How Exotic Mangrove Species Sonnoratia Apetala And Native Species Kandelia Obovata Response To Global Changes

The present study aimed to explore the responding mechanisms of non-native mangrove species,Sonneratia apetala and native mangrove species,Kandelia obovate,to warming and rising sea level.We set up a set of marsh organ to simulate the scenarios of future sea level with 40-cm rising and 80-cm rising in the field tidal conditions in three study sites,Aojiang in Wenzhou,Yunxiao in Fujian and Dongzhaigang in Hainan.We also set up open top chambers as warming treatments.According to the elevation survey,the sea levels of the experimental platform were divided into four levels,which were HW(high-water level,the elevation of the existing mangrove forest side),MW(medium-water level average elevation of the existing mangrove forest edge),LW(low-water level,40-cm rising sea level)and LLW(lowest-water level,80 cm's rising sea level).The synergistic effects of warming and sea-level risewere discussed,By combining the elevation survey of natural dispersal S.apetala seedlings in Yunxiao,we predicted the future distribution pattern of the non-native species under global change conditions.The results of this study were as follows.Firstly,the growth patterns of the two mangrove species are different in different sea-level treatments.With the increase of sea-level,the two species greatly increased seedling height,butincreased the stem diameter slowly.Both species seemed to grow taller to alleviate the hypoxia stress.Due to rapid growth rate,K.apetala seedlings got higher to avoid the stress of sea-level rise,and turned to normal vegetative growth.Secondly,the biomass accumulate rate of S.apetala was faster than that of K.obovate seedlings.In two period of growth,the 6th month and the 12th month,biomass partitions of seedlings were different.In the former 6 months,the biomass of S.apetala seedling was mostly accumulated n roots and stems.As sea-level rised,root biomass proportion decreased gradually,while stem biomass proportion increased gradually.In the 12m month,Sonneratia apetala,the root to shoot ratios at all levels were higher than those in the 6th months,which was more than 1.While the partition of biomass of K.obovata seedlings,which was si1ilar to that in the 6th month.In the 12th month,the stem still occupied the highest proportion of biomass,indicating the facts of the biomass accumulation on belowground biomass to resist the sea-level risingstress.Thirdly,the results of the same water level platform in Aojiang,Yunxiao and Haiku are various.In both Aojiang and Haikou,the growth of the two species seedlings in rising sea-level treatments were inhibited and even died.In three places,the seedling height,basal diameter and biomass accumulation were the highest in MW treatment.S.apetala had higher seedling height compared to K.obovata in each treatment.Fourthly,open top chambers experiment could increase about 0.92 to 2.42 ?inside chambers on Yunxiao marsh organs.Warning had a significant promotion on the biomass of S.apetala in LW treatment and K.obovata in MW treatment.Warming and sea-level rise did not show significantly interaction.The last,natural dispersed S.apetala seedlings in Yunxiao were mostly distributed on mudflats outside the mangrove and between the Spartina alternriflora patches,and its distribution elevation were lower than natural mangrove edges within the range of simulated sea level rise.There was a significantly linear relationship between plant height of S.apetala and the elevation.Combined with marsh organ results,we deduced that S.apetala was possibility to settle down and disperse to the core protected areas in Yunxiao mangroves in the future.