Biological legacies and mimicking natural disturbance regimes in Sierra Nevada forests

Background/Question/Methods

A central challenge in managing Sierra Nevada forests has been trying to reduce fuel accumulations from decades of fire suppression without adversely impacting ecosystem attributes.  In particular, fuels treatments are often slowed or stalled by concerns for maintaining or improving habitat for threatened species.  Over the last decade, however, substantial ecological and silvicultural research suggests practices could be modified to reconcile some of these different objectives. 

Results/Conclusions

Historically fire was the strongest evolutionary force shaping ecosystem processes and forest structure.  Reconstruction studies suggest fire intensity and frequency topographically varied by moisture microsite within stands, and by slope position and aspect across watersheds.  Managing fuels and forest structure to match these scales of variability could provide different wildlife habitats.  These conditions would include areas of dense canopy cover associated with sensitive species such as the California spotted owl and Pacific fisher, and more open forest and shrub conditions favored by other species including several important small mammal prey.  While fire appears essential to restoring many ecosystem processes, prescribed burns cannot be applied in some conditions.  Mechanically manipulating fuels and forest structure by topography, however, may still be a careful approach to partially mimicking historical conditions and influencing burn intensity when wildfire occurs.  Topographically varying fuel load and forest structure may be a cautious approach to managing Sierran forest in congruence with the disturbance force that historically shaped their ecological processes.