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CHANGES IN BIRD ABUNDANCE AFTER WILDFIRE: IMPORTANCE OF FIRE SEVERITY AND TIME SINCE FIRE

CHANGES IN BIRD ABUNDANCE AFTER WILDFIRE: IMPORTANCE OF FIRE SEVERITY AND TIME SINCE FIRE Fire can cause profound changes in the composition and abundance of plant and animal species, but logistics, unpredictability of weather, and inherent danger make it nearly impossible to study high-severity fire effects experimentally. We took advantage of a unique opportunity to use a before––after/control––impact (BACI) approach to analyze changes in bird assemblages after the severe fires of 2000 in the Bitterroot Valley, Montana. Observers surveyed birds using 10-minute point counts and collected vegetation data from 13 burned and 13 unburned transects for five years before fire and three years after fire. We compared changes in vegetation variables and relative bird abundance from before to after fire between the set of points that burned and the set of points that did not burn. The magnitude of change in vegetation variables from before to after fire increased with fire severity. The relative abundances of nine bird species showed significantly greater changes from before to after fire at burned points compared with unburned points. Moreover, when burned points were separated by whether they burned at low, moderate, or high severity, an additional 10 species showed significant changes in relative abundance from before to after fire at one or more severities. Overall, almost twice as many bird species increased as decreased significantly in response to fire. We also found changes in abundance between one year after and two years after fire for most species that responded to fire. Thus, species that have been termed ““mixed responders”” in the literature appear to be responding differently to different fire severities or different time periods since fire, rather than responding variably to the same fire conditions. These findings underscore the importance of fire severity and time since fire and imply that both factors must be considered to understand the complexities of fire effects on biological communities. Because different bird species responded positively to different fire severities, our results suggest a need to manage public lands for the maintenance of all kinds of fires, not just the low-severity, understory burns that dominate most discussions revolving around the use of fire in forest restoration. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ecological Applications Ecological Society of America

CHANGES IN BIRD ABUNDANCE AFTER WILDFIRE: IMPORTANCE OF FIRE SEVERITY AND TIME SINCE FIRE

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References (44)

Publisher
Ecological Society of America
Copyright
Copyright © 2005 by the Ecological Society of America
Subject
Regular Article
ISSN
1051-0761
DOI
10.1890/04-1353
Publisher site
See Article on Publisher Site

Abstract

Fire can cause profound changes in the composition and abundance of plant and animal species, but logistics, unpredictability of weather, and inherent danger make it nearly impossible to study high-severity fire effects experimentally. We took advantage of a unique opportunity to use a before––after/control––impact (BACI) approach to analyze changes in bird assemblages after the severe fires of 2000 in the Bitterroot Valley, Montana. Observers surveyed birds using 10-minute point counts and collected vegetation data from 13 burned and 13 unburned transects for five years before fire and three years after fire. We compared changes in vegetation variables and relative bird abundance from before to after fire between the set of points that burned and the set of points that did not burn. The magnitude of change in vegetation variables from before to after fire increased with fire severity. The relative abundances of nine bird species showed significantly greater changes from before to after fire at burned points compared with unburned points. Moreover, when burned points were separated by whether they burned at low, moderate, or high severity, an additional 10 species showed significant changes in relative abundance from before to after fire at one or more severities. Overall, almost twice as many bird species increased as decreased significantly in response to fire. We also found changes in abundance between one year after and two years after fire for most species that responded to fire. Thus, species that have been termed ““mixed responders”” in the literature appear to be responding differently to different fire severities or different time periods since fire, rather than responding variably to the same fire conditions. These findings underscore the importance of fire severity and time since fire and imply that both factors must be considered to understand the complexities of fire effects on biological communities. Because different bird species responded positively to different fire severities, our results suggest a need to manage public lands for the maintenance of all kinds of fires, not just the low-severity, understory burns that dominate most discussions revolving around the use of fire in forest restoration.

Journal

Ecological Applications – Ecological Society of America

Published: Oct 1, 2005

Keywords: avian communities ; BACI approach ; before––after comparison ; bird abundance ; conifer forest ; fire effects ; fire severity ; mixed-severity fire ; Northern Rocky Mountains ; wildfire

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