Postfire regeneration of resprouting mountain fynbos shrubs: differentiating obligate resprouters and facultative seeders

Abstract

Plant species in Mediterranean-type climate regions have a diversity of traits that facilitate their persistence under a given fire regime. Obligate resprouters (OR) are dependent on resprouting to persist through a burn episode, as their seeds are killed by fire. Facultative seeders (FS) combine strategies by resprouting and recruiting new seedlings after fire. We hypothesised that these life history differences would lead to differential resprout success and we predicted that OR would be more successful than FS. We performed a 2-year study to assess resprout success of co-occurring Western Cape mountain fynbos FS and OR species, and to determine predictors of resprout success following a wildfire. All the FS species recruited seedlings postfire, whereas the OR did not. OR demonstrated near complete (99 %) survival after 2 years and all resprouted within 4 months postfire. In contrast, only 81 % of FS resprouted with only 65 % surviving 2 years postfire. Numerous factors were linked to resprout success: decreased lignotuber exposure and pre-fire vigour (number of pre-fire shoots) were significantly associated with postfire resprouting, while early resprouting (days to first resprout) and growth rate were significant predictors of post-resprout survival. The difference in resprout survival between the FS and OR may also be partially due to phylogenetic differences. These findings confirm the heterogeneity and complexity of postfire resprouting and support the distinction of OS and FS life history types.