Study On Spartina Alterniflora Marsh Landscape Evolution Mechanism In Coastal Wetlands

The research devoted to intrinsic mechanism of Spartina alterniflora marsh landscape evolution in Muddy coastal wetlands. It has important guiding significance to biological conservation, climate change, habitat management and ecological restoration decision. The main impact factors on Spartina alterniflora marsh landscape changes include Climate, topography, soils, hydrology and vegetation. In this study, the main line is from landscape pattern temporal dynamics analysis to mechanism of eco-driven; and to model simulation and predict. We launched a prediction of spatial and temporal dynamics of Spartina alterniflora marsh, ecological processes and their dynamics model to simulate and prediction the landscape change in typical regional of the Yancheng Nature Reserve. By analyzing the Spartina alterniflora marsh landscape expanded basic characteristics, the law of temporal and spatial evolution and ecology-driven mechanism. We established a more comprehensive coastal wetlands cellular automata (CA) model system to simulate and predict the distribution pattern of the Spartina alterniflora landscape.We proposed measures of Spartina alterniflora marsh landscape conservation and management in Yancheng coastal wetlands based on the invasion status quo of Spartina alterniflora landscape and its impact on coastal wetlands. Conclusions are as follows:(1) The whole structure and function of Yancheng coastal wetland landscape has undergone tremendous change because of Spartina alterniflora invasion. The landscape evolution has become one of the distinct features.15years, Spartina alterniflora marsh landscape has evolved from scattered patches to continuous zonal distribution as a whole, occupies the entire lower part of inter-tidal zone. During this period, Spartina alterniflora marsh area of rapid expansion and continuous zonal distribution completely separated zonal distribution of Suaeda salsa and mudflats landscape.Research of the landscape indices shows that the patches shape tends to be simple; the aggregation degree of landscape is strengthened in the wetlands. Spartina alterniflora marsh area increased by2942.6hm2, reducing363.02hm2during15years. The major shift is to S. salsa and mudflat marsh. The annual expansion rate is similar between to the sea and to the land.The biggest annual expansion rate is in6a～10a.The second is in10a-16a; and the smallest is in2a-6a.(2) Topography, soil, biological productivity and other factors are the main ecological and environmental factors driving Spartina alterniflora marsh landscape evolution in different periods.Under the influence of Spartina alterniflora.dilstion, tidal elevation (DEM) changes significantly.A typical profile analysis showed that the distribution trends of tidal elevation shows middle higher, but lower sides in Spartina alterniflora.marsh. The elevation’s mean changes from1.79m to2.07m, with an annual increase of more than3cm. In addition, other factors in addition to terrain elevation occurred changing in varying degrees from2002a to2011a.The soil properties of Spartina alterniflora.marsh are significantly different in every period. From the seaward, the soil bulk density showed a gradual increasing trend; both the soil salinity and the soil nutrients are lower two sides, higher in the middle. Moisture is higher two sides, lower in the middle. Principal component analysis showed that soil bulk density, moisture and salinity are the main soil factors that drive landscapes evolution in Spartina alterniflora.’’s marsh.Vegetation community factors indicated obvious regularity in the direction of the sea and the land. In the forefront of the expansion of the sea, the height, vegetation density, cover and the biomass (above ground) are lower; at the forefront of the landward expansion, vegetation plants grow shorter, diameter decreases and the coverage is reduced. Further studies showed that vegetation biomass and soil organic matter, bulk density exist significant correlation.(3) We constructed the cellular automata (CA) model to simulate and predict the landscape pattern changes of Spartina alterniflora marsh. The strategies were raised about coastal wetland landscape management against existing problems.We Used the C programming language and the method of software See5.0to mining landscape transformation rules. The main factors’thresholds determine by rules.We integrated the cellular automata (CA) model and GIS to get the spatial variables, the initial state and the neighbor configuration. Finally the model simulation and prediction driven by the landscape ecological processes realized in the software Matlab. Upon examination, the overall accuracy of the model reached95.20%. Kappa coefficient is0.7589. Experiments show that cellular automata (CA) model and GIS support each other. On the basis of the study that the CA model simulation> prediction and the impaction on the overall landscape and biodiversity.We imposed landscape patterns and ecosystem protection and management measures.