天山北坡绿州土壤总碳"源/汇"特征及其驱动机制研究

项目名称： 天山北坡绿州土壤总碳"源/汇"特征及其驱动机制研究

项目编号： No.40801113

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 建筑科学

项目作者： 许文强

作者单位： 中国科学院新疆生态与地理研究所

项目金额： 20万元

中文摘要： 近半个世纪以来，干旱区大规模开发活动改变了水土资源的时空分布，扩展了绿洲的面积，灌溉、施肥等人类耕作活动使得干旱区土壤碳库发生了显著变化。本项目选择干旱区典型的三工河流域绿洲，估算绿洲土壤碳库，并利用CENTURY模型探讨绿洲土壤有机碳变化的驱动机制，借助碳稳定同位素方法，分析干旱区人类耕作活动对绿洲土壤碳的影响。基于网格的土壤类型法计算显示，在0-20cm深度，流域土壤碳密度为6.7 kgC/m2，土壤碳储量为14.3 Tg；CENTURY模型模拟结果表明：研究区荒漠灌木林地被开垦为人工绿洲后的50年，平均土壤有机碳呈先增后减再增的"N"型变化趋势，但最终土壤有机碳超过了原始自然状态下的有机碳，说明土壤碳总体呈"碳汇"趋势，这与热带地区森林、非洲稀树草原、中国北部半干旱草原开垦为耕地后土壤有机碳逐步降低的结论相反。基于碳稳定同位素方法研究发现，准噶尔盆地南缘三工河流域荒漠区植被演替可能存在C3草地转化为C4灌丛植被的过程，而在绿洲区发现人类耕作活动对绿洲土壤无机碳δC值具有显著影响。本项目研究结果揭示了干旱区人类活动对绿洲土壤碳循环的影响机理，拓展了干旱区土壤碳循环研究的新领域。

中文关键词： 土壤有机碳；土壤无机碳；土壤碳"源/汇"； CENTURY模型；碳稳定同位素

英文摘要： Large-scale reclamation of arid land in North-western China over the past 50 years has converted the natural desert landscape into anthropogenic oasis, particularly in the lower part of watersheds. Drastic human activities may have caused the change of soil organic carbon (SOC) in anthropogenic oasis. This study selects the Sangong river watershed oasis of the northern slope of the Tianshan Mountains as research area. The main objective is (1) to estimate the soil organic carbon storage and reconstruction the soil carbon dynamic process in order to analyze the carbon source or sink effect according to soil profile data of 1980, 1999, 2003 and 2009 and soil type method base on gridding, (2) to explore the driving mechanism of soil organic and inorganic carbon base on the modified CENTURY model and the stable carbon isotope method of carbonate, (3) to discuss the response of soil carbon dynamic to human cultivation activities of arid region oasis and reveal the soil carbon cycle mechanism of arid region. The results showed that the total soil organic carbon storage in 0-20cm depth was 14.3 Tg, mean soil organic carbon density was 6.70 kgC/m2. The model successfully simulated the SOC dynamics of the top layer soil (0-20 cm) in the different periods. Over the 50 years' cultivation (1959-2008), the mean change in total SOC exhibited complex ways. SOC increased rapidly in the first 2 years (1959-1960) after shrubland reclamation, and declined slowly during the period 1961-1984 and then decreased rapidly from 1985 to 1992. Between 1993 and 1998, it remained relatively stable, and climbed rapidly again during 1999-2008. The trend in total SOC showed "N" shape, i.e., increase, decrease, then increase. Finally, total SOC is greater (8.2%) in 2008 than the original level of SOC under the natural desert shrub. The results were different from the conclusions that loss of soil organic carbon would happen due to reclamation and continuous farming in tropical forests, semiarid grasslands of northern China and Nigerian semiarid Savannah. The vegetation Succession process form C3 grassland to C4 shrubland maybe exist in the Sangong river watershed base on the stable carbon isotope method. The human cultivation activities have significant effect to δC value of soil inorganic carbon. The significance of this research is open up a new research field of soil carbon cycle in arid region and provide a new idea for the global missing carbon sink study.

英文关键词： soil SOC; soil SIC; soil carbon sink/source; CENTURY model; the stable carbon isotope