温暖化加剧青藏高原高寒草甸土非生长季冻融循环
Warming Enhances Soil Freezing and Thawing Circles in the Non-growing Season in a Tibetan Alpine Grassland

摘要 在2013年10月至次年4月, 首次利用微根管直接观测和土壤温度间接观测相结合的方法, 研究增温对青藏高原高寒草甸土壤冻融循环过程的影响。结果显示: 1) 全年增温和冬季增温均显著增加非生长季 5, 10, 20cm的土壤温度, 而且冬季增温处理下的5~20cm土壤非生长季月平均温度比全年增温处理下的高0.01~0.18oC; 2) 全年增温和冬季增温显著降低了完全冻结期和冬春解冻期的冻土层厚度, 而对秋冬始冻期的冻土层厚度没有影响; 3) 全年增温和冬季增温显著减少了完全冻结期的持续天数和增加冬春解冻期的持续天数, 而对秋冬始冻期的持续天数没有影响; 4) 冬季增温比全年增温对冻土层厚度和冻融循环持续天数的影响更加显著。研究表明, 在青藏高原高寒草甸气候温暖化的趋势下, 非生长季土壤冻融交替天数的增加, 可能会进一步对高寒地区的地下碳氮循环产生重要的影响。
Abstract Seasonal freezing and thawing process occurs in the non-growing season in the alpine grassland on the Tibetan Plateau. However, it is still unclear that how warming would affect this process in the alpine zone. From October 2013 to April 2014, the research used minirhizotron directily and soil temperature indirectly to investigate the effects of warming on the freezing and thawing process. The results showed that, warming significently increased soil temperature at the depths of 5, 10 and 20 cm, and soil temperatue in the winter warming plots was 0.01–0.18oC higher than that in the annual warming plots. Wamrming significantly decreased the depth of soil frozen layer in the frozen period and thawing period of winter spring, but had no effect on the the depth of soil frozen layer in the thawing period of fall-winter. It is due to warming-induced redution on soil miosture. Warming significantly reduced lasting days of frozen period and increased lasting days thawing period of winter-spring, and did not affect the lasting days of freezing period of fall-winter. Effects of winter warming on frozen soil depths and lasting days were much greater than annual warming. The reults suggest that the enhanced freezing and thawing circles with a warming trend may subsequently affect soil carbon (C) and nitrogen (N) in this region.