Friday, August 6, 2010: 8:40 AM
329, David L Lawrence Convention Center
Background/Question/Methods Annual regeneration and sustainability of perennial grass populations rely heavily on the belowground bud bank, yet the production and dynamics of grass bud banks, the stages of bud development, and bud-tiller transitions have not been explored. Since the two major photosynthetic guilds of grasses vary in their aboveground dynamics, their belowground bud bank dynamics likely vary as well. In this study, we examined the bud banks of Dichanthelium oligosanthes, a representative C3 grass, and Andropogon gerardii, a representative C4 grass, bi-weekly throughout an entire annual cycle in tallgrass prairie.
Results/Conclusions Each species has distinct bud morphology and developmental stages, allowing species identification from belowground structures. The bud bank of A. gerardii was synchronous in its development and was composed of viable buds from multiple annual cohorts while the bud bank of D. oligosanthes was asynchronous in its development and was comprised of a single bud cohort. The inter-specific differences in bud bank development and age distribution were related to differences in bud longevity, quality, and control of dormancy. These differences in individual bud characteristics indicated different roles of the bud bank for each species. Although both A. gerardii and D. oligosanthes were inactive over the winter season, D. oligosanthes also reduced its activity during the peak temperatures of summer due to its cool-season growth phenology. Dichanthelium oligosanthes, which tillers in the fall, survived over this short summer dormancy period as dormant and active buds, and survived over the longer winter dormancy period in the juvenile tiller stage. In contrast, A. gerardii overwintered exclusively in the dormant bud stage. Thus, the bud bank characteristics of each species were determined by the bud’s role in the life history of the plant. The longer-lived buds and mixed-cohort bud bank of A. gerardii may buffer aboveground population dynamics, similar to longer-lived seed banks, whereas aboveground populations with shorter-lived buds, such as D. oligosanthes, may more closely track environmental changes. Knowledge of bud bank dynamics, as it offers insight into the control of grass regeneration and regulation of aboveground net primary production, will be useful in understanding the underlying mechanisms by which management practices and environmental change can alter perennial grasslands.
Results/Conclusions Each species has distinct bud morphology and developmental stages, allowing species identification from belowground structures. The bud bank of A. gerardii was synchronous in its development and was composed of viable buds from multiple annual cohorts while the bud bank of D. oligosanthes was asynchronous in its development and was comprised of a single bud cohort. The inter-specific differences in bud bank development and age distribution were related to differences in bud longevity, quality, and control of dormancy. These differences in individual bud characteristics indicated different roles of the bud bank for each species. Although both A. gerardii and D. oligosanthes were inactive over the winter season, D. oligosanthes also reduced its activity during the peak temperatures of summer due to its cool-season growth phenology. Dichanthelium oligosanthes, which tillers in the fall, survived over this short summer dormancy period as dormant and active buds, and survived over the longer winter dormancy period in the juvenile tiller stage. In contrast, A. gerardii overwintered exclusively in the dormant bud stage. Thus, the bud bank characteristics of each species were determined by the bud’s role in the life history of the plant. The longer-lived buds and mixed-cohort bud bank of A. gerardii may buffer aboveground population dynamics, similar to longer-lived seed banks, whereas aboveground populations with shorter-lived buds, such as D. oligosanthes, may more closely track environmental changes. Knowledge of bud bank dynamics, as it offers insight into the control of grass regeneration and regulation of aboveground net primary production, will be useful in understanding the underlying mechanisms by which management practices and environmental change can alter perennial grasslands.
