Invasive species and fire cycles in sagebrush steppe ecosystems.
Rasmussen, G.*,1, 1 Texas A&M University - Kingsville, Kingsville, TX, USA
ABSTRACT- Fire has been a critical component in shaping the sagebrush steppe ecosystems. The historic fire cycles have been altered by both increasing and decreasing the fire return intervals. Invasive species have taken advantage of the altered fire return intervals and have helped cause the changes. Depending on the area many sagebrush steppe ecosystems had a fire occurring between 25-50 years. In the drier sites the fire return interval can be longer. The most common problem associated with settlement has been the attempt to remove fire. This has lengthened the fire return interval allowing shrubby species like Juniperus spp. to become invasive. Because of the reduced level of disturbance, juniper has been able to displace sagebrush system so when a fire does occur there are few sources of seeds to allow for a recovery. An additional problem in the sagebrush steppe ecosystem is the introduction of Bromus tectorum which has shortened the fire return interval. Many of these areas now burn on 2-5 year cycles. B. tectorum alters the fuel bed by increasing the fuel continuity, is very flashy, and has a longer burning season. In addition, its annual growth form allows it to be very adapted to this high level of disturbance. As the fire return interval is altered the invasive species fuel characteristics help perpetuate the new fire return interval. In summary invasive plants are able to exploit and help perpetuate the current disturbance patterns cause by the shortened and lengthened fire cycles.
Key words: Fire, Ecosystems, Invasive, Sagebrush
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