Establishment and early persistence of tree seedlings in an annually burned savanna
Article first published online: 19 MAR 2009
© 2009 The Authors. Journal compilation © 2009 British Ecological Society
Journal of Ecology
Volume 97, Issue 3, pages 484–495, May 2009
How to Cite
Gignoux, J., Lahoreau, G., Julliard, R. and Barot, S. (2009), Establishment and early persistence of tree seedlings in an annually burned savanna. Journal of Ecology, 97: 484–495. doi: 10.1111/j.1365-2745.2009.01493.x
- Issue published online: 8 APR 2009
- Article first published online: 19 MAR 2009
- Received 27 August 2008; accepted 10 February 2009Handling Editor: Peter Bellingham
- persistence niche;
- resprouting ability;
- seedling survival;
- tree demography;
- tropical savanna
- 1In severely disturbed habitats, the onset of resprouting as a persistence strategy might be problematic for tree species which do not accumulate sufficient reserves before the first disturbance event. This is due to the trade-off between the growth of reserves required to recover after disturbance and that of photosynthetic tissues.
- 2In humid savannas, fire prevents trees from invading the whole landscape and nearby gallery forests have a completely different floristic composition. We test if the variations of survival during the first years of a young tree's life can explain the exclusion of forest species and the dominance pattern within savanna species.
- 3Every six months for four years, we censused all seedlings and resprouts in 1 ha area of an annually burned savanna, to estimate their seasonal survival rates. We used capture–recapture statistical models to control for the probability of missing seedlings in the tall grass.
- 4There were two main distinct patterns of survival among seedlings: ‘fire-responding’ species showed a 20–80% decrease in survival during the dry season, interpreted as mainly due to fire; ‘drought-responding’ species showed 20–80% variations in survival positively correlated to early-growing-season rainfall.
- 5Yearly averaged survival probabilities of seedlings ranged between 0.10 and 0.63, reaching 0.850–0.996 for > 3-year-old resprouts of savanna species. Forest species showed no increase in survival with age.
- 6A 4-year-survival-probability analysis showed that forest species were excluded from the savanna at the seedling stage. No parameter of the early survival curve related to the abundance of savanna species at the adult stage.
- 7Synthesis. Savanna tree species follow two mutually exclusive main patterns of early survival probably related to fire and early-wet-season drought. The exclusion of forest species is consistent with a build up of reserves that is too slow due to the growth-resistance trade-off. We conclude from these findings that the use of resprouting as a persistence strategy is heavily constrained by disturbance frequency and imposes strong trade-offs on plant growth strategy.