Because anthropogenic stressors have caused mire degradations in the subarctic northern Japan such as the drying and the invasion of alder-dominant shrub forest, the Japanese governments recently started a new project to restore a meandering former river channel in the catchment in order to diminish shrub forest and to recover mire ecosystem. The author has so far developed the process-based model, called NIES Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a, 2008b, 2010; Nakayama & Fujita, 2010; Nakayama & Watanabe, 2004, 2006, 2008a, 2008b; Nakayama et al., 2006, 2007), which includes surface-unsaturated-saturated water processes and assimilates land-surface processes with satellite data describing the variation in phenology. In this study, the author further developed the integrated catchment-based eco-hydrology model to include a mutual interaction and feedback of hydro-geologic and vegetation dynamics in the mire.
Results/Conclusions
NICE simulated the hydrologic cycle, elevation change, and vegetation succession processes iteratively including the competition between two vegetation types (alder-dominant shrub forest and reed-sedge vegetation) in order to evaluate the nonlinear relationship between drying and alder invasion in the mire and to clarify a method for mire recovery. NICE reproduced well the heterogeneous alder invasion in the mire so far by various anthropogenic stressors. This implies that the study made some progress in the understanding of positive feedback between geomorphology and eco-hydrology in irregular slope and heterogeneous vegetation, whereas most of previous researches have treated regular slope and its relation to string or maze pattern. Simulation results also predicted that restoring meanders to the river channel could be effective for decrease in discharge and sediment loading of the river, increase in groundwater level at the downstream, and the mire recovery more or less in the future. Furthermore, the author gave some consideration to this heterogeneous succession in relation to self-organization and regime shift. These results suggest the effectiveness of river restoration as one of mire conservation plans for mire recovery, and the importance of the process-based model to assess the linkage of hydrological change and vegetation succession.
Reference
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