黑土农田冻结-融化期土壤剖面温度变化特征

Soil Profile Temperature Variation in Farmlands During Freeze-thaw Period in Mollisol Region

[目的]研究东北黑土区农地土壤温度变化特征,为冻融作用程度量化分析和冻融作用对土壤侵蚀影响提供基础数据。[方法]利用2015—2018年黑龙江省宾州河流域典型农地2m土壤剖面11月至翌年4月土壤温度观测资料以及气温数据,分析了冻结和融化过程中土壤温度变化特征以及土壤温度对气温变化的响应,确定土壤冻结与融化过程中耕层土壤冻融循环次数。[结果]11月至翌年2月的冻结期,土壤温度随土层深度的增加而增加;3—4月份土壤温度梯度发生反向改变,当土壤完全消融后,土壤温度随着土层深度的增加而递减,土壤最大冻结深度为80cm。研究结果还表明,0—60cm土层的土壤温度均与气温呈极显著正相关,其相关性随土壤深度增加而减小;而80cm以下土层,土壤温度均与气温呈负相关。[结论]研究区土壤冻结和融化过程分别呈单向冻结和双向融化现象,冻融循环主要发生在农地耕层0—20cm土层,其年最大冻融循环次数分别为12次和7次,为设计黑土冻融循环模拟试验提供了数据支持。

[Objective] This study explored the characteristics of soil temperature changes in farmlands of Mollisol region in Northeast China in order to provide basic data for quantifying the degree of freeze-thaw action and its impacts on soil erosion.[Methods] Based on the data of soil temperature in 2 m soil profile and air temperature from November to next April in 2015-2018 at the typical farmland in Binzhou River basin of Heilongjiang Province,we analyzed the characteristics of soil temperature variation and its responses to air temperature changes during freeze-thaw processes and freeze-thaw times in plough layer in farmlands.[Results] The soil temperature increased with the increase of soil depth from November to next February,while declined with the increase of soil depth when the soil was completely melted. The maximum frozen depth was 80 cm in farmlands of the research region. Meanwhile,there was a significant positive correlation between soil temperature in 0-60 cm depth and air temperature,and this correlation decreased with the increase of soil depth. In contrast,soil temperature under 80 cm depth was negatively correlated with air temperature.[Conclusion] There was a unidirectional freezing and bidirectional thawing in the study area. The freeze-thaw action mainly occurred at 0-20 cm in the topsoil layer of farmland,both maxinum freeze-thaw cycle times were 12 and 7,respectively,which provided the scientific basis for the design of simulated Mollisol freeze-thaw cycle experiments.