The pedosphere acts as the mediator of chemical and biogeochemical flux into and out of these respective systems and is made up of gaseous, mineralic, fluid and biologic components.
[2] Soil formation begins with the chemical and/or physical breakdown of minerals to form the initial material that overlies the bedrock substrate.
Particular biologic pioneers are lichen, mosses and seed bearing plants,[3] but many other inorganic reactions take place that diversify the chemical makeup of the early soil layer.
Phosphatic shale (< 15% P2O5) and phosphorite (> 15% P2O5) form in anoxic deep water basins that preserve organic material.
The breakdown of the Na-feldspar, albite, by carbonic acid to form kaolinite clay is as follows:[4] Evidence of this reaction in the field would be elevated levels of bicarbonate (HCO−3), sodium and silica ions in the water runoff.
Sulfur, a byproduct of decaying organic material, will also react with iron to form pyrite (FeS2) in reducing environments.
Pyrite dissolution leads to low pH levels due to elevated H+ ions and further precipitation of Fe2O3[4] ultimately changing the redox conditions of the environment.
[9] Lichen has long been viewed as the pioneers of soil development as the following 1997 Isozaki statement suggests: The initial conversion of rock into soil is carried on by the pioneer lichens and their successors, the mosses, in which the hair-like rhizoids assume the role of roots in breaking down the surface into fine dust.
Nonetheless, lichen can certainly withstand harsher conditions than most vascular plants, and although they have slower colonization rates, they do form the dominant group in alpine regions.
Small burrowing mammals store food, grow young and may hibernate in the pedosphere altering the course of soil evolution.
Some anaerobic microbial processes include denitrification, sulfate reduction and methanogenesis and are responsible for the release of N2 (nitrogen), H2S (hydrogen sulfide) and CH4 (methane).
[4] The reduction potential describes which way chemical reactions will proceed in oxygen deficient soils and controls the nutrient cycling in flooded systems.
Acetate, a compound that is a byproduct of fermenting cellulose is split by methanogenic bacteria to produce methane (CH4) and carbon dioxide (CO2), which are released to the atmosphere.
Gases that escape from the pedosphere to the atmosphere include the gaseous byproducts of carbonate dissolution, decomposition, redox reactions and microbial photosynthesis.
[4] Soil is well developed in the forest as suggested by the thick humus layers, rich diversity of large trees and animals that live there.
In forests, precipitation exceeds evapotranspiration which results in an excess of water that percolates downward through the soil layers.
Slow rates of decomposition leads to large amounts of fulvic acid, greatly enhancing chemical weathering.
[4] Tropical forests receive more insolation and rainfall over longer growing seasons than any other environment on earth.
Increased rates of decomposition cause smaller amounts of fulvic acid to percolate and leach metals from the zone of active weathering.
Instead, the mobile metals Mg, Fe and Al are precipitated as oxide minerals giving the soil a rusty red color.
Low amounts of precipitation and high levels of evapotranspiration limit the downward percolation of water and organic acids, reducing chemical weathering and soil development.