Treatments with a severe summer fire combined with more moderate winter fire a few years later were able to do that. However, Ansley said, a combination of two severe summer fires "overshifted the grass composition toward warm-season shortgrass dominance as opposed to warm-season midgrass dominance. It improved palatability, but not production."

Ansley's research was conducted on a 300-acre fenced enclosure south of Vernon. Livestock grazing was excluded during the study period in order to identify effects of fire season alone on post-fire changes in grass community composition, he said.

Ansley's tests compared the results of a no-fire control, three winter fires in five years, two summer fires in three years, and alternate season fires with one summer fire between two winter fires. Grass composition was measured for 10 years after all fires were stopped.

The original purpose of the treatments was to determine if a concentrated series of repeated fires in different seasons could increase mesquite mortality and restore grass production, he said. All of the treatments top-killed most of the mesquite, but did not kill many plants outright and they resprouted, Ansley said. However, there were remarkable differences in how the grass community and the three perennial grass functional groups responded to the treatments.

The alternate-season fire treatment was the only treatment that increased warm-season midgrass cover, he said. This treatment was also most effective at increasing grass diversity by generating a better balance in basal cover among the three perennial grass functional groups.

The repeated summer fire treatment increased warm-season shortgrass cover, but did not increase warm-season midgrasses, Ansley said. Grasses in the repeated winter-fire treatment stayed mainly as Texas wintergrass.

Current commercial livestock grazing operations in the High Plains and Rolling Plains that utilize prescribed fire as a management tool typically burn every 10-15 years, he said. Grass production and precipitation are not sufficient to both maintain livestock grazing and burn annually or biennially as is found in the tall-grass prairie regions of eastern Kansas.

The frequency of fire treatments in Ansley’s study would not be possible in a commercial operation in Texas; however, he says the study shows that a combination of the winter and summer fires may be necessary to bring a balance of grasses back to the pastures.

SKledbetter@ag.tamu.edu