Study On Divergence Of Functional Traits And Ecological Strategies Of Phragmite Australis Population In A Coastal Wetland Based On CSR And LHS System

Analyzing the functional traits and ecological strategies of plant populations may be helpful for correctly understanding the adaptive modes of a species.The divergence of plant functional traits and ecological strategies of a population has an important effect on community structure and function.The existing research methods for plant ecological strategies analyze plant population as a whole,which may not be appropriate for a population with a large spatio-temporal variation.Phragmite australis population distributing along the tidal flat in Chongming Dongtan wetland showed high intra-population trait variability in both spatial and temporal dimensions,indicating the possible divergence of ecological strategies in P.australis population.In order to investigate the intra-population divergence of functional traits and ecological strategies of P.australis in Chongming Dongtan wetland,the P.australis population was divided into 3 subpopulations according to the morphological and distribution characteristics,namely,seaward subpopulation,middle subpopulation and landward subpopulation.Using ANOVA,principal component analysis and plant ecological strategy systems(CSR and LHS),the divergence of the ecological strategies among 3 subpopulations and among the different growth periods of each subpopulation were studied.The main results were as follows:1.The functional traits and ecological strategies of P.australis population in Chongming Dongtan wetland showed significant intra-population divergence in spatial dimension.The seaward subpopulation preferred resource acquisition strategy(R strategy),the middle subpopulation preferred resource storage strategy(S strategy),and the landward subpopulation preferred to allocate energy in plant size dimension(C strategy).From the early to the end of growing season,the main different traits among the subpopulations changed from leaf traits to the size of stem and the whole plants.2.PCA analysis of functional traits variation space of P.australis population showed that the variation patterns of leaf traits,plant size and sexual reproduction traits were relatively independent.Therefore,the LHS system containing these 3 traits was more effective than the CSR system based on leaf traits when identifying the divergence of ecological strategies within P.australis population.Based on the boundary line of SLA=11.5mm~2/mg,plant height=175cm and inflorescence weight=4g,the ecological strategies of 3 subpopulations were differentiated.3.The ecological strategy of each P.australis subpopulation in Chongming Dongtan was significantly different in different growth periods,but the divergent pattern was affected by the population dynamics.In the seaward subpopulation and the middle subpopulation,there was no significant difference in biomass accumulation time between the reproductive and the vegetative ramets at the early stages of the growing season,due to the death of ramets during the vegetative growth period.The divergences of ecological strategies among the different growth periods in these 2subpopulations were mainly caused by leaf traits.The habitat of the landward subpopulation was relatively stable,and the biomass accumulation process of ramets in this subpopulation increased continuously,therefore,in the landward subpopulation,the divergences of ecological strategies among the different growth periods were mainly due to the differences in stem and plant size.4.At the end of the growing season,there were both reproductive and vegetative ramets in P.australis population.The density ratios of these 2 types of ramets in the seaward,middle and landward subpopulation were 87.94%-12.06%,73.56%-26.44%and 77.59%-22.41%,respectively.The plant size,LDMC value and leaf mortality of the reproductive ramets were significantly higher than those of the vegetative ramets,but the SLA value and chlorophyll content of the former were significantly lower than those of the latter,indicating that reproductive ramets were more inclined to the resource storage strategy(S strategy),while the vegetative ramets were inclined to the resource acquisition strategy(R strategy).5.At the end of the growing season,a number of"worker-ant-like"vegetative ramets sprouted in P.australis population in the Chongming Dongtan wetland.Since the time of germination was near winter,most of these vegetative ramets might not enter the stage of sexual reproduction.Different from the vegetative ramets in the early growing season and the reproductive ramets in the late growing season,the vegetative ramets in the late growing season(work-ant-like ramets)of P.australis population had smaller size,relatively stronger photosynthetic capacity and resource acquisition ability(R strategy).The acquired resources were not mainly used for their own use(since they had low LDMC value and S strategy score),but transported to their connected ramets or underground rhizomes.The results on the divergence of functional traits and ecological strategies of P.australis population in the coastal wetland might be helpful for providing the important theoretical reference and technical support for the ecological conservation and restoration of P.australis population in the coastal wetland.