Simulated Effects of Wind and Harvesting on Detritus, Soil Organic Carbon, and Species Composition in Northern Wisconsin

Total forest carbon (C) storage is determined by forest succession, multiple interacting disturbances, climate and the edaphic properties of a site or region, including soil texture and depth. How these complex processes interact will determine forest carbon dynamics at landscape and regional scales. We have developed a new succession extension for the LANDIS-II forest landscape simulation model that incorporates the belowground soil C dynamics of the Century soil model. This extension simulates three primary soil organic matter (SOM) pools (fast, slow, passive), litter dynamics, and nitrogen (N) feedbacks to overstory production. The extension was validated against data from the Willow Creek experimental forest in Wisconsin, USA. We subsequently initialized the full model to simulate forest dynamics of 9800 ha of the surrounding forest landscape with harvesting and wind, two common disturbances in mesic forests of the Lake States. We simulated three management scenarios: no harvesting, standard harvesting with slash left in place, and whole tree harvesting where all slash is removed. A historic wind throw regime (50 year wind rotation period, including light, moderate, and extreme events) was included in all scenarios. We estimated forest compositional change and C storage. Our results indicate a strong feedback from harvesting to litter C and the slow SOM pools. The fast and passive SOM pool was not significantly altered. Overall, the simulations with no harvesting had substantially greater total C and continued to sequester C. Standard harvest simulations had more C than the whole tree harvest simulations, although the differences were slight. Under both harvest regimes, C accrual was not evident after 150 years. In conclusion, we have developed a robust model of C and N cycling that leverages an existing forest modeling framework to simulate landscape and regional scale interactions among forest disturbances, climate change, and soil processes