| As the abundant species composition and complex structures of tropical rainforests,such ecological research was very difficult.Compared with species richness,ecological research with plenty of soft functional traits and functional diversity,not only can more directly reflect ecosystem processes and functions,but also can greatly reduce the difficulty.Tropical rainforest in Xishuangbanna was one of the most biodiversity-rich areas.It was also considered important to protect the biodiversity center,with a high conservation value In the international arena.In this thesis,based on field investigations of communities and measurements of functional traits(a total of 12 functional traits,including leaf characteristics-specific leaf area of trees and seedlings,leaf dry matter content,leaf nitrogen content,leaf phosphorus content,leaf potassium content,leaf total organic carbon content;growing characters-potential maximum height and wood density;update characters-seed mass,seed size and fruit size)and environmental factors(a total of 11 environmental factors,including elevation,canopy openness,soil moisture content,soil organic matter content,soil pH value,total nitrogen,total phosphorus,total potassium,available nitrogen,available phosphorus and available potassium)at 68 plots in tropical lowland forests,montane forests and seasonal forests of different successional stages after shifting cultivation in Xishuangbanna.We explored the species composition of various types of plant communities and the ecological significance of them by applying indicator species analysis.We used correlation analysis and principal component analysis to reveal key functional traits.We explored variations of functional traits,species diversity,functional diversity and phylogenetic diversity during different successional stages across three types rainforests by two-way ANOVA and multiple comparison analysis.We used multiple regression analysis to estimate the relationship between functional traits,diversity indices and environmental variables across three types rainforests.And we used null model based on functional traits,functional diversity and phylogenetic diversity to reconstruction the changes of plant communities,analyzed of the driving mechanism.The main results are as follows:① In lowland rainforests,the indicator species of 40 years forests were Ficus langkokensis and Castanopsis indica.The indicator species of 60 years forests were Litchi chinensis and Cinnamomum tamala.The indicator species of original forests were Parashorea chinensis,Gironniera subaequalis,Dysoxylum excelsum and Knema linifolia.These trees were require a relatively high water resourse,often grown in moist lowland forests.Parashorea chinensis usually seated in the original lowland forests.In montane rainforests,the indicator species of 60 years forests was Betula alnoides and the indicator species of original forests was Cinnamomum tenuipilum.These species hi light,shade intolerant,were tolerant of poor soil fertility.And,Betula alnoides was the pioneer species for the secondary evergreen broad-leaved forests.In seasonal rainforests,the indicator species of 10 years forests were Macaranga denticulate,Pithecellobium clypearia and Schefflera octophylla.The indicator species of original forests were Dillenia turbinate,Phoebe puwenensis,Pometia tomentosa,Polyalthia cheliensis,Garcinia lancilimba and Drypetes indica.Theses species were born in shaded terrain,high heat conditions,distinct wet and dry season conditions.And,Pometia tomentosa was one of the dominant tree species in southern seasonal forests of Yunnan.② Functional traits influenced the spatial distribution of plant communities mainly including potential height and leaf characteristics(including specific leaf area,dry matter content of leaves,leaf nitrogen,phosphorus,potassium,carbon content),followed by plant regeneration characteristics(including seed mass,seed size and fruit size),while the contribution of deciduous and wood density were small.In lowland rainforest secondary succession series,the maximum potential height and seed mass were higher in original forests than in 40 years and 60 years forests.The differences about specific leaf area,dry matter content,leaf nitrogen content,phosphorus content,potassium content,carbon content,fruit size,seed size,wood density and deciduous in each stage of succession were not significant.In montane rainforests secondary succession series,specific leaf area and leaf phosphorus content were significantly lower in 60 years forests than original forest,and leaf dry matter content was higher.Leaf nitrogen content,seed mass,seed size and fruit size in original forests were significantly higher than secondary forests.The differences about maximum potential height,leaf potassium content,leaf carbon content,wood density and deciduous in each stage of succession was not significant.In seasonal rainforests secondary succession series,specific leaf area,fruit size in 10 years secondary forests and original forests were significantly higher than 40 years and 60 years forests,but leaf dry matter contentc was lower.Leaf nitrogen,phosphorus and potassium content was significantly higher in the original forests than secondary forests.Wood density in original forests was significantly higher than 10 years forests.Seed size of 10 years forests was significantly higher than 40 years forests,60 years forests,and original forests.The differences about potential maximum height,leaf carbon content,seed mass,deciduous in each stage of succession were not significant.As the three different types of communities,in secondary forests,specific leaf area,leaf nitrogen,phosphorus and potassium,fruit size were significantly higher in lowlan forests than in motane forests and seasonal forests,but leaf dry matter content was lower.In original forests,the maximum potential height in the lowland forests was significantly higher than montane forests and seasonal forests.Seed size was significantly higher in the montane forests than lowland forests and seasonal forests.Seed mass was significantly lower in seasonal forests than in montane forests and lowland forests.The differences of leaf carbon content,wood density in three different types of communities were not significant.③ In lowland rainforests secondary succession series,species richness and phylogenetic diversity in original forests were significantly higher than 40 years secondary forests,while the functional divergence was lower.The differences of Shannon Wiener index,Pielou’s evenness,functinonal richness,functional evenness,function dispersion,Rao’s entropy in each stage of succession were not significant.In montane forests secondary succession series,Shannon Wiener index,Pielou’s evenness,functional divergence were significantly higher in original forests than 60 years forests.The differences of Species richness,functional richness,functional evenness,functional dispersion,Rao’s entropy,phylogenetic diversity were not significant.In seasonal rainforests secondary succession series,species richness and phylogenetic diversity in original forests were significantly higher than 40 years secondary forest.Shannon Wiener index,Pielou’s evenness,functional dispersion and functional divergence in 10 years secondary forests and original forests were significantly higher than 40 years and 60 years secondary forests.Functinal evenness and Rao’s entropy in 10 years was significantly higher than 40 years,60 years and original forests.The differences of functional richness was not significant in the various stages of succession.As the three different types of communities,in secondary forests,Shannon Wiener index,Pielou’s evenness,functional dispersion,functional divergence and and Rao’s entropy in lowland forests were significantly higher than montane forests and seasonal forests.Only in 60 years secondary forests,phylogenetic diversity was significantly higher in lowland forests than montane forests and seasonal forests.The differences of species richness,functional richness,functional evenness in the three different types of communities were not significant.④ In lowland rainforests secondary succession series,the larger contribution of environmental factors including elevation,soil moisture content,soil organic matter content,total nitrogen,total phosphorus and available nitrogen.In montane rainforests secondary succession series,the larger contribution of environmental factors including elevation,canopy openness,soil pH value,organic matter content,total phosphorus,available nitrogen,phosphorus and potassium.In seasonal rainforests secondary succession series,the larger contribution of environmental factors including soil pH valve,total nitrogen,total phosphorus,total potassium and potassium.⑤ As the drive factors of community assembly during different successional stages across three types rainforests showed that:functional richness was driven by habitat filtering,functional eveness was driven by randomize,functional divergence and phylogenetic diversity were driven by competitive interactions in seasonal rainforests,lowland rainforests and montane rainforests.Functional dispersion and Rao’s entropy were driven by competitive interactions to habitat filtering in the process of community assembly in seasonal rainforests.Functional dispersion was driven by competitive interactions,Rao’s entropy was driven by competitive interactions to habitat filtering in the process of community assembly in lowland rainforests.Functional dispersion and Rao’s entropy were driven by habitat filtering in the process of community assembly in montane rainforests. |
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