old) in Japan and British Columbia. The geologists found hematite throughout the early and middle Permian but began to find the reduced form of iron in pyrite within the ancient soils near the end of the Permian and into the Triassic. These results suggested that conditions became less oxygen rich, even anoxic, during the late Permian, which eventually led to the greatest extinction in earth’s history, the P-T extinction. Decomposition in anoxic or reduced soils is also carried out by sulfur-reducing bacteria which, instead of O2 use as an electron acceptor and produce hydrogen sulfide (H2S) and carbon dioxide in the process: 2 H+ + SO4^2- + 2 [CH2O] <=> 2 CO2 + H2S + 2 H2O The H2S gas percolates upwards and reacts with Fe2+ and precipitates pyrite, acting as a trap for the toxic H2S gas. However, H2S is still a large fraction of emissions from wetland soils. In most freshwater wetlands there is little sulfate () so methanogenesis becomes the dominant form of decomposition by methanogenic bacteria only when sulfate is depleted. 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. Methane is also released during the reduction of CO2 by the same bacteria. Atmosphere In the pedosphere it is safe to assume that gases are in equilibrium with the atmosphere. Because plant roots and soil microbes release CO2 to the soil, the concentration of bicarbonate () in soil waters is much greater than that in equilibrium with the atmosphere, the high concentration of CO2 and the occurrence of metals in soil solutions results in lower pH levels in the soil. Gases that escape from the pedosphere to the atmosphere include the gaseous byproducts of carbonate dissolution, decomposition, redox reactions and microbial photosynthesis. The main inputs from the atmosphere are aeolian sedimentation, rainfall and gas diffusion. Eolian sedimentation includes anything that can be entrained by wind or that stays suspended, seemingly indefinitely, in air and includes a wide variety of aerosol particles, biological particles like pollen and dust to pure quartz sand. Nitrogen is the most abundant constituent in rain (after water), as water vapor utilizes aerosol particles to nucleate rain droplets. Soil in forests Soil is well developed in the forest as suggested by the thick humus layers, rich diversity of large trees and animals that