Because most shoot recruitment in perennial grasses occurs from belowground axillary buds, bud dynamics determine plant population dynamics and meristem limitation to population growth. Therefore, grassland vegetation responses to environmental change or disturbance may be influenced by interspecific differences in bud banks and the patterns and environmental controls of bud development and demography. We examined bud bank dynamics in Andropogon gerardii and Dichanthelium oligosanthes in tallgrass prairie by enumerating and classifying buds throughout 15 months to determine whether grass buds live for multiple years and accumulate; whether bud natality, dormancy and outgrowth are synchronous or variable; and whether bud bank dynamics differ between these co-occurring species. Andropogon gerardii (a C4 species) maintained a larger dormant bud bank, showed synchrony in bud development and transition to tiller, and its buds lived for multiple years. Thus, multiple previous years’ bud cohorts contributed to recruitment. By contrast, D. oligosanthes (a C3 species) maintained a smaller dormant bud bank, had asynchronous bud development with active buds present year-round, and its buds lived for 1 year. Buds played different roles in the dynamics of each species, allowing A. gerardii to over-winter and recruit new spring tillers and D. oligosanthes to survive and recruit new tillers following summer dormancy. These differences in bud bank age structure, phenology, and dynamics between these species suggest greater demographic buffering and time-lag effects in A. gerardii populations. Interspecific differences in bud bank structure and dynamics may explain and help predict grassland responses to environmental change.
MeristemPhotosynthetic pathwayPlant demographyPlant population dynamicsTiller recruitmentVegetative reproduction
Fate of buds produced on (a) pre-2007 and (b) 2007 tillers of Andropogon gerardii between October 2007 and October 2008. Buds were either developing or mature (DMB) or activated (AB) or had grown out into vegetative (VT) or flowering (FT) tillers. Fewer buds from the pre-2007 cohort (13 ± 1 %) transitioned to the activated stage than from the 2007 cohort (34 ± 1 %). However, after floral initiation, a larger percentage of the pre-2007 cohort’s vegetative tillers (32 ± 5 %) became flowering tillers than the 2007 cohort’s vegetative tillers (19 ± 2 %). (TIFF 25205 kb)
Fate of buds produced on (a) 2007 and (b) 2008 mature tillers of Dichanthelium oligosanthes. Buds were either mature (MB), activated (AB), or photosynthesizing (PB) or had grown out into juvenile (JT), vegetative (VT) or flowering (FT) tillers. The flowering status of some tillers was unknown (UT) due to culm damage. When considering the bud bank collectively, an asynchrony in bud development was evident. By July 2008, almost all of the buds from the 2007 cohort had either died or had transitioned to tillers. (TIFF 26179 kb)