藏东南色季拉山急尖长苞冷杉(Abies georgei var. smithii)林线的生态气候特征

Characteristics of eco-climate at smith fir timberline in the Sergyemla Mountains,Southeast Tibetan Plateau

高山林线因其对气候因子的敏感性和自身结构的不稳定性而被视为气候变化的"监视器",通过自动微气象站对藏东南色季拉山急尖长苞冷杉(Abies georgeivar.smithii)林线气象因子的连续监测,探讨了色季拉山高山林线的生态气候特征。结果表明:在色季拉山急尖长苞冷杉林线处,年平均温度为1.3℃,年平均相对湿度为79.4%,全年降水量为892.6 mm,主要集中在6、7、8、9月4个月份。林线最热月平均温度为9.4℃,最冷月平均温度为-6.4℃,年生物温度为3.1℃,温暖指数是11.6℃月,寒冷指数是-55.9℃月,生长季内平均温度为7.7℃,生长季长度为133d,大陆度指数为34.0,湿润指数为217.5。其温暖指数与我国两种山地森林树种祁连圆柏和喜马拉雅冷杉的分布上限较为接近。林线的最热月温度、年生物学温度和生长季平均温度与全国高山林线的平均值十分接近。从全球范围来看,色季拉山林线最热月平均温度9.4℃与全球均值10℃很接近。生长季内10cm深度的土壤均温为6.22℃,接近Krner观测的(6.7±0.8)℃全球均值。

The alpine timberline has been considered as a ＂monitor＂ of climatic change because of its sensitivity to climatic factors and non-stability in its structure.In this study,we investigated the eco-climatic characteristics at the alpine timberline of smith fir（Abies georgei var.smithii） in Tibetan Plateau using continuous data collected from micro-meteorological station.The results indicated that at the smith fir timberline in the Sergyemla Mountains,annual mean temperature and relative humidity were 1.3℃ and 79.4%,respectively.Annual precipitation was 892.6mm,most of which occurred between June and September.Mean temperatures for the warmest month and the coldest month were 9.4℃ and-7.4℃,respectively.The annual bio-temperature,warmth index and cold index were 3.1℃,11.6℃.month and-55.9℃.month,respectively.The growing season length was 133 days,and the seasonal mean temperature was 7.7℃.The continentality index and moisture index were 34.0 and 217.5,respectively.The warmth index at smith fir timberline was close to that at the upper limits of Qilian savin（Sabina przewalskii） and Himalayan fir（Abies spectabilis）.Moreover,the mean temperature for the warmest month,the annual bio-temperature,and the mean temperature for growing seasons at smith fir timberline were very close to the averaged values of alpine timberlines across china.The mean temperature for the warmest month at alpine timberline in Sergyemla Mountains,9.4℃ was also close to the averaged value in the world（10℃）.At the Sergyemla Mountains timberline,the mean soil temperature in 10cm depth during the growing season was 6.22℃,which was close to the averaged value（（6.7±0.8） ℃） in the world observed by Krner.