Grass bud responses to fire in a semiarid savanna system

• Published in: Ecology and evolution Vol. 11; no. 11; pp. 6620 - 6633
• Main Authors: Hiers, Quinn A., Treadwell, Morgan L., Dickinson, Matthew B., Kavanagh, Kathleen L., Lodge, Alexandra G., Starns, Heath D., Tolleson, Doug R., Twidwell, Dirac, Wonkka, Carissa L., Rogers, William E.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.06.2021; John Wiley and Sons Inc; Wiley
• Subjects: bud dormancy; Buds; Burns; Divergence; Dormancy; Ecosystem assessment; Encroachment; Energy; fire management; Fires; Grasses; herbaceous perennial resprouting; Hilaria belangeri; Land management; Mortality; Original Research; plant mortality; Plot (Narrative); Precipitation; Prescribed fire; Savannahs; Species; vegetative tiller reproduction; Woody plants; Edwards Plateau; fire management; vegetative tiller reproduction; plant mortality; bud dormancy; herbaceous perennial resprouting
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.7516

Increasingly, land managers have attempted to use extreme prescribed fire as a method to address woody plant encroachment in savanna ecosystems. The effect that these fires have on herbaceous vegetation is poorly understood. We experimentally examined immediate (<24 hr) bud response of two dominant graminoids, a C3 caespitose grass, Nassella leucotricha, and a C4 stoloniferous grass, Hilaria belangeri, following fires of varying energy (J/m2) in a semiarid savanna in the Edwards Plateau ecoregion of Texas. Treatments included high‐ and low‐energy fires determined by contrasting fuel loading and a no burn (control) treatment. Belowground axillary buds were counted and their activities classified to determine immediate effects of fire energy on bud activity, dormancy, and mortality. High‐energy burns resulted in immediate mortality of N. leucotricha and H. belangeri buds (p < .05). Active buds decreased following high‐energy and low‐energy burns for both species (p < .05). In contrast, bud activity, dormancy, and mortality remained constant in the control. In the high‐energy treatment, 100% (n = 24) of N. leucotricha individuals resprouted while only 25% (n = 24) of H. belangeri individuals resprouted (p < .0001) 3 weeks following treatment application. Bud depths differed between species and may account for this divergence, with average bud depths for N. leucotricha 1.3 cm deeper than H. belangeri (p < .0001). Synthesis and applications: Our results suggest that fire energy directly affects bud activity and mortality through soil heating for these two species. It is imperative to understand how fire energy impacts the bud banks of grasses to better predict grass response to increased use of extreme prescribed fire in land management. We experimentally examined the immediate (<24 hr) belowground bud responses of two dominant graminoids, a C3 caespitose grass, Nassella leucotricha, and a C4 stoloniferous grass, Hilaria belangeri, following fires of varying energy (J/m2) in a semiarid savanna in the Edwards Plateau ecoregion of Texas. Our results suggest that fire energy may directly affect bud activity and mortality for these two species. It is imperative to understand how fire energy impacts the bud banks of grasses to better predict grass response to increased use of extreme prescribed fire in land management.