土地利用变化对陆地生态系统碳贮量的影响

陆地生态系统是重要的碳库之一，在碳素生物地球化学循环中起着重要作用．本文就森林、农田生态系统，综述了土地利用变化对陆地生态系统碳贮量的影响及其可能的作用机制．土地利用变化显著地影响陆地生态系统的结构和功能，造成系统碳贮量的变化，这很大程度取决于生态系统类型和土地利用方式的改变．森林砍伐后变为农田和草地，使生态系统中植被和土壤碳贮量大大降低．土壤碳含量的降低主要是由于凋落物输入的减少，有机质分解速度的提高，以及耕种措施对有机质物理保护的破坏造成的．土壤碳损失主要发生在森林砍伐后较短的时期内，而其降低速率取决于诸多因素以及土壤理化和生物过程．农田和草地弃耕恢复为森林，以及农田保护性管理措施的利用．能够使大气中的碳在植被和土壤中得到汇集．森林恢复过程中植被可以大量汇集大气中的碳，而由于农田耕种历史不同以及土壤空间异质性。导致土壤碳汇集速率差异极大．保护性农田管理措施(诸如免耕、合理的种植制度、化肥的施用等)可以影响土壤理化特性、作物根系生长以及残茬数量和质量、土壤微生物数量和活性，维持和提高土壤碳含量水平．

Effects of land use change on carbon storage in terrestrial ecosystem

Terrestrial ecosystem is an important carbon pool, which plays a crucial role in carbon biogeochemical cycle. Human activities such as fossil fuel combustion and land use change have resulted in carbon fluxes from terrestrial ecosystem to the atmosphere, which increased the atmospheric CO 2 concentration, and reinforced the greenhouse effect. Land use change affects the structure and function of the terrestrial ecosystem, which causes its change of carbon storage. To a great extent, the change of carbon storage lies in the type of ecosystem and the change of land use patterns. The conversion of forest to agricultural land and pasture causes a large reduction of carbon storage in vegetation and soil, and the decrease of soil carbon concentration is mainly caused by the reduction of detritus, the acceleration of soil organic matter decomposition, and the destroy of physical protection to organic matter due to agricultural practices. The loss of soil organic matter appears at the early stage after deforestation, and the loss rate is influenced by many factors and soil physical, chemical and biological processes. The conversion of agricultural land and pasture to forest and many conservative agricultural practices can sequester atmospheric carbon in vegetation and soil. Vegetation can sequester large amounts of carbon from atmosphere, while carbon accumulation in soil varies greatly because of farming history and soil spatial heterogeneity.Conservative agricultural practices such as no tillage, reasonable cropping system,and fertilization can influence soil physical and chemical characters , plant growth , quality and quantity of stubble,and soil microbial biomass and its activity,and hence, maintain and increase soil carbon concentration.