- Soil carbon
Soil carbon is the generic name for
carbonheld within the soil, primarily in association with its organic content. This discussion begins with a brief introduction to soil carbon, its function within the soil, influences on soil carbon, and finally the impacts that might be expected from increasing soil carbon.
Between 1200 and 1800 Gt of carbon is stored in soils worldwide, twice the amount that is stored in all
terrestrial plants. Carbon is exchanged between the soil and atmosphere in a cycle that is overwhelmingly driven by photosynthesis.Cite book | title = Cycles of life: civilization and the biosphere | last = Smil | first = V. | date = 1997 | publisher = Scientific American Library | location = New York | isbn = 0-7167-6039-8 | url = http://www.whfreeman.com/GeneralReaders/book.asp?id_product=1149000045]
Plants absorb atmospheric
carbon dioxide(CO2), which is then reduced through photosynthesis so that the carbon component is retained and the oxygenis returned to the atmosphere. The carbon that is retained by plants may be transferred to the soil via roots or decomposing plant residues. Soil carbon may be returned directly to the atmosphere from the soil, when the organic material in which it is held is oxidized by decompositionor burning.
There are two discrete pools in which soil carbon is stored:Cite book | title = The Biology of Soil: A Community and Ecosystem Approach | last = Bardgett | first = R.D. | date = 2005 | publisher =
Oxford University Press| location = New York | isbn = 0198525036 | url = http://books.google.com/books?id=iX1oLTDGbmkC] the soil’s microbialbiomass and easily-decomposed plant residues that are cycled rapidly and in which carbon may reside for as little as a few weeks, and; the pool in which carbon is more tightly held by physical encapsulation within soil aggregates (singular masses of coherent soil particles, or peds) or chemical complexing—here, carbon may reside for tens of thousands of years. Soil organic carbon(SOC) refers to the amount of carbon stored in the soil—it is expressed as a percentage by weight (g C/kg soil). SOC is closely related to the amount of organic matter in the soil ( soil organic matter(SOM)), according to the approximation: SOC × 1.72 = SOM.Cite book | title = Soils in the Australian landscape | last = Young | first = A. | coauthors = Young, R. | date = 2001 | publisher = Oxford University Press| location = Melbourne | isbn = 9780195515503 | url = http://www.oup.com.au/content/General.asp?ContentID=1057] The SOM of Australian soils ranges from 50 per cent in alpine humussoils to less than one per cent in desert loams. Across Victoria the SOM range of both agricultural and non-agricultural surface soils is from 1.3 to 10.5 per cent.
oil carbon and soil health
Soil carbon improves the physical properties of soil. It increases the cation exchange capacity (CEC) and
water-holding capacity of sandy soil and it contributes to the structural stability of clay soils by helping to bind particles into aggregates.Cite book | title = Soil science, an introduction | edition = 5th edn | last = Leeper | first = G.W. | coauthors = Uren, N.C. | date = 1993 | publisher = Melbourne University Press| location = Melbourne | isbn = 0-522-84464-2 | url = http://www.mup.unimelb.edu.au/catalogue/0-522-84464-2.html] Soil organic matter, of which carbon is a major part, holds a great proportion of nutrients, cations and trace elements that are of importance to plant growth. It prevents nutrient leaching and is integral to the organic acids that make minerals available to plants. It also buffers soil from strong changes in pH.Cite journal | last = Leu | first = A | title = Organics and soil carbon: increasing soil carbon, crop productivity and farm profitability | date = 2007 | url = http://www.amazingcarbon.com/Leu%20-%20Organics%20and%20soil%20carbon.pdf] It is widely accepted that the carbon content of soil is a major factor in its overall health.
Managing soil carbon
Natural variations in SOM occur as a result of climate, organisms, parent material, time and relief. The greatest contemporary influence has been that of humans; for example, historical SOM in Australian agricultural soils may have been twice the present range that is typically from 1.6 to 4.6 per cent.Cite book | title = Soils, their properties and management | edition = 2nd edn | last = Charman | first = P.E.V. | coauthors = Murphy, B.W. | date = 2000 | publisher =
Oxford University Press| location = Melbourne | isbn = 9780195517620 | url = http://au.oup.com/content/general.asp?ContentID=1882]
It has long been encouraged that farmers adjust practices to maintain or increase the organic component in the soil—on one hand, practices that hasten oxidation of carbon, such as burning crop stubbles or over-cultivation are discouraged; on the other hand, incorporation or organic material, such as manuring has been encouraged. Increasing soil carbon is not a straightforward matter—it is made complex by the relative activity of soil biota, which can consume and release carbon and are made more active by the addition of nitrogen
Managing for catchment health
Much of the contemporary literature on soil carbon relates to its role, or potential, as an atmospheric carbon sink to offset climate change. Despite this emphasis, a much wider range of soil and
catchmenthealth aspects are improved as soil carbon is increased. These benefits are difficult to quantify due to the complexity of natural resource systems and the interpretation of what constitutes soil health; nonetheless, several benefits are proposed in the following points:
erosion, sedimentation: increased soil aggregate stability means greater resistance to erosion; mass movement is less likely when soils are able to retain structural strength under greater moisture levels.
*Greater productivity: healthier and more productive soils can contribute to positive socio-economic circumstances.
*Cleaner waterways, nutrients and
turbidity: nutrients and sediment tend to be retained by the soil rather than leach or wash off, and are so kept from waterways.
*Water balance: greater soil water holding capacity reduces overland flow and recharge to groundwater; the water saved and held by the soil remains available for use by plants.
*Climate change: Soils have the ability to retain carbon that may otherwise exist as atmospheric CO2 and contribute to greenhouse warming.
biodiversity: soil organic matter contributes to the health of soil flora and accordingly, the natural links with biodiversity in the greater biosphere.
The exchange of carbon between soils and the atmosphere is a significant part of the world carbon cycle, which is extensive both spatially and temporally. Carbon, as it relates to the organic matter of soils, is a major component of soil and catchment health. Several factors affect the variation that exists in soil organic matter and soil carbon—the most significant has, in contemporary times, been the influence of humans and agricultural systems. There are clear benefits for catchment health by focusing on soil carbon – efforts would need to be extensive and economical for the collective benefit to be realized.
Wikimedia Foundation. 2010.
См. также в других словарях:
soil carbon — /ˈsɔɪl kabən/ (say soyl kahbuhn) noun carbon dioxide trapped in the soil which can be released by deforestation or increased by pasture improvement or reafforestation … Australian-English dictionary
Australian Soil Carbon Accreditation Scheme — noun a soil carbon auditing scheme, initiated in 2007, under which the carbon sequestered on farm land is measured and assigned carbon credits which can then be sold on behalf of the owner or manager of the farm. Abbrev.: ASCAS … Australian-English dictionary
Carbon sequestration — is the capture of carbon dioxide (CO2) and may refer specifically to: The process of removing carbon from the atmosphere and depositing it in a reservoir.  When carried out deliberately, this may also be referred to as carbon dioxide removal,… … Wikipedia
Soil science — is the study of soil as a natural resource on the surface of the earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and… … Wikipedia
Soil health — is an assessment of ability of a soil to meet its range of ecosystem functions as appropriate to its environment. Aspects of soil health The term soil health is used to assess the ability of a soil to: *Sustain plant and animal productivity and… … Wikipedia
soil — soil1 soilless, adj. /soyl/, n. 1. the portion of the earth s surface consisting of disintegrated rock and humus. 2. a particular kind of earth: sandy soil. 3. the ground as producing vegetation or as cultivated for its crops: fertile soil. 4. a… … Universalium
Carbon sink — A carbon sink is reservoir of carbon that accumulates and stores carbon for an indefinite period. The main natural sinks are: # Absorption of carbon dioxide by the oceans # Photosynthesis by plants and algae The process by which carbon sinks… … Wikipedia
Soil — For other uses, see Soil (disambiguation). A represents soil; B represents laterite, a regolith; C represents saprolite, a less weathered regolith; the bottommost layer represents bedrock … Wikipedia
Carbon offset — Part of a series on Green economics Concepts … Wikipedia
Carbon cycle — The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.The cycle is usually thought of as four major reservoirs of carbon interconnected by… … Wikipedia