雪被厚度对冻融过程中土壤CO_2短期排放的影响

Effect of snow cover on short-term CO_2 emission from the soil in freeze-thaw cycles

气候变化对全球中纬度地区降雪和雪被有着重要的影响,冬季土壤呼吸对区域和全球碳循环的贡献更为重要。本研究以干旱区典型高寒湿地和农田灰漠土为研究对象,冬季在室外模拟研究了雪被厚度和水分对两种类型土壤CO_2短期排放的影响,结果表明:(1)在干旱区不同有机碳含量土壤冻融循环过程中,雪被厚度的增加会影响土壤的CO_2排放特征;在冻融过程初期雪被厚度增加会导致土壤CO_2排放峰值出现滞后,在消融期CO_2排放量会明显增加,并随着冻融循环次数增加而逐渐减小。(2)土壤起始含水量的高低及雪被厚度对土壤CO_2短期排放速率及其与温度的关系具有直接影响。在起始土壤饱和含水量为20-30%条件下,农田HW10与HW130处理间CO_2平均排放速率差异显著(P<0.05);当雪被厚度增加,两种土壤CO_2排放与地表、大气和5cm土层温度之间均呈现极显著正相关性(P<0.01);在起始土壤饱和含水量为50-60%条件下,雪被厚度对农田和湿地土壤CO_2平均排放速率影响不显著(P>0.05),然而在农田土壤雪被厚度30cm和湿地土壤雪被15cm处理下,CO_2排放与地表和5 cm土层温度呈现极显著正相关(P<0.01),但受大气温度影响不显著。以上结果表明气候剧烈变化导致的季节性降雪雪被的变化会对干旱区不同土壤CO_2短期排放产生重要的影响。

Climate change has an important impact on snow and snow cover in the mid latitude region of the world,and the contribution of soil respiration to regional and global carbon cycles is more important in winter.The effects of snow cover and water content on the short-term CO2 fluxes during freeze-thaw cycles were evaluated for the undisturbed soil columns of Typical Alpine Wetland and farmland grey desert soil outdoors in winter.Our results showed that the dynamics of soil CO2 fluxes during the freeze-thaw cycles were affected by snow cover and soil organic carbon content. Soil CO2 emissions generally enhanced during the first freeze-thaw cycle,and gradually decreased with successive cycles. The increase of snow cover thickness delayed the CO2 emission peak in the early stage of freezing and thawing process. In addition,there was a significant difference in the average CO2 emission rate between HW10 and HW130 treatments（ P 0. 05） under the condition of initial soil saturated water content of 20-30%,and when the snow thickness was increased,the CO2 emission from two soils showed a significant positive correlation with the ground surface,the atmosphere and the temperature of 5 cm soil layer respectively（ P 0. 01）. Snow cover thickness had no significant effect on the average CO2 emission rate of farmland and wetland soil（ P 0. 05） under the condition of initial soil saturated water content of 50-60%,However,CO2 emission from farmland soil snow cover treated with 30 cm and wetland soil snow cover treated with15 cm was significantly positively correlated with soil surface temperature and soil temperature at 5 cm（ P 0.01）,but not significantly affected by atmospheric temperature. The above results suggest that the seasonal change of the snow has an important impact on short-term soil CO2 emissions in the arid area because of climate changes.