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Development of edge effects around experimental ecosystem hotspots is affected by hotspot density and matrix type

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Abstract

Context

Ecological edge effects are sensitive to landscape context, including matrix type and the presence of other nearby edges. In sub-Saharan Africa, temporary cattle corrals (bomas) develop into productive nutrient hotspots (glades) that attract diverse wildlife and persist for decades.

Objectives

Building on previous descriptive work, we experimentally altered boma configurations in an African savanna and asked how boma density and matrix type (open plains vs. bushland) influence the development of edge effects around abandoned bomas.

Methods

We randomly assigned eleven plots to three treatments: one boma, two bomas 200 m apart, or two bomas 100 m apart. Before boma establishment and ≥18 months after boma abandonment, we sampled soil nutrients, foliar nutrients, plant communities, and large herbivore use at each plot.

Results

Bomas developed into glade hotspots with elevated nutrient concentrations, altered vegetation, and elevated use by large herbivores. Few edge effects were detectable at distances ≥50 m. Both glade density and matrix type affected the development of edge effects around experimental glades. When compared to patterns around single glades, the presence of a second glade 100 m away strengthened glade edge effects (more difference between glade and matrix), but the presence of a second glade 200 m away weakened edge effects. Vegetation edge effects were stronger in bushland areas than open plains, while wildlife shifts were strongest along the bushland-plain interface.

Conclusions

Our results highlight the potential for edge effect variability in complex landscapes, and show that manipulative experiments can help illuminate causes and consequences of that variability.

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Acknowledgments

We thank Ol Pejeta Conservancy for the opportunity to conduct this research. Fredrick Erii, John Lochukuya, Mathew Namoni, Jackson Ekadeli, James Wambogo, Wilson Murithi, Solveig Franziska Bucher, Michael Ellis, John Porensky, Johnathon Choge, Solomon Kipngeno Mutai, and Robert Osusu provided invaluable field assistance. We thank Giles Prettejohn, Nathan Gichohi, Samuel Mutisya, Joseph Mathenge, Batian Craig, Martin Mulama, Douglas Kamaru, Irene Anyango, and Caroline Ngweno for advice, assistance with experimental setup, and logistical support. We received helpful advice on experimental design and comments on the manuscript from V. Eviner, M. L. Cadenasso, K. E. Veblen, and five anonymous reviewers. This research complies with Kenyan law and was approved by the Kenyan Ministry of Science and Technology. Financial support came from National Science Foundation (NSF) GRF, NSF DDIG (09-09539), and UC Davis Plant Sciences Departmental Fellowships, Jastro-Shields and Benjamin Madson Research Scholarships (to LEM), and NSF LTREB DEB-08-16453 (to TPY).

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  1. Lauren M. Porensky

    Present address: USDA-ARS Rangeland Resources Research Unit, 1701 Centre Ave, Fort Collins, CO, 80526, USA

Authors and Affiliations

  1. Department of Plant Sciences, University of California, Davis, CA, 95616, USA

    Lauren M. Porensky & Truman P. Young

  2. Mpala Research Centre, P.O. Box 555, Nanyuki, 10400, Kenya

    Lauren M. Porensky & Truman P. Young

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  1. Lauren M. Porensky
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Correspondence to Lauren M. Porensky.

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Porensky, L.M., Young, T.P. Development of edge effects around experimental ecosystem hotspots is affected by hotspot density and matrix type. Landscape Ecol 31, 1663–1680 (2016). https://doi.org/10.1007/s10980-016-0344-3

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