草地土壤固碳潜力研究进展

土壤固碳功能和固碳潜力已成为全球气候变化和陆地生态系统研究的重点。草地土壤有机碳库,作为陆地土壤有机碳库的重要组成部分,其较小幅度的波动,将会影响整个陆地生态系统碳循环,进而影响全球气候变化。因此,深入研究草地土壤固碳功能和固碳潜力对于适应和减缓气候变化具有重要意义。在土壤固碳潜力相关概念界定基础上,结合《2006年IPCC国家温室气体清单指南》,从样点及区域尺度上综述了目前关于草地土壤固碳潜力的一般估算方法,同时对各类方法的特点及适用性进行了评述,提出了草地生态系统固碳潜力研究概念模型。最后在对草地土壤固碳的影响因素及固碳措施总结的基础上,阐明了草地土壤有机碳固定研究中存在的问题和发展前景。

Review on soil carbon sequestration potential in grassland ecosystems

Global climate change has aroused wide concern from the international community, and national or regional GHG (greenhouse gas) emission has become a focus of the intergovernmental diplomatic dispute and mediation. The stability, release or increment of the soil carbon stock is closely related to the change of the atmospheric carbon stock. Even a minor change in soil organic carbon (SOC) storage may result in a significant change in atmospheric CO₂ concentration. Whether the soil carbon stock can increase becomes an essential theoretical basis for terrestrial ecosystems to absorb atmospheric CO₂, and serve as carbon sink. Therefore, increasing soil carbon sink in terrestrial ecosystems has become an important strategy for controlling the rise in atmospheric CO₂ concentration. As one of the world''s most widespread terrestrial ecosystems, covering over 15% of the world''s land surface, grassland ecosystems account for over 10% of the total carbon storage in terrestrial ecosystems, with nearly 90% of the carbon storing in top soil. Besides, grassland soil organic carbon could be strongly influenced by management practices. During the past decades, owing to the climate change, overgrazing and other unreasonable management practices, the grasslands in the world had been seriously degraded and the soil organic carbon had significantly decreased. However, improved management practices such as enclosure and recovery of degraded grassland and conversion of cropland to abandoned fields, may reverse the loss of soil organic carbon, and even help to sequestrate carbon in the atmosphere. Therefore, under the background of climate change, the function and potential of soil organic carbon sequestration in grassland ecosystems has become a key issue. In this essay, the recent research on soil carbon sequestration potential was reviewed, including quantitative methods for estimating soil carbon sequestration potential on both regional and sample scales, dominant affecting factors and management practices of carbon sequestration, and future research direction was also proposed lastly. Research on quantitative estimation of soil carbon sequestration in grassland ecosystems had been well developed in recent years, from simple statistics on sample scale to mechanism modeling coupled with GIS and RS on regional scale. IPCC also issued guidelines for national greenhouse gas inventories so as to provide a relatively uniform method for national carbon sequestration estimation, which contained three tiers on estimation of soil organic carbon storage in grassland: Tier1, Tier2, and Tier3. Among all the quantitative methods, mechanism modeling of soil carbon cycle became a major method to assess the carbon sequestration of terrestrial ecosystems and the reduction of greenhouse gas emission in the world. The dominant factors affecting soil organic carbon sequestration included natural factors (temperature, precipitation and CO₂ concentration etc.) and human factors (reclamation, grazing, fire, enclosure, fertilization, irrigation and reseeding etc.), which held complicated influences on carbon sequestration with various time and intensity of management practices. There also existed many problems needed to be solved in the future, such as the methodology and adaptability of models and the uncertainty of estimation on regional scale. The potential and mechanism of carbon sequestration, and the relationship between carbon sequestration and environmental effects would be the key scientific problems.