冻融期秸秆和积雪覆盖条件下土壤热容量的特性研究

Characteristics of Soil Heat Capacity Under Different Straw and Snow Covers in Freezing and Thawing Period

为了揭示冻融期不同秸秆和积雪覆盖条件下土壤热容量的时空分布特征,通过冬季大田试验,设置裸地（BL）、6 000kg/hm^2秸秆覆盖（SM1）、12 000kg/hm^2秸秆覆盖（SM2）和18 000kg/hm^2秸秆覆盖（SM3）4种不同处理,采用中子仪和和时域反射仪分别测定土壤的总含水率和液态含水率,进而计算出土壤热容量.研究结果表明,在冻融期,土壤热容量随着土壤冻结的发生逐渐降低,当土壤完全冻结以后,土壤热容量基本不变,在土壤融化时,土壤热容量又逐渐増加.在冻结期,秸秆和积雪双重覆盖会延缓土壤热容量减小的时间,增加土壤热容量,减小土壤热容量的变化幅度;在融化期,秸秆和积雪双重覆盖会延缓土壤热容量增大的时间,同时增加了融雪水入渗,所以增加了土壤热容量,增大了土壤热容量的变化幅度.在冻结期,随着土层深度的增加,土壤热容量减小的时间逐渐变晚,土壤热容量逐渐增加,土壤热容量变化幅度逐渐减小;在融化期,20cm土层土壤热容量最先增加,60cm土层土壤热容量增加的时间最晚,40cm土层土壤热容量的变化幅度最大.SM1、SM2和SM3这3种处理融化期的土壤热容量和变化幅度都比冻结期大.

In order to discover the temporal and spatial distribution characteristics of soil heat capacity under different straw and snow covers in freezing and thawing period; we measured total water content and liquid water content of soil with neutron instrument and time domain reflectometry under four different treatments（ bare land,6 000 kg/hm^2 straw mulching,12 000 kg/hm^2 straw mulching,18 000 kg/hm^2 straw mulching） and then calculated soil heat capacity. Results showed that in freezing and thawing period,the soil heat capacity decreased when soil was freezing,maintained constant when soil was frozen,and increased during the thawing period. During the freezing period,straw and snow cover delayed the decrease of soil heat capacity,increased the soil heat capacity and reduced the variation of soil heat capacity. In the thawing period,straw and snow coverdelayed the increase of soil heat capacity,increased the soil heat capacity and increased the range of soil heat capacity. During the freezing period,with the increase of soil depth,the time when the soil heat capacity decreasedwas laterand the soil heat capacity increased. In the thawing period,the soil heat capacity increased firstly in 20 cm soil layerand itincreased lastly in 60 cmsoil layer. The change of soil heat capacity in 40 cm soil layer was the largest. The soil heat capacity and the change range of SM1,SM2 and SM3 in the thawing period were larger than that in the freezing period.