Spatio-temporal Process,influencing Factors And Self-organization Behaviors Of The Dynamic Evolution On Scirpus Mariqueter Wetland

Coastal wetland ecosystem locates at the intersection of land and ocean.The complete coastal wetland ecosystem provides the biological habitats for ecological and economic species and contributes to resist coastal risks.But the unique geographical location induces its habitats to be sensitive and vulnerable.The increasing invasions of human activities such as reclamations and urbanizations have caused the extrusion of wetland areas,destruction of structures and functions.With the recognition of the extremely remarkable ecological value of coastal wetlands in recent years,ecological restoration projects of coastal wetlands have risen worldwide.Studying different backgrounds that driving the wetlands degradations and tracking the specifically ecological restoration process may provide a feasible solution to effectively prevent redegradation after repair.In this paper,the ecological restoration of Scirpus Mariqueter(S.Mariqueter)wetland in Nanhui Dongtan was considered as the baseline.We explored the driving forces of wetland evolution and degradation by characterizing the landscape pattern evolution of the Yangtze River estuary wetland across 60-year scale.On the other hand,the relationships between the vegetation spatial pattern and the core factors,i.e.,soil salinity and surface elevation,were explored by investigating and charactering their dynamic changes.And revealed the complex Hydrodynamics and sedimentations on Nanhui Dongtan wetland.Finally,the self-organizing behaviors of S.Mariqueter patches were studied,and an effective scheme for the managements and re-remediations of ecological restoration on coastal wetland was proposed.1)Dynamic Evolution and Driving Forces of Wetland Landscape in the Yangtze River Estuary in the Past 60 YearsIn this study,the land use/cover vector data for 1960,1980,1990,2000,2010,and 2015 were used to calculate and characterize the landscape metrics and dynamics of the Yangtze Estuary.The hypsometric 6 m curve was first delineated and considered in the research of the Yangtze Estuary wetlands landscape patterns.The associated landscape-changing driving forces were then analyzed through correlation analyses using socioeconomic variables.Three main conclusions were obtained from the results.First,from 1960,the total area of coastal wetlands consistently increased while the trend of landscape patterns became more complicated.According to the associated economic development policy during the studied period,the year 2000 was found to be a boundary after which the landscape metrics differed from prior years.Second,the hypsometric 6 m curve can provide indispensable information for characterizing wetland patterns.Even though the patterns are similar when the hypsometric 6 m curve is not considered,the change range of the landscape metrics differs,and the extent and intensity of the metrics are higher than when the hypsometric 6 m curve is not considered.Third,agriculture and urban development are recognized as the major factors driving landscape evolution.This study emphasizes the importance of integrating land and sea when crafting wetlands conservation policies on coasts around the world.2)Spatial Differentiation and its Influencing Factors of Scirpus Mariqueter on Nanhui Dongtan WetlandAlthough the factors that dominate the spatial pattern of vegetation are somewhat different geographically,salinity is the primary control factor for most coastal vegetation species.This paper runs synchronously with the main line of the ecological restoration process on Nanhui coasts where seasonal changes of three core factors,i.e.,vegetation density,soil salinity and coastal elevation are recorded detailly.These factors interact with each other and progressively reveal a coincided distribution trend.The whole process was classified into four periods to characterize the restoration process according to vegetation community dynamics.By regression analysis the results reveal elevation,not soil salinity,is the most critical factor that dominates the vegetation spatial pattern of survival,expansion and extinction on Nanhui coasts.Vegetation extinction pattern performs certain influences on salt marshes especially in environments with intricate hydrological and sedimentary dynamics such as Nanhui coasts.Without vegetation communities the deficient resilience may cause the extinction when facing the strong hydro-environment.The “vulnerable zone” between vegetation communities and bare beach is critical zone which could determine the success of coastal restoration.3)Self-Organizing Behavior of Patches Dynamic in Scirpus MariqueterWith the successful colonization of saltmarsh vegetations,most species tend to shape patch patterns in search of further expansion.The effective function model selected by combining various models with natural growth curve of S.Mariqueter and then was used to fit and compare the growth curve of experimental patches.ANOVA one-way analysis of variance was used to explore the effective expansion of S.Mariqueter with different elevations and scales of patches.The results show that: 1)the self-organizing behavior is an important expansion strategy of S.Mariqueter.2)The asymptotic regression model can reflect the changes of S.Mariqueter in the natural growth,and the growth pattern of self-organization patches is consistent with natural growth in the appropriate elevation interval(2.7m-3.7m).3)S.Mariqueter patches present the most effective expansion pattern within the elevation of 3.2m and patch size of 1 × 1m2.Meanwhile,this study discussed the existence of the scale-dependence feedback between S.Mariqueter and the sediments,which would determine survival,expansion and extinction of vegetation patches.When the effect of local positive feedback is greater than that of negative,the vegetation patches will expand;while the negative feedback effect is greater,the vegetation patches will disappear.Finally,this study proposes that along the process of ecological restorations,especially for the coastal wetlands with deteriorating habitats,supplementary planting of patches,which resist external disturbances effectively,can alleviate the extrusion process of vegetation.