Carbon dioxide mixing with water forms carbonic acid. The complex chemical effects that occur as a result of chelation . Chelation is a biological process where organism produce organic substances, known as chelates , that have the ability to decompose minerals and rocks by the removal of metallic cations . Organism can influence the moisture regime in soils and therefore enhance weathering. Shade from aerial leaves and stems, the presence of roots masses, and humus all act to increase the availability of water in the soil profile.
Water is a necessary component in several physical and chemical weathering processes.
Organisms can influence the pH of the soil solution. Respiration from plant roots releases carbon dioxide. If the carbon dioxide mixes with water carbonic acid is formed which lowers soil pH. Cation exchange reactions by which plants absorb nutrients from the soil can also cause pH changes. The absorption processes often involves the exchange of basic cations for hydrogen ions. Generally, the higher the concentration of hydrogen ions the more acidic a soil becomes.