Fact Sheet: Unsupported inferences of high-severity fire in historical dry forests of the western United States: response to Williams and Baker.

A recent study in Global Ecology and Biogeography (Williams and Baker 2012, hereafter W&B) described the historical conditions of forest structure and fire regimes on four large landscapes in Arizona, Colorado and Oregon. W&B used notes made by land surveyors who worked in these landscapes in the late 1800s and early 1900s, a period before many impacts of modern land uses, such as large-scale fire control, took place. Based on these data, W&B developed an interpretation of past conditions in ponderosa pine and dry mixed conifer forests that differs from previous research. W&B asserted that these forests historically included relatively high densities because of past fire regimes of moderate to high severity fires. Natural regeneration following such fires would lead to numerous, small and similar aged trees. W&B concluded that current management practices of thinning small trees and using low-severity prescribed burns would damage forests, rather than restore them. The inferences drawn by W&B about past forest ecology contrast sharply those reported by numerous previous researchers, who used tree-ring and historical data to show that dry forests had predominantly surface fire regimes with relatively open, uneven-aged forests. A group of 18 forest ecologists, concerned about the lack of scientific support for the conclusions by W&B, wrote a response (Fule et al. 2013). This fact sheet summarizes the key issues of our response. A rebuttal to the response was published by Williams and Baker (2014)