气候变化背景下冻融过程对土壤水分的调节作用研究

Climatic warming and drying is the basic characteristics of climate change in the black soil region.Both increasing temperature and decreasing precipitation could result in the decrease of agricultural water resources,but increase of spring drought,consequently, have an effect on crop yield. Melt water derived from the thawing process of seasonal frozen soil layer play very important role in the early crop growth stages, which could alleviate the harm on crop growth caused by spring drought.The study would be performed at National Obseration Station of Hailun Agro-ecology System located in the north centre of black soil regin of songnen plain. According to the fact that northeast agriculture encounter water shortage,using field experiment and simulation, the objectives of this study are to:(1) investigate the effects of climatic warming and drying on seasonal freezing-thawing development process in black soil region and its soil water dynamics;(2)combing with the index of crop growth and yield,elucidate the regulating capacity of seasonal freezing-thawing on water stress caused by spring drought. Research results could contribute to establish economical and effective field water management system coping with climate change, furthermore, provide scientific basis for grain production in black soil region under climate change.

气候暖干化是近年东北黑土区气候变化的基本特征。温度升高和降水减少导致农业可用水资源减少，春旱灾害增加，从而影响作物产量。黑土区季节性冻层释放的融冻水是作物生长前期重要水分来源，能够减缓春旱对作物生长的危害。本项目拟在松嫩平原黑土区中北部的海伦农业生态实验站，针对东北农业面临水资源短缺的发展趋势，通过野外控制试验和模型模拟，研究气候暖干化对黑土区季节性冻融过程以及土壤水分动态变化的影响；结合作物生长与产量指标，明确气候暖干化背景下黑土区季节性冻层对作物春旱水分胁迫的调节能力。研究成果有助于建立应对气候变化的、经济有效的农田水分管理体系，并为气候变化背景下黑土区的粮食生产提供科学依据。

东北黑土区是我国典型季节性冻土区，也是我国对气候变化响应比较敏感地区之一。本项目通过采取红外辐射加热器模拟增温的方法，研究黑土区季节性冻土对气候变化的响应。研究结果表明：在地表（0-10cm）土壤温度增加3-4℃条件下，增温引起土壤冻结时间滞后和融化时间提前，从而导致冻层发育和全部活动时间历时天数缩短了14天，最大冻结深度减小了30cm。冻融循环频率呈现显著的双峰型月变化，并且融化过程的冻融循环频率相对较大。增温使不同深度的冻融循环频率增加了46次，冻融循环强度减少0.35℃。增温提高了冻结期根层（0-100）土壤水分聚集程度，从而使大豆产量增加了14.3%。本项目阐明了季节性冻土对气候变化的响应的同时，也为黑土区建立应对气候变化、经济有效的农田水分管理体系，提供了科学依据。