wAbstract
@Plants fractionate Si isotopes which provides a useful Si tracer
in the Si soil-plant cycle. This study reports plant Si content
and Si-isotopic signatures in mature banana plants grown on soils
with different weathering degree, but all developed from basaltic
pyroclasts in the Mungo area, Cameroon. The Β30Si compositions
were determined in various plant parts and soil surface horizons
by MC-ICP-MS in dry plasma mode with external Mg doping to a precision
of }0.15ρ (}2ΠSD). The Si-isotopic compositions
in banana plants grown on weathered clayey soils (+0.54}0.15ρ)
are heavier than on weakly developed soils rich in fresh ash and
pumice (+0.02}0.15ρ). The corresponding bulk soils display lower
Β30Si value in weathered soil (-1.41ρ) than in poorly
developed soil (-0.41ρ). We suggest that the dissolved Si source
for the plant, governed firstly by dissolution of easily weatherable
minerals, was isotopically enriched in heavy isotopes through
clay formation over long periods. At seasonal to annual time scale,
this source is influenced by a combination of following processes:
Si adsorption of light isotopes onto Fe oxides, plant Si uptake
and recycling in surface horizons. This would provide an isotopically
heavier Si source in the more weathered soil since the Fe oxides
content increases with weathering. Plant Si-isotopic signature
might thus reflect the soil weathering degree. This study further
suggests that in addition to weathering processes, rivers isotopic
signatures likely depend on the fate of phytoliths in the soil-plant-river
system.
Keywords: Isotopic fractionation; Musa; Si cycle; Cameroon;
Soil; Weathering sequencex
Introduction
Materials and methods
@Study area
@Sampling
@Bulk elemental, chemical and physical analyses
@Silicon isotopes analyses
Results
@Soil properties
@Mineral content in plants
@Si-isotopic compositions in banana plants
Discussion
@Si content in banana
@Intra-plant Si-isotopic fractionation
@Plant Β30Si might reflect the weathering degree of
soils
@Implications
Conclusion
Acknowledgments
References