| As the core content of community ecology, the exploration of species coexistence and community construction mechanism has important meaning in development of the biological diversity theory and practice protection. In recent years, ecologists have carried out a lot of theoretical research around this topic. The most attractive ones are the niche differentiation theory and neutral theory, and the research of the both theories in the role of community construction has become a hot field for the international ecological community. For a long time, related researches usually focus on the woody plant in a single climate zone, but the study in the ecological transition zone between adjacent climate zones is rarely reported. Therefore, this article based on the first investigation data of 5 randomly selected 1 ha typical forest community plots in the 625 ha transition zone between warm temperate zone and north subtropical zone, using the structural equation model, species habitat correlation analysis, PCNM space model, multi-variable variance decomposition, spatial point pattern analysis and spatial distribution model fitting method, to analyze the community structure characteristics of spermatophyte and bryophytes in deciduous broad-leaved forest at Baotianman Henan, China. The article studied the influence of environment spatial heterogeneity on the communities construction of the above two kinds of plants, and proved that the ecological niche process and neutral process are both important factors influencing the species diversity in this region.This study firstly introduces the basic situation of woody plants in the 5 1ha dynamic plots. In these plots there are 162 kinds of woody plants, belonging to 40 families and 79 genera, and the composition of its flora is dominated by temperate zone characteristics. Most individuals are in small diameter classes and the diameter structure was an inversed J type. Dominant species is obviously in the community. The spatial distribution pattern of the whole community and species populations mainly showed aggregated distribution pattern, but the aggregation intensity decreases with the change of scales.Based on our preliminary research, in order to further understand the mechanism of species coexistence and community construction, we analyzed the vertical structure of woody plant communities in 5 plots, studied the interaction among topographic habitat, dominant species, canopy layer, sub-canopy layer and shrub layer in these plots, and examined the association between different vertical layers and the topographic habitat. Results showed that the dominant species influences the species diversity of vertical layers in different degrees in each community. Topography have different influences of species diversity in each vertical layer, there are 51.52%, 22.73% and 42.86% of trees, sub-trees and shrubs respectively show significant correlation with the habitat. These proved that in this area the dominant species is an important factor influencing the community vertical structure, and the differences in the use of resources of each vertical layer promoting the coexistence of species in different vertical layers. Species in different vertical layers have different habitat preferences in terrain.We took the Quercus aliena var. acutiserrata which has the highest richness in the plots as the research object, using the principal coordinates of neighbor matrices(PCNM) combined with multiple linear regression to analyzes the spatial structure characteristics of plant community, through the variance decomposition to quantify the contribution rate of topographic variables, soil variables, spatial variables and stand density to species distribution. The results suggest that there is widespread variability in plant community structure on different scales, and the spatial variable is its common characteristics. Topography variables, soil variables and PCNM variables all together explained 31.48% of total variance in species distribution. The stand density can explain 19.49% after introduced in the variance decomposition. These proved that the space variable is an important factor affecting community structure, since it had the higher explanation proportion in species distribution. The soil variables are important determinants of species distribution at small scales, the explanation proportion of topographic variables is low, and the density dependent effect is one of the important mechanisms in the formation of species distribution pattern.In order to explore the effects of environmental heterogeneity to the higher plants in other taxa, this paper studied the construction mechanism of epiphytic bryophytes on the platform of permanent plots for the first time. We quantified the spatial position of epiphytic bryophytes with the aid of the rich spatial information in permanent plots, optimized the processing method in dealing with the abundance, tested the association between the epiphytic bryophytes and the terrain habitat, and analyzed the contribution rate of topography variables and spatial variables in species distribution at different scale and in different community types. Results revealed that there are 20.99% of bryophytes have the preference in terrain habitat. Spatial variables and topographic variables together explained 18.69% in the distribution of all bryophytes species, 34.71% in the distribution of the aggregated distributing bryophytes species, 18.00% in the distribution of the random distributing bryophytes species, and explained 52.02%~20.50% in the distribution of three different bryophytes associations. These demonstrate that, represented by the micro topography variables and spatial variables, environmental spatial heterogeneity has an impact on the community construction of epiphytic bryophytes in this zone, and this impact will change with the variation of external environmental conditions. Meanwhile the contribution rate of neutral process, which is represented by spatial variables, is larger than the contribution rate of niche process, which is represented by micro topographic variables.Finally, in order to explore the effects of forest community on the construction of epiphytic bryophyte communities, we used the linear regression analysis to study the effects of host trees and stand structure on the community diversity and species distribution of epiphytic bryophytes. The results showed that the relationship of host trees and epiphytic bryophytes is weak in this area. There are significant correlations among stand structure, the species diversity of epiphytic bryophytes and species distribution. Represented by the three significant indexes of density, DBH and basal area, stand structure explained 20.79% in the distribution of bryophytes species. After the control of spatial variables and environmental variables, the explanation of the pure stand structure in the distribution of bryophytes species is still up to 12.71%. These all proved that the stand structure plays an important role in the distribution and community construction of epiphytic bryophytes.The results of the study showed that the environmental spatial heterogeneity has played an important role in the species distribution and community construction of spermatophytes and bryophytes in Baotianman Henan, China, the niche theory is one of the main mechanisms of species coexistence, in addition, neutral process and density dependence also produce important influences on species distribution in this area. But the contribution of each factor is not that big, so the species diversity maintaining mechanism needs further study in this area, especially in the research of bryophytes. |
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