Abstract

Management of natural landscapes requires knowledge of key disturbance processes and their effects. Fire and forest histories provide valuable insight into how fire and vegetation varied and interacted in the past. I constructed multi-century fire chronologies for 10 sites on six mountain ranges representative of the eastern Great Basin (USA), a region in which historic fire information was lacking. I also constructed tree recruitment chronologies for two sites. I use these chronologies to address three research foci. First, using fire-scar data from four heterogeneous sites, I assert that mean fire interval (MFI) values calculated from composite chronologies provide suitable estimates of point MFI (PMFI) when sample area size is ≈&frac; ha. I also suggest that MFI values for single trees can be used to estimate PMFI after applying a correction factor. Next, I infer climate effects on regional fire patterns using 10 site chronologies and tree-ring-based indices of drought and of El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation ([PDO), Pacific Ocean surface temperature variability known to affect North American climate. Regional fire years (≥33% of recording sites) were synchronized by wet-dry cycles where the probability of occurrence was highest in the first year of drought following a wet phase and lowest when climate conditions transitioned from dry to wet. Regional fire probability was highest when ENSO and PDO were negative (Southwest pattern). Local fire years occurred under a broad range of conditions. Fire seasonality was bimodal with early and late-season fires dominant. I imply that Native American burning practices were responsible for differences in historic and modern fire seasonality. Lastly, I assess fire regime and tree recruitment variability within two fire-sheds. PMFI varied more than 10-fold within each site. A mixed-severity regime was dominant. A majority (>60%) of fires were small (<10 ha) but together accounted for a minor proportion of area burned. Recruitment pulses varied spatially from stand to landscape-scales and were often synchronous with multi-decade, fire-quiescent periods. I recommend that management strategies employ fire and fire-surrogate treatments to restore disturbance processes to these and similar landscapes at spatial and temporal scales consistent with the historic record.

Degree

PhD

College and Department

Life Sciences; Plant and Wildlife Sciences

Rights

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