Fire Ecology and Management of Southwestern Forests

Forests in the southwestern USA are well adapted to dry conditions. High lightning incidence, long human habitation, and frequently windy conditions make the Southwest stand out for a high pace of burning. Forests are structured by climatic gradients created by elevation and topography. Low-elevation woodlands experience the driest conditions, but low productivity limits fuels. At the other extreme, high-elevation forests produce abundant fuels but are rarely dry enough to burn. The "sweet spot" in the middle elevations, dominated by pines and other mixed conifers, is characterized by frequently recurring weather conditions suitable for fire, and has a contiguous fuelbed of litter and herbaceous plants. This makes for one of the most frequent fire regimes in the world, comprised primarily of surface fire. Prior to Euro-American settlement, Native Americans used fire and co-existed with the landscape's fire regime, but colonists brought different perspectives and land uses, excluding fire from most southwestern forests for well over a century. Severe fires are becoming larger, threatening people and structures as well as ecosystem sustainability. Coupled with several recent decades of steadily warming temperatures and much hotter scenarios predicted through the twenty-first century, future southwestern forests are likely to be drastically altered by interacting effects of wildfire, biotic disturbances, and drought.