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Avian Response to Post Wildland Fire Reseeding Treatments in Great Basin ShrubsteppeBrewerton, Adam B. 01 May 2012 (has links)
We investigated the effects of different fire restoration treatments on five shrubsteppe bird species in the Great Basin of central Utah. Sagebrush communities and the associated avifauna are under particular threat due to changing fire regimes. Although fires are locally destructive, it is hypothesized that they improve habitat by increasing landscape-level heterogeneity. As long as fire follows a historic fire regime, the plant and animal communities can usually recover. However, fires can and often do burn outside of the normal regime. The Milford Flat Fire, which occurred in west-central Utah, was the largest wildfire recorded in the Great Basin. Considered catastrophic, concern existed that natural recovery of sagebrush and its avifauna would be unlikely. To prevent this, vegetation reseeding treatments were applied immediately post-fire. These treatments included two seed mix types, with or without a shrub component, and three mechanical applications, drill seeding, aerial seeding followed by chaining, and aerial seeding only. We surveyed the avian community in the different treatment types and in untreated areas within the fire using line transect distance sampling methods. Using a space for time substitution, we sampled nearby unburned areas as reference to represent pre-fire conditions. We hypothesized that the treatment areas would be more similar to the reference than the untreated areas, and that the treatments would all have similar effects. We found some effect on the presence and extirpation of the birds at the guild and overall bird level. We found no significant effect from the treatments on the five study species at the species level, and no effects on bird densities. The effects of the restoration treatments were overshadowed by the effect of the fire on changing the habitat, namely, the density of sagebrush. We saw a pattern of birds responding to the removal or survival of sagebrush and the treatments were insufficient in affecting a short term response.
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Historic Fire Regimes on Eastern Great Basin (USA) Mountains Reconstructed from Tree RingsKitchen, Stanley G. 08 March 2010 (has links) (PDF)
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.
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