Studies On Structrue And Dynamics Of Salix Shrub Community And Dominant Populations In Alpine Area Of East Qilian Mountain

The thesis, through sampling and investigating within eighteen plots with contiguous grid quadrat method whose size was 16mX 16m and distributed where plants spred continuously and altitude graduate was obvious from 3050m to 3450m, analysed the main constituent part of alpine vegetation - alpine Salix shrub community and its dominant populations in alpine area of east Qilian mountain. It was studied systematically for the community and the populations on the structure, component, intraspecies relationship, interspecies relationship, the level of species diversity, age structure and distribution patter at the genet and the ramet level. Importance value (IV) had been used to describe community' component and construction, index of species diversity to indicate species diversity level of the community1, associate coefficient and the percentage of the simultaneous emergence to determine the interspecies relationship, static life stable and survival curve to express age distribution, ratio of variance to mean value(v/m). negative binominal parameter(k). Green's index (GI). Index of dispersion(I f,), Cassie indexs (Ca), index of clumping(I) , index of mean crowding(m ), index of patchiness( m*/m) and HAOV to measure the crowding and the scale of the distribution pattern of the population.The results showed that Salix shrub community was mainly consisted of 13 shrub plants and 17 herbs. In the shrub layer, Salix oritrepha is a dominant community- and constructive species whose IV was 3.1012~2.848. Dasiphora fmticosa. Spiraea alpina. Rhododendron capitatum were subdominant species constituting the community and IV of them were 2.0657 ~ 1.8827, 1.1292- 0.943 and 0.847-1.2002 respectively. Salix myrtillacea, S. rehderiana, R. przewalskii. R. anthogonoides, R. thymifolium. Caragana jubata were companion species constituting the community (0.1< IV <0.5). Berberis diaphana and Lonicera hispida were rare species in the community (IV<0.1). In the herb layer, Polygonum sphaerostachyum with 7Fof 1.9517- 1.8579, and P. viviparum with IV of 1.7483-1.7042 were dominant species constituting the community. Subdonminant species was consisted of Kobresia humilis. Carex atrofusca, Poa spp. and Helictotrichon tibeticum (0.51e synusia in which Salix oritrepha. Salix myrtillacea, S. rehderiana and S.ciipularis, Dasiphore fniticosa, Spiraea alpina, Rhododendron capitatum were phanerophytes , Polygonum sphaerostachyim. P. viviparum, Helictotrichon tibeticum , Gentiana spp., Oxytropis kansiiensis and Saiissnrea spp. were hemircyptoph\tes and Kobresia humilis, Carex atrofiisca. Poa spp., Pedicularis spp., Leontopodium leontopodioie.Meconopsis spp. were geophytessynusias.It was approvided that the diversity indices based on cover value had more ecological significance than that based on important valu...