Plant population persistence throughout the Great Plains, especially of the dominant grasses, is dependent on stem recruitment from the belowground bud bank. For example, >99% of aboveground stems in undisturbed tallgrass prairie were recruited from buds while <1% were recruited from seeds. Even in grazed or disturbed sites in tallgrass prairie, belowground buds make a significantly larger contribution to plant recruitment than seeds. Few grass seeds persist in the soil more than 5 years, with the seeds of some species living less than 1 year. Although a plant population’s long-term adaptation potential relies upon sexual reproduction via seed to enable shifts in genetic diversity to occur, short-term resiliency of grassland structure and function, including factors such as biomass and community composition, is mediated by the bud bank.
In northern mixed-grass prairie, native plant communities often include the rhizomatous grass Pascopyrum smithii (western wheatgrass) but are increasingly invaded by the rhizomatous grass Bromus inermis (smooth brome). The response of bud outgrowth (i.e. tiller initiation) and tiller survival of B. inermis and P. smithii to grazing and environmental conditions affects their abundance and could impact grassland resiliency to climate change. The vegetative reproduction of these two species is to be examined in two stages: 1) Spring bud availability and outgrowth in growth chamber experiments (conducted in 2014-2015) and 2) Tiller survival in greenhouse experiments (projected for 2016). Two journal articles will be published from these experiments and results will be presented at regional workshops/conferences.
Bud outgrowth of both species was assessed at three temperatures (night/day: 10/16 C, 16/22 C, 22/28 C) under well-watered conditions and at two watering frequencies under spring temperatures (10/16C) in a growth chamber experiment. The effect of clipping on bud outgrowth was also assessed for P. smithii.
Overall, the bud supply and tiller initiation capability of the invasive B. inermis remained superior to the native P. smithii under a wide range of temperatures and short-term drought. Bud banks offer insight into the control of grass population regeneration and regulation of aboveground vegetation production and composition. Knowledge of bud bank responses to temperature, soil moisture availability, and grazing will be useful in understanding the underlying mechanisms that can alter perennial grasslands. This knowledge will provide managers with the biological background of how management practices and climate change will affect our rangelands.