Using the Vegetation Dynamics Development Tool (VDDT), we constructed state-and-transition models (STM) for cold ponderosa pine bunchgrass systems of northern Arizona. We included historic and contemporary fire frequencies in the respective models, and integrated forest insect and disease events. For the contemporary model, we added anthropogenic transitions based on the types and frequencies of current management activities. We calculated the historic proportion of each vegetation state by averaging model outputs from multiple 1000 yr simulations. We summarized current conditions from remote-sensing based existing vegetation map data, and then used the contemporary model to generate out-year projections as expressions of current management practices. Finally, we generated ecological departure ratings based on disparities between current and historic conditions, and between projected and historic conditions. Our analysis indicated that fire suppression coupled with infrequent management activities contributed to already significant trends in departure from reference conditions. We concluded by recommending additional steps for evaluating the effects of climate change, as well as the effects of alternative management scenarios for addressing climate change issues.

Weisz, Reuben, Jack Tripeke and RossTruman. Fire Ecology 5(1): 100-114