中文摘要：

从亚高山森林到高山林线,逐渐严酷的生长环境影响了生物量的积累和分配。本研究采用相对生长法和样方收获法估算了藏东南色季拉山急尖长苞冷杉林在不同海拔（4 190 m,4 270 m和4 326 m）的地上生物量,分析了群落中不同层次地上生物量、各器官生物量及其分配比例随海拔的变化格局。结果表明：1.急尖长苞冷杉群落地上生物量在181~284 t/hm2之间,其中,乔木层在117~248 t/hm2,灌木层为35~62 t/hm2,草本层为0.9~1.5 t/hm2;2.群落地上生物量随海拔升高急剧降低,降低的平均幅度为73.1 t/（hm2.100 m）;3.随海拔升高,群落地上生物量分配到非光合器官（树干和枝条）的比例显著降低,分配到叶的比例呈增加趋势。随海拔的增加,急尖长苞冷杉群落通过增加叶生物量所占比例（高叶寿命）以延长养分在植物体内的存留时间,提高生态系统的养分利用效率,从而适应高海拔地区的低温胁迫环境。

英文摘要：

Environment becomes harsh with increasing altitude,which has major effects on forest biomass accumulation and its allocation to woody and foliage components.In this study,we compared aboveground biomass and its allocation pattern of Abies georgei[ var.smithii along a transect from sub-alpine forest to alpine timberline in the Sergyemla Mountain,southeast Tibet.We estimated different components of aboveground biomass for Abies trees and undergrowth Rhododendron shrubs by using allometric regressions.The aboveground biomass of undergrowth herbs was measured by harvesting in 0.5 m×0.5 m quadrats.Aboveground biomasses were 181~284 t/hm2,117~248 t/hm2,35~62 t/hm2 and 0.9~1.5 t/hm2 for whole community,trees,undergrowth shrubs and herbs,respectively.Aboveground biomass of the whole community decreased significantly with increasing elevation,and the decreasing rate was 73.1 t/hm2 per 100 m.Furthermore,the Abies forest stand at higher elevation tended to reduce biomass allocation to non-photosynthesis organs（stem and branch）,and to increase the allocation to long-lived needles.The increased biomass allocation to long-lived needles at higher elevations may extend the mean residence time of nutrients in plants,and then enhance nutrient use efficiency of dry mass production to adapt to the low temperature environment at alpine timberlines.