The southeastern Tibetan Plateau has the highest timberlines in the world and climate change affects this area to a considerable extent. Quantification of vegetation biomass in the forests at the timberline is essenti...The southeastern Tibetan Plateau has the highest timberlines in the world and climate change affects this area to a considerable extent. Quantification of vegetation biomass in the forests at the timberline is essential for understanding carbon balance, forest structure and functional changes in the forests at timberlines. We describe biomass and its constituent components of a smith fir tim- berline forest occurring at an elevation of 4320 m on the Sergyemla Mountain in the southeastern Tibetan Plateau. The results show that, in the tree layer, the average diameter at breast height （DBH） was 35.6 cm, the density 251 trees per hectare with a total biomass of 309.9 t.ha 1. Of the total biomass, the tnmks accounted for 70.49%, branches for 9.09%, leaves for 5.57% and roots for 14.85%. The total biomass in the shrub layer was 77.9 t＇ha-~ of which the biomass of trunks, branches, leaves and roots accounted for 42.8, 14.9, 4.6 and 15.6 t.ha-1, respectively. The total biomass in the herb layer was 3.0 t.ha-1. The total vegetation biomass in the smith fir timberline forest was 390.9 t-ha-l, to which the tree layer contributed the most （79.3%）, followed by shrubs （19.9%） and herbs （0.8%）. We estimate that the smith fir forest stand at the timberline had a higher total biomass than other fir or spruce forest stands in the surrounding area.展开更多
为分析季节性冻融对土壤团聚体稳定性的影响,以藏东南色季拉山森林土壤为研究对象,通过野外控制性试验利用湿筛法测定团聚体组成,分析了0—10 cm, 10—20 cm, 20—30 cm深度土层各粒径团粒结构变化,以及土壤含水量(SWC),0.25 mm水稳性...为分析季节性冻融对土壤团聚体稳定性的影响,以藏东南色季拉山森林土壤为研究对象,通过野外控制性试验利用湿筛法测定团聚体组成,分析了0—10 cm, 10—20 cm, 20—30 cm深度土层各粒径团粒结构变化,以及土壤含水量(SWC),0.25 mm水稳性团聚体含量(WSA)、平均质量直径(MWD)、平均几何直径(GMD)、分形维数D、可蚀性K值各指标之间的关系。结果表明:(1)季节性冻融导致大团粒含量减少,小团粒含量增加,土壤结构失调。(2)含水量是影响团聚体稳定性的重要因素之一。(3)季节性冻融作用整体上导致MWD,GMD变小,D值与K值变大,降低了土壤团聚体稳定性。(4)当土壤冻融次数在一定范围内STF-One中,WSA有所增加,土壤稳定性有所增强。(5)土壤团聚体WSA,MWD和GMD均与D值和K值呈负相关。(6)在SFT-Ys类型土壤中土壤结构变化,0.5 mm粒级是重要临界点。综上,研究为季节性冻融对土壤稳定性的影响提供数据支持,为冻土潜在受侵蚀情况提供理论依据。展开更多
基金supported by an IFS research grant (No. D/4048-1)the National Natural Science Foundation of China (Grant No. 40701008)
文摘The southeastern Tibetan Plateau has the highest timberlines in the world and climate change affects this area to a considerable extent. Quantification of vegetation biomass in the forests at the timberline is essential for understanding carbon balance, forest structure and functional changes in the forests at timberlines. We describe biomass and its constituent components of a smith fir tim- berline forest occurring at an elevation of 4320 m on the Sergyemla Mountain in the southeastern Tibetan Plateau. The results show that, in the tree layer, the average diameter at breast height （DBH） was 35.6 cm, the density 251 trees per hectare with a total biomass of 309.9 t.ha 1. Of the total biomass, the tnmks accounted for 70.49%, branches for 9.09%, leaves for 5.57% and roots for 14.85%. The total biomass in the shrub layer was 77.9 t＇ha-~ of which the biomass of trunks, branches, leaves and roots accounted for 42.8, 14.9, 4.6 and 15.6 t.ha-1, respectively. The total biomass in the herb layer was 3.0 t.ha-1. The total vegetation biomass in the smith fir timberline forest was 390.9 t-ha-l, to which the tree layer contributed the most （79.3%）, followed by shrubs （19.9%） and herbs （0.8%）. We estimate that the smith fir forest stand at the timberline had a higher total biomass than other fir or spruce forest stands in the surrounding area.
文摘为分析季节性冻融对土壤团聚体稳定性的影响,以藏东南色季拉山森林土壤为研究对象,通过野外控制性试验利用湿筛法测定团聚体组成,分析了0—10 cm, 10—20 cm, 20—30 cm深度土层各粒径团粒结构变化,以及土壤含水量(SWC),0.25 mm水稳性团聚体含量(WSA)、平均质量直径(MWD)、平均几何直径(GMD)、分形维数D、可蚀性K值各指标之间的关系。结果表明:(1)季节性冻融导致大团粒含量减少,小团粒含量增加,土壤结构失调。(2)含水量是影响团聚体稳定性的重要因素之一。(3)季节性冻融作用整体上导致MWD,GMD变小,D值与K值变大,降低了土壤团聚体稳定性。(4)当土壤冻融次数在一定范围内STF-One中,WSA有所增加,土壤稳定性有所增强。(5)土壤团聚体WSA,MWD和GMD均与D值和K值呈负相关。(6)在SFT-Ys类型土壤中土壤结构变化,0.5 mm粒级是重要临界点。综上,研究为季节性冻融对土壤稳定性的影响提供数据支持,为冻土潜在受侵蚀情况提供理论依据。
