SYMP 10-4 - Ecological silviculture in the frequent fire domain

Dry, frequent-fire forests share many of the same historical land-use legacies, ecological drivers, management challenges, and desired outcomes for how they function and the services they provide. Consequently, there are common threads describing how concepts of ecological silviculture can be practiced when aiming to meet the objective of sustained resilience. We discuss these commonalities for longleaf pine and pine-oak forest types in the U.S. southeast as well as interior ponderosa pine and mixed-conifer forest types in the U.S. west. One commonality in frequent-fire forests was the need to restore and sustain pine species. A focus on pine species is related to the need to address the preferential removal of pine in the past, but also the benefit of pine litter layers to facilitate prescribed fire in the future. A second commonality is the need to practice various versions of transformation silviculture, where single-cohort, high-density stands can be gradually transformed into low-basal area, large-tree dominated, multi-cohort stands with heterogeneity occurring primarily at the ~0.1 to 1 ha scale. This again is related to past practices, especially clearcut harvesting and suppression-caused high-severity fires that have resulted in single-cohort stands. It is also related to the need for open yet complex structures that will be more likely to burn with low intensity during wildfires. Desired future structures for these types are described as savannas or woodlands, maintained with tree biomass densities far below their maximum carrying capacities. Some larger, harvest-created patches (>1 ha) are described as aligned with natural disturbance regimes, but only when retention of legacies (large trees/snags) is included. Ecological silviculture for these forest types emphasizes the explicit need for prescribed fire to be ubiquitous in all silvicultural planning. Except for some limited situations where prescribed fire may be undesirable, prescribed fire has a critical role regardless of the stage of forest development or the given starting forest structure. In addition to its functioning as a keystone ecological process, it is also recognized that it is the most practical and effective silvicultural tool for reducing surface fuels and future wildfire severity. Accordingly, many of the thinning and harvesting practices recommended across these forest types are suggested as a means to increase the feasibility of using prescribed fire in the future.