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Keywords:

  • climate change;
  • Durango pine;
  • fire;
  • Jeffrey pine;
  • ponderosa pine

Abstract

Forest restoration guided by historical reference conditions of fire regime, forest structure, and composition has been increasingly and successfully applied in fire-adapted forests of western North America. But because climate change is expected to alter vegetation distributions and foster severe disturbances, does it make sense to restore the ecological role of wildland fire through management burning and related activities such as tree thinning? I suggest that some site- and date-specific historical conditions may be less relevant, but reference conditions in the broad sense are still useful. Reference conditions encompass not only the recent past but also evolutionary history, reflecting the role of fire as a selective force over millennia. Taking a long-term functional view of historical reference conditions as the result of evolutionary processes can provide insights into past forest adaptations and migrations under various climates. As future climates change, historical reference data from lower, southerly, and drier sites may be useful in places that are higher, northerly, and currently wetter. Almost all models suggest that the future will have substantial increases in wildfire occurrence, but prior to recent human-caused fire exclusion, fire-adapted pine forests of western North America were among the most frequently burned in the world. Restoration of patterns of burning and fuels/forest structure that reasonably emulate historical conditions prior to fire exclusion is consistent with reducing the susceptibility of these ecosystems to catastrophic loss. Priorities may include fire and thinning treatments of upper elevation ecotones to facilitate forest migration, whereas vulnerable low-elevation forests may merit less management investment.