Effects Of Scales And Habitat Heterogeneity On Species Diversity And Above-Ground Biomass Of Quercus Aliena Var.Acuteserrata Forest In Taibai Mountain

The Qinling Mountains are the hotspot of biodiversity study in China with rich vegetation resources and high species diversity.To study the maintenance mechanism of biodiversity and ecosystem function during vegetation restoration in the Qinling Mountains,the effect of scale and habitat heterogeneity were analyzed on community structure characteristics,species-abundance distribution patterns,above-ground biomass distribution and the relationship between species diversity and above-ground biomass based on all trees with DBH ?1 cm in two 1.5 ha permanent plots which were Quercus aliena var.acuteserrata primary forest(PF)and secondary forest(SF)on the northern slope of the Taibai Mountain.The results were as follows:1.2,840 and 2,839 trees were recorded in the PF and SF plots,respectively.Most species were mainly distributed in the northern temperate zone.The two plots belonged to high and moderate minglings.The diameter of Q.aliena var.acuteserrata in the two plots followed a unimodal distribution(more younger trees than older trees),and the companion species(e.g.,Sorbus alnifolia,Acer davidii,Cornus kousa and Staphylea holocarpa)were inverted ?J? shapes.Tree individuals in communities followed an aggregated distribution.The aggregation of dominant species were the strongest at 0?2 m scales,while it gradually changed to random or uniform distribution as scale increases.2.Significant effects of scale were found on ecological processes of the primary and secondary forest communities construction.Niche models and neutral model could fit the species-abundance distribution at small scale in PF,while the significance of neutral processes gradually disappeared as scale increased.Niche process and neutral process effected the species-abundance distribution at small and medium scales in the SF plot,whereas neutral process dominanted at 100 m×100 m scale.In addition,relative importance of different ecological processes in community construction was also effected by habitat heterogeneity.3.At the same sampling scale,above-ground biomass in the PF plot was higher than that in the SF plot.No significant correlation was found between above-ground biomass and sampling scale in each plot.Meanwhile,habitat heterogeneity and diameter class structure would affect the distribution of above-ground biomass in plots.4.Species diversity significantly affected above-ground biomass at 20 m×20 m scale in the PF plot.Above-ground biomass gradually decreased when species diversity increased.The species diversity was positively correlated with above-ground biomass at 10 m×10 m scale,while negatively correlated at 30 m×30 m scale in the SF plot.Species diversity was positively correlated with above-ground biomass in habitats with high available phosphorus and low convexity in the SF plot.