COS 50-2
Life history and physiological factors associated with post-fire resprout success during drought in mediterranean-type shrublands in South Africa and California
Resprouting is an important trait that allows an individual to persist after disturbance. Species widely differ in resprouting ability and there currently is no general consensus as to the causes of these differences. We examined resprout success (survival) of shrubs in fynbos vegetation in South Africa and chaparral in southern California, and factors that we predicted would be linked with success. We also surveyed the literature to examine how species with different life history types differ with respect to resprouting. We hypothesized that resprout success in these crown fire systems would be controlled by physiological traits related to carbon balance, drought resistance, and life history traits.
Results/Conclusions
We found in fynbos and chaparral that shrubs with an obligate resprouting life history type, i.e. they only resprout after fire and do not recruit post-fire seedlings, had greater post-fire resprout success than facultative seeder life history types, i.e. those that resprout and recruit seedlings post-fire from a fire-cued seed bank. Resprout success was positively associated with traits related to carbon balance such as early resprouting, growth rate, and pre-fire vigor. During a 2007 drought in California that occurred in the first year after a fire at one of our study sites, resprout survival ranged from 100% to 20%. Plants with low survival generally had highly negative water potentials, low stem hydraulic conductivities, tissue carbohydrate concentrations, and net carbon assimilation. This suggests that extensive xylem cavitation and carbohydrate deficits were likely agents of mortality. We conclude that resprouters are not a homogenous group and that resprout success is linked to life history type. Intense droughts, like the one currently gripping California, have the potential to interact with fire and cause substantial mortality in some resprouting species. These results highlight the importance of incorporating resprouting information into vegetation models that aim to predict vegetation response to climate change and disturbance.