Prescribed Fire Increases Seedling Recruitment in a Natural Pitch Pine (Pinus rigida) Population at its Northern Range Limit

Disturbances, including wildfire, play an important role in forest maintenance, and have been modified over time. Determining the importance of historical disturbance can be complex, especially if disturbance regimes differ over a species' range. Pinus rigida (pitch pine) is associated with wildfire in the core of its range; however, the association becomes less certain toward its range margins, including at the northeast extent of its range in the Thousand Islands Ecosystem (TIE), Ontario, where the species is rare. To test for fire dependence of seedling recruitment in a natural pitch pine population at this range limit, we compared the efficiency of prescribed fire to mechanical and control treatments. We used a Before–After Control–Impact (BACI) design at two sites in the TIE, controlling for the effects of canopy cover, understory cover, and depth to mineral soil. Pitch pine seedlings were observed for the first time in decades in the TIE following treatment; only fire had a significant positive effect on recruitment. Our results suggest that prescribed fire is effective in increasing pitch pine seedling recruitment even in a marginal natural pitch pine population. We discuss what mechanisms might explain these results, as well as restoration considerations including the potential for modified mechanical disturbance treatments where prescribed fires might not be feasible.