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Cited by 117Rangeland and Wildlife ManagementRangeland Management and Livestock EcologySoil Carbon and Nitrogen Dynamics

Plant productivity and soil nitrogen as a function of grazing, migration and fire in an African savanna.

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HOLDO, RICARDO M., HOLT, ROBERT D., COUGHENOUR, MICHAEL B., RITCHIE, MARK E.·2007·Journal of Ecology
DOI 10.1111/j.1365-2745.2006.01192.x
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Abstract

Summary: Herbivores can play a key role in affecting ecosystem function, but their direct and indirect effects are often confounded with each other and have rarely been dissected. Predictions for open systems, i.e. those with cross‐habitat nutrient fluxes and dispersal, may differ from those expected in closed systems, where no such transfers occur, but these differences have only recently begun to be characterized. We present a theoretical model of plant productivity and soil nitrogen (N) based on the Serengeti ecosystem in order to investigate the interplay among herbivore movement, nutrient transport across habitats (spatial subsidies), the fire regime and the effects of herbivores on N cycling. Model results suggest that the fire regime and herbivore migration are key determinants of primary productivity and fertility, and that the impact of these factors depends on grazing intensity. At low intensity, high grass biomass leads to extensive fires and N volatilization, but this effect is reduced at high grazing intensity. Without migration, the model predicts that primary productivity and fertility initially increase, then decline with increasing grazing intensity. Conversely, seasonal migration decouples the growing and grazing seasons, leading to a monotonic increase in productivity with grazing intensity. Cross‐habitat N transport has a relatively modest effect on N dynamics, and the magnitude of the seasonality effect outweighs the spatial subsidy effect. Our model suggests that herbivores and fire may play key interactive roles in regulating producers and determining ecosystem functional properties in grazing systems, both through consumption and via indirect effects on nutrient availability. The direction and magnitude of these effects could potentially vary greatly among ecosystems with resident vs. migratory herbivores, suggesting that spatial coupling through animal movement can be important at both the population and ecosystem levels. This study suggests that the degree to which trophic interactions influence ecosystem function may be strongly modulated by whether systems are open or closed. It also suggests that direct and indirect effects of consumers on their resources (top‐down effects) may be far more important than nutrient subsidies in open terrestrial systems.

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Crossref · 10.1111/j.1365-2745.2006.01192.x

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87 of 87 references verified0 citation errors · 0 not checkable

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  • Grazing intensity enhances the size of the soil organic matter pool in the Serengeti.

    “Grazing intensity (GI) and fire have been shown theoretically [18] and empirically (unpublished data) [19] to enhance and reduce the size of the soil organic matter pool in the Serengeti, respectively.”

    From A Disease-Mediated Trophic Cascade in the Serengeti and its Implications for Ecosystem C (2009) · cites this paper as [18]

    In “Effects of herbivory and fire,” the paper says its Serengeti model predicts that grazing increases soil nitrogen when herbivores migrate. It does not report an increase in the size of the soil organic matter pool; its measured outcome is soil nitrogen, and the predicted relationship depends on whether herbivores migrate. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • Fire reduces the size of the soil organic matter pool in the Serengeti.

    “Grazing intensity (GI) and fire have been shown theoretically [18] and empirically (unpublished data) [19] to enhance and reduce the size of the soil organic matter pool in the Serengeti, respectively.”

    From A Disease-Mediated Trophic Cascade in the Serengeti and its Implications for Ecosystem C (2009) · cites this paper as [18]

    In “Effects of herbivory and fire” (page unavailable), the Serengeti model predicts that fire exclusion increases soil nitrogen, supporting a modeled reduction in soil nitrogen when fire occurs. The paper models organic soil nitrogen pools, but the cited passages do not establish that fire reduces the size of the soil organic matter pool itself. (LLM, conf=0.85)

    Experimental — accuracy not yet measured

  • Recent empirical and modeling studies support the existence of dominant fire and grazing effects on soil organic carbon.

    “recent empirical and modeling studies support the existence of dominant fire and grazing effects on SOC (unpublished data) [18],[19]”

    From A Disease-Mediated Trophic Cascade in the Serengeti and its Implications for Ecosystem C (2009) · cites this paper as [18]

    The fire–herbivore effects section reports marked effects of their interaction on soil nitrogen, supporting the claim’s modeling component. But the Model description specifies that the state variables are measured in nitrogen units and carbon-to-nitrogen ratios are assumed fixed; it does not directly establish dominant effects on soil organic carbon. (LLM, conf=0.84)

    Experimental — accuracy not yet measured

  • Maximum annual soil organic matter and soil organic carbon losses are 0.8% y−1 with an annual fire regime.

    “We estimated maximum annual SOM (and SOC) losses of 0.8% y−1 with an annual fire regime (F t = 1).”

    From A Disease-Mediated Trophic Cascade in the Serengeti and its Implications for Ecosystem C (2009) · cites this paper as [18]

    The Fire section models nitrogen lost through burning, while the N cycling section gives soil organic matter decomposition parameters; neither reports annual SOM or SOC losses of 0.8% under annual fire. Searches for the 0.8% figure and for annual fire-related SOM or carbon loss found no passage addressing that estimate. Page numbers were not available in our copy. (LLM, conf=0.75)

    Experimental — accuracy not yet measured

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Authors
HOLDO, R. M., HOLT, R. D., COUGHENOUR, M. B., & RITCHIE, M. E.
Affiliations
University of Florida (US)
ORCID
Venue
Journal of Ecology
Publisher
Wiley
Published
2006-11-27
Volume
95
Issue
1
Pages
115-128
ISSN
  • 0022-0477 (ISSN-L)
  • 1365-2745
DOI
10.1111/j.1365-2745.2006.01192.x
OpenAlex
W2157270203
Cited by
117
References
87
Citations by year
2026: 5 · 2025: 5 · 2024: 4 · 2023: 6 · 2022: 8 · 2021: 2 · 2020: 5 · 2019: 10 · 2018: 11 · 2017: 7 · 2016: 4 · 2015: 5 · 2014: 8 · 2013: 6 · 2012: 5
FWCI
3.63
Type
journal article
Language
en
Open access
Licence
onlinelibrary.wiley.com/termsAndConditions#vor (vor)
Locations
Journal of Ecology (publishedVersion)
Funders
  • National Science Foundation (0308486)
  • University of Florida Foundation
  • University of Florida
Topics
  • Physical Sciences › Environmental Science › Ecology › Rangeland and Wildlife Management
  • Physical Sciences › Environmental Science › Management, Monitoring, Policy and Law › Rangeland Management and Livestock Ecology
  • Life Sciences › Agricultural and Biological Sciences › Soil Science › Soil Carbon and Nitrogen Dynamics
Keywords
grazing intensity, fire regimes, soil nitrogen, plant productivity, nutrient subsidies, top-down effects, Serengeti, savanna, nitrogen volatilization, seasonal migration, trophic interactions, ecosystem functioning

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