关键词: 祁连山, 灌丛生物量, 海拔梯度, 生物量分配

Abstract: Qilian Mountains, which sites at the northeast line of the Tibet Plateau, is the major ecological barrier of the Hexi Corridor and the provinces and regions in the downstream, and its ecosystem is complex and fragile. Under the background of global climate change, the accelerating melting glaciers will influence the global climate, threaten the security of the human living condition and it may change the ecotope and habit of much propagation. The alpine shrubs of the Qilian Mountains, which sits beyond the tree line of the[WTBX] Picea crassifolia[WTBZ] forest, is the most effective forest type, therefore, to study the biomass of the alpine shrubs in the Qilian Mountains is the main reflection of the productivity of the ecosystem, the main measure of the structure and function of the community. And because the biomass of the shrubs is impacted by the elevation gradient and environmental factors, including the limitation of the field investigation in the high altitude, the response process made by shrub biomass to the elevation gradient is not clear. So, this study took the alpine shrubs at the elevation of 3 300-3 700 m in the Pailugou Catchment of the Qilian Mountains as the research object, the plot, subplot harvesting method and mining trenches method were used to observe the total biomass and organic biomass of the shrubs with various elevation gradients and also to analyze the relationship between the distribution characteristics of the shrubs biomass and environmental factors. The aim of this paper is to provide important theoretical basis and data for the protection of ecological environment of watershed and the response of alpine shrub to global climate change. Taking the alpine shrubs above timberline of Picea crassifolia in the Qilian Mountains as a test object, the traditional harvesting method and mining trenches method were used to observe the alpine shrubs organic biomass. The dry weight data and distribution characteristics of the leaf biomass, shoot biomass, fibrous root biomass, rootlet biomass, and thick root biomass were analyzed. The results show that the total biomass of alpine shrubs in the Qilian Mountains is 12 869.39±3 306.16 kg/hm2( Mean±Sd,n=10),  for the distribution of the organic biomass, the stem takes the biggest part which accounts for 32.21%, the ratio of leaf biomass, fibrous root biomass, rootlet biomass, thick root biomass are 15.70%、14.06%、11.13% and 26.90% separately.  In the different altitudes the ratio of the organic biomass is with significant difference, the average value of aboveground biomass is 6 097.17 kg/hm², and underground biomass is 6 772.22 kg/hm². And the ratios of root biomass to stem biomass are between 0.56-1.93, with the biggest ratio at an elevation of 3 500 m. There is an obvious negative relationship (R² = 0.898 7，p<0.01) between biomass of alpine shrubs and altitudes. As the altitude increases, the total biomass, aboveground biomass and underground biomass of the alpine shrubs all reduce.

Key words: Qilian Mountain, biomass of shrubs, elevation gradient, biomass distribution