Fire regime characteristics in relation to physiography at local and landscape scales in Lake States pine forests

Abstract

Examining fire regime characteristics across temporal and spatial scales is critical to understanding relationships between fire and landscape physiography. In the Lake States (Wisconsin, Michigan, Minnesota) we have often relied on either broad extrapolation from local studies, and/or interpretations of coarse-scale Euro settlement era records tied to landscape-scale physiography to understand complex fire regimes. In this study, we used detailed fire frequency and origin-to-first-scar (OFS, patterns of fire-scar formation) intervals to evaluate fire characteristics in relation to physiography at local and landscape scales. We found frequent fires (mean fire return intervals, MFRI = 8 years) and widespread fire years were common among our sites. OFS intervals were also less than half as long (µ = 18.3) as intervals often deemed necessary for seedlings to survive fires (ca. 50 years). We found no differences in either MFRI or OFS intervals nor physiographic effects (topography and water features) at broad ecological landscape scales. Most variability in OFS was accounted for at a site scale with increased water features and topographical ruggedness both resulting in shorter OFS intervals (trees surviving and recording fires at a younger age). We found few differences in MFRI’s among sites, which ranged from 4 to 13 years. Relationships between fire resistance and stand level physiography, which was highly variable, may have a greater role than recognized in forest successional stages and stand dynamics.