雪被斑块对川西亚高山冷杉林土壤氮转化酶活性的影响

Effects of snow pack on soil nitrogen transformation enzyme activities in a subalpine Abies faxioniana forest of western Sichuan,China

在2012和2013年冬季雪被形成的3个关键时期（雪被形成期、稳定期和消融期），测定川西亚高山岷江冷杉林3类雪被斑块（厚雪被斑块、中厚度雪被斑块和浅雪被斑块）土壤有机层和矿质土壤层的脲酶、硝酸还原酶和亚硝酸还原酶活性特征.结果表明：整个冬季，厚雪被斑块土壤温度比中厚度雪被斑块和浅雪被斑块土壤温度分别增加46.2％和26.2％，浅雪被斑块的3种土壤氮转化酶活性是厚雪被斑块的0.8～3.9倍.在雪被形成期和消融期，浅雪被斑块显著增加了土壤有机层和矿质土壤层3种氮转化酶活性；而在雪被稳定期，中厚度雪被斑块或厚雪被斑块土壤具有较高的氮转化酶活性，但与浅雪被斑块的土壤氮转化酶活性差异均不显著；整个冬季，雪被对土壤氮转化酶活性的影响与采样时期、土壤层次和酶种类有关；3种土壤氮转化酶活性在整个冬季均具有明显动态变化；土壤有机层的氮转化酶活性显著高于矿质土壤层；脲酶、硝酸还原酶和亚硝酸还原酶活性与温度、水分密切相关.短期内气候变暖情景下冬季雪被减少可能提高土壤氮转化酶活性，进而加速了亚高山森林冬季土壤氮转化i寸程.

This study characterized the dynamics of the activities of urease, nitrate reductase and nitrite reductase in both soil organic layer and mineral soil layer under three depths of snow pack （deep snowpack, moderate snowpack and shallow snowpack） over the three critical periods （snow formed period, snow stable period, and snow melt period） in the subalpine Abiesfaxoniana forest of western Sichuan in the winter of 2012 and 2013. Throughout the winter, soil temperature under deep snowpack increased by 46.2% and 26.2%, respectively in comparison with moderate snow pack and shallow snowpack. In general, the three nitrogenrelated soil enzyme activities under shal low snowpack were 0.8 to 3.9 times of those under deep snowpack during the winter. In the begin ning and thawing periods of seasonal snow pack, shallow snowpack significantly increased the activ ities of urease, nitrate and nitrite reductase enzyme in both soil organic layer and mineral soil layer. Although the activities of the studied enzymes in soil organic layer and mineral soil layer were ob served to be higher than those under deep and moderate snowpacks in deep winter, no significant difference was found under the three snow packs. Meanwhile, the effects of snowpack on the activi ties of the measured enzymes were related with season, soil layer and enzyme type. Significant vari ations of the activities of nitrogenrelated enzymes were found in three critical periods over the win ter, and the three measured soil enzymes were significantly higher in organic layer than in minerallayer. In addition, the activities of the three measured soil enzymes were closely related with tem perature and moisture in soils. In conclusion, the decrease of snow pack induced by winter warming might increase the activities of soil enzymes related with nitrogen transformation and further stimu late the process of wintertime nitrogen transformation in soils of the subalpine forest.