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Avian Response to Frost-Damaged Aspen in the Wasatch Mountains of Northern Utah
Andreas Leidolf and Ronald J. Ryel, Utah State University, Logan, UT
We examined the avian community response to frost-damaged aspen in the Wasatch Mountains of northern Utah as part of an avian monitoring program at Deseret Land & Livestock Company (DLL). In early May of 2007, DLL experienced a period of prolonged warmer-than-normal temperatures, followed by a frost event that killed most of the new aspen foliage. We used this event to assess the effects of a transitory disturbance on the aspen bird community by comparing avian monitoring data collected during 2005 and 2006 (pre-disturbance) to data from 2007 (post-disturbance). We compared relevant avian community summary statistics among years and three levels of frost damage severity (low, intermediate, severe). Interestingly, bird total abundance, species richness, and species diversity did not differ significantly among years. However, there were significant year-by-frost damage severity interactions, with plots with low levels of frost damage having significantly higher total abundance, richness and diversity. Our results suggest that 1) the post-disturbance avian community was essentially identical to the pre-disturbance community in terms of the number of individuals, as well as the composition and structure of the avian community, at the landscape level; 2) there was a pronounced shift in the spatial distribution of birds at the plot and stand level, with most individuals favoring stands with low levels of frost damage over those with intermediate and high levels of frost damage. We discuss implications of these findings for regional avian population dynamics and aspen management in the Intermountain West.