Wildland Fire: Understanding and Maintaining an Ecological Baseline

The goal was to synthesize the literature on wildland fires, how they create resilient landscape mosaics that affect ecosystem function and maintenance of biodiversity, and how the fires themselves are affected by wilderness edge effects and climate change. The emphasis is on cold-temperate and boreal forests. The interactions of fires with landforms create large-magnitude spatial and temporal heterogeneity in fire severity that cannot be seen in smaller natural areas. Patterns of live and dead biomass and characteristic syndromes of fire-species interactions determine future successional trajectories and spatial-temporal dynamics of landscape mosaics. Therefore, wildlands with freely occurring fires provide a scientific baseline for complexity of vegetation structure and maintenance of biodiversity and ecosystem processes on time scales from years to centuries and millennia. Although wildlands are impacted by climate change, they may have considerable resilience, partly due to fire occurrence, and may still serve as a moving baseline. Thus, the patterns observed in wildlands can be used as blueprints for restoration of landscape structure, biodiversity, and ecosystem function in human-dominated ecosystems. Wildland fires play an important role in maintenance of ecological function and biodiversity, even on landscapes where fire is considered to be rare. At time scales of centuries, fires in large wilderness areas maintain a balance among successional stages, and although early and late-successional stages are rarely absent, their occurrences change in space and time, possibly leading to metapopulation dynamics for species that depend on certain successional stages. Over thousands of years, fires influence the trajectory of ecosystem retrogression, and in cold climates, fires can prevent ecosystem acidification that reduces forest productivity. Fire regimes within large wildlands are subject to change caused by fragmentation effects at large spatial extents; this can result in increased or reduced fire frequencies (disturbance dilution effect) within wildlands. Wildland managers need to think about how changes in the surrounding landscape influence the integrity of the natural disturbance baseline, while forest managers need to think about how harvesting compares to the baseline with respect to maintenance of productivity and biodiversity.