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Ecological effects of the Hayman Fire - Part 1: Historical (pre-1860) and current (1860-2002) fire regimes

To address historical and current fire regimes in the Hayman landscape, we first present the concepts of “historical range of variability” and ”fire regime” to provide the necessary conceptual tools for evaluating fire occurrence, fire behavior, and fire effects. Next we summarize historical (pre-1860) fire frequency and fire effects for the major forest types of the Colorado Front Range, to illustrate and emphasize the key point that the ecological role of fire is dramatically different in the various forest types that are found in and around the area burned by the Hayman Fire. We consider the magnitude by which these different kinds of fire regimes in the Colorado Front Range have been altered (or not altered) by human actions, notably 20 century fire exclusion. Finally, we focus on the Hayman Fire itself, to evaluate the extent to which this large, severe fire can be regarded as either a “natural” or an “unprecedented” event in this ecosystem. Because future Front Range fires will likely occur outside the Hayman area, and because one purpose of this report is to provide a scientific basis for developing fire management policy, we believe it is important to place our assessment of the Hayman Fire into a broader context. For this reason, we discuss the role of fire in some forest types that actually are uncommon within the Hayman Fire perimeter per se (for example, spruce-fir), recognizing that the next big Front Range fire may well occur in these other kinds of ecosystems. Moreover, an understanding of the fire ecology of other ecosystems adjacent to the Hayman area helps clarify some of the unique features of the Hayman landscape. Thus, our treatment moves from basic concepts of fire and landscape dynamics in general, to a description of broad fire and landscape patterns in the Colorado Front Range, to a specific analysis of fire and landscape history within the specific area where the Hayman Fire occurred. “Historical Range of Variability” (HRV)