不同退耕还草方式下宁夏南部山区土壤氮素转化速率与微生物变化的耦合关系  

Coupling Relations of Nitrogen Transformation Rate and Microbial Changes During Soil Mineralization Under Different Methods of Returning Farmland and Grassland in the Mountainous Area of Southern Ningxia,Northwest China

作　　者：牛丹[1] 黄懿梅[1] 倪银霞 赵彤[1] 蒋跃利[1] 闫浩[1] 

机构地区：[1]西北农林科技大学资源环境学院,农业部西北植物营养与农业环境重点实验室,陕西杨凌712100

出　　处：《环境科学研究》2015年第10期1586-1595,共10页Research of Environmental Sciences

基　　金：国家自然科学基金项目(41101254);中央高校基本科研业务费专项(QN2011020)

摘　　要：为了明确不同退耕还草方式下土壤养分转化的机理及其影响因素,以宁夏南部山区（下称宁南山区）天然草地、人工草地和撂荒地土壤为研究对象,运用PVC顶盖埋管法对3种类型草地土壤中氮素的净转化速率、微生物区系和氮素微生物生理群进行了研究,探讨土壤氮素净转化速率与微生物的关系.结果表明：1在培养过程中,3种草地类型土壤中细菌、放线菌和真菌数量平均值分别为9.6×105、3.8×104和4.0×101CFU/g（以干土计）,氮素微生物生理群数量表现为氨化细菌（4.5×104CFU/g）〉自生固氮菌（4.3×103CFU/g）〉硝化细菌（6.5×102CFU/g）〉反硝化细菌（3.9×102CFU/g）〉亚硝化细菌（1.7×102CFU/g）,其中,人工草地土壤中微生物数量最高;2细菌、真菌、反硝化细菌与亚硝化细菌数量的峰值均出现在培养第120天,放线菌和自生固氮菌数量的峰值均出现在第240天,硝化细菌数量的峰值出现在第60天,而氨化细菌数量在各类型草地土壤中出现峰值的时间不统一;3各类型草地土壤氮素的净矿化速率、净氨化速率、净硝化速率均在61~120 d内最低,净矿化速率与净硝化速率在181~240 d内最高,净氨化速率在241~360 d内最高,微生物固氮速率的峰值出现在121~180 d,最低值出现在241~360 d.在该区土壤氮素转化速率与微生物数量紧密相关,土壤温度、土壤水分通过影响微生物数量而成为影响土壤氮素矿化的主要因素;土壤氮素的生物固持过程比有机氮矿化过程更为活跃;种植苜蓿的人工草地比天然草地和撂荒地更有利于微生物的繁殖与土壤氮素的矿化.In order to understand the relationship between nitrogen transformation rate and microorganisms of three different grasslands（ natural grassland,artificial grassland and abandoned land） in the mountainous area of southern Ningxia,northwest China,microflora,nitrogen physiological groups and net N mineralization rate,net ammonification rate and net nitrification rate as well as the microbial immobilization were examined with the method of in stiu closed-top PVC tube incubation for a period of 360 days. The results showed that：1） The average number of bacteria,fungi and actinomycetes among the three grasslands was 9. 6 × 105,3. 8 × 104 and 4. 0 × 101CFU/g（ dry soil）,respectively. The highest amount of microbes was found in the artificial grassland among the three grasslands. Soil nitrogen bacteria groups decreased with an order of ammonifier（ 4. 5 × 104CFU/g） azotobacter（ 4. 3 × 103CFU/g） nitrifier（ 6. 5 × 102CFU/g） denitrifier（ 3. 9 × 102CFU/g） nitrite bacteria（ 1. 7 × 102CFU/g）. 2） The time of microbes thatreached the peak varied,being 60 days for nitrifier,120 days for bacteria,fungi,nitrite bacteria and denitrifier,240 days for actinomycetes and azotobater; however,there was no unique pattern for ammonifying bacteria. 3） The lowest net N mineralization rate,net ammonification rate and net nitrification rate were similarly distributed at 61-120 days among the three grasslands. Net N mineralization rate and nitrification rate were all highest during the time span of 181-240 days,while net ammonification rate was delayed to 241-360 days. The microbially N-fixing rate was maximized at 121-180 days but minimized at 241-360 days,with an overall higher value in the abandoned land than in the artificial grassland. Soil nitrogen transformation rate was closely related to microbial numbers; the soil temperature and moisture were the main factors affecting the soil nitrogen mineralization by affecting the number of microorganisms.Immobilization process of soil nitrogen was more a

关 键 词：氮素微生物生理群 天然草地 人工草地 撂荒地 微生物区系 原位矿化 

分 类 号：X171.4[环境科学与工程—环境科学]