Toward better understanding of heterogeneous succession process in mire

Background/Question/Methods

Japanese governments recently started a nature conservation project to prevent invasive forest species and to recover the original mire ecosystem because various anthropogenic stressors have caused mire degradation of drying and alder invasion in northern subarctic Japan. The mire has important influences on the hydrologic cycle and helps preserve valuable species. The author has so far developed the process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a, 2008b, 2010, 2011a, 2011b; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Watanabe, 2004, 2006, 2008a, 2008b; Nakayama et al., 2006, 2007, 2010, in press), which includes complex interactions between the forest canopy, surface water, the unsaturated zone, aquifers, lakes, and rivers, and simulated iteratively nonlinear interactions between hydro-geomorphic and vegetation dynamics including competition between native reed-sedge vegetation and invasive alder. In this study, he further extended previous researches about regular string and maze patterns by using several simultaneous partial differential equations (Rietkerk et al., 2004; Van de Koppel et al., 2005) to clarify heterogeneous succession process.

Results/Conclusions

After improving this process-based model to include down-scaling process from regional simulation to local simulation with finer resolution, he tried to extract the impact of groundwater level change, sediment deposition, and nutrient availability on the complex alder invasion pattern, and vice versa, through comparison with observed groundwater level, elevation change, and nutrient concentration in the aquifer. He also evaluated the interaction between groundwater and inundated flow and its effect on vegetation change, which shed light on two conflicting conceptualizations of peatland hydrology, so-called, shallow-flow and groundwater-flow models (Reeve et al., 2000). This integrated system also throws some light on the improvement in boundless biogeochemical cycle along terrestrial-aquatic continuum for global environmental change (Cole et al., 2007; Battin et al., 2009) because boreal and subarctic peatlands store about 15-30% of the world’s soil carbon as peat (Limpens et al., 2008) and affect the dynamics of greenhouse gases such as methane.