封育草地与弃耕地土壤碳氮固持及固持速率动态

Dynamics of soil carbon and nitrogen sequestration and sequestration rate following long-term fencing of grasslands and abandoned farmlands

研究植被恢复对土壤碳氮动态的影响,对了解陆地生态系统碳氮循环,应对全球温室效应具有重要意义。本研究以黄土高原丘陵区封育草地和弃耕地为对象,分别以放牧草地和农田为参照,对比分析了封育14年草地和弃耕地0-300cm土层土壤有机碳（SOC）和土壤全氮（STN）储量、固持量及固持速率。结果表明,封育草地和弃耕地显著增加SOC储量,并且二者封育14年后SOC储量相同;在0-200cm土壤中,封育14年草地与弃耕地STN储量相对于对照并无增加,0-300cm土壤中,封育14年草地STN储量显著高于弃耕地（P〈0.05）;弃耕地SOC固持及固持速率显著高于封育草地,封育14年弃耕地SOC固持主要发生在0-140cm表层土壤;0-100cm土壤弃耕地STN固持及固持速率显著高于封育草地,0-300cm土壤弃耕地STN固持及固持速率显著低于封育草地。以上结果表明,封育和弃耕均可显著提高土壤碳储量,并未明显提升土壤氮储量,弃耕地有较高的SOC固持量及固持速率。

Determining the effects of different vegetation restoration measures on soil organic carbon（SOC）and total soil nitrogen（TSN）can increase our understanding of carbon and nitrogen cycling in terrestrial ecosystems,which play important roles in moderating the global greenhouse effect.In this study,we evaluated carbon and nitrogen cycling in fenced grassland and abandoned farmland on the Loess Plateau,using grazed grassland and alfalfa farmland as the control and reference sites,respectively.We analyzed SOC storage,TSN storage,SOC sequestration,TSN sequestration,and their sequestration rates in grassland that had been fenced for14 years and in abandoned farmland（0-300 cm soil depth）.The results showed that SOC storage was significantly increased in 14-year-fenced grassland and abandoned farmland,compared with the reference and control sites.The mean values of SOC storage were similar in 14-year-fenced grassland and abandoned farmland;at 0-200 cm depth soil,STN storage in 14-year-fenced grassland was not significantly higher than that in grazed grassland,but at 0-300 cm soil depth,the STN storage was significantly higher in the 14-year-fenced grassland than in abandoned farmland（P〈0.05）.The amount of SOC sequestration and its rate were significantly higher in abandoned farmland than in fenced grassland.The SOC sequestration in abandoned farmland was almost completely limited to the 0-140 cm depth soil.At 0-100 cm soil depth,the amount of STN sequestration and its rate were significantly higher in abandoned farmland than in fenced grassland,but at 0-300 cm soil depth,the amount of STN sequestration and its rate were significantly lower in abandoned farmland than in fenced grassland.Therefore,14 years of fencing of grassland and abandoned farmland could significantly increase SOC,but not TSN storage.Compared with fenced grassland,abandoned farmland had a higher SOC sequestration capacity and sequestration rate.