A forest growth and biomass module for a landscape simulation model, LANDIS: design, validation, and application

Predicting the long-term dynamics of forest systems depends on understanding multiple processes that often operate at vastly different scales. Disturbance and seed dispersal are landscape-scale phenomena and are spatially linked across the landscape. Ecosystem processes (e.g., growth and decomposition) have high annual and inter-specific variation and are generally quantified at the scale of a forest stand. To link these widely scaled processes, we used biomass (living and dead) as an integrating variable that provides feedbacks between disturbance and ecosystem processes and feedbacks among multiple disturbances. We integrated a simple model of biomass growth, mortality, and decay into LANDIS, a spatially dynamic landscape simulation model. The new biomass module was statically linked to PnET-II, a generalized ecosystem process model. The combined model simulates disturbances (fire, wind, harvesting), dispersal, forest biomass growth and mortality, and inter- and intra-specific competition. We used the model to quantify how fire and windthrow alter forest succession, living biomass and dead biomass across an artificial landscape representative of northern Wisconsin, USA. In addition, model validation and a sensitivity analysis were conducted.