Factors controlling vegetation succession in Kushiro Mire

The NIES integrated catchment-based eco-hydrology (NICE) model was expanded to include the vegetation succession processes in the Kucyoro River catchment, Japan (NICE-VEG). The NICE-VEG simulated the water/heat budget and dynamic vegetation processes iteratively. The simulation results indicated that the spatial occupation rate of alder invasion is positively correlated with hydrogeological changes. Some discrepancies are attributable to local heterogeneity of changes in groundwater level, porosity, deposited sediments, and other limiting factors (nutrients, soil moisture, light, temperature). Furthermore, simulation of channelized rivers showed that the recharge rate of Kushiro Mire decreases greatly. This indicates that channelization will also cause an increase of sedimentation/nutrient load and flooding in the downstream area around the mire. The NICE-VEG reproduced excellently the invasion of alder in the mire over the last 30 years, which represents a dramatic advance in our understanding of the drying phenomenon associated with alder invasion. The reproducibility of these simulation results suggests that the NICE-VEG includes some of the important factors affecting vegetation succession in Kushiro Mire.