, Volume 97, Issue 2–3, pp 263–278 | Cite as

Fire and grazing impacts on silica production and storage in grass dominated ecosystems

  • Susan E. MelzerEmail author
  • Alan K. Knapp
  • Kevin P. Kirkman
  • Melinda D. Smith
  • John M. Blair
  • Eugene F. Kelly


Grassland ecosystems are an important terrestrial component of the global biogeochemical silicon cycle. Although the structure and ecological functioning of grasslands are strongly influenced by fire and grazing, the role of these key ecological drivers in the production and storage of silicon represents a significant knowledge gap, particularly since they are being altered worldwide by human activities. We evaluated the effects of fire and grazing on the range and variability of plant derived biogenic silica stored in plant biomass and soils by sampling plants and soils from long-term experimental plots with known fire and grazing histories. Overall, plants and soils from grazed sites in the South African ecosystems had up to 76 and 54% greater biogenic silica totals (kg ha−1), respectively, than grazed North American sites. In North American soils, the combination of grazing and annual fire resulted in the greatest abundance of biogenic silica, whereas South African soils had the highest biogenic silica content where grazed regardless of burn frequency. These results as well as those that show greater Si concentrations in grazed South African plants indicate that South African plants and soils responded somewhat differently to fire and grazing with respect to silicon cycling, which may be linked to differences in the evolutionary history and in the grazer diversity and grazing intensity of these ecosystems. We conclude that although fire and grazing (as interactive and/or independent factors) do not affect the concentration of Si taken up by plants, they do promote increased silicon storage in aboveground biomass and soil as a result of directly affecting other site factors such as aboveground net primary productivity. Therefore, as management practices, fire and grazing have important implications for assessing global change impacts on the terrestrial biogeochemical cycling of silicon.


Biogenic silica North American grasslands Soil South African savannas Terrestrial plants 



Annually burned


Analysis of variance


Aboveground net primary productivity


Biogenic silica


Belowground net primary productivity




Intermediate burned


Long Term Ecological Research


Soil organic carbon






World Reference Base



Support was provided by the Shortgrass Steppe Long Term Ecological Research Group, a partnership between Colorado State University, U.S. Department of Agriculture, Agricultural Research Service, and U.S. Forest Service Pawnee National Grasslands, through a grant from the National Science Foundation Long Term Ecological Research Program and NSF award DEB -074386. The authors extend thanks to persons supporting us in the field on the experimental burn plots in the Kruger National Park, Ukulinga Research Station, and Konza Prairie Biological Station. Additional thanks are extended to Caroline Yonker for assistance in vegetative sampling, Greg Buis for providing the biomass numbers and Dan Reuss at the Natural Resources Ecology Laboratory and Dr. Thomas Borch in the Soil and Crop Sciences Department at Colorado State University for their analytical expertise.


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Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • Susan E. Melzer
    • 1
    Email author
  • Alan K. Knapp
    • 2
  • Kevin P. Kirkman
    • 3
  • Melinda D. Smith
    • 4
  • John M. Blair
    • 5
  • Eugene F. Kelly
    • 1
  1. 1.Department of Soil and Crop SciencesColorado State UniversityFort CollinsUSA
  2. 2.Department of Biology and Graduate Degree Program in EcologyColorado State UniversityFort CollinsUSA
  3. 3.School of Biological and Conservation SciencesUniversity of KwaZulu-NatalKwaZulu-NatalSouth Africa
  4. 4.Department of Ecology and Evolutionary BiologyYale UniversityNew HavenUSA
  5. 5.Division of BiologyKansas State UniversityManhattanUSA

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