Effects of mowing on cool-season invasive prairie grass bud bank: Smooth brome

Background/Question/Methods

Smooth brome (Bromus inermis) is an introduced cool-season, sod forming, fast-growing, perennial rhizomatous grass.  It is a highly competitive species, spreading by both seeds and rhizomes.  Once established, it can form a dense monoculture that displaces native species, reduces biodiversity, and alters ecological processes.  Although prolific seed production provides an avenue for smooth brome dispersal and initial colonization, vegetative reproduction via the belowground bud bank is the primary means for its local spread and persistence.  Different management practices have been applied to control smooth brome, however, there is a body of evidence demonstrating these managements have only minimal and short-term effects. Even though aboveground perennial grasses population persistence is strongly determined by the tiller reproduction from the belowground bud bank, effects of these managements on the belowground bud bank of smooth brome has not been evaluated.  The objective of this study was to examine the effects of simulated grazing (mowing) on smooth brome bud bank.  Experiment was a complete random block design with 4 treatments by mowing and 4 replications.  Prior to each treatment, stem density was recorded within two 0.1m²quadrats.  Three tillers were randomly selected from each treatment plot and excavated to determine total number of buds and viability.

Results/Conclusions

Results showed that mowing once at the boot stage significantly reduced total number of buds, active buds, and tiller density, but increased the percentage of bud outgrowth into tiller by the end of growing season, and tiller : bud ratio.  Mowing twice at the later growing season decreased the percentage of bud outgrowth into tiller and tiller : bud ratio, indicating smooth brome may exhaust its buds and reserved resource, or lack of adequate growing period to initiate new tillers. Understanding how a species bud bank functions will allow managers to properly prescribe timing and methods of prescribed burning, grazing, or combinations, which will influence bud bank and aboveground tiller population dynamics. This will lead to development of adaptive management strategies that sustain long-term effectiveness of control management practices, and simultaneously promote desirable native species.