青海南部高寒草地土壤冻融交替期水热特征分析

Characteristics of Hydrothermal Factors in Soil Freezing and Thawing Alternation over Southern Alpine Grasslands in Qinghai Province

为进一步了解高寒草地土壤冻融交替过程及其对水热因子的响应机制,通过2014年8月1日至2015年8月1日不同土层土壤温度和水分观测资料的对比分析,较为系统地探讨了青南高寒草地土壤冻融期不同深度土层土壤温度和水分的变化特征。结果表明,青南高寒草地土壤冻融阶段大体可分为初冻期、稳定冻结中期、稳定冻结后期和消融期4个时期;不同土层土壤温度随气温的变化呈周期性波动,且随着土层的加深变幅减小;不同冻融期表层和亚表层土壤温度和水分波动幅度较大,下层土壤对水热因子的敏感性较小;土壤完全冻结的天数达44~115d,日冻融交替过程主要发生在表层和亚表层土壤。土壤冻融交替增强了土壤的保水性,对该区草地植被提前返青和初级生产力的提高具有促进作用。

In order to understand the freezing and thawing alternation process of soil and the response mechanisms to hydrothermal factors in the alpine meadows further,the soil temperature and moisture observation data of different soil layers from 1 August 2014 to 1 August 15 are used to study the dynamic characteristics of the soil temperature and moisture at different soil depths in the freezing-thawing periods over alpine grasslands in the southern pastoral area of Qinghai Province.The results show that the soil freezing-thawing duration of alpine grasslands in the southern pastoral area of Qinghai Province generally can be divided into 4 stages：early freezing,early frozen period,stable frozen period,and thawing period.Soil temperatures in different soil layers varied as cyclical fluctuations with the change of air temperature,and the amplitude decreased with the increase of the soil depth.In addition,the fluctuation of soil temperature and moisture in surface and subsurface layers was relatively bigger,and the sensitivity of the subsoil to hydrothermal factors was weaker.The number of completely frozen days ranges from 44 to 115,and the daily soil freezing-thawing alternation process mainly occurred in the surface soil.Soil freezingthawing alternation is conducive to the soil water retention,and has a vital role in advancing the reviving dates of grassland vegetation and promoting the primary productivity.