『Abstract
The efficacy of higher plants at mining Si from primary and secondary
minerals in terrestrial ecosystems is now recognized as an important
weathering mechanism. Grassland ecosystems are a particularly
large reservoir of biogenic silica and are thus likely to be a
key regulator of Si mobilization. Herein, we examine the effects
of parent material (basaltic and granitic rocks) on the range
and variability of biogenic silica pools in grass-dominated ecosystems
along two precipitation gradients of Kruger National Park, South
Africa. Four soil pedons and adjacent dominant plant species were
characterized for biogenic silica content. Our results indicate
that although soils derived from basalt had less total Si and
dissolved Si than soils derived from granite, a greater proportion
of the total Si was made up of biogenically derived silica. In
general, plants and soils overlying basaltic versus granitic parent
material stored greater quantities of biogenic silica and had
longer turnover times of the biogenic silica pool in soils. Additionally,
the relative abundance of biogenic silica was greater at the drier
sites along the precipitation gradient regardless of parent material.
These results suggest that the biogeochemical cycling of Si is
strongly influenced by parent material and the hydrologic controls
parent material imparts on soils. While soils derived from both
basalt and granite are strongly regulated by biological uptake,
the former is a “tighter” system with less loss of Si than the
latter which, although more dependent on biogenic silica dissolution,
has greater losses of total Si. Lithologic discontinuities span
beyond grasslands and are predicted to also influence biogenic
silica cycling in other ecosystems.
Keywords: Biogenic silica; Soil; Parent material; South African
savannas; Terrestrial plants』
Abbreviation
Introduction
Methods
Study area
Field sampling
Soil and water analyses
Biogenic silica analyses
Mass balance
Results
Physical, chemical and mineralogical composition of the soils
Pedon transformation and elemental transfers
Si transformations, transfers and losses
Discussion
Conclusions
Acknowledgments
References