Planting for tomorrow: What drives post-fire larch reforestation success?

Photo Credit

USDA Forest Service photo by Kimberley Davis

A planted western larch seedling growing in a burned area in western Montana. 

Wildfires are burning more area across the western United States than they have in the recent past, driving an increased need for post-fire reforestation. At the same time, trees are struggling to keep up with climate change. Post-fire tree planting may present an opportunity to plant seedlings from lower-elevation seed sources that are adapted to hotter and drier conditions. Researchers from the Forest Service and University of Montana conducted a post-fire planting experiment in western Montana to see whether western larch (Larix occidentalis) seedlings from a low-elevation seed source were more successful in hot, dry conditions than seedlings from a high elevation seed source. 

Survival of western larch seedlings planted after the fire was driven mostly by site conditions—hot, dry, southwest‑facing locations had far higher mortality regardless of seed source. Seedlings from low‑elevation seed sources handled heat better, but the biggest determinant of success was simply planting in cooler, moister microsites. In practice, this means site selection will matter more than seed source, though choosing warmer‑adapted seed sources may help increase seedling survival and growth under future climate conditions.

These findings give managers clearer guidance on where post‑fire planting is most likely to succeed. Site conditions—maximum temperature, aspect, and soil moisture—are the dominant drivers of survival, so prioritizing cooler, moister microsites will yield better outcomes than focusing solely on seed source. At the same time, the study provides evidence that warmer‑adapted seed sources can buffer seedlings against high‑temperature stress, supporting cautious, climate‑informed assisted population migration. For researchers, the work highlights the need for longer‑term monitoring and more post‑fire provenance trials, since short‑term survival alone may not capture how seed sources respond as warming accelerates.

The project delivers evidence about post‑fire larch reforestation using a field-based experimental design combined with an operational post-fire planting effort. It combines a controlled seed‑source experiment with true post‑wildfire conditions, nearly 1,000 seedlings, and three years of monitoring across a steep elevation and microclimate gradient, producing insights that greenhouse studies cannot. The study’s findings imply that planting in cooler, moister microsites can reduce larch mortality, a difference that translates directly into cost savings, efficiency gains, and more acres successfully reforested.