| Zhalong Wetland National Reserve is known as home to the red crowned crane.Owing to the most primitive wetland ecosystem,it was included on list of wetlands of international importance in 1992.Phragraites australis in the reserve not only forms a large area of dominant species community,but also forms a sub dominant species or symbiotic community,both of which play an important role in maintaining the structure and stability of wetland ecosystems.As one of the most widespread species in the world,Phragmites australis will undergo a series of ecological plasticity responses by changing its morphological structure and the process of growth as an individual while the population will be adjusted by the change of quantitative characteristics.But there is a lack of systematic experimental study on the individual morphological change,growth plasticity and adaptability of the individual,the response and regulation of quantitative characteristics of module to the change of environmental factors of P.australis population in heterogeneous habitats.Therefore,making a study on the relationship between dynamics on modular level of P.australis population and environmental factors can not only reveal the growth rhythm of different modules and populations of P.australis,but also can explain the influence of environmental conditions on the modules and populations,thus providing a basis for further revealing the mechanism of divergent adaptation of the widespread species,and a scientific reference for the management on Zhalong Wetland National Reserve.In this paper,the methods of investigation and analysis of plant population ecology were used.A dynamic field study was conducted on the modules of tiller,rhizome and rhizome bud in different temporal series of P.australis populations in the four habitats(Xeric habitat;Wet habitat;Aquatic habitat;Saline-alkali habitat.)in Zhalong Wetland Reserve.The differences of structure characteristics and temporal-spatial variation of modules of P.australis population were compared and the effects of soil environmental factors on tiller,rhizome and rhizome bud were analyzed.Also,the microscopic characteristics of P.australis leaves in different habitats were observed and compared with the methods of plant tissue anatomy.The main results are as follows:(1)In the four habitats,there was a great plasticity in the individual growth and production of P.australis populations.Among them,the height and biomass of tillers at different growing periods were the highest in the aquatic habitat and the lowest in the saline alkali habitat.The average maximal value of tiller height was 1.5-2.3 times that of the minimum value.The coefficient of variation in the same habitat was 8.07%-17.61%,while it was 19.45%-31.56% among different habitats;the average maximal value of tiller biomass was 2.0-5.1 times that of the minimum value;the coefficient of variation in the same habitat was 24.92%-79.82%,while it was 33.43-55.61% among different habitats.(2)In the four habitats,there were a relatively stable difference and order of difference in the number of tillers,rhizome,rhizome buds of P.australis populations in different habitats,and there were significant environmental effects on population dynamics.Among them,in different growing periods,the density of P.australis population in wetland habitat was the largest,which was 287-455 tillers/m2,while it was the smallest in saline-alkali habitat,which was 128-305 tillers/m2;the biomass of population was the largest in aquatic habitat,which was 644.7-5818.9 g/m2,while it was the smallest in saline-alkali habitat,which was 194.4-874.8 g/m2.The rhizome length and rhizome biomass of population were the largest in wetland habitat,which were 13754-17446 cm/m3 and 1063.6-1379.6 g/m3 respectively,while they were the smallest in saline-alkali habitat,which were 7898-9877 cm/m3 and 587.0-787.3 g/m3 respectively;the dry matter storage of population was the largest in xeric habitat,which was 8.0-9.6 g/100 cm,and the smallest was 5.4-6.6 g/100 cm in saline-alkali habitat.The rhizome bud storage and input of population were the largest in wetland habitat,which were 2245-3159 buds /m3 and 327-2197 buds/m3 respectively,while they were the smallest in saline-alkali habitat,which were 1399-1598 buds /m3 and 114-960 buds /m3 respectively;the output in aquatic habitat was 673-663 buds /m3,which was the largest and the smallest was 261-357 buds /m3 in saline-alkali habitat;The dormancy was the largest in saline-alkali habitat,which was 962-2245 buds /m3 and the smallest was 631-1286 buds /m3 in aquatic habitat.(3)In the four habitats,there were a relatively stable regularity on seasonal dynamics of the number of tillers,rhizome,rhizome buds of P.australis populations,and the stability of this regularity was mainly controlled by genetic factors.Among them,the height of tillers and density of populations continued to increase until August;the biomass of both individual tillers and populations continued to increase until September;there was an increasing trend of rhizome length during the whole growing period;the rhizome biomass,dry matter storage and rhizome bud storage decreased gradually from June to August,with the smallest in August and the largest in October;After July,the rhizome bud input and input rate increased gradually.In each growing period,the rhizome bud output was relatively stable;the dormancy,dormancy rate and output rate showed a decreasing trend;the rhizome bud death and death rate were lower and fluctuated irregularly.(4)In the four habitats,the seasonality of tillers,rhizome,rhizome buds and change with age class of P.australis populations can be quantitatively described by the fitting equation.Among them,the height and density of tillers,the biomass of tiller and population and the actual growth time after turning green were consistent with a logarithmic function;the length of rhizome,the input and input rate and the dormancy and dormancy rate of rhizome bud,the ratios of rhizome length and biomass of different age classes,the number and ratios of rhizome bud of different age classes,dormancy rate and germination rate of rhizome bud and age classes and the actual growth time after turning green were consistent with a linear function;the biomass and dry matter storage of rhizome,the biomass and dry matter storage of rhizome of different age classes,rhizome bud storage and the actual growth time after turning green,rhizome dry matter storage and age classes were consistent with a quadratic function correlation.The fitting equation reached a significant level at 0.05.(5)In the four habitats,there was an interdependent relationship between the quantitative characters of modules of P.Australis populations including tiller,rhizome,rhizome bud.Among them,there was a significant(P<0.05)or extremely significant(P<0.01)positive correlation between tiller height,density,tiller and population biomass.There was a significant or extremely significant positive correlation between tiller density and rhizome length,rhizome bud storage and input,and a significant negative correlation with rhizome bud dormancy.There was a significant or extremely significant positive correlation between rhizome bud storage,input and output and rhizome length.(6)In the four habitats,the five soil factors had different driving effects on the tiller,rhizome and rhizome bud of P.Australis populations.The correlation analysis showed that soil moisture and pH had the most driving effects on the number of tillers.Among them,the moisture was positive,and pH was negative;while on the number of rhizome,moisture,organic matter,available nitrogen were positive,pH was negative;on the number of rhizome buds,moisture,organic matter,available nitrogen were positive,while pH and available phosphorus were negative.(7)In the four habitats,the rhizome and rhizome buds of P.Australis populations were composed of five age classes(2nd-6th)in June,and were composed of six age classes(1st-6th)from July to October.With the processes of growing period,the length,biomass and dry matter storage of 1st age class were increasing,the rhizome length of 2nd age class and 3rd age class were relatively stable,and the rhizome length of 4th age class to 6th age class were decreasing;the rhizome biomass of 2nd age class to 4th age class decreased first and then increased,and 5th age class and 6th age class decreased gradually;the dry matter storage of 2nd age class to 5th age class decreased first and then increased,and 6th age class decreased gradually;the number of rhizome buds of 1st age class increased gradually,and 2nd age class to 6th age class decreased gradually;the rhizome and rhizome bud appeared a declining age structures in the early and middle growing period,while transformed into an expanding age structures at the end of growing period.P.Australis population can maintain stability and regeneration by self-regulating and forming a relatively stable age structure on rhizome and rhizome buds.(8)In the four habitats,there were corresponding changes of divergent adaptation on vein,trichomes,stomata,anatomy structure and chloroplasts in morphology,number and distribution of P.Australis leaves.Among them,the distance among the veins distributed evenly in wetland and aquatic habitats;in the xeric and saline-alkali habitats,it showed a feature of alternate width;the sclerenchymatous cells of veins changed their shape from square to similar square,even to saddle or crescent;there were three columns of trichomes in wetland and aquatic habitats while there were four columns of trichomes in xeric and saline-alkali habitats.The trichome density was the largest in saline-alkali habitat and the smallest in aquatic habitat;the number of stomata was the largest in saline-alkali habitat and the smallest in aquatic habitats;the rate of stomata square with leaf was the largest in aquatic habitat and the lowest in saline-alkali habitat;the chloroplasts in xeric and saline habitats were long spindle shaped,small in size,and distributed mostly adherent to the wall;while they were round or oval in wetland and aquatic habitats,large in size,and distributed throughout the mesophyll cells. |
PDF Full Text Request