Quantitative Characteristics Of Different Growth Forms Of Phragmites Australis Population In Alkali Habitats In The Songnen Plain

Phragmites australis is widely distributed in various habitats of the world.In the bare alkali spot of Songnenplain,reed can still grow relying on vegetative propagation,but the size and morphologyof ramets vary obviously.Reed ramets usually appear four kinds of growth forms: erect ramet,slanting ramet,crouching ramet,creeping ramet.In this paper,we studiedreed populations in different alkaline habitats(H1: reed,H2: reed + annual plant,H3: reed+ perennial plant)by the methods of termly sampling,including the plasticity of quantative attributes of different growth-form ramets and temporal and spatial variations,which will provide a scientific basis for further understanding the adaptationmechanism of reedthe population to adverse environmentand provide theoretical support for the efficient utilization of reed.The main results are as follows:(1)Under three kinds of heterogeneous habitats,the number distribution of reed ramets has obvious spatial difference.In H1 habitat,the number of ramets among three growth forms had not significant difference.In H2 habitat,the number of slanting-type ramets is the most in each growing period,which has significant difference with the other two growing forms.In H3 habitat,the number of erect ramets was significantly higher than the slanting-type ramets in each growth period,and crouching ramets were unusual.In three types of habitats,from H1 to H3 habiat,the proportion of the number of erect-type ramets gradually increased,and that of crouching typegradually decreased and that of slanting-type was relatively stable.(2)Reed population all decreased quantitative allocation to erect ramets in three habitats.The number of erect ramets showed a decreased trend with the process of growing season,while the number of other two growth-type ramets showed quadratic parabola law.(3)The aboveground biomass of reed population and the number of ramets in different growth forms showed a significantly positive correlations.The change process of aboveground biomass and the number of ramets population all had certain orderliness and different rules of different growth-form reed populations in three habitats.(4)The ramet height,ramet biomass,leaf number,leaf biomass,stem biomass in two mixed habitats(H2 and H3)were significantly higher than that of bare alkali spot(H1)with the process of growing season.The trend of biomass allocation was highly coincident in different growth forms in three kinds of habitats.From H3 to H1,three growth forms of reed all showed a trend that biomass allocation to leaf gradually increased.(5)The relationships between quantitative characteristics of reed ramets and days after reviving basically reached significant or extrmely significant positive correlation(P<0.05 or P<0.01).However,increase rates of these quantitative characteristics with days after reviving were not at a constant level,and the relationships were quadratic function,power function or exponential function.The growth rates of height plant biomass of ramets gradually increased with the process of growing season.The growth rate of leaf number,leaf biomass and stem biomass showed different rules with the process of growing season.(6)The relationships between ramet biomass,stem biomass and ramet height showed extremely significant allometric growth law(P<0.01)and the R2 value is between 0.7145-0.954,indicating the relationships between them were mainly influenced by genetic factors.There was a significant positive correlation between leaf number,leaf biomass and plant height(P<0.01).There was a significant positive correlation between the number of leaves,leaf biomass and ramet biomass(P<0.01)and the coefficient of determination R~2 value between leaf biomass and ramet biomass was 0.8789-0.9747,indicatingthe relationships was mainly affected by genetic factors.The relationships between leaf biomass and ramet biomass showed isogony orapproximate isogony(the b value was about 1).There was no significant relationship between leaf biomass allocation and ramet biomass and the percentage of biomass allocation was mainly from 40% to 60%.(7)The ecological plasticity of functional leaf biomass was higher than that of leaf length in different growth-form reed populations in three alkaline habitats(The coefficient of variation of the former was 11.74%-29.17%,that of the later was 24.39%-52.94%).Functional leaf length,functional leaf biomass and ramet height showed both the isogony and the allometric growth in three alkaline habitats.