Stability Of Several Communities In Deciduous Broad-leaved Forest In Jiajin Mountains Giant Panda Habitat

The stability of forest communities is critical to the long-term sustainability of forest ecosystem functions and services,and deciduous broad-leaved forests play a significant role in the conservation of biodiversity and ecological environment in alpine subalpine regions.Differences in vegetation productivity,community structure,soil nutrients and soil structure among different constructive species,environmental heterogeneity and asynchronous successional processes in deciduous broad-leaved forests control the stability dynamics of different deciduous broad-leaved forest communities.Since the establishment of the Giant Panda National Park,Jiajin Mountains has been planned as a key objective for the restoration of giant panda habitat and the construction of the giant panda corridor,and the stability of deciduous broad-leaved forest communities in Jiajin Mountains have important research value.Based on this,this study investigates the influences of community type on species diversity,community structure,biomass,soil physical and chemical properties,soil antiscourability,root system characteristics and soil enzyme activity,and evaluates the stability of six deciduous broad-leaved forest communities using the integrated evaluation method of principal component analysis,the subordinate function method of fuzzy mathematics and the M.Godron stability index method.The study analyzes the differences in the stability of different deciduous broad-leaved forest communities and their causes,and provides a theoretical basis for the maintenance of community biodiversity and the conservation of giant panda habitats in the region.The main conclusions of the study are as follows:(1)A total of 162 species of plants belonging to 62 families and 103 genera in the tree,shrub and herbaceous layers of six different deciduous broad-leaved forests in the Jiajin Mountains,and each community is named according to the community appearance and community-building species.They are termed for each community according to the appearance of the community and the species in which it is built.The community(Ⅰ)of Padus grayana-Pterocarya macroptera var.insignis is mainly composed of Padus grayana and Pterocarya macroptera var.insignis;Juglans mandshurica-Pterocarya macroptera var.insignis community(Ⅱ)formed by Juglans mandshurica and Pterocarya macroptera var.insignis;Acer caudatum-Betula utilis community(Ⅲ)formed by Acer caudatum and Betula utilis;Betula albosinensis-Tilia tuan community(IV)formed by Betula albosinensis and Tilia tuan;Betula albosinensis-Rhododendron vernicosum community(V)formed by Betula albosinensis and Rhododendron vernicosum;Community(Ⅵ)of Betula albosinensis-Betula utilis formed by Betula albosinensis and Betula utilis.Among the six community types,the species diversity of the tree layer of Community IV is not the highest among all the communities and is at an intermediate level;the species richness index,Shannon diversity index and Simpson dominance index of the shrub layer of Community IV are higher than those of the other communities.(2)The diameter and height structure of the tree layer in the deciduous broad-leaved forest of the Jiajin Mountains did not match completely,and the diameter and height structure of Community IV were distributed in a single-peaked pattern,and medium-sized individuals were predominant within the community.The average diameter at breast height of the tree layer in Community IV is the smallest,and the tree species focus on tall growth.The average density of the shrub layer in Community I is the smallest;the average density and average height of the herbaceous layer have their maximum values in Community I.(3)The total biomass of shrubs and herbs in deciduous broad-leaved forest communityⅣ in Jiajin Mountains is significantly greater than that of other communities;the variation of total shrub biomass was mainly from aboveground biomass,and the results of redundancy analysis showed that the biomass of shrub layer was strongly correlated with soil organic matter and total nitrogen content;the difference between aboveground and belowground biomass of herbs was not significant in different communities.(4)Soil nutrient concentrations differed significantly among different communities in the deciduous broad-leaved forest of the Jiajin Mountains,and soil organic matter,total potassium,and total nitrogen concentrations were highest in community IV.The importance value of arrowroot may have influenced soil nutrient return and complementary utilization of soil nutrients by multiple species.Community type had a significant influence on soil anti-scourability,and soil anti-scourability in community IV was second only to that in community III.Soil urease,phosphatase,cellulase and polyphenol oxidase activities differed significantly among communities,and the pattern of change of different soil enzyme activities was inconsistent,with only soil polyphenol oxidase activity reaching a peak in community IV.The results of the principal component analysis showed that soil antiscourability and soil enzyme activity were not the main contributors to community stability,and the results of the redundancy analysis concluded that soil organic matter,total potassium and total phosphorus were the soil factors that mainly influenced community vegetation.(5)The results of the ranking of the three community stability evaluation methods differ,but the evaluation results all showed that the Betula albosinensis-Tilia tuan community(IV)was relatively the most stable.The principal component analysis in the integrated evaluation method considered soil nutrients as an important influencing factor in determining community stability,and the results of partial least squares structural equation modeling indicated that soil factors and tree layer diversity directly and significantly influenced community stability.To sum up,the explanations for the stability of different communities in the deciduous broad-leaved forest in the Jiajin Mountains can be mutually supported from the soil and vegetation perspectives,and that soil nutrients play an important role in explaining the changes in vegetation factors in the deciduous broad-leaved forest communities.