The Effects Of Dwarf Bamboo Fargesia Nitida On The Establishment Of Abies Faxoniana In The Subalpine Coniferous Forest In Wolong Nature Reserve

During the subalpine forest community succession, there are interaction between the regeneration of dwarf bamboo and dominant tree seedlings. Dwarf bamboo Fargesia nitida and Abies faxoniana are the dominant species in the shrub layer and tree layer, respectively. Many researches have shown that the interlaced roots of dwarf bamboo can influence the regeneration of trees and the growth of seedlings and saplings through competition for light, water and nutriments. We explore the effect of dwarf bamboo on the regeneration of A.faxoniana and estimate the effect of dwarf bamboo on the dispersal and community development.Regeneration and growth of A. faxoniana seedlings were restrained in the F. nitida-dominated zones and dispersal of the A. faxoniana population and development of an A. faxoniana-dominated community were affected. Closer to F. nitida clusters, the number of old seedlings and the efficiency of transformation (seedling number ratio of next BD class to the preceding BD class) were reduced (the older the A. faxoniana seedlings, the smaller the efficiency of transformation); the peak of number of seedlings moved from larger (â…¢) to the smallest size (â… ); the total biomass and allocation of biomass aboveground of A. faxoniana seedlings decreased; and the presence of F. nitida restrained the height growth of small (â… ) A. faxoniana seedlings (confirmed by regression of basal diameter and height). The expansion of crown of bigger (â…¢) seedlings increased in moderate density (Zone 4) of F. nitida.The effect of F.nitida on the regeneration and on the dynamics of the dominant population in subalpine dark coniferous forest, A.faxoniana, was analyzed in different environments of the dwarf bamboo. The results were as follows: in all stands, the survival curve of the A.faxoniana initial population appeared to be a type of Deevey-â…¢with an abundant seedling bank, high mortality rate in sapling stage and a higher life expectancy in small tree stage. The A.faxoniana initial population appeared to be a type of Deevey-â…¡I in LB, and a type of Deevey-â…¢in WB. There was a larger seedling bank but much lower mortality rate of seedlings in WB than those in LB. The curve of disappearance rate reached two peaks at the stage of seedling and small tree in LB, but just one at the stage of sapling in WB. During the stage from seedling to sapling, the number of A.faxoniana individuals was always larger in WB than those in LB, and it's reversed in the late stage of sapling. Both of the leaf weight ratio and the allometry (height / basal diameter) increased in HB. Our work shows that the A.faxoniana seedling establishment is prohibited intensively by a dense population of F.nitida, but the effect of low density of F.nitida may be two-sided.The role of canopy condition in the interaction between F.nitida and A.faxoniana seedlings was analysized. The results were: 1) the light condition under the canopy was different in different seasons and different canopies. The RPFD in the patch of coniferous forest was significantly lower than those in both of patch of board-leaved forest and patch of mixed forest. The RPFD in autumn was significantly higher than those in summer; 2) the F.nitida growed well under patch of board-leaved forest; 3) the more the board-leaved trees, the better the light condition and the well the growth of F.nitida. There was a significantly positively correlation between sum of basal area of board-leaved trees and RPFD under the canopy, and there was an opposite correlation between sum of basal area of coniferous trees and RPFD under the canopy or charactericstics of F.nidita; 4) the seedling establishment was influenced by both of the canopy condition and the F.nidita. There was a significantly negative correlation between characteristics of A.faxoniana seedlings and RPFD in summer. And there were the same correlation between characteristics of A.faxoniana seedlings and sum of basal area of board-leaved trees or characteristics of F.nitida. The number and height of A.faxoniana seedlings in the patch of coniferous forest was significantly higher than those in the other two patches of foests. The growth of F.nitida was different in different forests, and the difference was appeared on the establishment of tree seedlings. The growth of F.nitida was significantly inhibited by the coniferous trees, and that was good to the successful establishment of tree seedlings.In a word, the structure and dynamics of young population of A.faxoniana were influenced by F.nitida population. Our work shows that the A.faxoniana seedling establishment is prohibited intensively by a dense population of F.nitida, but the effect of low density of F.nitida may be two-sided. The growth of F.nitida was significantly inhibited by the coniferous trees, and that was good to the successful establishment of tree seedlings.