The Influence Of Enviroment And Phylogenic Background On Plant Functional Trait In Yanhe River Catchment

The assembly of plant community may be affected by both abiotic and biotic processes.Therefore, understanding of the process of plant community assembly and related ecologicalprocess is of great importance to the ecological restoration and practice. This paper, takeYanhe River catchment as a case study area, measured the main plant functional traits ofdifferent communities along the environmental gradient of the watershed, and analyzed thecovariation between different plant traits and their relations to environmental gradients. Wealso discussed the variation of plant functional traits among different plant families andgrowth forms, and relative importance of abiotic and biotic processes in the assembly of plantcommunities at the watershed scale. The main results are as follows:(1) At the community level, plant leaf, root, seed traits were positively correlated. Thetraits relationship at the community level were more obvious than that of at the species level.(2) In southeast of the catchment with relatively high rainfall and suitable temperatures,the plants seemed to have lower specific leaf area, higher leaf density and larger and heavierseeds while in the northern part of the Yanhe River catchment the plants usually have thickerleaves, less biomass, deeper roots and smaller and lighter seeds. This spatial pattern offunctional traits indicated that the environment filtering was obvious during the communityassembly in Yanhe River catchment.(3) Species of different families has developed different functional traits to deal withenvironmental changes. The results indicated that specific leaf area, root density, leaf nitrogenper mass and root nitrogen per mass varied significantly among different families (P <0.01).The significant differences were also found in mean leaf density among families (P <0.05).The leaf nitrogen and root nitrogen content of the Leguminosae plants are much higher thanother species, the Cyperaceae plants have higher leaf density and root density, theBignoniaceae plants have higher specific root length and the lower root density, theGramineae and the Bignoniaceae plants have relatively higher specific leaf area and specificroot length. Specific leaf area, root density, leaf nitrogen and root nitrogen per mass show avery significant difference in different growth forms (P <0.01), mean leaf thickness showedsignificant difference at0.05level. The deciduous lianas have the thickest leaves and the lowest specific leaf area. The perennial grasses and forbs have relatively larger plant specificleaf area and longer specific root length. The forbs have relatively higher root nitrogen permass among the six growth forms.(4) The general linear model of different traits showed that the plant family have thegreatest influences on the variability of plant functional traits across the watershed, meaningthat the phylogeny background, namely the different composition of vegetation communitiesacross the watershed may have great impact on the variation of functional traits at communitylevel. These results suggested that the environment filtering play an important role in thecommunities assembly in Yanhe River catchment.(5) The assembly of plant communities was not only influenced by environment filteringbut also by the interaction among species within communities. However, their effects mightvary along different environmental gradients. In this study, we just inferred that theenvironment filtering played a more important role in community assembly in poor areaswhile biotic interaction among species are relatively more important when the environmentalconditions became more suitable.