Effects of landscape patterns of fire severity on regenerating ponderosa pine forests (Pinus ponderosa) in New Mexico and Arizona, USA
The authors examined how patterns of fire severity at multiple spatial scales affect long-term (30 to 50 years) ponderosa pine regeneration and survivalunder current altered fire regimes. They also considered how subsequent entries of fire influenced seedling survival, as well as biotic and abiotic factors (e.g., topographical and elevational gradients) that affect survival, germination, and growth of ponderosa pine.
The authors found that large, mixed-severity fires can result in greater heterogeneity of spatial patterns of fire. High-severity patch size varied considerably across both fires in the study. Regeneration also varied considerably within high-severity patches with most seedlings establishing and surviving after 5-10 years post-fire.
Despite subsequent management and other disturbance, including fire, on these study sites, the authors found that the spatial pattern of fire severity was still significantly tied to ponderosa pine regeneration patterns and still impacted the sites decades after the fire. Regenerating seedling density of ponderosa pine decreased with increasing distance to seed source in the high severity patches of fire. Though long-distance dispersal did occur, the rate of recovery was slower with increasing distance to seed source in the larger high-severity patches.
General climate trends after the fires did not relate clearly to forest regeneration for either site, and despite periods of wet years and drought years, forest regeneration occurred at both sites. Therefore, the authors stated that future large fires are not necessarily catastrophic to ecosystems and that process-based restoration may provide resiliency in the forests in the face of changing fire regimes.