Perennial grasses with different life histories maintain population stability under fire in North and Central American pine savannas

Background Although survival has been shown to be a strong driver of perennial grass population persistence in savanna understories, it is unclear how this pattern compares across species that display variation in reproductive strategies. We modeled the demography of four C4 perennial grass species with varying degrees of fire-stimulated flowering in the frequently burned pine savannas across North and Central America. We collected annual demographic data and modeled their population demography in annual transitions with and without fire using integral projection models. Results Although the species showed different reproductive patterns, all exhibited stable or growing populations across all transitions. Species balanced variable survival with relatively consistent reproduction and recruitment, whereas those with reproductive patterns more strongly affected by fire showed very high survival. Overall, survival was high across all species regardless of fire, and estimated recruitment for any species and year was low. Conclusions Survival and slow growth of adult individuals under frequent fire regimes are important for maintaining the persistence of perennial grass populations in these North and Central American savanna ecosystems. The perennial grasses we studied exhibit life history strategies typical of old-growth savanna species with extensive and protected bud banks. The sensitivity of bud banks to fire varies among species, which may have influenced variable vital rates and patterns resulting from trade-offs between vegetative and sexual reproduction.