Comparing historical and current wildfire regimes in the Northern Rocky Mountains using a landscape succession model

• Developed a method to simulate historical and current fire regimes.
• Compared historical and current fire regimes for a large study area in the Northern Rocky Mountains, USA.
• Derived current fire characteristics from 27-year remote sensing data.
• Current fire regimes of most forest ecosystems in the study area have moderate departures from historical conditions.

Wildland fire is a key ecosystem process that shapes the landscape of Western United States. Changes in fire regimes can therefore have profound impact on ecosystem functions and services, including carbon cycling, habitat conditions, and biodiversity. This study examined fire regime changes in the Northern Rocky Mountain region using a landscape succession model (LANDSUMv4). The objective is to report a new method to develop fire regime condition class (FRCC) maps by comparing historical reference conditions of fire regimes – simulated using historical fire record and the LANDSUMv4 model – with current fire regimes developed using 27 years remote sensing fire product and LANDSUMv4. Results of this study indicate that most forest ecosystems in the study region experienced less frequent but more severe fires during the contemporary time period compared to the historical conditions. Fire regimes have changed the most for montane forests which historically were dominated by frequent and nonlethal fires. Forest ecosystems characterized by infrequent stand replacement fires also experienced moderate departure from historical fire conditions. FRCC assessment method proposed in this study can be applied to other areas of U.S. The findings of this study will help reveal contemporary fire dynamics in this region and serve for future fire and fuel studies and other forest management applications.