Biomass Allocation Pattern Of Understory Vegetation In Different Succession Stages In Dashan Zongyang.

In this study,three representative succession stages of forest community have been selected in Dashan Village,Zongyang Country,namely: the secondaryShrubbery,Coniferous forest and Coniferous broad-leaved mixed forest.There were 9 sample plots in three representative succession stages and it was setted that a standard of 20m×20m in each investigation plots. Biomass of understory vegetation were determinated by using clear cut; Comparing different successional stages of understory vegetation biomass allocation pattern was made with the principle of ecological succession series; Single-factor analysis of variances for physical and chemical properties of soil at different succession stages was taken by DPS V.3.01 software;analyzing the relativities of understory vegetation biomass allocation pattern and physical and chemical properties of soil were done by SPSS statistical software; the results showed that:(1)The comparative study on total understory vegetation biomass of different succession stages,knowing:total understory vegetation biomass of the secondary Shrubbery was the largest, that was 2680.098g/m2,which contained the shrub layer biomass 2555.262g/m2 and the herb layer biomass 124.84g/m2;Coniferous forest follows, where total understory vegetation biomass was1632.553 g/m2,which contained the shrub layer biomass1495.535 g/m2 and the herb layer biomass 137.018 g/m2; and then Coniferous broad-leaved mixed forest,where total understory vegetation biomass was 736.204 g/m2, which contained the shrub layer biomass 550.692 g/m2and the herb layer biomass 185.512 g/m2.(2)From the comparison of layer allocation of total understory vegetation biomass in different succession stages,drawing: the biomass of shrub layer and the biomass of herb layer accounted for 95.34% and 4.66% of total understory vegetation biomass in the secondary Shrubbery,91.61% and 8.39% in the Coniferous forest,and 74.80% and 25.20% in the Coniferous broad-leaved mixed forest.It showed that the biomass of shrub layer>the biomass of herb layer in different succession stages.In the progress of succession,it gradually decreased that the gap between the proportion of the biomass allocation to shrub layer and the proportion of the biomass allocation to herb layer.(3)Compared with different succession stages, the biomass of understory plant species exists significant difference.In the secondary Shrubbery, the biomass of shrub layer focused on a few understory plant species including Clerodendron cyrtophyllum, Melia azedaeach, Mallotus apelta,Vitex negundo,They accounted for 31.76%, 28.05%, 12.87%, and 12.28% of the shrub layer biomass respectively. In the Coniferous forest, the biomass of shrub layer focused on such understory plant species as Quercus fabri, Platycarya strobilacea, Pinus massoniana, Dalbergia hupeana, Wisteria sinensis. They accounted for 23.85%,14.88%,14.02%,13.80%,and 9.53% of the shrub layer biomass respectively. And in the Coniferous broad-leaved mixed forest, the biomass of shrub layer focused on such understory plant species as Euscaphis japonica, Castanea seguinii, Lindera glauca,and Vitex negundo. They accounted for 22.74%,15.35%,10.56% and 8.65% of the shrub layer biomass respectively.With the positive succession of the community,it reduced gradually that the gap among the biomass allocation of understory plant species . Dominant species were more and more obvious in the shrub layer.(4)By the comparison of organ distribution of understory vegetation biomass in different successional stages,deriving: the proportion of root biomass was the largest in the shrub layer,appoximately accounted for 50% of total shrub layer biomass, followed by the proportion of stem biomass,and leave is the fewest.While aboveground biomass of the herb layer was much less than the underground biomass. But with the restoration succession,the gap among organs allocation proportion of the shrub biomass gradually reduced. And the gap between aboveground biomass proportion and underground biomass proportion also narrowed in the herb layer.(5)Based on the study of soil physicochemical property ,it was founded that progressive succession could improve the physical condition of soil ,increased soil fertility and reserved soil nutrients.In the progress of succession,siol bulk density from large to small was the secondary Shrubbery>the Coniferous forest>the Coniferous broad-leaved mixed forest, but it increased in turn that soil water content and>0.25mm water-stable aggregate content. Especially in the 0 -10cm soil layer, the law was obvious, but as the soil depth increased, the difference was not significant.Except the content of Available Phosphorus,which was relatively stable,the rest soil nutrient content gradually increase in the progress of succession.As the soil depth increased ,the difference was in decline.The nutrient content of topsoil was higher than the subsoil in every successional stage .(6)The correlation analysis of understory vegetation biomass allocation and soil physicochemical property showed that there was negative correlation between the proportion of shrub layer root biomass,shrub layer stem biomass, herb layer underground biomass and the content of soil water, organic matter, total N, available nutrients,which was correlative with the proportion of shrub leave biomass and herb aboveground biomass.The topsoil physicochemical property influnenced the distribution of herb layer biomass largely,while the physicochemical property of subsoil correlated evidently with the allocation proportion of shrub layer biomass. Soil pH correlated weakly with the allocation proportion of understory vegetation biomass.