Study On The Community Characteristics And Biomass Allocation Of Different Plant Communities In Eastern Qilian Mountains

From 2018 to 2019,through observing the height,coverage,species number,vegetation composition and biomass of shrub and grass,the species importance value,diversity index and biomass of alpine shrub community were systematically analyzed;the correlation between community characteristics,diversity and biomass was discussed,and the community biomass model in the study area was constructed In order to clarify the plant community characteristics,resource status and regional community productivity in the eastern part of Qilian Mountains.The main results of this study:(1)The alpine shrub community in the eastern part of Qilian Mountains was investigated.Six species of shrub species belonging to 3 families and 4 genera were recorded.There are 86 species of grass belonging to 53 genera and 21 families.Salix oritepha,Salix sclerophylla and Spiraea alpina communities were distributed on the sunny slope,while Rhododendron capitatum,Rhododendron thymifolium and Potentilla fruticosa communities were distributed on the shady slope.Polygonum viviparum was the dominant species in grass layer.The shrub layer height and coverage of Salix oritepha and Salix sclerophylla were significantly higher than those of other communities(P<0.05);the shrub layer density of Rhododendron capitatum community was significantly higher than that of other plant communities(P<0.05);the height,coverage and density of herb layer had no significant difference(P>0.05).(2)The results showed that the species richness index of shrub layer and herb layer of Rhododendron thymifolium community was the largest;the species diversity index of shrub layer of Rhododendron thymifolium community was the largest,the species diversity index of grass layer of Salix oritepha community was the largest;the species evenness index of shrub layer of Rhododendron thymifolium community was the largest.The species evenness index of herb layer of Salix oritepha community was the highest.There was significant difference in diversity index of shrub layer among different communities(P<0.05),but there was no significant difference in herb layer among different communities(P>0.05).(3)The aboveground biomass of shrub in communities in alpine shrub community was 529.80 to 1 126.73 g·m^-2,and that of grass layer was 156.58 to200.65 g·m^-2.The belowground biomass of shrub was 1 895.81 to 4 614.81 g·m^-2,the belowground biomass of grass layer was 427.30 to 864.18 g·m^-2,the root shoot ratio of shrub layer and herb layer in Rhododendron capitatum,Rhododendron thymifolium and Potentilla fruticosa community were significantly higher than those of Spiraea alpina,Salix oritrepha and Salix screlophylla(P<0.05).The distribution range of aboveground and underground biomass in shrub layer was different in different communities;the distribution pattern of underground biomass in vertical structure of grass layer was different,but there was no significant difference in aboveground biomass distribution pattern(P>0.05).(4)The aboveground biomass of shrub layer was positively correlated with coverage,height,crown width and shrub volume per unit area(P<0.01),while species richness index,diversity index and evenness index were negatively correlated with aboveground biomass(P<0.01).Regression analysis showed that the biomass model based on coverage fitted the equation y=19.62x+276.54;the underground biomass of shrub was significantly positively correlated with shrub density,species diversity index and evenness index(P<0.01),positively correlated with species richness index(P<0.05),and negatively correlated with average shrub height(P<0.01).Regression analysis showed that the biomass model based on density fitted the equation y=2739.23x+987.92.(5)Aspect has significant effect on Shrub distribution(P<0.05),which was reflected in individual characteristics,community characteristics and diversity distribution pattern of shrub layer.The effect of slope aspect on grass layer was not significant(P>0.05),but there was no significant difference in height,coverage and density of grass layer in different aspects(P>0.05).The effect of aspect on community biomass was not consistent with shrub layer and grass layer.The aboveground biomass of shrub layer on sunny slope was significantly higher than that on shady slope,while underground biomass was significantly lower than that on shady slope(P<0.05).There was no significant difference in grass aboveground biomass between sunny slope and shady slope,but underground biomass was significantly lower than that in shady slope(P<0.05).