喜马拉雅山西部Askot野生动物保护区内粗木质残体沿山高度分布格局与现状

在印度Askot野生动物保护区Goriganga流域的3个分水岭(Charigad,Dogarhigad和upper Gosigad)内,沿着海拔高度900～2600m设置5条曲线调查样带(样带A、B、C、D和E),调查了粗木质残体的分布格局和状况.海拔高度每升高100 m设置一块1 hm2的样地.结果表明,不同演替阶段的粗木质残体百分比贡献率按降低顺序排列依次是:枯立木--相位Ⅰ>相位Ⅱ>相位Ⅳ>相位Ⅲ;而原木-相位Ⅲ>相位Ⅱ>相位Ⅳ.调查样带A内喜马拉雅长叶松(Pinus roxburghii)林内枯立木密度在1500m处较高,调查样带B通麦栎(Quercus lanata)林的枯立木密度在2300米处较高(10个/hm2).喜马拉雅长叶松林的枯立木和原木总获得量为13.9 t,其中枯立木和原木分别占41%和59%;而通麦栎林枯立木和原木总量仅为5.6 t,枯立木和原木分别占60%和40%.此外,粗木质残体的存在,有利于为当地生长的兰花营造良好的生长环境.在喜马拉雅长叶松林中等高度区域内,高密度的枯立木和原木导致该区内物种丰富度较低,地被物密度也较低.这主要是由于该区光线充足、土壤水分含量低,只有优势种才能占领这样生境.

Status and distribution pattern of coarse woody debris along an altitudinal gradient in Askot Wildlife Sanctuary, Uttarakhand, West Himalaya

A rapid assessment on the status and distribution patterns of coarse woody debris (CWD) was conducted by laying five curvilinear transects (transects A, B, C, D and E; major trails), along an altitudinal gradient starting from 900 to 2 600 m, in three major watersheds (Charigad, Dogarhigad and upper Gosigad) of Goriganga catchment in Askot Wildlife Sanctuary, India. At every 100 m rise in altitude a hectare plot (100 m × 100 m) was selected. Results showed that the percentage contribution by different succession phases was in the decreasing order: phase I > phase II > phase IV > phase III for snags, and phase III > phase II > phase IV > phase I for logs. Snag density in chir pine forest was high in transect A (11 snags·ha⁻¹) at 1 500 m, and the value in rianj oak forest was high in transect B (10 snags·ha⁻¹) at 2 300 m. The total available mass of snags and logs in chir pine forest was 13.9 t, of which snags mass accounted for 41% of the total mass and logs mass for 59%. While the total value was 5.6 t in rianj oak forest, of which snags and logs accounted for 60% and 40% of the total mass, respectively. Moreover, the presence of CWD in the study area if not harvested, would provide a great opportunity to the orchids in future to flourish by providing protection. The high densities of snags and logs in chir pine forest at mid-altitudinal zone led to less species richness and lower density of ground flora as the zone receives more light, accompanying with lower soil moisture, and thus only the dominant species occupy the habitat.