Wildfires blaze through the American Southwest each summer, threatening homes, damaging fragile ecosystems and scarring majestic public lands that attract tourists from around the world. According to a recent study by UNLV ecologist Scott Abella, full recovery of desert ecosystems after a wildfire can take up to 65 years and is often complicated by climatic shifts and an assault from invasive plants and grasses that squeeze out native vegetation.
For a study published in the April 2010 International Journal of Environmental Research and Public Health, Abella examined 47 documented instances of fire, land clearing or road building in the Mojave and Sonoran deserts. He measured how long each disturbed area took to fully re-establish and identified which plant species were among the first to appear and which were unable to recover.
"As fires burn through arid lands, fast-growing invasive grasses like red brome tend to repopulate post-fire sites faster than native plants and trees," says Abella, who heads the UNLV desert and dryland forest research group. "Subsequently, invasive plants and fire management practices have led to fires where they're not historically likely or more severe fires in predisposed areas."
Sites damaged by wildfires recovered faster, on average, than those affected by other disturbances. The average recovery time for all disturbed areas was 76 years. Though fire influences the chemical properties of soil, the soils themselves remain intact, leaving roots and seeds that enhance the recovery process. Abella found that common desert vegetation like creosote and blackbrush were able to recover; others, including saguaro cacti and Joshua trees, reside in areas not historically susceptible to fire and were not likely to reappear.
Climate also changes the makeup of recovery, as shifts in temperature and the appearance of non-native plant species provide a much different ecological picture today than when the original landscapes were established. For example, Southern Nevada's Spring Mountains - due to both climate change and fire suppression practices - have seen a dramatic increase in white fir, a ladder fuel that can carry surface fires up into taller pines.
"Large fires in our deserts and forests are becoming more frequent and severe, which makes aggressive post-fire establishment of native vegetation critical to ecosystem recovery," says Abella. "The more we understand about how natural recovery works, the better able we'll be to introduce successful and cost-effective management strategies."
The study, "Disturbance and Plant Succession in the Mojave and Sonoran Deserts of the American Southwest," appeared in the April 2010 issue of the International Journal of Environmental Research and Public Health.
