Characteristics Of Soil Seed Bank And Its Species Similarity With Aboveground Vegetation Of Tianshan Spruce Forest In The Middle Of Northern Slope Of Tianshan Mountains

Tianshan Spruce(Picea schrenkiana var.tianshanica),as the most widely distributed and large-area ecologic al tree species in Xinjiang.Based on the existing research on the soil seed bank in Tianshan Spruce forest,this study carried out research on the soil seed bank at altitude(1 600～2 700 m).By combining soil seed bank sampling,indoor germination identification and vegetation survey,we studied the species composition,species diversity,plant life type and relationship between soil seed banks and aboveground vegetation in different elevation gradients,analyzed the distribution characteristics of soil seed banks,distribution characteristics of above-ground vegetation and species similarity between soil seed banks and above-ground vegetation,and provided theoretical basis for the conservation of plant community species diversity.The results of the study are as follows:Soil seed bank germination identified 29 families,70 genera,86 species.Among them,2 species of trees are Picea schrenkiana var.tianshanica and Betula tianschanica Rupr;2 species of shrubs are Cotoneaster melanocarpus Lodd and Geum chiloense Balb.ex Ser;82 species of herbs,and the soil seed bank is dominated by herbs.Perennial herbaceous plants are distributed in each transect.The number of 1-year-old or 2-year-old herbaceous species in the soil seed bank showed a single-peak distribution trend with the increase of altitude gradient.The number of species,the number of shared species and the seed density of the soil seed bank showed an increase and then a decrease with elevation.The highest number of species and the highest density of soil seed bank were found at 1,800 m elevation.The trend between above-ground vegetation community characteristics and elevation gradient in Tianshan spruce forests showed a quadratic function.At different elevation gradients,plant height tended to decrease with increasing elevation,and plant density,species richness and cover tended to increase first and then decrease.The α-diversity tends to be single-peaked with increasing altitude.β-diversity tends to increase,then decrease and then increase with increasing altitude between adjacent altitude gradients,while the Cody index is the opposite;the Sorensen index tends to decrease with increasing altitude between different altitude gradients,while the Cody index is the opposite.The Sorensen index generally decreases with increasing altitude,while the Cody index is the opposite.The overall association of the 8 dominant species in the above-ground vegetation communities of Tianshan Spruce forests was positive.The soil seed bank and above-ground vegetation of Tianshan spruce forest identified a total of 123 species in 99 genera of 41 families and 101 species in 87 genera of 36 families,with a total of 60 species in both,26 species unique to the soil seed bank and 41 species unique to the above-ground vegetation.The number of above-ground vegetation species was significantly higher than the number of soil seed bank species at different elevation gradients.The soil seed bank was moderately dissimilar to the aboveground vegetation species with low similarity.The similarity between soil seed bank and above-ground vegetation species showed an increase and then decrease with increasing elevation.The species diversity of the soil seed bank was lower than that of the above-ground vegetation,and the species diversity of the two was highly significantly and positively correlated.