Termite mounds mitigate against 50 years of herbivore-induced reduction of functional diversity of savanna woody plants

Joseph, Grant S., Makumbe, Milton, Seymour, Colleen L., Cumming, Graeme S., Mahlangu, Zacheus, and Cumming, David H.M. (2015) Termite mounds mitigate against 50 years of herbivore-induced reduction of functional diversity of savanna woody plants. Landscape Ecology, 30 (10). pp. 2161-2174.

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Abstract

Context: Spatially heterogeneous habitats often promote woody plant species and functional diversity (FD). Ungulate herbivory can have the opposite effect. Across the globe, the type and intensity of herbivory is changing, as domestic livestock replace wild ungulates, which are increasingly confined to protected areas. Despite recognition of the importance of FD for ecosystem functioning, the interactive effect of soil-related fine-scale heterogeneity and larger-scale ungulate herbivory on woody plant FD is little-known.

Objectives: In miombo woodland of Zimbabwe, we investigated (1) how bottom-up fine-scale heterogeneity created by Macrotermes termitaria interacts with top-down effects of herbivore foraging-guilds on woody plant FD; and (2) whether browsing combined with grazing impacts FD more than grazing alone.

Methods: The three different herbivore treatments (grazing, combined browsing-and-grazing, and exclusion) had been maintained for 50 years. We surveyed 10 termite mound-matrix plots within three sites per treatment. We assessed woody plant traits and FD across treatments (herbivore feeding-guild) and position (mound or woodland-matrix), and interactive effects between these.

Results: Woody plant FD was greater on mounds, and lowest overall with browsing-and-grazing. Specific traits were associated with position (e.g. palatability was greater for mounds), and treatment (e.g. spinescence increased with grazing).

Conclusions: Long-term enclosure of ungulate herbivores (browsing-and-grazing, and grazing alone) decreased woody FD, but this was mitigated by termitaria. The novel finding is that at regional scales, mounds can enhance woody plant FD despite the impacts of herbivory. At broader scales encompassing the miombo system, potential exists for mounds to stabilise woody plant FD from livestock-induced impacts.

Item ID: 40820
Item Type: Article (Refereed Research - C1)
Keywords: bottom-up versus top-down effects, functional divergence, functional evenness, functional richness, spatial heterogeneity, termitaria
ISSN: 1572-9761
Funders: NRF-SADC
Date Deposited: 13 Oct 2015 10:15
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050104 Landscape Ecology @ 33%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060202 Community Ecology (excl Invasive Species Ecology) @ 33%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060299 Ecology not elsewhere classified @ 34%
SEO Codes: 96 ENVIRONMENT > 9613 Remnant Vegetation and Protected Conservation Areas > 961308 Remnant Vegetation and Protected Conservation Areas at Regional or Larger Scales @ 50%
97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 50%
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