Effects Of Simulated Warming On The Growth And Reproducetion Of Phragmites Australis And Spartina Alterniflora In Yangtze River Wetlands

The fifth comprehensive assessment report of the IPCC showed that global warming is continuing and expanding since the last century and it is expected that by the end of this century,the global average temperature may increase by 2.6-4.8°C.Similarly,average temperature in China will increase by 2.3-3.3°C in the next 50 years.The impact of elevated atmospheric temperature on plant growth and reproduction is a hot issue in current global change research field.The effect of climate warming on the competitiveness of invasive plants has also become one of the research hotspots.The C4 plant Spartina alterniflora is one of the exotic plants in the salt marsh wetland in China.It has great competitive pressure on the community structure and function of the local C3 plant Phragmites australis.Whether the increase in atmospheric temperature will affect plant growth,reproduction and change the relative competitiveness of the plants,there is a few of the relevant research currently.In this study,both P.australis and S.alterniflora in the Yangtze River Estuary Wetland were used as the research object,and the open top chamber was used to simulate the increase of atmospheric temperature,and four different density planting patternss were studied(P4(100 P.australis),S4(100 S.alterniflora),P1S3(25 P.australis,75 S.alterniflora),P2S2(50 P.australis,50 S.alterniflora),P3S1(75 P.australis,25 S.alterniflora))the responses of the morphological and reproductive characteristics of the two plants,and their responses to increasing temperature(annual mean air temperature in the two-year OTC increased by 2.00 ± 0.17 °C and 2.00 ± 0.98 °C,respectively).By analysis of the differences in morphological and structural characteristics with responses to warming to explore the effects of warming on interspecific competition.We hope to provide deep understanding of the Yangtze River Estuary wetland ecosystem competition response to climate warming.The main findings are as follows:1.Compared with the control,P.australis and S.alterniflora under increasing temperature,the total leaf area and leaf area index increased significantly.There was no significant difference in the stem diameter between the two plants.There was no significant difference in the plant height and leaf number of P.australis in the two years.The first year of warming had no significant effect on the plant height and leaf number of S.alterniflora.The increase in temperature in the second year significantly promoted the plant height growth of S.alterniflora.Compared with the one-year warming period,the height,stem diameter,leaf area parameters and leaf number of P.australis increased significantly in the second year;the plant height,base diameter and leaf area parameters of S.alterniflora increased significantly,but the number of leaves did not.The warming brought the phlegm time of the P.australis to 3 days ahead of schedule,7 days ahead of schedule.The phenological period of the S.alterniflora was 3 days ahead of schedule and 4 days later.2.Compared with the control,the increase in temperature significantly promoted the aboveground biomass of P.australis and S.alterniflora in different cultivation patterns,and the plant stem biomass,leaf biomass,and total aboveground biomass increased significantly.The increase in temperature had no significant effect on the asexual reproduction of P.australis,and its sexual reproduction was significantly inhibited.For S.alterniflora,warming significantly promoted sexual reproduction of S.alterniflora,but the first year of warming had no significant effect on its tillering rate,and the second year of warming significantly inhibited its asexual reproduction.3.There are significant differences in the growth and reproduction of P.australis and S.alterniflora under different planting patternss.With the increase of planting density of the competitive plants,the mutual inhibitory effect is more significant.Both plants have good competitiveness under the conditions of increasing temperature and at the same time have higher Stronger competitiveness under higher planting densities in addition to increasing temperature and different planting patterns,the interactions between the two also affect the growth and reproduction.4.Since the increasing temperature has no significant effect on the asexual reproduction of S.alterniflora,it significantly promotes its sexual reproduction.In the future,it can strengthen the cuttage and increase the density of P.australis to reduce the population growth of S.alterniflora to limit its competitiveness and protect local plants,protect the safety of wetlands.