Fire return intervals explain different vegetation cover responses to wildfire restoration in two Sierra Nevada basins

Abstract

A simple dynamical model was used to explore the forest cover dynamics for two basins in the Sierra Nevada of California, Illilouette Creek Basin (ICB) in Yosemite National Park and Sugarloaf Creek Basin (SCB) in Sequoia-Kings Canyon National Park. Since the 1970s, fire management in these basins has attempted to restore a near-natural fire regime, after nearly a century of fire exclusion and suppression. The model describes two canopy layers, representing mixed conifer and shrub-dominated landcover types, and is calibrated using landcover maps and fire recurrence and severity data from the ICB. The calibrated model is used to explore several scenarios pertaining to increasing fire severity and return interval in the ICB, and to explore the differences between the ICB and SCB. The results indicate that (i) the ICB in 2012 had not yet reached steady state forest cover, (ii) potential future changes in fire severity and frequency will yield reductions in forest cover, and (iii) differences in forest cover change in response to fire regime restoration between basins can be explained by differences in fire histories.