wAbstract
@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.
Keywords: Biogenic silica; North American grasslands; Soil; South
African savannas; Terrestrial plantsx
Abbreviations
Introduction
Methods
@Study areas
@Field sampling
@Analytical methods
Biogenic silica
@Statistics
Results
@Plant biogenic silica
@Soil biogenic silica
@Soil to plant BSi ratios
Discussion
Summary and conclusions
Acknowledgments
References