Exotic annual grass invasion alters fuel amounts, continuity and moisture content
Kirk W. Davies A C and Aleta M. Nafus B
+ Author Affiliations
- Author Affiliations
A USDA Agricultural Research Service, 67826-A Highway 205, Burns, OR 97720, USA.
B Oregon State University, Eastern Oregon Agricultural Research Center, Burns, OR 97720, USA.
C Corresponding author. Email: kirk.davies@oregonstate.edu
International Journal of Wildland Fire 22(3) 353-358 https://doi.org/10.1071/WF11161
Submitted: 11 November 2011 Accepted: 14 June 2012 Published: 3 October 2012
Abstract
Many exotic annual grasses are believed to increase wildfire frequency to the detriment of native vegetation by increasing fine fuels and thus, creating a grass-fire cycle. However, information on differences in fuel characteristics between invaded and non-invaded plant communities is lacking, or is based mainly on speculation and anecdotal evidence. We compared fuel biomass, cover, continuity and moisture content in plant communities invaded and not invaded by cheatgrass (Bromus tectorum L.), an exotic annual grass, in 2010 and 2011 in south-eastern Oregon, USA. Annual grass-invaded communities had higher fine fuel amounts, greater fuel continuity, smaller fuel gaps and lower fuel moisture content than did non-invaded plant communities. These conditions would increase the probability that ignition sources would contact combustible fuels and that fires would propagate. Fuel characteristics in the annual grass-invaded communities in our study may also support faster spreading fires. Fuel moisture content was low enough to burn readily more than a month earlier in annual grass-invaded communities than in non-invaded communities, thereby expanding the wildfire season. The cumulative effect of these differences in fuel characteristics between exotic annual grass-invaded and non-invaded plant communities is an increased potential for frequent, large-scale, fast-spreading wildfires. We suggest that research is needed to develop methods to mediate and reverse these changes in fuel characteristics associated with B. tectorum invasion.
Additional keywords: cheatgrass, fire risk, invasive plants, wildfire.
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