In grassland and savanna ecosystems, the population of belowground vegetative buds (the bud bank) plays a key role in local plant population persistence and dynamics. In many grasslands, this bud bank, rather than seeds, is the primary source for plant reproduction, the seasonal regeneration of stems, and local population sustainability. In fact, in tallgrass prairie as many as 99.6% of plant stems are derived from buds, not seeds. Bud banks may play a key role in the response of grasslands to global environmental change. Unlike soil seed banks, whose general ecology has been well studied, the importance of bud banks remains under-appreciated and poorly understood. This research addresses four questions about the effects of bud banks on vegetation and ecosystem dynamics, and test the hypothesis that in North American grasslands, the effects of key factors such as fire, grazing, and climatic variability on plant community diversity and productivity may be mediated principally through their effects on belowground bud bank dynamics. This dissertation enhancement project tests the generality of these ecological hypotheses and the roles of fire and grazing across North American grasslands, and extends the research to test the key role of bud banks in the grass-dominated ecosystem of the Okavango Delta region of Botswana, an area of great ecological and socio-economic importance in southern Africa. Understanding bud bank dynamics will help predict responses of grasslands and savannas to long-term environmental change and to alterations in their three main ecological drivers: fire, grazing, and hydrologic regimes.
