季节性雪被对川西亚高山针叶林土壤温度的影响

Effect of seasonal snow cover on soil temperature in a conifer forest of western Sichuan,China

季节性雪被对冬季寒冷区域土壤有潜在保温作用.采用人工遮雪法研究季节性雪被对川西亚高山针叶林土壤温度的影响.结果表明:川西亚高山冬季雪被具有明显的动态变化特征;雪被能有效减少土壤与空气之间的热量交换,使冬季土壤温度保持稳定.雪被去除使得0、5、10和20 cm土壤日均温度分别降低1.12、0.83、0.33和0.16℃,最低温度分别降低7.33、2.10、1.17和0.75℃.冬季土壤冻结状况与雪被条件密切相关,雪被去除使得0、5、10和20 cm土壤冻结时间分别缩短19、16、11和2 d,而冻融循环则分别增加39、12、6和1次.综上所述,川西亚高山季节性雪被对冬季土壤具有一定的保温作用,雪被效应随土壤深度增加而降低;因此未来气候变化引发的川西地区季节性雪被时空格局变化,可能对区域冬季和生长季土壤水热动态产生深刻影响.

Seasonal snow cover has a significant effect on soil thermal dynamics. In order to understand the relationship between snow cover and soil temperature, a snow-shading experiment was carried out to evaluate the effect of snow cover on soil temperature at 4 depths in a subalpine forest. There was a significant seasonal change in snow cover in the subalpine forest of western Sichuan. Snow cover decoupled the thermal exchange between the soil and the atmosphere, and was efficient to maintain a stable soil temperature. The average daily soil temperature at the depths of 0 cm, 5 cm, 10 cm, and 20 cm were 1.12 ℃, 0.83 ℃, 0.33 ℃, and 0.16 ℃ higher, respectively, in the control plots than in the snow removal plots. Likewise, the minimum soil temperature at the depths of 0 cm, 5 cm, 10 cm, and 20 cm were 7.33 ℃, 2.10 ℃, 1.17 ℃, and 0.75 ℃ higher in the control plots, respectively, than in the snow removal plots. In addition, snow cover had a substantial effect on frozen soil. Snow removal reduced the freezing timing of the 0 cm, 5 cm, 10 cm, and 20 cm soil depths by 19 d, 16 d, 11 d, and 2 d, respectively; however, it increased the freeze-thaw cycles of the 0 cm, 5 cm, 10 cm, and 20 cm soil depths by 39 times, 12 times, 6 times, and 1 time, respectively. Taken together, seasonal snow cover was shown to have a significant effect on soil thermal dynamics in the conifer forest of western Sichuan, and the effect of snow cover on soil temperature was dependent on soil depth. Thus, warming-induced changes in spatial-temporal patterns in seasonal snow cover may have a significant effect on soil water and temperature dynamics in the study area in the future.