Ants, fire, and bark traits affect how African savanna trees recover following damage

Bark damage resulting from elephant feeding is common in African savanna trees with subsequent interactions with fire, insects, and other pathogens often resulting in tree mortality. Yet, surprisingly little is known about how savanna trees respond to bark damage. We addressed this by investigating...

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Bibliographic Details
Published in:Biotropica 2019-09, Vol.51 (5), p.682-691
Main Authors: Wigley, Benjamin J., Coetsee, Corli, Kruger, Laurence M., Ratnam, Jayashree, Sankaran, Mahesh
Format: Article
Language:English
Subjects:
Bark
bark damage
bark traits
Colonization
Dry matter
Dry matter content
Elephants
Fire damage
Fires
Insects
interactions
Kruger National Park
long‐term fire experiment
National parks
Pathogens
Phylogeny
Recovery
Species
Thickness
Trees
Wood
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Summary:Bark damage resulting from elephant feeding is common in African savanna trees with subsequent interactions with fire, insects, and other pathogens often resulting in tree mortality. Yet, surprisingly little is known about how savanna trees respond to bark damage. We addressed this by investigating how the inner bark of marula (Sclerocarya birrea), a widespread tree species favoured by elephants, recovers after bark damage. We used a long‐term fire experiment in the Kruger National Park to measure bark recovery with and without fire. At 24 months post‐damage, mean wound closure was 98, 92, and 72%, respectively, in annual and biennial burns and fire‐exclusion treatments. Fire exclusion resulted in higher rates of ant colonization of bark wounds, and such ant colonization resulted in significantly lower bark recovery. We also investigated how ten common savanna tree species respond to bark damage and tested for relationships between bark damage, bark recovery, and bark traits while accounting for phylogeny. We found phylogenetic signal in bark dry matter content, bark N and bark P, but not in bark thickness. Bark recovery and damage was highest in species which had thick moist inner bark and low wood densities (Anacardiaceae), intermediate in species which had moderate inner bark thickness and wood densities (Fabaceae) and lowest in species which had thin inner bark and high wood densities (Combretaceae). Elephants prefer species with thick, moist inner bark, traits that also appear to result in faster recovery rates.
ISSN:0006-3606
1744-7429
DOI:10.1111/btp.12683