Functional Trait-based Study Of Community Assembly In Temperate Forests Of Different Succession Stages In Changbai Mountains

The study of community assembly mechanism is one of the hotspots of ecolog.In Changbai Mountains Nature Reserve,There is a complete original broad-leaved Korean pine forest ecosystem.In recent years,the loss of species diversity has become more serious,study of exploring the community assembly mechanism of this region is particularly important.Three permanent large plots with each area of 5,2 hm2 in Changbai Mountains along suessional stages secondary poplar and birch mixed forest;secondary mixed conifer and broad-leaved forest;and natural mixed linden and Korean pine forest were chosen as study object.Seven functional traits of main trees were obtained(inculding leaf area,specific leaf area,leaf thickness,maximum tree height,leaf nitrogen content and leaf phosphorus content).The change of trait space volume at different spatial scales(5×5 m,10×10 m,20×20 m,30×30 m.40×40 m,50×50 m and 60×60 m).By comparing the observed results with expected resultsof null models,the community assembly mechanism of Changbai mountains forest was discussed.The results show that the size of species pool has an important impact on the research results.Early in succession,the observed observed trait space volume was lower than thtrait space volume was higher than the expected values.At intermediate and late successional stages,the e expected values.According to the analysis of multiple community fuctional diversity indices,the results showed that the combined processes of habitat filtring and competitive exclusion are the main determinants of the species composition of the top community in this region.Early in succession,a large number of species immigrated,there are strong resource competition among the species within community.With the processing of succession,some species were excluded,the strength of competition reduced,while habitat filtering showing strong effect.