Subalpine forests occur in the highest mountains of the Northern Rockies. Because these ecosystems only experience fire every 100-250 years, it is unclear how these forests recover after fires, which are expected to happen more often in the future. 

To determine how resilient these forests have been to past climate and fire events, researchers supported by the North Central CASC used lake sediment cores from Silver Lake, Montana to look back 4,800 years into the history of these ecosystems. Balancing on inflatable rafts on Silver Lake, Montana in the Northern Rockies, researchers extracted 13 sediment cores, drilling down to 7 meters in the sediment through more than 50 feet of water. Lake sediments are a linear record of the past, with deeper layers revealing older natural events that have left signatures in the sediment through pollen or charcoal, for example. Published in the Journal of Ecology, their study looked into the past by slicing each sediment core into half centimeter increments – approximating ten-year increments of time. While the researchers expected to find different recovery responses based on climate, they instead found surprisingly consistent recovery after both wet and dry climatic periods, and after fires.  

Despite the forests’ historical resilience, concerns arise about their future adaptability as temperatures continue to rise and conditions continue to become drier. The researchers predict that small increases in fire activity could still fall into the range of historical patterns, but they caution that ongoing climate change may lead to fires that surpass what the forests have previously experienced. 

This work is supported by the North Central CASC Project "Science to Inform Post-fire Conifer Regeneration and Reforestation Strategies Under Changing Climate Conditions.”