Designing a fire module for LANDIS PRO to simulate variable intensity fire regimes on forest landscapes

Background/Question/Methods

Fire is an important disturbance component in many forest ecosystems at multiple spatial scales. Most forest landscape models (FLMs) simulate fires as stand-replacing events. However, in central hardwood and temperate forests these high intensity/high frequency fires are uncommon. When modeling an area with a low intensity fire regime the FLM must be capable of simulating partial mortality of smaller age cohorts within the stand. This work builds upon the new development of the LANDIS PRO FLM which tracks tree density and size for each age cohort within a pixel. This data structure is more compatible with common forest sampling field data than previous presence/absence based structures used by the LANDIS model.  Thus, we designed a fire module that uses species characteristics, such as fire tolerance and size, to interact dynamically with fire events to simulate mortality within each age cohort present. To test the realism of fire effects at the stand level we simulated a forest landscape in the Ozark Highlands of Missouri and compared the results to continuous field inventory data collected within the area at the Missouri Ozark Forest Ecosystem Project (MOFEP).

Results/Conclusions

Results at the species level show that post-fire mortality within individual size classes of Quercus alba, Quercus velutina, Acer saccharum and Carya spp. was similar to observed values from controlled field experiments at MOFEP. Modeled post-fire stand responses such as tree density, stocking percent and quadratic mean diameter followed trends observed in MOFEP plots following low intensity fires. These results show that the fire module can realistically simulate at a stand level the low-intensity, medium-frequency fire regime that has been observed within the study area. This increases the utility of LANDIS PRO as a tool for assessing the effects of anthropogenic or natural changes to an ecosystem.