Soil organic carbon decomposition

Ise, T. and P. R. Moorcroft. 2006. The global-scale temperature and moisture dependencies of soil organic carbon decomposition an analysis using a mechanistic decomposition model. Biogeochemistry 80 217-231. 

Figure 2.1. Diagram of factors controlling the main inputs and outputs of soil carbon, superimposed over a global map of soil organic carbon stocks. DOC, POC, and DIC stand for dissolved organic C, particulate organic C, and dissolved inorganic C, respectively. The background soil organic carbon (SOC) map (Miller Projection 1 100,000,000). See color insert. Reprinted from Davidson, E. A., and Janssens, I. A. (2006). Temperature sensitivity of soil carbon decomposition and feedbacks to climate change. Nature 440,165-173, with permission from Macmillan.

Happen J. D. and Chanton J. P. (1993) Carbon remineralization in a North Florida swamp forest effects of water level on the pathways and rates of soil organic matter decomposition. Global Biogeochem. Cycles 7, 475 -490. 

In wetland soils, organic matter decomposition is frequently limited by electron acceptor availability, rather than carbon availability as in upland ecosystems. The concentration and type of electron acceptors available in soils determine the types of microbial communities involved and the rate of decomposition process. Much of the detrital matter produced in wetlands is deposited on the soil surface. It is unlikely that there is enough oxygen in this matrix to decompose this material. Therefore, the decomposition of detrital matter is also dependent on the activity of anaerobic microorganisms using alternate electron acceptors. Similarly, the rate of organic matter decomposition in soils is dependent on the availability of electron acceptors (see for discussion in Chapters 3 and 4). 

Several authors have applied in situ pulse labeling of plants (grasses and crops) with C-CO2 under field conditions with the objective of quantifying the gross annual fluxes of carbon (net assimilation, shoot and root turnover, and decomposition) in production grasslands and so assess the net input of carbon (total input minus root respiration minus microbial respiration on the basis of rhizodeposition and soil organic matter) and carbon fixation in soil under ambient climatic conditions in the field. 

D. A. Wedin, L. L. Tieszen, B. Dewey, and J. Pastor, Carbon isotope dynamics during grass decomposition and soil organic matter formation. Ecology 76 1383 (1995). 

Golchin A, Baldock JA, Oades JM (1998) A model linking organic matter decomposition, chemistry, and aggregate dynamics. In Lai R, Kimble JM, Follett RF, Stewart BA (eds). Soil processes and the carbon cycle. CRC Press, Boca Raton, pp 245-266... 

UNFCCC (1997) Kyoto protocol to the United Nations Framework Convention on climate change. Document FCCC/CP/1997/7/ Add 1, http //www.unfccc.de Van Cleve K, Powers RF (1995) Soil carbon, soil formation, and ecosystem development. In McFee WW, Kelly JM (eds) Carbon forms and functions in forest soils. Soil Science Society of America, Madison, WI, pp 155-200 Wedin TA, Tieszen LL, Dewey B, Pastor J (1995) Carbon isotope dynamics during grass decomposition and soil organic matter formation. Ecology 76 1383-1392... 

Kuzyakov Y, Cheng W (2001) Photosynthesis controls of rhizosphere respiration and organic matter decomposition. Soil Biol Biochem 33 1915-1925 Kuzyakov Y, Domanski G (2000) Carbon inputs by plants into the soil. Rev J Plant Nutr Soil Sci 163 421—431... 

Alternately, the weight lost when the carbonate is reacted with HC1 can be determined. Heating carbonates results in their decomposition. Thus, soils containing carbonate can be heated to the appropriate temperature and the loss of weight measured. In this approach, the loss of organic matter and water of hydration of various components in soil must be accounted for in order to determine the weight of carbon dioxide [7],... 

Water is modified by soil when added as either rain or irrigation [2], The modifiers are plants, plant roots, organic matter, organic matter decomposition products, carbon dioxide and other gases in the soil atmosphere, and dissolved inorganic compounds, commonly salts. Of particular importance is the change in pH that accompanies this modification of water. Thus, components obtained from soil by added extraction water will be significantly different from... 

In a further study the oxidation of the methyl carbon of methanearsonate was associated with the oxidation of soil organic matter in a number of soils. Additions of organic matter to a Norfolk loamy sand greatly increased the decomposition of methanearsonate. In three of the soils, there was no evidence of microbiological adaptation to methanearsonate. In Norfolk loamy sand, however, increasing decomposition of methanearsonate relative to soil organic matter occurred with time of incubation. 

The USDA (1999) defines organic wetland soils as having an organic carbon content of at least 12 % if the mineral fraction has no clay, 18 % if > 60 % clay, or 12-18 % if < 60 % clay. Further differentiation is based on the botanical origin of the organic matter-whether mosses, herbaceous plants, or woody plants-and its state of decomposition fibrists contain predominantly recognizable, little-decomposed plant debris, saprists predominantly well-decomposed plant debris. 

Carbon is released into the atmosphere as carbon dioxide as part of the process of respiration. The decomposition of the remains and wastes of living things by bacteria and other soil organisms also releases carbon dioxide into the atmosphere. In addition, carbon dioxide is released into the atmosphere by fires and other types of burning, including the burning of fossil fuels and erupting volcanoes. 

---