| In the way of surveying in permanent sample plot, the paper studies the dynamic character of the plant community of Wulingshan Natural Reserve between middle and lower ectone during its embryoism stage of cutting succession and concludes the dynamic regularity of the main ecological indexes. The main result is as below:(1) the dynamic of population density The density of most of the herbs is relatively low before cutting and raises all during succession stage. It's obviously lower in year 2000 than each year before. The density of heliophilic herbs declines stepwisely. To the shrubs, the density of them gets higher during the succession stage than before cutting. The density of the main species in the plot at different altitude shows different dynamic character, it's caused by variant environmental condition. The density elevation of the species in the plot at lower altitude is more conspicuous than that of the higher. To the arbors, the density of most of them in plot 8 is visibly lower than the same species in plot 4. With the developing of the succession, all kinds of them have lower density in year 2000 than in year 1992.(2) the dynamic of population spatial pattern Among the herbs, the plant which has broader ecological amplitude has higher degree of aggregation during the embryoism stage of cutting succession, the I indexes of them are higher than others. The strong heliophilic species presents in the plot only in year 1992, no matter it's I index is high or not, it distinguishes from the community soon. The photophygous species appear in the plot late, the I indexes of them are low. Developing to year 2000, the index of the main herbs shows the character of regression back to the stage before cutting. To the shrubs, the plants that have strong competing power grow prosperity, the number of their individual increases, and the I index raises also. The weak plant is inverse. From year 1992 to year 2000, the ratio of the species that have higher I index increases in the shrub layer. To the arbors, the I index of all the species are in the lowest level before cutting. After succession, the I indexes of them are higher than before cutting all. The I index of the same species raises more in the lower altitude plot than in higher plot. When the succession developed to year 2000, the I index of main arbor species declined obviously, but still contagious distribution.(3) the dynamic of species Comparing with the herb species before cutting, the quantity of them increases visibly during the succession stage. The species in the plot73changes much in different year, it shows that the plant community is in the very unstable stage. The shrub species shows the dynamic character of number increasing, compositional structure changing complex, the ratio of photophygous species growing large. To the arbors, the species number in the succession stage is more than before, but it changes inconspicuously during the succession stage. Most of the species present in the plot in year 1992 reserve in year 2000.(4) the dynamic of importance value The herb species having broader ecological amplitude are in the dominance position permanently during the succession stage. Influenced by the proliferation of the plant in the upper layer, the importance value of the heliophilic species descends and that of the photophygous species elevates. The shrubs show similar dynamic character as the herbs. The dominance position of broad ecological amplitude shrubs gets visible step by step. To year 2000, the shrubs layer shows dominance position in the community; they are in their prosperity stage.(5) the dynamic of diversity index and evenness index The diversity index and the evenness index of the herbs is higher in the stage of embryoism succession than before cutting. They decline to the lowest level in year 1995 but elevates in year 2000 again. The two indexes of shrubs show great difference between plot 4 and plot 8. They decline to the lowest level in year 1995 in plot 4, but elevate continua...
|
PDF Full Text Request