Spatial And Temporal Pattern Of Biodiversity And Its Correlation With Aboveground Biomass In Coniferous And Broadleaved Mixed Forests Of Jiaohe,Jilin

The effect of biodiversity on ecosystem functioning has long been a hot spot in the scientific and public focuses. Based on field investigation and plant functional trait measurement as well as DNA barcode sequences in the coniferous broadleaved mixed forests of different successional stages after selective cutting in Jiaohe, Jilin Province, we investigated the spatial and temporal patterns of biodiversity with forest successional stages (half-mature forest, near-mature forest, mature forest, primary forest) and with habitat types (low valley, downhill, high valley, hillside, mountaintop). The relationship between biodiversity and aboveground biomass in the forests with different successional stages was also explored. The main results were as follows:(1) With forest development from half-mature forest, near-mature forest, mature forest to primary forest, the dominance of dominant tree species, such as Pinus koraiensis and Tilia amurensis was enhanced and pioneer tree species were also replaced by shade-tolerance tree species. The size-class distributions were inverse "J" type for the whole individuals in the four forest stands.(2) The aboveground biomass increased from half-mature forest to mature forest, however, there were no significant differences between mature forest and primary forest for the aboveground biomass (p>0.05). In the primary forest, aboveground biomass showed an increase from the low valley to the mountaintop. Topographic factors had no significant effect on the aboveground biomass in the half-mature forest, near-mature forest and mature forest (p>0.05), while aboveground biomass in the primary forest was significantly affected by elevation and convex (p<0.05).(3) There were significant differences among plant functional traits in the forests with different successional stages. There were no significant correlations between aboveground biomass and specific leaf area as well leaf nitrogen content in both half-mature forest and near-mature forest, however, signifcantly negative correlations were occurred in both mature forest and primary forest (p<0.05). In the primary forest, aboveground biomass was significantly negative correlated with the specific leaf area and leaf nitrogen content in the habitats of downhill and mountaintop (p<0.05).(4) Species richness and Shannon-weiner index showed a trend of increase with forest development, however, there were no significant differences for the Pielou’s evenness index among the forests of different successional stages (p>0.05). With forest development from half-mature forest to primary forest, functional richness, functional evenness and Rao’s secondary entropy were firstly decreased and then increased, net relatedeness index (NRI) and nearest taxon index (NTI) were gradually decreased while phylogenetic diversity PD showed a trend of gradual increase. In the primary forest, the NRI showed a trend of decrease while NTI was firstly increased and then decreased from the low valley to the mountaintop. Species richness, functional richneass and phylogenetic diversity were significantly positively related for each other (p<0.05).(5) The aboveground biomass was significantly positively related to the species richness, functional richness and phylogenetic diversity in the primary forest (p<0.05). Functional richness explained 5% and 12% variations of the aboveground biomass in the near-mature forest and primary forest, respectively. Significant positive correlations between phylogenetic diversity and aboveground biomass in the other three forest stands except no significant correlation in the near-mature forest. In the primary forest, aboveground biomass was significantly positively correlated with the species richneass and functional richness in the habitats of low valley and mountaintop. Moreover, species richness explained more variations of the aboveground biomass than functional richness.In general, topographic factor had a significant effect on aboveground biomass, plant functional traits and biodiversity in the forests with different successsional stages, and a strong effect in the primary forest. There were some correlations between aboveground biomass and plant functional traits, especially for the specific leaf area and leaf nitrogen content. Moreover, these correlations were significant in both mature forest and primary forest, and in both habitats of low valley and mountaintop. In addition, biodiversity can be recognized as an important drive to the aboveground biomass.