Population Structure Of Tree Species And Environmental Interpretation In Coniferous And Broadleaved Mixed Forest In Changbai Mountain

The original broad-leaved Korean pine forest is the zonal climax vegetation type in the western of Changbai Mountain.Since the 20th century,the resource of original broad-leaved Korean pine forest has been seriously destroyed in Changbai Mountain,which resulting in a large area of secondary forest community.Though the conservation of original broad-leaved Korean pine forest and restoration of degraded secondary forest community are extremely urgent,our knowledge about the structure characteristics of population and community in the forest ecosystem are still limited.Spatial structure of tree species was analyzed in secondary poplar-birch forests,secondary mixed conifer and broad-leaved forest and original broad-leaved Korean pine forest in Changbai Mountain in this paper. In order to enrich and extend the theories of trees coexistence,we studied the relationships between spatial distribution of trees and local habitat factors and the sex ratio pattern of dioecious tree species. And competition between same-sex trees and between opposite-sex trees was analyzed to reveal the effect of inter- and intra-sexual competition on radial growth.This paper aims to provide theories for restoration and management of broad-leaved Korean pine forest in Changbai Mountain.The brief results are as follows:1.The spatial distribution of tree species and environmental interpretations in the mixed forest.In secondary poplar-birch forests:environment factors regulated mainly the spatial pattern of saplings and small trees,but there was little effect on the distribution of big trees.Soil moisture and soil pH showed significant influence on the distribution pattern of most tree species,and soil nutrition (including total N,total P,total K) showed a little effect.Environment factors showed a poor interpretation on spatial variation of tree species(including variation interpreted by environment alone and variation interpreted by environment and space in common),but pure spatial variables exhibited strong interpretation power.And only 8%of the variation in community structure could be accounted by environment variables.In secondary conifer and broadleaved mixed forest:dominant trees of Pinus koraiensis and Quercus mongolica and smaller trees of Q.mongolica tended to random spatial distributions at almost all scales.Soil moisture and soil pH were key environmental factors regulating the spatial structure of the community and individual tree species.Environment factors greatly affected the spatial distribution of Acer barbinerve,A.pseudo-sieboldianum,Picea jezoensis and Fraxinus mandshurica, but there was little effect on other tree species.Altogether 21%of the variation in community structure could be accounted by environment variables.In original broad-leaved Korean pine forest:P.koraiensis,Q.mongolica,Malus baccata and Maackia amurensis were distributed randomly in the study plot,and A.mono,F.mandshurica and Tilia amurensis were in a clumped pattern at most studied scales.Among 10 species pairs which consisted of five dominant tree species,there were three species pairs(P.koraiensis-F.mandshurica; P.koraiensis-Q.mongolica;Q.mongolica-F.mandshurica) which showed independence.Others showed mutual attraction at several scales.Among six species groups which consisted of five dominant tree species,one species groups(P.koraiensis-Q.mongolica-F.mandshurica) showed independence.Other species groups(P.koraiensis-Q.mongolica-A.mono;P.koraiensis-Q.mongolica -T.amurensis;Q.mongolica-A.mono-F.mandshurica;Q.mongolica-A.mono-T.amurensis; A.mono-F.mandshurica-T.amurensis) showed mutual attraction at several scales.The groups of five tree species showed mutual attraction at 1-12m scales.Environment factors exhibited low explanations for spatial structure of tree populations and community.2.Sex ratios and radial growth pattern in dioecious tree speciesThe diameters between genders were not significantly different in the secondary forests,but the diameters of male trees were significantly greater than those of female trees in the old-growth forest. The sex ratio did not significantly deviate from 1:1 in the secondary forests,but was male-biased in the old-growth forest.Spatial segregation between genders within F.mandshurica population was found in secondary forests,but the male trees and female trees were spatially independent in the old-growth forest.Significant segregation between small females versus big males,and big females versus small males was found in the secondary forests,this may also exhibit an intersexual competition effect,which limits the occurrence of small individuals in the vicinity of opposite-sexual big trees in dioecious tree species.The numbers of males and females increased as increasing sample areas for dioecious tree species,F.mandshurica and Populus davidiana.Sex ratios exhibited significant density-dependent for two dioecious species.Sex ratios decreased with increasing local stand density for F.mandshurica and P.davidiana.Sex ratios showed different responses to density of reproductive individuals and population density in different forest types.The sex ratios of P.davidiana decreased as increasing stem density of reproductive individuals and population density,and those of F.mandshurica increased as increasing stem density of reproductive individuals and population density in secondary poplar-birch forests.But contrary results were found in secondary conifer and broadleaved mixed forest.Male trees had a faster stem growth rate than female trees in secondary poplar-birch forests. Stem growth rates are positively affected by soil moisture and tree size for both genders.And female trees are more responsive to climate variations than male trees.The growth rates of female trees were negatively affected by neighboring competition from other female trees at all neighborhood distances between 1 and 10m,but were not significantly affected by male trees.The growth rates of male trees were negatively affected by neighboring competition from male trees,but were not significantly affected by female trees.These results suggest that intrasexuai competition(male-male competition and female-female competition) may cause difference in stem growth for both genders.The radial growth rate of males was significantly larger than that of females in Taxus cuspidata. The radial growth rate associated negatively with neighboring competition for both sex.And female trees were affected more negatively by neighboring competition than males.Different response way to climate factors for males and females was found.Female trees tended to be more sensitive to the variations of temperature in previous August and October.