覆盖度、土壤有机质、pH、无机氮形态与土壤微生物数量和功能相关性较强。狗牙根、香附子覆盖区土壤有机氮氨化过程弱于苍耳和玉米,而亚硝化、硝化、反硝化过程强于苍耳和玉米,有利于有机态氮的保持和铵态氮迅速转化,为消落带植被恢复和重建提供参考。

The biological geochemical cycle of the soil in the drawdown zone of the Three Gorges Reservoir（ TGR） has changed as a result of long-term winter flooding,summer drought,and vegetation covering. The loss of soil nitrogen in the drawdown zone poses a threat to the water environment in TGR. The Pengxi River,an important anabranch,which has the largest drawdown area,was selected as the study area in the present study.The soil in three distribution areas with different soil types（ Paddy soil,Purple soil and Fluvo-aquic soils） that included four typical vegetation types（ Cynodon dactylon,Cyperus rotundus,Anthium sibiricum,and Zea mays L.） were studied to measure nitrogen forms,N-transforming bacteria,and biochemical action intensity. The results showed the following： soil nitrogen forms were obviously affected by the vegetation cover type,whereby the content of nitrogen（ NO-3-N） and nitrite nitrogen（ NO-2-N） of the soil with C. rotundus and C. dactylon cover was higher than those with A. sibiricum and Z. mays cover. The quantity of nitrobacteria and denitrifying bacteria in the soil with C. rotundus and C. dactylon was higher than that in the soil with A. sibiricum and Z. mays,and the same was observed in the intensity of nitrosation,nitrification,and denitrification. Soil organic matter,pH,and the three inorganic N forms,which were influenced by plant cover,may be the most important factors influencing N-transforming bacterial quantity and biochemical action intensity. Our research provides evidence that the drawdown zone with C. rotundus and C. dactylon cover is more advantageous with regard to the enhancement of soil organonitrogen holding and ammonium nitrogen transformation compared to A. sibiricum and Z. mays cover. Vegetation recovery in the drawdown zone is not only important for the restoration of vegetation,but also for the restoration of the underground soil microbial community.