A Study On The Effect Of Fire On Plant Community Assembly In Two Evergreen Broad-leaved Forest Of Yunnan

In terrestrial ecosystems fire is a common ecological factor,which affects the evolution of plants and the assembly of plant communities.In plant community assembly fire was viewed as a environmental filter,which remove species with no fire-adaptive traits out of communities in fire-prone environment.The functional traits of plants had be used to develop an excellent framework to explain the theory of community assembly,and to test the mechanism of community assembly in communities.The community of semi-humid evergreen broad-leaved forest?SEBF?in Qiongzhusi and monsoon evergreen broad-leaved forest?MEBF?in Guomenshan were studied in this paper.Twelve plant functional traits were selected,including specific leaf area and so on.Of them leaf area,leaf length,leaf dry matter content,twig dry matter content,relative bark thickness,inner bark and outer bark are the fire-related traits.Using R software,four functional diversity indices(FR_ic,Rao_Q,FD_iv,FE_ve)were calculated,the phylogenetic signals of each functional trait were detected.The phylogenetic diversity indices?PD?,net relatedness index?NRI?,nearest taxon index?NTI?,standardized effect size of mean pairwise trait distance?S.E.S.PW?and standardized effect size of mean nearest neighbor trait distance?S.E.S.NN?were calculated.Based on the community phylogenetic structure combined the functional structure of fire-related functional traits?Protective traits,Physiologic traits,Flammability traits?,the main ecological processes affecting community assembly were verified.Thus,the influence and function of fire in community assembly are inferred.The results show that:?1?Both the SEBF in the Qiongzhusi and the MEBF in the Guomenshan had fire-adaptive traits.In Qihuzhusi SEBF had higher flammability;there was more biomass accumulation in MEBF in Guomenshan;there was no significant difference in the protective traits of two habitats.?2?The Functional richness(FR_ic)of each plot in the SEBF in Qihuzhusi and the MEBF in Guomenshan were not significantly different.Rao's quadratic entropy?Rao_Q?and functional divergence(FD_iv),the functional evenness(FE_ve)was not significantly different,but the FRic of the SEBF in Qiongzhusi was significantly greater than that of the MEBF in Guomenshan.?3?We not found significant phylogenetic signals for SEBF of Qiongzhusi in 12functional traits analysed.Strong phylogenetic signals were observed in wood density,inner bark and outer bark of the MEBF of Guomenshan,but no significant phylogenetic signals were detected in the other 9 traits.?4?The PD values of species of SEBF and the MEBF that were more distantly related than expected by chance,that was,they were non-random process.The habitat of the SEBF in Qiongzhusi were composed of species that were more closely related than expected by chance,their phylogenetic structure were clustered,and the functionalstructure of the community was overdispersion based on the set of physiological traits,flammable traits and protection traits;The habitat of the MEBF in Guomenshan were composed of species that were more closely related than expected by chance,their phylogenetic structure were clustered.The functional structure was clustering based on the set of physiological traits and the set of protection traits,But overdisersion based on the set of all traits and the set of flammable traits.Both the SEBF in Qiongzhusi and the MEBF in Guomenshan were in in the monsoon climate and was in fire-prone environment.Many species in the community had fire-adaptive traits.Closed broadleaved forests fundamentally changed fire regimes by producing a vegetation structure that intrinsically reduce fires.we did not find which fire affect on the community assembly in these two types of forest.Our results did not support the hypothesis that the fire was a habitat filter and affected the community assembly in SEBF in Qiongzhusi and MEBF in Guomenshan.