Study On Phylogenetic Structure Of Deciduous Broad-leaved Forest In Xiaoqinling Nature Reserve

It can deepen people’s understanding of the pattern of biodiversity and its causes to understand the pattern of biodiversity based on different scales and models from the perspective of systematic evolution.Therefore,based on the 1 hm2 plot of deciduous broad-leaved forest in Xiaoqinling Nature Reserve,this study analyzed the phylogenetic structure characteristics of the woody plant community,and assessed the Impact on community phylogenetic structure of deciduous broad-leaved forest in Xiaoqinling Nature Reserve from topographic environment and spatial characteristics of the woody plant..Using the constrained and unconstrained zero models,the phylogenetic structure characteristics of the community were explored based on the spatial scales of 10m×10m,20m×20m,and 25m×25m.The results are as follows:(1)Based on different models,the zero model plays an important role in the distribution of the pedigree structure.In contrast,the constraint zero model can better detect the actual distribution of the pedigree structure of the study area on different research scales.The results show that the NRI and NTI values are consistent across the three different research scales using the unconstrained zero model simulation and are positive.The phylogenetic structure pattern is aggregated;the constraint zero model shows different results on three different scales: both NRI and NTI show aggregated pedigree structure at 10m×10m and 20m×20m research scales.Distribution,divergence distribution of spectrum structure at 25m×25m research scale.(2)Based on different spatial scales,It is found that the choice of study scale has a great influence on the distribution of the community phylogenetic structure pattern.With the increasing of spatial scale,the phylogenetic structure of the 1 hm2 plot of Xiaoqinling Nature Reserve tends to disperse or aggregation distribution of the degree reduced.It is found that the effect of spatial scale on the community pattern is mainly reflected in the selection of species library through comparative analysis.The larger the spatial scale of the selected study,the larger the species pool,the more the community spectrum structure tends to converge and distribute;on the contrary,the smaller the spatial scale is.The species pool is relatively small,and the community lineage structure tends to be distributed.(3)Based on the structural characteristics of woody plant phylogeny,it is found that the community structure of the convergent or divergent community is the main manifestation of this region,and it does not appear to be random.It is inconsistent with the random pattern proposed by the neutral process and follows the niche hypothesis.In the hypothesis of niche conservation,when the unconstrained zero models is simulated,the phylogenetic pattern presents a convergent distribution,so the habitat filtering effect is stronger.The woody plants with similar genetic relationships are brought together and become the important ecological process which influence coexistence of the existing species in the study region.In the constrained model simulation,on the scale of 10m×10 m and 20m×20m,the distribution of phylogenetic structure patterns can be used to infer that the habitat filtering effect is stronger;on the spatial scale of 25m×25m,the phylogenetic structure pattern is distributed.So competitively excluded is the main reason for the scattered distribution of plant community phylogenetic on this scale.In order to further explore the influence of environmental factors on the distribution of species pedigree structure of deciduous broad-leaved forest communities in this area,the effects of terrain factors and spatial factors were studied using the linear model,principal axis neighborhood method,variance decomposition method,and the results are as follows:(1)Spatial factors are important environmental factors that affect the distribution of species structure of woody plant species in deciduous broad-leaved forests of Xiaoqinling Nature Reserve;different spatial scales have important influence on the community lineage structure;different zero models have little effect on the structure of the tree lineage.Topographic factors interpret the pedigree of the community in the study area very low,and their contributions to the pedigree structure are not significant.However,as the spatial scale becomes larger,the interpretation of topographic factors also increases.This may be because the plot area is too small.The terrain structure did not change much and it failed to show the influence of terrain factors on the structure of the spectrum.Comparing three research scales and two zero models,the effect of environmental and spatial factors on the spectrum structure was evaluated by variance decomposition.The results showed that pure spatial factors accounted for more than 10% of the spectral structure of the deciduous broad-leaved forest community in this region.Pure terrain The interpretation rate of the factor is basically below 10%.It can be seen that the degree of influence on the formation of the spectral pattern distribution is larger than the terrain factor.With the increasing the spatial scale,the pure terrain factor,the pure space factor and the two affect each other.The overall rate of interpretation has been strengthened.According to the hypothesis of the proportion of resources in the niche theory,it shows that the niche theory plays an important role in the coexistence of communities in the region.(2)With the increasing of altitude,the phylogenetic structure of Xiaoqinling shows an increasing distribution pattern of aggregation.The coexistence of species in the Xiaoqinling Nature Reserve was affected by the two ecological processes of habitat filtration and competition exclusion.There is a certain degree of competition in the low-altitude area;the significance of the t-test of the spectral structure index with altitude changes decreases.The clustering degree of the 10m×10m and 20m×20m lineages at the study scale showed a significant and significant positive relationship with different altitudes.On the scale of 25m×25m,the phylogenetic clustering degree increased with elevation.Different zero models show no significant.In conclusion,based on this study,we explored the characteristics of community pedigree structure of deciduous broad-leaved forests in the warm temperate zone-northern subtropical transition zone on different scales and models,and discussed the influence of topographic environment and spatial characteristics on the phylogenetic structure of communities in the montane deciduous broad-leaved forest.A more in-depth analysis was carried out,and the results of the study will provide people with a new level of understanding of the mechanisms for maintaining the biodiversity of the transitional area and the causes of the biodiversity pattern,and promote the protection of regional biodiversity.