黄土高原半干旱草地封育后土壤碳氮矿化特征

Abstract

PDF HTML阅读 XML下载 导出引用 引用提醒 黄土高原半干旱草地封育后土壤碳氮矿化特征 DOI: 10.5846/stxb201508101688 作者: 作者单位: 中国科学院教育部水土保持与生态环境研究中心,西北农林科技大学资环学院,西北农林科技大学资环学院,中国科学院教育部水土保持与生态环境研究中心,中国科学院教育部水土保持与生态环境研究中心,中国科学院教育部水土保持与生态环境研究中心,中国科学院教育部水土保持与生态环境研究中心 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（41271315，41571296）；教育部新世纪优秀人才支持计划资助项目（NCET-13-0487）；中国科学院青年创新促进会科研专项资助项目（2014371） Influence of grazing exclusion on soil organic carbon and nitrogen mineralization in semiarid grasslands of the Loess Plateau Author: Affiliation: Institute of Soil and Water Conservation,CAS & MWR,,,Institute of Soil and Water Conservation,CAS & MWR,Institute of Soil and Water Conservation,CAS & MWR,Institute of Soil and Water Conservation,CAS & MWR,Institute of Soil and Water Conservation,CAS & MWR Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤有机碳和全氮的分布与矿化是退化草地封育后土壤生态效应研究的重要内容和指标。结合野外调查和室内培养实验，研究了半干旱黄土区不同封育年限草地土壤有机碳和全氮的含量变化及其矿化特征。结果表明，封育对半干旱黄土区退化草地土壤有机碳和全氮的影响主要体现在0-40 cm土层，封育超过17a后，封育年限的影响逐渐减弱。封育显著增加了土壤有机碳矿化速率和Cmin/C0，封育对有机碳矿化速率的影响与封育年限和土层深度无关，而对Cmin/C0的影响则与封育年限和土层深度有关。封育显著提高了0-40 cm土层土壤氮素矿化速率，但是降低了40-80 cm土层土壤氮矿化速率，并且降低了0-80 cm土层Nmin/N0。碳氮矿化速率与有机碳和全氮之间显著相关，而与碳氮比之间的相关性较小。这些结果表明，退化草地封育后土壤碳氮元素的转化主要受土层深度、封育年限以及土壤碳氮含量的影响。 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. 参考文献 相似文献 引证文献