Maintenance Mechanisms Of Species Diversity At Different Spatial Scales In Gaole Mountain National Nature Reserve

Species diversity is an indicator of species richness in a region,and it is also the basis of maintaining ecological stability.Gaole Mountain National Nature Reserve is located in the transitional zone of climate between north and south of China,with diverse community types and rich biodiversity.By studying the maintenance mechanism and construction process of species diversity in this area,it can provide research references for the conservation of species diversity and the construction of near-natural communities.This study took temperate deciduous broad-leaved forest as the research object,three 1hm2 forest monitoring plots were set up in Gaole Mountain National Nature Reserve in Henan Province.Through the investigation of all species information and environmental factors in the sample site,Spatial point pattern analysis,species abundance model fitting and community pedigree structure were used to comprehensively and systematically analyze the internal mechanisms of species diversity maintenance at different spatial scales.The main research results are as follows:(1)There are 31 species of woody plants in plot 1,with a total of 2789 plants.Among them,Quercus variabilis 34.68%,Quercus acutissima 30.76%,Vitex negundo var.cannabifolia 9.67%,Lindera glauca 6.25%and Cotinus coggygria 4.44%ranked the top 5 in importance values,which were dominant in the sample land and were the main tree species in the stand.(2)It was found that the overall diameter class structure of the community was inverted "J" type,which belonged to the growth type community.In terms of species distribution,Pistacia chinensis,Dalbergia hupeana,Morus mongolica,Vitis amurensis and Diospyros kaki were randomly distributed,while Cotinus coggygria,Quercus acacia,Vitexia vitae,Pepper oryzae and Quercus variabilis showed obvious aggregation distribution.The six common populations in the sample plot all showed an aggregation distribution state at small scale.With the increase of the scale,the aggregation degree of the population gradually weakened,and finally presented a random distribution,uniform distribution or random distribution and uniform distribution alternately.(3)The interspecific association analysis showed that:Quercus variabilis and Quercus acacia,Quercus variabilis and Cotinus coggygria,Piper aspergillus and Cotinus coggygria showed negative spatial correlation,and there was a competitive and exclusive effect.The spatial correlation between Quercus variabilis and Vitex vitex,Quercus variabilis and Peppercorns var.variabilis was mainly positive with the increase of scale,which indicated that the demand for environmental resources was similar or complementary at large scale.(4)The lognormal model,Zipf-Mandelbrot model,broken stick model,niche priority occupation model,composite community zero-sum polynomial model and Volkov model were used to fit species abundance distribution at six sampling scales.It was found that the optimal fitting models for the distribution of woody and herbage species abundance in the study area were all neutral theoretical models.(5)The community diversity index(PD)gradually increased with the increase of scale,and the increase trend was obvious.The diversity of the community was significantly different among different scales,and reached the maximum when the scale was 50m×50m.The results indicated that different spatial scales had significant effects on the community diversity,and the larger the scale,the higher the diversity of the community.(6)Both NRI and NTI lineage indices indicated that community phylogeny first converged and then diverged with the increase of study scale.The community phylogeny structure at different spatial scales showed that the community phylogeny was aggregated at small scales,indicating that habitat filtration dominated the community species coexistence at this scale.The divergence of species lineages at large scales suggests that the coexistence of species in the community has been transformed from habitat filtering mechanism to competitive exclusion.The research results based on point pattern analysis and pedigree structure method are more inclined to the species coexistence caused by the deterministic process of niche theory,and it is greatly affected by the spatial scale.Based on species abundance model fitting,it is found that neutral processes are the internal mechanism of species diversity maintenance at any scale,Therefore,the niche-neutral continuum hypothesis of integration theory is more convincing for the formation of species diversity in protected areas.This study provides scientific guidance for the conservation of species diversity and ecological restoration in the reserve,at the same time,the mechanism of species diversity construction can also be applied to the construction of near-natural communities in cities.