『Abstract
Parent material has a profound impact on chemical weathering,
mineral transformation and chemical denudation. However, there
remains a relative paucity of lithosequence studies that directly
examine parent material control on pedogenic processes. We sampled
a lithosequence of four parent materials (rhyolite, granite, basalt,
dolostone/volcanic cinders) under Pinus ponderosa in mesic
and ustic soil moisture and temperature regimes of central and
southern Arizona, USA to a quantify the contribution of parent
material to chemical weathering and elemental mass flux. We quantified
chemical weathering and mass flux using a combination of quantitative
X-ray diffraction and elemental mass balance. Mass flux calculations
were confounded by the addition of volcanic cinders in the dolostone
soils and addition of eolian materials in both the basalt and
dolostone soils. These variations in parent material were accounted
for using a combination of refractory element indices and X-ray
diffraction. Results indicated significant differences in profile
characteristics and chemical weathering among parent materials.
Chemical mass loss from the basalt and dolostone soils were balanced
or exceeded by addition of eolian materials, leading to positive
and highly variable mass fluxes of 14±48 kg m-2 and
-10±22 kg m-2, respectively. Rhyolite and granite soils
exhibited large differences in chemical mass flux despite nearly
identical elemental and mineralogical compositions of the respective
parent materials. Total chemical mass flux from the granite soils
averaged -173±31 kg m-2, whereas mass flux from the
rhyolite soils was much larger, on the order of -930±71 kg m-2.
These large differences result from the variation of parent material
grain size and bulk density. The data demonstrate strong control
of parent material on chemical weathering and mass flux in cool,
semiarid forested ecosystems.
Keywords: Lithosequence; Pedogenesis; Inorganic C cycling; Soil
mineralogy; Mass balance』
1. Introduction
2. Methods
2.1. Field sites
2.2. General soil characteristics
2.3. Soil mineralogical characterization
2.4. Elemental mass balance and chemical mass flux
2.5. Accounting for the influence of eolian dust and volcanic
cinder deposits
2.6. Estimation of CO2 consumption by mineral
weathering
3. Results and discussion
3.1. General soil characterization
3.1.1. Clay content and CEC
3.1.2. Selective dissolution
3.1.3. Specific surface area
3.2. Mineralogical characterization
3.2.1. Rhyolite
3.2.2. Granite
3.2.3. Basalt
3.2.4. Dolostone
3.3. Total elemental analysis and chemical mass flux
3.3.1. Rhyolite soils
3.3.2. Granite soils
3.3.3. Basalt soils
3.3.4. Dolostone soils
3.4. CO2 consumption during pedogenesis
4. Summary
Acknowledgments
References