西南喀斯特生态系统氮素循环特征及其固碳效应  

Nitrogen biogeochemical cycling and its effects on carbon sequestration in karst ecosystems, southwest China

作　　者：李德军[1,2] 陈浩[1,2] 肖孔操 张伟[1,2] 王克林[1,2] LI De-jun, CHEN Hao, XIAO Kong-cao, ZHANG Wei, WANG Ke-lin(1. Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan 410125, China; 2. Huanjiang Observation and Research Station for Karst Ecosystems, Chinese Academy of Sciences, Huanjiang, Guangxi 547100, China)

机构地区：[1]中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室,湖南长沙410125 [2]中国科学院环江喀斯特生态系统观测研究站,广西环江547100

出　　处：《农业现代化研究》2018年第6期916-921,共6页Research of Agricultural Modernization

基　　金：国家重点研发计划项目(2016YFC0502404);国家重点基础研究发展计划项目(2015CB452703)~~

摘　　要：评估生态系统氮状况对预测全球变化背景下生态系统的固碳潜力及生态演替的方向与进程均具有重要的意义。近年我们开展了比较系统的研究以回答二个关键科学问题,即氮是否限制喀斯特区植被恢复,以及喀斯特森林氮状况与邻近的非喀斯特森林相比有何差异?基于多尺度演替序列研究,发现退耕后喀斯特土壤总氮快速累积。氮的累积相应促进土壤有机碳快速累积,且有机碳累积的相对速率高于总氮累积的相对速率。恢复初期(草丛阶段)植被受氮限制,而在次生林阶段则表现出明显的氮饱和特征。基于土壤初级氮转化速率和胞外酶活性化学计量特征的证据表明氮饱和是喀斯特森林的独有特征,而邻近的非喀斯特森林普遍受氮限制。我们的研究意味着:1)西南喀斯特山区退耕后的生态恢复仅在早期受氮限制,而中后期则不受氮限制;2)充足的氮供应可保障生态恢复工程的固碳效应;3)喀斯特森林氮循环具有其独特性,在全球变化背景下,其响应与适应性也可能异于其他区域/类型森林。Knowledge on ecosystem nitrogen status is necessary for assessing ecosystem carbon sequestration capacity under global change and for predicting the direction and velocity of secondary succession. Although several ecological restoration projects have been implemented over the past 20 years, whether ecological restoration is limited by nitrogen remains unresolved in the karst region of southwest China. Additionally, it is still not clear whether the nitrogen status differs between karst and non-karst forests. Here, we synthesized the main findings obtained by our research group during the past several years. Studies based on a post-agricultural succession sequence or across a karst region show that soil total nitrogen pool can accumulate rapidly following agricultural abandonment. Due to the tight coupling of carbon and nitrogen cycles, soil organic carbon pool can also accumulate rapidly with the relative accumulation rate of soil organic carbon greater than that of total nitrogen. Across the post-agricultural succession sequence, plants and microbes are limited by nitrogen in grassland stage, but the secondary forests show clear symptoms of nitrogen saturation. Several lines of evidence supports that nitrogen saturation is a unique characteristic for karst forests, since the surrounding non- karst forests are limited by nitrogen. Our findings suggest that （1） nitrogen is the limiting nutrient only in a short period of the early succession stage following agricultural abandonment in the karst region of southwest China, （2） sufficient nitrogen supply ensures relatively high carbon sequestration after the ecological restoration project implementation in the karst region, （3） due to their unique nitrogen biogeochemical cycling, the responses and adaptation of karst forests to global change may be different from other types of forests.

关 键 词：喀斯特生态系统 生态恢复 氮循环 固碳效应 氮状况 氮饱和 

分 类 号：S154.1[农业科学—土壤学]