Short-Term Vegetation Response to Wildfire

The Rockhouse Fire in Presidio and Jeff Davis Counties in April of 2012 burned almost 314,500 acres, including a significant portion of the Mimms Ranch within the Marfa grassland plateau.  The ranch features three different ecological sites—loamy mixed prairie, shallow mixed prairie, and igneous hills mixed prairie.   The first two are normally dominated by blue grama and purple three-awn and low shrub densities and the latter by black grama and somewhat higher shrub densities including beargrass and yucca.

We sampled vegetation before and after the fire along a total of 37 50-meter transects, 18 of which were in areas subject to cattle grazing and the rest within 1-acre exclosures.  Additionally, a burn assessment was conducted immediately following the fire.

Data suggest that the drought and fire have generally resulted in a decrease in perennial grass cover, but an increase in fall and spring forb cover.  This response was similar for grazed and ungrazed sites.  This finding may have positive implications for wildlife management, but not for livestock forage production.  Therefore, where the latter is a consideration, grassland recovery should be closely monitored following such a fire event.  

graph

Decline in grass cover on all soil types on grazed areas from winter 2010 through spring 2012.

 

postfire

Mimms Ranch, immediately following the Rockhouse Wildfire, April 9, 2011.