Forests in mountainous terrain are facing larger and more severe fires due to higher temperatures, earlier spring snowmelt, and longer fire seasons associated with socio-environmental change. To steward these forests, ecologists and managers increasingly rely on processes underpinning forest resilience to increasing fire activity. One important process is seed dispersal, given that seeds promote recovery in areas that burned at high severity. In the field, seed dispersal is often accounted for using the straight-line distance to live seed source. However, especially in mountainous terrain, distance does not capture spatial pattern and scale-dependent effects that determine seed supply and delivery. Measuring live seed source pattern could be a strong alternative, but little is known about its relative merit against distance and how its interactions with scale and terrain shape post-fire tree recovery. Therefore our research questions were: Does live seed source pattern outperform distance to live seed source when modeling tree species presence and post-fire regeneration density? If yes, does live seed source pattern have scale-dependent or terrain-dependent effects on post-fire regeneration density? We answered these questions using recent fires in the Gros Ventre Range southeast of Jackson, Wyoming, USA. We measured live seed source pattern and terrain at nested spatial extents around 71 burn sites, which we then related to local post-fire tree recovery.
Results/Conclusions
We found that live seed source pattern was useful for anticipating post-fire regeneration density. However, live seed source pattern was relevant at species-dependent spatial extents, reflecting different tree regeneration traits in the area (wind-dispersed, serotiny, and sprouting). Additionally, for wind-dispersed species, we found that terrain must be considered when anticipating post-fire regeneration density. Even though a burn site is surrounded with sufficient live seed source, its position in the landscape can impede recovery. Specifically, burn sites positioned above the surrounding terrain are most at risk of not restocking naturally. Finding avenues to better incorporate these interactions among live seed source pattern, tree regeneration traits, scale, and terrain into spatial planning will be needed as forests face larger and more severe fires in complex topography.