Bud-bank and tiller dynamics of co-occurring C3caespitose grasses in mixed-grass prairie

PREMISE OF THE STUDY: Tiller recruitment from the belowground bud bank of caespitose grasses infl uences their ability to monopolize local resources and, hence, their genet fi tness. Diff erences in bud production and outgrowth among tiller types within a genet and among species may explain co-occurrence of caespitose grasses. This study aimed to characterize genet bud-bank and tiller production and dynamics in two co-occurring species and compare their vegetative reproductive strategies. METHODS: Bud-bank and tiller dynamics of Hesperostipa comata and Nassella viridula , dominant C 3 caespitose grasses in the northern mixed-grass prairie of North America, were assessed throughout an annual cycle. KEY RESULTS: The two species showed similar strategies, maintaining polycyclic tillers and thus creating mixed-age genet bud banks comprising multiple bud cohorts produced in diff erent years. Vegetative tillers produced the majority of buds, whereas fl owering tillers contributed little to the bud bank. Buds lived for at least 2 yr and were maintained in multiple developmental stages throughout the year. Because bud longevity rarely exceeded tiller longevity, tiller longevity drove turnover within the bud bank. Tiller population dynamics, more than bud production per tiller, determined the diff erential contribution of tiller types to the bud bank. Nassella viridula had higher bud production per tiller, a consistent annual tiller recruitment density, and greater longevity of buds on senesced and fl owering tillers than H. comata . CONCLUSIONS: Co-occurring C 3 caespitose grasses had similar bud-bank and tiller dynamics contributing to genet persistence but diff ered in bud characteristics that could aff ect genet longevity and species coexistence.