| Vegetation restoration is an important measure for the management of damaged or degraded forests and the improvement of forest quality and functions,and different restoration modes will have long-term effects on forest vegetation communities and soils.The forest apoplast and soil interface area is the most active level of material cycling,energy flow and microbial activity.In this paper,three typical forest stands in the South Asian tropics,Aquilaria sinensis,Acacia mangium and Natural secondary broad-leaved mixed forests,were planted and closed in Shenzhen around 1990 s.The C/N/P ecological stoichiometry ratios,soil bacterial community composition and diversity characteristics and their interrelationships of different forest stands were compared by setting up fixed sample plots for seasonal collection of apoplankton and soil samples within one year,and by analyzing and measuring soil physicochemical indicators and determining bacterial community composition using high-throughput sequencing technology.This study provides a scientific basis for studying the effects of different vegetation restoration modes on the stability and ecological functions of the southern subtropical ecosystem and the sustainable management of planted and natural secondary forests.The results of the study showed that:1)Aquilaria sinensis apoplastic organic carbon content was significantly lower than that of Acacia mangium and natural secondary forests,and there was no significant difference in total nitrogen content.Natural secondary broad-leaved mixed forests had significantly lower apoplastic total phosphorus content than Aquilaria sinensis and Acacia mangium;apoplastic organic carbon content was significantly higher in September than in February and May.The interaction between sampling season and stand type had significant differences on the organic carbon content of apoplastic matter,but not on other indicators of apoplastic matter;the organic carbon content and total nitrogen content of soils in different stands were Natural secondary broad-leaved mixed forests > Acacia mangium > Aquilaria sinensis.Natural secondary broad-leaved mixed forests had lower contents than the two plantations.The trends of soil C/N,C/P and N/P ratio were as follows: Natural secondary broad-leaved mixed forests > Acacia mangium > Aquilaria sinensis.2)The dominant groups of soil bacterial community composition in different forest stands were mainly Acidobacteria,Proteobacteria,Actinobacteria,and so on;while Acidobacteria.6 and Pedosphaerae were only found in Natural secondary broad-leaved mixed forests soils,and Thermoleophilia were only found in Acacia mangium soils.3)The Shannon and Simpson indices of soil bacteria did not differ significantly at the gate level among different restoration modes,and the Richness and Chao1 indices of Natural secondary broad-leaved mixed forests soil bacterial communities were significantly higher than those of the two plantations;the Richness and Chao1 indices were significantly higher in September than in February and May.Correlation analysis showed that apoplastic organic carbon,apoplastic C/N,soil organic matter,soil C/N ratio,and soil C/P were closely related to each diversity index of soil bacteria.The above results show that the ecological quality and diversity of the three different restoration modes in the study area are generally natural secondary forest >Acacia mangium forest > Aquilaria sinensis forest.forest,which requires us to minimize the destruction of natural vegetation in forest management and restoration of degraded forests,and to adopt the allogeneic-complex-layer-mixed approach in forest management.In addition,this study found that the P-element phase is the limiting factor of the carbon,nitrogen and phosphorus material cycle in the forest in this study area,and the supplementation of soil phosphorus nutrients should be emphasized in the future forest management. |
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