Development and evaluation of a nutrient cycling extension for the LANDIS-II landscape simulation model

Long-term nutrient cycling dynamics are the result of interactions between forest succession, disturbance, nutrient cycling, and other forest processes. We developed NuCycling-Succession, a simple nutrient cycling and succession extension for the LANDIS-II landscape model of forest dynamics, to examine the interactions between these forest processes in order to develop more realistic predictions of forest response to management practices and global change. NuCycling-Succession models carbon, nitrogen, and phosphorus nutrient fluxes and masses associated with the living biomass, dead biomass, soil organic matter, soil mineral N and P, charcoal, and bedrock nutrient pools. It includes direct effects of disturbance events on nutrient cycling as well as indirect effects mediated through changes in forest composition and structure. NuCycling-Succession represents the continuum of decomposition and associated changes in chemistry using annual cohorts of leaf and fine root litter. This formulation includes the interaction of decomposition dynamics with disturbances that affect the forest floor, such as fire. Evaluation of model results relative to field data and results reported in the literature indicate the model adequately represents nutrient pools and fluxes. We present a case study of the effects of changing fire and biomass harvesting regimes on nutrient cycling in the Lake Tahoe Basin. Model results suggest that fire exclusion has resulted in substantially increased mass of nutrient pools. The NuCycling-Succession extension provides a useful simulation framework for exploring how global change factors (climate change, altered disturbance regimes) may influence nutrient cycling processes and nutrient budgets in forested ecosystems.

► We developed a nutrient cycling extension for the LANDIS-II landscape model.
► Our novel approach simulates nutrient cycling processes at the landscape level.
► Interactions among succession, fire and other forest processes are simulated.
► The extension represents fluxes of C, N and P within observed ranges.
► Results show fire exclusion has led to larger nutrient pools in the Lake Tahoe Basin.