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The exchange of carbon between soils and the atmosphere is a significant part of the world carbon cycle. [33] Carbon, as it relates to the organic matter of soils, is a major component of soil and catchment health.
Each year, the ocean and atmosphere exchange large amounts of carbon. A major controlling factor in oceanic-atmospheric carbon exchange is thermohaline circulation. In regions of ocean upwelling, carbon-rich water from the deep ocean comes to the surface and releases carbon into the atmosphere as carbon dioxide.
The exchange between the ocean and atmosphere can take centuries, and the weathering of rocks can take millions of years. Carbon in the ocean precipitates to the ocean floor where it can form sedimentary rock and be subducted into the Earth's mantle. Mountain building processes result in the return of this geologic carbon to the Earth's surface.
Part of the net primary production, or the remaining carbon absorbed by the biosphere, is emitted back into the atmosphere through fires and heterotrophic respiration. The rest is converted into soil organic carbon, which is released more slowly, or "inert" dissolved carbon, which can remain in the biosphere for an unknown period of time. [3]
Soil carbon storage is an important function of terrestrial ecosystems. Soil contains more carbon than plants and the atmosphere combined. [1] Understanding what maintains the soil carbon pool is important to understand the current distribution of carbon on Earth, and how it will respond to environmental change.
Soil gases (soil atmosphere [1]) are the gases found in the air space between soil components. The spaces between the solid soil particles, if they do not contain water, are filled with air. The primary soil gases are nitrogen, carbon dioxide and oxygen. [2] Oxygen is critical because it allows for respiration of both plant roots and soil ...
The global soils contain up to 3150 Pg of carbon, of which 450 Pg exist in wetlands and 400 Pg in permanently frozen soils. The soils contain more than four times the carbon as the atmosphere. [30] Researchers have estimated that soil respiration accounts for 77 Pg of carbon released to the atmosphere each year. [31]
Carbon sequestration is part of the natural carbon cycle by which carbon is exchanged among the biosphere, pedosphere (soil), geosphere, hydrosphere, and atmosphere of Earth. [ citation needed ] Carbon dioxide is naturally captured from the atmosphere through biological, chemical, or physical processes, and stored in long-term reservoirs.