Prescribed burning to affect a state transition in a shrub-encroached desert grassland

Authors: Havstad, Kris; James, Darren

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/2010
Publication Date: 7/1/2010
Citation: Havstad, K.M., James, D.K. 2010. Prescribed burning to affect a state transition in a shrub-encroached desert grassland. Journal of Arid Environments. 74:1324-1328.

Interpretive Summary: Prescribed burning is a commonly advocated and historical practice for controlign the spread of brush, including mesquite, into grasslands on all continents. However, deserts often lack the fuel loads to effectively carry a prescribed fire in most years, and burning is seldom used as a management tools for brush control in these drier regions. Yet, when fuel is available following high rainfall years, it may be possible to control initial invasions of brush into desert grasslands. This study looked at a long-term response of honey mesquite infested grassland to a single prescribed fire. Though the prescribed burn initially removed brush from the grassland, 14 years after fire the amount of brush in burned areas was similar to unburned areas. Given that it takes approximately 10 years for the grasses to recover from fire, and that it requiares repeated burning to control mesquite, it may be unreasonable to use fire as a management tool in these deserts. Control of brush would likely require 2 or 3 prescribed burns over a 20-30 year period. Yet, prescribed fire is a relatively inexpensive practice for brush control compared to use of herbicides or mechanical cutting treatments. Burning may be an appropriate long-term infrequent tool to maintain desert grasslands under some conditions.

Technical Abstract: Prescribed burning is a commonly advocated and historical practice for control of woody species encroachment into grasslands on all continents. However, desert grasslands of the southwestern United States often lack needed herbaceous fuel loads for effective prescriptions, dominant perennial graminoids may have poor fire tolerance, and some systems contain fire-tolerant invasive species. We examined long term vegetation responses of black grama grassland that had been invaded by honey mesquite following a single prescribed burn. Vegetation responses to a 1995 prescribed burn were evaluated in a replicated randomized complete block design with a 2x2 factorial treatment structure. Treatments were prescribed burning and livestock exclusion for both a grassland-dominated and a shrub-encroached grassland state within a complex of sandy and shallow sandy ecological sites. Vegetation responses were measured in 2008, 13 years after the burn treatment application. Neither black grama basal cover not honey mesquite canopy cover were responsive (P<0.05) to any treatment. A single prescribed burn would be ineffective as a shrub control practice in this environment. Repeated but infrequent prescribed burning within shrub encroached vegetative states, when used in combination with managed grazing, may be the management required for a transition to desert grassland states within these ecological sites.