雪被斑块对川西亚高山冷杉林冬季土壤活性氮库及氮矿化潜力的影响

Effects of snow pack on winter soil labile nitrogen pools and nitrogen mineralization potential in an subalpine Abies faxoniana forest of western Sichuan

于2012年11月中旬-2013年3月中旬,分3个关键雪被时期(雪被形成期、稳定期和融化期)采集川西亚高山冷杉林内不同厚度雪被处理(浅雪被、中度厚度雪被和厚雪被)的土样,测定土壤活性氮库、土壤硝化和氮矿化潜力以期了解高寒森林土壤氮素生态过程.结果表明:冬季土壤温度在一定程度上随着雪被厚度的增加而升高;冬季土壤活性氮库(铵态氮、硝态氮、微生物生物量氮和可溶性有机氮)存在明显的动态变化,各形态土壤氮库都以雪被融化期最高,而土壤氮硝化潜力(7.36-8.44 mg kg-1 d-1)和矿化潜力(7.22-8.23 mg kg-1 d-1)则以雪被融化期最小;硝态氮是冬季土壤无机氮库的主体,占无机氮总量的95%左右;雪被厚度对各土壤氮组分总体影响不大.亚高山森林土壤活性氮库及氮矿化随雪被进程发生显著变化,可见雪被覆盖可能改变亚高山森林冬季土壤活性氮库及土壤氮转化时间动态格局.

In this study, we estimated winter soil labile nitrogen pools, nitrification and mineralization potentials under three depths of snow pack （deep, middle and shallow snowpacks） during the three critical periods （snow forming period, snow stable period and snow melting period） in a subalpine Abiesfaxoniana forest of west Sichuan in the winter of 2012-2013 to better understand the ecological process of soil nitrogen. Soil temperature increased with the increased depth of snow pack. Labile soil nitrogen pools （ammonium, nitrate, microbial biomass nitrogen and dissolved organic nitrogen） had obvious temporal dynamics. The concentration of each nitrogen pool was the highest in the snow melting period. On the contrary, nitrification potential （7.36-8.44 mg kg-~ d-z） and nitrogen mineralization potential （7.22-8.23 mg kg-~ fit） were the lowest in this period. Nitrate is the main form of winter soil inorganic nitrogen pool, accounting for around 95% of the total. The changes in snow pack depth did not affect soil nitrogen components. There were obvious dynamics in soil labile nitrogen pools and nitrogen mineralization during the different stages of snow cover. Thus, changes in snow cover might alter seasonal patterns of soil labile nitrogen pools and nitrogen transformation in the subalpine forests of Western Sichuan during the wintertime.