| The natural regeneration of plants is an important ecological process.In response to changes in the external environment,plants will produce different characteristics of regeneration variation.Phoebe bournei is a national class II protected plant.Its unique use value and slow growth characteristics lead to the rare complete natural forest of Phoebe bournei.Based on plant functional traits and ecological stoichiometric theory,this study took the secondary forest of Phoebe bournei under the natural regeneration process as the main research object.By measuring the leaf morphological characters and nutrient characters,litter nutrient content,soil nutrient content,and soil microbial community composition and diversity in Phoebe bournei forest in different regeneration stages,the functional traits of leaves and litter in the natural regeneration process were explored.Nutrient characteristics,soil nutrient content variation characteristics,and soil microbial community composition and diversity variation characteristics in Phoebe bournei forests of different regeneration stages;combined with plant-soil nutrient characteristics correlation analysis,fitting of plant-soil nutrient homeostasis models,and RDA redundancy analysis of plants-The influence of soil environment on soil microorganisms,thereby revealing the changes in survival strategies of Phoebe bournei sylvatica adapting to changes in different regeneration stages and the key environmental factors affecting the natural regeneration of Phoebe bournei forests,and explaining the functional traits of leaves and nutrient characteristics of litter in the secondary forests of Phoebe bournei,soil nutrient characteristics and the regulatory relationship between soil microbial communities.It is expected to provide theoretical and data support for the study of the specific renewal mechanism of Phoebe bournei forest in response to ecological environment changes and the protection and restoration of natural Phoebe bournei forest resources.The main findings are as follows:(1)With the progress of natural regeneration,the leaves of Phoebe bournei will produce variation in adaptive functional traits in order to adapt to environmental changes.Among the leaf morphological traits,leaf area,specific leaf area and leaf width are more likely to be affected by their own growth and development and environmental changes.The morphological indicators The intraspecific coefficient of variation of the species varied from 8.84%to 30.18%.With the advancement of regeneration,the growth rate of Phoebe bournei was significantly increased while the nutrient utilization efficiency decreased.Phoebe bournei leaves were mainly restricted by P element in the early stage of regeneration,but the limiting effect tended to weaken with the progress of regeneration,and became restricted by N element in the later stage of regeneration.The coefficient of variation of litter nutrient content in Phoebe bournei forest ranged from 4.58%to 23.3%.The changes of soil nutrient content in different regeneration stages in different growing seasons were similar,that is,the non-growing season was higher than the growth season.In the later stage of regeneration,the decomposition rate of litter decreased and the amount of nutrient returned gradually decreased.In addition,litter is also limited by the P element when decomposing.(2)The soil physical properties and nutrient content of the natural regeneration of Phoebe bournei forest changed significantly.Soil bulk density,soil moisture content,and soil pH all increased with the deepening of the soil layer.The C and N contents in the soil showed higher values,but the P content was lower,and the soil P availability decreased significantly in the later stage of regeneration.The coefficient of variation of each nutrient index ranged from 9.81%to 53.64%,the coefficient of variation of soil C and C:P was the largest,and the coefficient of variation of soil P was relatively small.The soil of Phoebe bournei forest in the process of regeneration is mainly limited by N,and the limiting effect becomes more and more significant with the progress of regeneration.Judging from the change of nutrient content in different soil layers,soil nutrients in the natural Phoebe bournei forest showed a certain surface aggregation effect.(3)The composition and structure of soil microbial community in the naturally renewed Phoebe bournei forest will change accordingly.At each taxonomic level,the abundance of bacterial species in the soil at different regeneration stages was significantly higher than that of fungal species.At the phylum classification level,the dominant phyla in the soil bacterial community in different renewal stages were consistently Proteobacteria,Acidobacteria,Actinobacteria and Chloroflexi,Basidiomycota,Ascomycota,Unclassified-k-Fungi was the dominant fungal phylum in the soil fungal community of Phoebe bournei forest,and the dominant fungal phylum accounted for more than 90%of the community composition.Alpha diversity analysis showed that natural regeneration had a significant impact on soil microbial community diversity.The soil bacterial community richness increased at the end of the renewal period,while the fungal community showed an opposite trend at the end of the renewal period;the Beta diversity of the soil bacterial community and fungal community both showed a separation effect in different renewal stages,and an aggregation effect in the same renewal stage.(4)There were significant correlations among the main stoichiometric indexes of the leaves,litter,and soil nutrient traits in the natural Phoebe bournei forest.Among them,soil organic C showed a stronger correlation with plant and litter nutrient indicators,which was the main factor affecting plant functional traits in Phoebe bournei forest in natural regeneration.The variation range of leaf nutrient and its stoichiometric ratio stability index is 2.33-16.78,and the litter nutrient and its stoichiometric ratio internal stability index range is 7.84-52.36.From the plant-soil nutrient stability model,it can be seen that,In this study,the natural regeneration of Phoebe bournei forest has a certain internal stability,and will adjust the nutrient utilization strategy to maintain the balance of its own nutrient elements when adapting to changes in the external environment.The plant-soil nutrient traits in the natural Phoebe bournei forest were significantly correlated with soil bacterial community and fungal community diversity.Overall,the impact on soil bacterial community diversity was stronger than that of soil fungal community.RDA analysis showed that LN,LC,LiC,and pH were the most influential environmental factors on soil bacterial community,while SN,LC,LiC,and pH were the most influential environmental factors on soil fungal community.The correlations between different soil microbial communities and plant-soil nutrients were different,but they all showed strong correlations with plant C content and soil pH.In the process of protecting the natural Phoebe bournei forest,it is not only necessary to supplement nitrogen and phosphate fertilizers in a timely manner,but also pay attention to adjusting the stand and tree species structure,so as to promote the better growth of Phoebe bournei forest in the natural environment. |
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