Small Mammal and Vegetative Response to Wildfire and Grazing in the Trans-Pecos, Texas

Small mammals are an integral component of semi-arid grassland ecosystems, and the small mammal community present in an area can be an indicator of available habitat and condition of the rangeland.  In 2009, we initiated a study looking at the relationship between vegetation and small mammal communities on the Marfa grasslands of west Texas.  Then, on April 9, 2011 the Rock House wild fire, west of Marfa, Texas, burned approximately 314,000 acres. With this fire came much damage to human structures and pastureland, but it also brought unique research opportunities for those of us interested in wildlife management. Fire has been an important factor in maintaining the health and integrity of semiarid grasslands in the Trans-Pecos for centuries, and the occurrence of the Rock House fire during the course of this research allowed us the chance to evaluate the response of vegetative and small mammal communities to wildfire.

Pre and post-fire measurements of vegetation were collected, and small mammal abundance was estimated using mark-recapture techniques.  All data was collected along transects established within representative ecological sites. After the fire, a burn assessment of the 36 vegetation transects indicated that 25 burned at 100%, 6 between 80% and 100%, 1 at 31%, and 4 at 0%. There were significant decreases in vegetation cover one season post-fire in all ecological sites and gaps between vegetation increased dramatically in size; although fall forbs increased. Small mammal populations had low abundance pre-fire, but saw a large decrease post-fire.

Timing of the recovery of the landscape relies on climatic patterns, notably precipitation, and other ecological factors like grazing. Precipitation was well below average for 2011, but was near average in 2012. There was a measurable increase in both perennial grasses and forbs for the spring and fall 2012 seasons, while gaps between vegetation were reduced. The small mammal populations responded with vegetation growth and saw increases close to pre-fire levels by fall 2012.

As the grasslands continue to recover from the Rock House fire, we are continuing to monitor the changes to the small mammal community, and compare the communities found in burned and unburned areas, as well as grazed and ungrazed areas.  Knowing how vegetative and small mammal communities respond to fire and grazing will give a more complete and accurate assessment of the effect that these processes have on the landscape.

small mammal

The abundance and species makeup of the small mammal community present in an area can provide valuable information on the condition of available habitat.

 

burned area

Continual monitoring of burned areas is helping researchers to better understand the factors which affect desert grassland recovery after a fire.