Browsing-induced Effects on Leaf Litter Quality and Decomposition in a Southern African Savanna |
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Authors: | D A Fornara J T Du Toit |
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Institution: | (1) Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota 55108, USA;(2) Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, 0002 Pretoria, South Africa;(3) Department of Wildland Resources, Utah State University, Logan, Utah 84322-5230, USA |
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Abstract: | We investigated the linkages between leaf litter quality and decomposability in a savanna plant community dominated by palatable-spinescent
tree species. We measured: (1) leaf litter decomposability across five woody species that differ in leaf chemistry; (2) mass
decomposition, nitrogen (N); and carbon (C) dynamics in leaf litter of a staple browse species (Acacia nigrescens) as well as (3) variation in litter composition across six sites that experienced very different histories of attack from
large herbivores. All decomposition trials included litter bags filled with chopped straw to control for variation in site
effects. We found a positive relationship between litter quality and decomposability, but we also found that Acacia and straw litter mass remaining did not significantly vary between heavily and lightly browsed sites. This is despite the
fact that both the quality and composition of litter returned to the soil were significantly different across sites. We observed
greater N resorption from senescing Acacia leaves at heavily browsed sites, which in turn contributed to increase the C:N ratio of leaf litter and caused greater litter
N immobilization over time. This, together with the significantly lower tree- and herb-leaf litter mass beneath heavily browsed
trees, should negatively affect decomposition rates. However, estimated dung and urine N deposition from both browsers and
grazers was significantly greater at high- than at low-herbivory sites. We hypothesize that N inputs from dung and urine boost
litter N mineralization and decomposition (especially following seasonal rainfall events), and thereby offset the effects
of poor leaf litter quality at chronically browsed sites.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Acacia plant defences ungulate herbivory ecosystem functioning nutrient cycling |
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