Study On Interspecific Association And Niche Characteristics Of Seven Bryophyte Species In Hani Peatland In Changbai Mountains

Based on investigation of typical bryophytes habitats, measurement of environmental factors and analysis of peat samples, the inter-specific relationships were analyzed in the methods including variance ratio,χ2-test , Spearman rank correlation and Jaccard index, and the niches and their differentiations of seven species of bryophyte were researched in the methods including Levins and Pianka formulas and canonical correspondence analysis (CCA). Furthermore, the relationships of interspecific association and niche were discussed. The main conclusions are as following:1)The interspecific association of Sphagnum magellanicum, S. fuscum, and Polytrichum juniperinum was positive, and in open area the interspecific associations were similar between the three bryophyte species and three vascular plants including Rhododendrom parvifolium, Smilacina japonica, Ledum palustre var. ngustum. The interspecific association of S. palustre and the three vascular plants was opposite to the three bryophytes'. The interspecific association of S. fallax and other bryophytes was negative, and S. capilifolium was as same as it. The interspecific association of Aulacomnium palustre and other bryophytes was neutral.2) Through comparison of interspecific association in two habitats, I found that canopy density was one of the most important environmental factors influencing vegetation distribution pattern in Hani Peatland. In this paper, ins open area (or forest edge) habitat the species of higher significant values appeared positive association and the species which have great difference of significant values in two different habitats appeared negative association.3) The niche breadths of the seven bryophytes decreased in the order of A. palustre(0.677)>S. fallax(0.670)>S. magellanicum(0.661)>S. capilifolium(0.651)=P. juniperinum(0.651)>S. palustre(0.547)>S. fuscum(0.512). S. fuscum was niche-specific specie, while A. palustre was niche-general specie.4)From the overall mean overlap values of environmental variables, the maximum occured in electrical conductivity gradient(0.9205) and the three low values occurred in depth to water table (0.625), tree coverage (0.7144)and pH of surface water (0.7553) gradients. Bryophytes niches mostly segregated along these three gradients. Depth to water table, tree coverage and pH were three most important environmental factors influencing distribution of bryophytes. Some bryophytes species-pairs with high overlap values in all niche dimensions lived in similar habitats in order to increase water use efficiency. The high overlap values could offer indirect evidence of competition, however, accurate results could be verified by transplant experiments.5)Canonical Correspondence Analysis accurately described the differentiation of bryophyte habitats. The niche differentiations were more obvious among S. capilifolium, S.palustre in tree coverage and pH gradients, S. fallax and A. palustre in depth to water table gradient. The niches in all environmental dimensions were similar among S.fuscum, P. juniperinum, S. magellanicum.6) The positive association went with large niche overlap in one or more niche dimension. The reasons of negative association were complicated. Firstly, when the habitats of species were different, in this case the niche overlap of the species was low. Secondly, while negative association may be caused by resource competition, the niche overlap of the species is high.