『Abstract
The contribution of plants to the biogeochemical cycle of Si
and related weathering processes was studied in an equatorial
rainforest ecosystem (Congo) where the biologic turnover of Si
is high (58 to 76 kg/ha/y). Litterfall leaves, a soil profile
and groundwaters were analysed. Phytoliths and organic matter
have a similar distribution with depth in the soil profile. The
model of a biocompartmental distribution of organic matter is
applied to phytolith distribution and shows that about 92% of
the biogenic silica input is rapidly recycled while about 8% of
the biogenic silica input supplies a stable pool of phytoliths,
with a lower turnover. Reprecipitation of silica was observed
at the base of the soil profile, indicating a local geochemical
environment that is oversaturated with respect to amorphous silica.
A balance in biogeochemical cycle of Si requires that the vegetation
absorb dissolved silicon released from weathering of minerals,
which otherwise would be available for mineral neoformation or
export from the profile towards regional drainages. Plant uptake
of Si increases the chemical weathering rate without increasing
the denudation rate. This study shows that the uptake, storage,
and release of Si by the vegetation have to be taken into account
when using dissolved Si for tracing chemical weathering dynamics.』
1. Introduction
2. Material and methods
3. Results
4. Discussion
Acknowledgments
References