关键词: 雪斑, 水解性氮, 净初级生产力, 土壤温度, 长白山高山苔原带, 杨树人工林, 生产力衰退, 细根根序, 碳氮分配格局

Abstract: Based on continuous observation of soil temperature and  in situ  incubation, this paper studied the effects of snow packs on soil temperature, soil nitrogen (N) mineralization, and primary productivity of  Rhododendron aureum community alpine tundra in Changbai Mountain. During the snow-covered period of non-growth season (from last  October to early May), test soil had an increasing N content, and accumulated sufficient mineralized N for plant growth in the coming year. The soil under snow packs in  snow-covered period had a mean temperature -3.0 ℃, and its N mineralization was more vigorous, with available N increased by 3.88 g·m^-2; while the soil with no snowpack had a mean temperature -7.5 ℃, and the available N only increased by 1.21 g·m^-2. During growth lseason (from mid May to late August), soil N content decreased.  In  autumn when plants stopped growing, soil available N content tended to increase. In winter, the soil temperature under snowpacks kept at around 0 ℃ or a little lower, which promoted soil N mineralization, while that with no snowpack was in a frozen status. The difference in soil N mineralization was the key factor resulting in the higher primary productivity of snowpack Rh. aureum community and the driving force for the spatial variation of vegetation.

Key words: snow pack, hydrolyzable nitrogen, net primary productivity, soil temperature, alpine tundra of Changbai Mountain, poplar plantation, productivity decline, fine root order, carbon and nitrogen allocation.