Research On Stellera Chamaejasme Community Seed Bank Function Grouping Characteristic And Plant Restoration In Alpine Degraded Grassland

Alpine degraded grassland of poisonous weed is the main kind of degenerated typesin northwest China. The diffusion and extension of degenerated grassland damaged theproduction capacity of quality herbage and threaten the production safety of livestock.Excessive use is the direct cause to the degradation of alpine degraded grassland, and thencaused a grassland vicious circle of"overgrazing－degradation－re-overgrazing". Soilseed bank characteristics of Stellera chamaejasme community in degraded grassland ofQilian Mountains were studied by adopting field investigation and laboratory analysis.The results shows that:1) A total of 18 species of plants belonging to the standing vegetation of Stellerachamaejasme community. among which, 4 species were grass, 3 species were legume and2 species were Compositae, and other plants 9 kinds; From the function Grouping ofVegetation; There are 5 species were Perennial grasses, 3 species were Annuals andbiennials and 10 species were perennial weeds. Under the vegetation gradient, perennialgrasses and perennial weeds in a dominant position, however, annuals and biennials witha low position. The biomass of different functional groups significant differences in thevegetation gradient.2) A total of 20 plant species belonging to 13 families were found in the soil seedbank, among which, 4 species were grass, 3 species were Compositae and legume, andother plants 1 kind; From the functional groups of soil seed bank there are 5 species ofannual and biennial, 4 species of perennial grass, 11 species of perennial weeds. Thedensities and quantities of poisonous weeds are predominate in the soil seed bank ofStellera chamaejasme community.3) The seed densities of perennial grasses are reduced, and even disappeared with theincrease in different vegetation gradient, while the perennial weeds widely exits in seedbank with greater density. There are obvious differences among each soil layer, and thedistribution law of the density and quantity of Stellera chamaejasme community shows asfollows: upper layer (0～5cm)> lower layers (10～15cm)> middle layer (5～10cm).4)The standing vegetation numerical of Ecological dominance,Shannon-Wienerdiversity index,Margalet richness index,Pielou evenness index sequencing was perennialweeds> Annuals and biennials> Perennial grasses. The dominance index of the soil seedbank in upper layer (0~15cm) has some differences with its change trend, but its othersindexes variation trends are similar, such as Shannon-Wiener index, evenness index and Richness index. In addition, the changes of species diversity in the upper layer(0~5cm) are high similar to that of the upper layer (0~15cm). While, the instability ofvertical direction is the largest in middle layer(5~10cm).5) The seed bank has smaller contribution rate on the vegetation regeneration oforiginal prairie grasses under vegetation gradients. And the community structure issignificant changed because of the mass rearing of poisonous weeds such as Stellerachamaejasm. During the degraded vegetation, there was obvious negatively correlationbetween the density of seed bank of perennial grasses and the cover of ground vegetation,but the correlation to the annuals,biennials and perennial weeds was not so obvious(P＜0.01).6) In the vegetation gradient, the dominance proportion of perennial grassespresented variation tendency as single peak fluctuation, the variation of perennial weedswas just contrary, the annuals and biennials weeds absented in gradient V andⅥ; the soilseed bank presented a more obvious regular change of dominance proportion, thedominance proportion of perennial weeds reached a high value as 57.8% and a moreobvious fluctuation change of dominance proportion; the dominance proportion ofperennial grasses reduces to 13.68%, but the dominance proportion of annuals andbiennials weeds presented a relative rising trend.The Potential of germination and restoration in Original prairie grasses becomessmaller in natural state. So, vegetation restoration has become a serious problem.