Article
Tree resprout dynamics following fire depend on herbivory by wild ungulate herbivores
Journal of Ecology
(2019)
Abstract
1. Savanna tree cover is dynamic due to disturbances such as fire and herbivory.
Frequent fires can limit a key demographic transition from sapling to adult height
classes in savanna trees. Saplings may be caught in a ‘fire trap’, wherein individuals
repeatedly resprout following fire top‐kill events. Saplings only rarely escape
the cycle by attaining a fire‐resistant height (e.g. taller than the minimum scorch
height) during fire‐free intervals.
2. Large mammalian herbivores also may trap trees in shorter size classes. Browsing
herbivores directly limit sapling height, while grazing herbivores such as cattle
facilitate sapling growth indirectly via grass removal. Experimental studies investigating
how meso‐wildlife, megaherbivores and domestic livestock affect height of
resprouts following fire are rare, but necessary for fully understanding how herbivory
may reinforce (or counteract) the fire trap. In our study system, interactive
fire–herbivore effects on transitions from sapling (<1 m) to adult tree (>1 m) height
classes may be further influenced by plant defences, such as symbiotic ants.
3. We used the Kenya Long‐term Exclosure Experiment (KLEE) to investigate how
post‐fire resprout size of a widespread monodominant East African tree, Acacia
drepanolobium was influenced by (a) herbivory by different combinations of cattle,
meso‐wildlife (15–1,000 kg) and megaherbivores (>1,000 kg) and (b) the presence
of acacia–ant mutualists that confer tree defences. We sampled height, stem
length and ant occupancy of resprouts exposed to different herbivore combinations
before and after controlled burns.
4. Resprout height of saplings that were short prior to fire (<1 m) was reduced
primarily by meso‐wildlife. Negative effects of elephants on post‐fire resprout
height increased with pre‐fire tree size, suggesting that resprouts of the tallest
trees (with the greatest potential to escape the fire trap cycle) were preferentially
browsed and reduced in height by elephants. There were no significant cattle
effects.
Keywords
- browse trap,
- bush encroachment,
- coppice,
- Crematogaster,
- recruitment limitation,
- sapling,
- storage effect,
- tree–grass co‐existence
Disciplines
Publication Date
2019
DOI
https://doi.org/10.1111/1365-2745.13186
Citation Information
Kari E. Veblen. "Tree resprout dynamics following fire depend on herbivory by wild ungulate herbivores" Journal of Ecology Vol. 107 Iss. 5 (2019) Available at: http://works.bepress.com/kari_veblen/73/