西南喀斯特峰丛洼地土壤养分的空间分异及其驱动机制

项目名称： 西南喀斯特峰丛洼地土壤养分的空间分异及其驱动机制

项目编号： No.30800162

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 生物科学

项目作者： 张伟

作者单位： 中国科学院亚热带农业生态研究所

项目金额： 23万元

中文摘要： 峰丛洼地是西南喀斯特地区生态环境最为脆弱、生态治理难度最大的地区，景观和土壤性质的高度异质性是该地貌类型区难以恢复重建的主要原因，探明峰丛洼地土壤性质的空间分异规律，揭示其对人为干扰的响应机制是本地区亟待解决的关键问题。通过系统的野外调查和室内分析，发现干扰区生态系统和原生林生态系统土壤养分具有不同的空间分异规律，干扰区土壤养分存在"养分倒置"现象，而原生林则表现出与其他地区相似的"洼积效应"；通过干扰历史-植被-凋落物-土壤等生态组分的耦合分析，明确了人为干扰是造成土壤养分空间格局变化的主要原因。人为干扰造成了植被群落结构和凋落物归还质量的变化，使下坡位土壤微生物熵和脲酶活性增强，有机质净矿化速率升高，生态系统养分循环加速，增加了土壤养分的流失风险；同时，由于人为干扰对土壤结构的破坏，下坡位土壤侵蚀和淋溶强度加大，导致土壤养分平衡发生改变，养分流失，形成了干扰区特殊的养分空间分异格局。本项目为今后进一步深入研究峰丛洼地土壤养分的迁移、流失和生物地球化学循环的响应机制奠定了基础，有助于促进该地区土地的可持续利用和适应性景观设计。

中文关键词： 喀斯特；养分循环；土壤侵蚀；化学计量学；空间分异

英文摘要： Karst peak-cluster depression ecosystems are most vulnerable to human disturbance, and belong to the most difficult region to restore in southwest of China, because it's high spatial heterogeneity of soil properties. Spatial pattern of soil nutrients provides useful information for improving ecological restoration and ecological management, but we still know little about the regular pattern of soil properties and its response mechanisms to human disturbance in this typical landscape. Based on extensive field investigation and examination, this study reveals that there were different spatial patterns of soil nutrients in the disturbance landscape and nature reserve area. Inverse spatial pattern of soil nutrients was found in the disturbance area, while down position accumulation pattern of soil nutrients, which same as the other landscape of red soil hilly region and loess plateau region, was found in the nature reserve area. Human disturbance was the most important driving factor which brought about the inverse pattern of soil nutrients in the disturbance landscape. On the one hand, human disturbance changed the plant community structures and litter mass qualities along the slope, which induced the increase of soil microbial quotient and urease activity in the downslope position, and therefore, result in the raise of decomposition and mineralization of organic matter, lead to positive feedback on nutrient cycling, Under these conditions greater runoff and leaching of nutrients may result. On the other hand, human disturbance damaged soil structure in the downslope position, enhanced soil erosion and leaching process, which eventually lead to the great loss of soil nutrients in the donslope position, formed the distinctive inverse pattern of soil nutrients. The results presented here have important significance for the restoration and sustainable land use of karst region. This study provides a basis for further unraveling the process of nutrients biogeochemical cycling and its response mechanisms in karst ecosystems.

英文关键词： Karst; nutrients cycling; soil erosion; stoichiometry; spatial heterogeneity