生态学报2017，Vol.37Issue(2)：378-386,9.DOI:10.5846/stxb201508101688
黄土高原半干旱草地封育后土壤碳氮矿化特征
Influence of grazing exclusion on soil organic carbon and nitrogen mineralization in semiarid grasslands of the Loess Plateau
摘要
Abstract
Grazing exclusion is an important method for rehabilitating degraded ecosystems in grassland-dominated parts of the semiarid region.However,how ecosystem processes respond to this rehabilitation has not been assessed well.For understanding how the carbon and nitrogen cycling in degraded grasslands responds to such grazing exclusions,it is essential to study the distribution and mineralization of soil organic carbon and nitrogen.Field measurements and laboratory incubations of soil (at 0-80 cm depth) from the Loess Plateau's semiarid region were combined to analyze the soil organic carbon and nitrogen distribution and mineralization after various years of grazing exclusion.Samples were collected from grasslands where grazing was excluded for 17,22,and 27 years,respectively.As a control,additional soil samples were collected from continuously grazed grasslands that neighbored the grazing exclusion ones.Organic carbon and nitrogen contents,as well as organic carbon and nitrogen mineralization rates,were measured.The effects of grazing exclusion on the distribution of organic carbon and nitrogen mainly occurred in the top 0-40 cm of the soil.Grazing exclusion significantly increased soil organic carbon and nitrogen content,with the largest increases being observed after 17 years of exclusion.However,beyond 17 years,the effects on organic carbon and nitrogen distribution became weaker with time.Furthermore,although for all treatments organic carbon mineralization rates decreased with soil depth,for grazing excluded grasslands the organic carbon mineralization ratio (Cmin/C0) increased more with soil depth.The grazing exclusion effects on mineralization rate were independent of exclusion years or soil layers,in contrast to the effects on Cmin/C0,which did correlate with both these factors.In addition,nitrification and mineralization rates of nitrogen decreased with soil depth,whereas in contrast,the ammonification rate increased.At 0-40 cm soil depth,nitrification rates ranged between 1.5 and 2.5μg g-1 d-1,and ammonification rates between-1.6 and 0.1 μg g-1 d-1.This indicates a nitrification dominated nitrogen mineralization in this soil layer.At 40-80 cm depth,nitrification and ammonification rates ranged between 1.3 and 1.8μg g-1 d 1,and between 0.7 and 0.8μg g-1 d-1,respectively,suggesting that nitrification and ammonification contributed similarly to nitrogen mineralization in deeper soils.Furthermore,grazing exclusion significantly increased the mineralization rate of nitrogen in the 0-40 cm layer,while it decreased this in the 40-80 cm layer.The overall nitrogen mineralization ratio (Nmin/N0)also decreased when grazing was excluded.Finally,the mineralization of organic carbon and nitrogen were significantly correlated with the soil organic carbon and nitrogen content,but less so with the soil carbon to nitrogen ratio (C/N).Overall,the results of this study indicate that the turnover of organic carbon and nitrogen in grazing excluded grassland was determined mainly by soil layer,grazing exclusion duration,and soil organic carbon and nitrogen content.关键词
退化草地封育/土壤有机碳/土壤全氮/剖面分布/矿化/土壤特性Key words
grazing management/soil organic carbon/nitrogen/soil profiles/carbon mineralization/soil properties引用本文复制引用
王玉红,马天娥,魏艳春,魏孝荣,邵明安,程积民,张兴昌..黄土高原半干旱草地封育后土壤碳氮矿化特征[J].生态学报,2017,37(2):378-386,9.基金项目
国家自然科学基金资助项目(41271315,41571296) （41271315,41571296）
教育部新世纪优秀人才支持计划资助项目(NCET-13-0487) （NCET-13-0487）
中国科学院青年创新促进会科研专项资助项目(2014371) （2014371）
