Study On The Regulation Of Degraded Wetland Ecosystem In The Buffer Zone Of Laoshan Bay

Lake buffering zone is an isolation niche regarding to the lake protection,since it is a space for avoiding or alleviating the damage,interference and pollution from different types of human activities or natural processes.The main functions of the lake buffering zone are buffering,improving ecological environment,and implementing special environmental economic policy and ecological compensation.Lake buffering zones also have a great significance in basic ecological health and lake water environmental quality.The current ecological environment function of lake buffering zones is undergoing severe degradation.The Zhushan Bay in Taihu Lake is particularly prominent as the heavy polluted area.The Zhushanhu wetland in the area of lake buffering zone of the Zhushan Bay was chosen as the research target.The biotic components were divided into 16 functional groups to construct the EWE model.Before the construction of the model,the biological parameters of the functional components were obtained through the detailed ecological investigation of the study area.The characteristics and state of the ecosystem and the interrelation between the functional groups were analyzed,according to EWE model's results.The results show that the range of effective trophic level in Zhushanhu wetland was 1?3.72,trophic flows were mainly concentrated in the first 4 trophic levels,most of the food chains were started from submerged plants and detritus.The total energy conversion efficiency of the wetland ecosystem is 5.1%,lower than the "1/10 law".This situation reflects that the current energy conversion efficiency is low.The sum of all production in the ecosystem is 2496.66t·km-2·a-1 and total system throughput is 10145.2 t·km-2 a-1.The value of Total Primary Production/Total Respiration(TPP/TR),Connectance Index(CI),System Omnivory Index(SOI),Finn's Cycling Index(FCI)and Finn's Mean Path Length(FMPL)were 2.365,0.236,0.069,29.1%and 4.377,respectively.Many kinds of characteristic parameters of ecosystem show that the current ecosystem is in the immature stage and internal contact complexity is also very low,not reaching the standard for a mature ecosystem.The investigation of regulation mechanism was carried out on the basis of the construction of the EWE model of the wetland ecosystem in the Zhushan bay lake buffering zone.The regulation mechanism of wetland ecosystem mainly includes biodiversity restoration,biological community structure optimization,reconstruction of food chain structure and biomass management as a series of ecological regulation and control measures.On the basis of the existing species structure,artificial proliferation of herbivorous fish species can be done to increase the biological diversity and improve the ecotrophic efficiency of primary producers.When the biomass of herbivorous fishes has increased to reach a proper amount,to a certain extent it can solve the problem of excess capacity of wetland primary production surely.According to the analysis of predator niche overlap and the calculation of proliferating ecological capacity:the ecological carrying capacity of MacC functional group is 3.05 t·km-2·a-1 indicating that the biomass of MacC functional group in current ecosystem is close to the capacity of the ecosystem.This also makes 51.1%of the group's material has not been used by the ecosystem and flow into the recycling and deposition.When the biomass of MacC functional group has 50%reduction compared to the status quo,the group's ecotrophic efficiency was doubled and the amount of detritus flows also decreased correspondingly.The LarC and OthP functional groups occupy the top of the food web,which play an important role in supporting the ecosystem's food web structure and their effective trophic levels were 3.587 and 3.333,respectively.Through the model's calculation,we found that the ecological capacity of these two groups had multiplication space with 46.38%and 50.07%,respectively.The scenario simulation of proliferation shows that the predicted result better conform to the theory of classical biomanipulation,the ecotrophic efficiency of filter-feeding cyprinidae fish and omnivorous fish have increased.At last,the simulation and analysis of the aquatic plant's harvest scenario were conducted,when the biomass of submerged macrophyte and emerged macrophyte were cut by 35%and 50%respectively,the rebalance of ecosystem's EWE model showed that the primary production decreased by 23%and part of the flows into detritus of primary production decreased by 30%.In characteristic parameters of ecosystem,the TPP/TR value was reduced from 2.365 to 1.657,which was close to the standard value of 1,which represented that the maturity of the ecosystem had improved to a certain degree;the FCI value changed from 4.337 to 5.097 and the FMPLvalue changed from 29.1%to 34.69%.The variations of the characteristic parameters indicated that the ecosystem's maturity had improved and was conducive to better achieve the effect of water purification.