Seasonal timing of fire alters biomass and species composition of northern mixed prairie

Authors: Vermeire, Lance; RUSSELL, MORGAN - Texas A&M University

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2018
Publication Date: 7/20/2018
Citation: Vermeire, L.T., Russell, M.L. 2018. Seasonal timing of fire alters biomass and species composition of northern mixed prairie. Rangeland Ecology and Management. 71(6):714-720. https://doi.org/10.1016/j.rama.2018.06.005.
DOI: https://doi.org/10.1016/j.rama.2018.06.005

Interpretive Summary: Fire plays a central role in influencing ecosystem patterns and processes. However, documentation of fire seasonality and plant community response is limited in semi-arid grasslands. Most prescribed burns occur during spring and fall, when windows of safe burning conditions are often broad. Burning under these conditions may not produce the natural range of fire severities and subsequent fire effects that typically result from naturally occurring fires. We evaluated aboveground biomass, cover, and frequency response to summer, fall, and spring fires and no fire on silty and clayey sites in semi-arid, cool-season-dominated grassland. The magnitude of change in biomass between years was greater than any differences among fire treatments. Still, differences existed among seasons of fire. Summer fire reduced non-native annual forb frequency (3 vs. 10 ± 2%) and needleandthread, reduced native annual forbs the first year, increased Sandberg bluegrass and bare ground, and increased sixweeks fescue the second year. Fall fire increased grass biomass (1224 vs. 1058 ± 56 kg·ha-1), but fall fire effects were generally similar to those of summer fire. Spring fire effects tended to be intermediate between those of no fire and those of summer and fall fire with the exception that spring fire was most detrimental to needleandthread the first growing season and did not increase bare ground. All seasons of fire reduced forb biomass, reduced frequency of Japanese brome and sages, reduced needleandthread, sixweeks fescue and native annual forbs the 1st year, and reduced litter, but increased basal cover of cool-season perennial grasses (2.2 vs. 0.6 ± 0.4%). Although species composition varied with season of fire, fire during any season increased dominance of native species compared to no fire (6.6 vs. 2.0 ± 1.0% basal cover) and maintained productivity.

Technical Abstract: Fire plays a central role in influencing ecosystem patterns and processes. However, documentation of fire seasonality and plant community response is limited in semi-arid grasslands. Most prescribed burns occur during spring and fall, when windows of safe burning conditions are often broad. Burning under these conditions may not produce the natural range of fire behavior and subsequent fire effects that typically result from naturally occurring fires. We evaluated aboveground biomass, cover, and frequency response to summer, fall, and spring fires and no fire on silty and clayey sites in semi-arid, C3-dominated grassland. The magnitude of change in biomass between years was greater than any differences among fire treatments. Still, differences existed among seasons of fire. Summer fire reduced non-native annual forb frequency (3 vs. 10 ± 2%) and Hesperostipa comata, reduced native annual forbs the first year, increased Poa secunda and bare ground, and increased Vulpia octoflora the second year. Fall fire increased grass biomass (1224 vs. 1058 ± 56 kg·ha-1), but fall fire effects were generally similar to those of summer fire. Spring fire effects tended to be intermediate between no fire and summer and fall fire with the exception that spring fire was most detrimental to H. comata the first growing season and did not increase bare ground. All seasons of fire reduced forb biomass, reduced frequency of Bromus japonicus and Artemisia spp., reduced H. comata, V. octoflora and native annual forbs the 1st year, and reduced litter, but increased basal cover of C3 perennial grasses (2.2 vs. 0.6 ± 0.4%). Although species composition varied with season of fire, fire during any season increased dominance of native species compared to no fire (6.6 vs. 2.0 ± 1.0% basal cover) and maintained productivity.