There have been several studies on forest disturbance or decline caused by deforestation or giant natural disasters, with varying durations of influence. Through over 30 years of catchment hydrology monitoring in the Kiryu Experimental Watershed (KEW), we found a significant and long-lasting (>25 years) enhancement of stream NO₃^- concentration after the dieback due to pine wilt disease (PWD) occurred from 1992-1994. We can hypothesize that some irreversible change has occurred in the internal nitrogen cycling system.
To elucidate the mechanism of how PWD disturbance changed the internal nitrogen cycle in this area, we measured the spatiotemporal distribution and vertical infiltration of soil inorganic N, the net rate of main nitrogen cycling processes, and soil microbial biomass. Additionally, we measured δ15N‐NO₃^- and δ18O‐NO₃^- from both soil extraction water and stream water to quantify the specific pathway of internal forest N cycling along the hydrological processes.
A Multi-Agent System (MAS) model of KEW's N cycling was built to explore how various environmental disturbances could affect forest N cycling. We propose that the MAS simulation, combined with field monitoring, helps to understand the response of forest ecological systems to large disturbances such as PWD, from the unity to the community scale.