Analysis Of Growth Porperities Of Stolon And Age Structure Of Sabina Vulgaris Population In Mu Us Sandy Land

In order to discuss the growth conditions,survival mechanisms and development rules of S.vulgaris population,the natural population of S.vulgaris was divided into four developmental stages(Ⅰ,Ⅱ,ⅢandⅣ)which based on the regenerate process of community in Mu Us sandy land.Using the WinDENDROTM analyzing system of tree-ring image measured the age and tree-ring width.Analysed the growth properities,time-specific life table,age structure and succession rules of S.vulgaris population,the results showed that:1.The annual radial growth curve of S.vulgaris presented unstable fluctuation and the variation coefficient was 48.61%,when the tree age was below 30 years.In the first 10 years of growth stage,S.vulgaris grew slowly.The radial fast-growth stage of S.vulgaris was from 11 years to 20years,then the annual radial increment declined with the increased age.The average tree-ring widths ofS.vulgaris were reflected that developmental stageⅡ＞developmental stageⅠ＞developmental stageⅢ＞developmental stageⅣ.There existed the exponential function between diameters and ages at the early-growth stage.Diameters were correlated linearly with ages in the maturing stage.These two growth models represented remarkably correlation at 0.01 levels.2.The stolon of S.vulgaris grew slowly in initial regenerate stage,the annual increment increased rapidly with the increased age,the peak value appeared when the age was 20 years old.Then the annual increment decresed fastly with the increased age and the annual increment kept stabilization.Annual increments were correlated linearly with ages in the early-growth stage.There existed the power function between annual increments and ages at the maturing stage.The coefficient of these two models were 0.74 and 0.85 at 0.01 levels.The ages of S.vulgaris individual were correlated linearly with shrub areas,the coefficient was 0.82 at 0.01 levels.3.There existed two peaks of mortality rate in the lifespan,one was in 1 a～10a age class,mortality rate reached to 94%,and the other started at 51 a～60a age class,mortality rate between 27%and 47%.Vanish rate had the similar fluctuation as the mortality rate. The survival curve of S.vulgaris population conformed to the type of DeeveyⅢ.This meant S.vulgaris population should be a increscent population.4.Age structure of S.vulgaris population were divided into three types.In development stageⅠandⅡ,displaying a pattern of pyramid typical of expanding populations.In development stageⅢ,the age structure of the plants was cone-shaped, indicating stable populations.In development stageⅣ,the age structure of the populations was seen as a reversed pyramid,indicating typical ageing populations.5.There was a clear trend of transition from the initial developmental stage,through the steady stage,to the ageing stage in S.vulgaris populations from flats to the ridge of the dunes.