User:Paleorthid/Sandbox/Article Nursery/Soil Carbon/References

-- Paleorthid (talk) 18:06, 13 January 2016 (UTC)

news articles

CSIRO study erodes credibility of key soil carbon model

college text books

Weil, Ray R.; Brady, Nyle C. (2016). The Nature and Properties of Soils (15th ed.). Columbus: Pearson (published April 11, 2016). p. 554. ISBN 9780133254488. LCCN 2016008568. OCLC 942464649.

page=544 |quote=Char is included with humus

page=548 |quote=By photosynthesis thousands of years ago (humus)

page=549 |quote=For more than 100 years soil scientists have used strong alkali (pH ~13) to extract organic matter from soils so they could quantify it and determine its nature in the lab

page=549 |quote=The alkaline extraction process itself creates giant polymers

page=554 |quote=Humus accounts for 50 to 90% of cation exchange capacity. Like clays, humus colloids and high surface area char hold nutrient cations

page= |quote=

Blume, H-P.; Wilke, B-M.; Kandeler, E.; Brümmer, G.W.; Fleige, H.; Kögel-Knabner, II.; Stahr, K.; Schad, P.; Horn, R.; Kretzschmar, R., eds. (2016). Scheffer/Schachtschabel Soil Science (1st ed.). New York; Berlin; Heidelberg: Springer-Verlag (published November 25, 2015). doi:10.1007/978-3-642-30642-7 (inactive 2022-06-26). ISBN 9783642309410. LCCN 2015937207. OCLC 946075808.{{cite book}}: CS1 maint: DOI inactive as of June 2022 (link)

|page=72. |quote=...black carbon, the decomposition product of charcoal resulting from vegetation fires, is stored in the soil....High proportions of black carbon have been documented in Chernozems...

|page=147 |quote=...humic substances are mostly negatively charged and have reactive functional groups (e.g. carboxylic, phenolic) therefore they can be a absorbed by electrostatic forces in specific interactions with surface functional groups on oxide and clay mineral surfaces. The sorption of humic substances to mineral services generally increases with decreasing pH and increasing ionic strength of the soil solution. ...Aromatic and high-molecular weight humic matter fractions are preferentially absorbed compared to aliphatic and low molecular weight humic substances

fire—soil references

References for background (chronological order):

V.N.Gorbachev and E.P. Popova (1996) Fires and Soil Formation. In: Goldammer J.G., Furyaev V.V. (eds) Fire in Ecosystems of Boreal Eurasia. Forestry Sciences, vol 48. Springer, Dordrecht "Forest fires have considerable effects on soil formation. Soils as an integral part of forest biogeocenoses undergo a versatile effect from fires."

I.Kögel-Knabner and M.W.ISchmidt, J.O.Skemstadt, and E.Gehrt (1999). The role of charred organic matter in the Pedogenesis of Chernozems in Geochemistry of the Earth's Surface, Armansson (ed.), ISBN 90 5809007306 "... due to its recalcitrant nature, char can be preserved in the pedosphere for long periods of time. This has major implications for the processes of pedogenesis in Chernozemic soils..."

M.W.I.Schmidt, and A.G.Noack (2000) Black carbon in soils and sediments: Analysis, distribution, implications, and current challenges. in Global Biogeochemical Cycles 2000 Vol.14 No.3 pp.777-793 ref.183 "On land, BC seems to be abundant in dark-coloured soils..."

E.V. Ponomarenko and D.W. Anderson (2001) Importance of charred organic matter in Black Chernozem soils of Saskatchewan "The present paradigm views humus as a system of heteropolycondensates, largely produced by the soil microflora, in varying associations with clay (Anderson 1979). Because this conceptual model, and simulation models rooted within the concept, do not accommodate a large char component, a considerable change in conceptual understanding (a paradigm shift) appears imminent."

M.W.I.Schmidt, J.O.Skjemstad, C.Jäger, (2002), "Carbon isotope geochemistry and nanomorphology of soil black carbon: Black chernozemic soils in central Europe originate from ancient biomass burning, Global Biogeochemical Cycles, 16 (4), doi:10.1029/2002GB001939. "These data challenge the common paradigm that chernozems are zonal soils with climate, parent material and bioturbation dominating soil formation, and introduce fire as a novel, important factor in the formation of these soils."

EC.Krug, S.E.Hollinger, Steven E. (2003). "Identification of Factors that Aid Carbon Sequestration in Illinois Agricultural Systems" (PDF). Champaign, Illinois: Illinois State Water Survey:

Krug (2003) page 8. ..."While humus (especially in organomineral form) helps give soils a black color (Duchaufour, 1978), the literature shows correlation between forest and grassland soil color to BC - the blacker the soil the higher its BC content (Schmidt and Noack, 2000)"

Krug (2003) page 10. ...Charcoal has been found to contribute up to 45 percent of SOC in grassland soils (Schmidt et al., 1999) and soil biota mix millimeter-sized BC throughout the soil profile (Carcaillet, 2001). .... By increasing biological productivity BC also may contribute to SOC indirectly. Charcoal has been widely used throughout the world as a soil conditioner to increase crop and tree growth, improve germination, and reduce disease (Tryon, 1948; Goldberg, 1985; Kishimoto and Sugiura, 1985; Schmidt and Noack, 2000). Root growth in charcoal-amended soils is enhanced. Production of various legume crops is increased by 20 to 30 percent (Iswaran et al., 1979; Kishimoto and Sugiura, 1985). Exceptionally heavy nodulation has been reported for soybeans grown in charcoal-enriched soils, along with increased yield and N content of roots and shoots. This has been documented even for charcoal added to organic-rich mineral soils and peats. It has been hypothesized that charcoal sorbs agents toxic to rhizobia and other microorganisms of the rhizosphere, and that this effect is general to legumes (Chakrapani and Tilak, 1974; Rajput et al., 1983). The literature shows that charcoal in soil sorbs heavy metals, organic toxins, stimulates microbial activity, acts as a substrate for enhanced microbial growth, and generally stimulates N fixation, ammonification, and nitrification (Tryon, 1948; Kishimoto and Sugiura, 1985; Pietikainen et al., 2000; Schmidt and Noack, 2000). The literature further shows that prairie burning enhances productivity, root biomass levels, root turnover, and arthropods - the latter being especially active in incorporating surface BC throughout the soil profile (Lussenhop, 1976). Frequent presettlement fires in Illinois created a multi-level, positive-feedback system for sequestering SOC and enhancing soil fertility."

E.Eckmeier, R.Gerlach,E.Gehrt, M.W.I.Schmidt (2007), "Pedogenesis of Chernozems in Central Europe — A review" (PDF), Geoderma, Elsevier B.V., 139: 288–299, doi:10.1016/j.geoderma.2007.01.009

E.Eckmeier (2007), Detecting prehistoric fire-based farming using biogeochemical markers, University of Zurich, Faculty of Science., doi:10.5167/uzh-3752. "It is now an open question as to whether Neolithic settlers did indeed prefer to grow crops where Chernozems occurred or if Neolithic burning formed the chernozemic soils."

H.Knicker (2011). Pyrogenic organic matter in soil: Its origin and occurrence, its chemistry and survival in soil environments. Quaternary International 243: 251–263.

"...PyOM can also be involved in pedogenic processes. The latter is expressed in the observation that human activity of Neolithic and earlier times contributed to the formation of soils with typical features. Thus, using fire and charcoal application as an agricultural practice, one has to account for the possibility that such an approach has formerly and will in future alter soil environments and properties not only on a short but also on a long-term scale."

J.D.Mao, R.L.Johnson, J.Lehmann, J.Olk, E.G.Neeves, M.L.Thompson, K.Schmidt-Rohr, (2012). "Abundant and stable char residues in soils: implications for soil fertility and carbon sequestration". Environmental Science and Technology. 46: 9571 – 9576. doi:10.1021/es301107c.

E.V. Ponomarenko and D.W. Anderson (2013) Signature of forest fires in prairie soils. in Proceedings of the Fourth International Meeting of Anthracology: Brussels, 8–13 September 2008, Royal Belgian Institute of Natural Sciences. ISBN 978 1 4073 1100 5

G.Certini (2014). "Fire as a Soil-Forming Factor". Ambio. Springer. 43 (2): 191–195. PMC 3906481 Freely accessible. doi:10.1007/s13280-013-0418-2. "...fire does not lack any crucial requisite to be recognized as a factor of pedogenesis on Earth, the seventh one together with parent material, climate, time, topography, living beings not endowed with the power of reason, and humans."

H.Knicker, M.Velasco-Molina, F.J.Gonzalez-Vila, J.A.Gonzalez-Perez, A.Berns, J.M. De La Rosa, and L.Clemente-Salas (2015) Charcoal - A soil forming factor in frequently burnt soils? "It is well accepted that an immediate effect of charcoal input represents the enhancement of the aromaticity of the soil organic matter (SOM) in particular of the topsoils. However, our knowledge about the longterm impact of this material on SOM and on general soil properties is still scarce."

C.Santın and S.H.Doerr (2016) Fire effects on soils: the human dimension. Phil. Trans. R. Soc. B 371: 20150171. http://dx.doi.org/10.1098/rstb.2015.0171 "The existence and fate of fire and soils are closely linked. The presence of soils is a principal prerequisite for the occurrence of fire, and fire can be both a forming and degrading agent for soils. Fire can alter the physical, chemical and biological characteristics of soils both during and after burning. These changes range from negligible to very severe, with their nature and direction depending on many factors and thresholds. In this complex fire–soil interaction, humans have exerted a key role since their early days."

H-P.Blume, B-M.Wilke, E.Kandeler, G.W.Brummer, H.Fleige, II.Kogel-Knabner, K.Stahr, P.Schad, R.Horn, R.Kretzschmar (2016). Scheffer/Schachtschabel Soil Science (1 ed.). Springer. ISBN 978-3642309410. p. 72. "...black carbon, the decomposition product of charcoal resulting from vegetation fires, is stored in the soil....High proportions of black carbon have been documented in Chernozems..."

Opportunities with soil carbon article

Soil carbon is the generic name for carbon held within the soil, primarily in association with its organic content. Soil carbon is the largest terrestrial pool of carbon, containing 2,200 gigatonnes (Gt) of it. Batjes, N.H. (1996). "Total carbon and nitrogen in the soils of the world". Soil Science 47 (2): 151–163. doi:10.1111/j.1365-2389.1996.tb01386.x.

Opportunity: bring out the relative role of mineral carbon.

Soil Organic Carbon Storage (Sequestration) Principles and Management

Sources cited in https://fortress.wa.gov/ecy/publications/publications/1507005.pdf

Vi

vi. Increasing the amount of organic C in soils may not only mitigate GHG emissions, but also benefit agricultural productivity through improvements in soil health and environmental quality by reducing soil erosion (Lal, 2004a; Pacala and Socolow, 2004).

vi. Soil C exists in two forms: inorganic and organic. Soil inorganic carbon (SIC) is the result of both weathering of the parent materials and carbonic acid (CO2 dissolved in water) in the soil, precipitating as C minerals such as calcite, aragonite, and dolomite (Lal, 2007).

vi. Soil organic carbon (SOC) is a complex of organic C compounds in the form of SOM. SOM includes everything in or on the soil that is of biological origin irrespective of origin or state of decomposition (Baldock and Skjemstad, 1999).

Baldock 1999

$150 Baldock, J.A., Skjemstad, J.O. 1999. Organic soil C/soil organic matter. In Prveril, K.I., Sparrow. L.A., Reuter, D. J. (Eds.), Soil Analysis: An interpretation manual. CSIRO Publishing: Collingwood, Victoria, pp. 159–170.

vi. It includes plants and animals in various states of decomposition, cells and tissues of soil organisms, and substances from plant roots and soil microbes. SOC originally comes from atmospheric CO2 that is captured by plants through the process of photosynthesis. The amount of SOC is a balance of C inputs and C losses of organic material (Burke et al., 1989).

vi

vii. Globally, soils contain about 3 times more C than the atmosphere and 4.5 times more C than all living things. A relatively small increase in C content in soils can make a significant contribution to reducing atmospheric CO2 levels. It is estimated that increasing SOM content in soils up to a 2-meter depth by 5-15% could decrease atmospheric CO2 concentrations by 16-30% (Baldock, 2007; Kell, 2011).

vii. These ideas have led to substantial attention to quantifying stocks of C in soils, mechanisms for stabilizing C in soils, and agricultural management practices, including application of recycled organic materials such as compost, biosolids, and biochar to increase soil organic matter (SOM) stocks (Lal, 2002; Smith, 2008).

vii. 2. In addition to helping mitigate climate change as resulted from increased soil C storage, use of recycled organic materials into soils results in a range of important environmental benefits (Lal, 2002; Smith, 2008). These benefits include: • Improved soil health, water saving, and crop productivity. • Reduced need for chemical fertilizers and pesticides. • Reduced soil erosions by water and wind. • Improved soil tilth.

3 inorganic C

3 Soil C refers to the total C in soil, and it includes both inorganic and organic C forms. Soil inorganic C (SIC) is the result of both weathering of the parent materials and Cic[???] acid (Carbon dioxide dissolved in water) in the soil, precipitating as C minerals such as calcite, aragonite, and dolomite (Lal, 2007).

Lal, R. 2007. C management in agricultural soils. Mitigation and Adaption Strategies for Global Change. 12:303-322.

https://www.researchgate.net/publication/227593261_Carbon_Management_in_Agricultural_Soils

304. Soil C pool comprises two components: soil organic carbon (SOC) and soil inorganic carbon (SIC). The SOC pool includes highly active humus and relatively inert charcoal C. Humus is a dark brown or black amorphous material characterized by a large surface area, high charge density, high affinity for water, and ability to form organomineral complexes through reaction with the clay fraction. Charcoal is a product of incomplete combustion of plants, and is recalcitrant with relatively long residence time.

304. The generic term soil organic matter (SOM) refers to the sum of all organic substances in the soil comprising: (i) a mixture of plant and animal residues at various stages of decomposition, (ii) substances synthesized through microbial and chemical reactions, (iii) and biomass of live soil micro-organisms and other fauna along with their metabolic products.

304. The SIC pool includes elemental C [char-C????] and carbonate minerals ...

304. The global soil C pool is estimated at 1550 Pg of SOC and 950 Pg of SIC to 1-m depth (Batjes 1996). The soil C pool is about 3.3 times the atmospheric pool (760 Pg) and 4.5 times the biotic pool (560 Pg) (Figure 1). Soil C pool can be a source or sink for atmospheric pool depending on land use and management. There is a direct relationship between soil C pool and the atmospheric pool. Increase of soil C pool by 1 Pg is equivalent to reduction in atmospheric CO2 concentration of 0.47 ppm, and vice versa.

4

4.1 Soils are the largest pool of terrestrial C

Soils are the largest stock of C in the terrestrial environment (Jobbágy and Jackson, 2000),

Jobbágy 2000

Jobbágy, E.G (2000). "The vertical distribution of soil organic C and its relation to climate and vegetation" (PDF). Ecological Applications. 10. Ecological Society of America: 423–436. doi:10.1890/1051-0761(2000)010[0423:TVDOSO]2.0.CO;2.

Schlesinger 1997

Schlesinger, W. H. 1997. Biogeochemistry, an analysis of global change. Academic Press, San Diego, California, USA.

and I have determined there is a revised edition

Schlesinger 2013

Biogeochemistry 3rd Edition: An Analysis of Global Change 2013 by W.H. Schlesinger and Emily S. Bernhardt ISBN 978-0123858740 ISBN 0123858747 or 57 depending

interested in reading

Schlesinger 1997

Schlesinger, W. H. 1977. Carbon balance in terrestrial detritus. Annual Review of Ecology and Systematics 8:51–81.

Galloway 2014

Recommended Citation for Chapter Galloway, J. N., W. H. Schlesinger, C. M. Clark, N. B. Grimm, R. B. Jackson, B. E. Law, P. E. Thornton, A. R. Townsend, and R. Martin, 2014: Ch. 15: Biogeochemical Cycles. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 350-368. doi:10.7930/J0X63JT0.

On the Web: http://nca2014.globalchange.gov/report/sectors/biogeochemical-cycles

Table 15.1. Carbon (C) sinks and uncertainty estimated by Pacala et al. for the first State of the Carbon Cycle Report. (Pacala 2007 = (23) Forests take up the highest percentage of carbon of all land-based carbon sinks. Due to a number of factors, there are high degrees of uncertainty in carbon sink estimates.

Pacala 2007

Pacala, S., R. A. Birdsey, S. D. Bridgham, R. T. Conant, K. Davis, B. Hales, R. A. Houghton, J. C. Jenkins, M. Johnston, G. Marland, and K. Paustian, 2007: Ch. 3: The North American carbon budget past and present. The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle, A. W. King, L. Dillling, G. P. Zimmerman, D. M. Fairman, R. A. Houghton, G. Marland, A. Z. Rose, and T. J. Wilbanks, Eds., 29-170. [Available online at http://nrs.fs.fed.us/pubs/jrnl/2007/nrs_2007_pacala_001.pdf

Hiederer 2009

Hiederer, R. (2009) Distribution of Organic Carbon in Soil Profile Data. EUR 23980

http://eusoils.jrc.ec.europa.eu/ESDB_Archive/eusoils_docs/other/EUR23980.pdf

4.2

.... with about 60% in the form of SOM, and the remaining 40% in the form of inorganic C (e.g. carbonate, or CaCO3). The total amount of C stored in the top meter of soil is estimated to be 2,500 Pg C globally (1 Pg = petagram = 1015 g), including about 1,500 Pg of SOC, and 950 Pg C of inorganic soil C (SIC). This is about 3.3 times the amount of C in the atmospheric pool (760 Pg C) and about 4.5 times (560 Pg C) the amount of C stored in living vegetation (Lal, 2004b).

4.3

The SOC pool plays an important role in the global C cycle and has a strong impact on agricultural sustainability, and environmental quality (Jenkinson et al., 1991; Stevenson, 1994).

4. The SIC pool is an important constituent in soils in arid and semiarid regions. It includes elemental C and carbonate and bicarbonate minerals (e.g. calcite and dolomite). There are two types of C[arbonates]ates: primary and secondary. The primary carbonates are derived from the weathering of the parent material, whereas the secondary Cates are formed through the conversion of CO2 in soil air into carbonic acid and its reaction with Ca2+ and Mg2+ (Lal and Kimble, 2000).

4. Land use changes can cause the depletion of SOC pools stored in global soils. Globally, it is estimated conversion of native vegetation for agricultural production has resulted in losses of about 78 Pg C, with about 26 Pg C resulted from erosion and 25 Pg C from mineralization (Lal, 2004b).

4. Guo and Gifford (2002) also estimated that about 42-59% SOC have been lost due to the conversion of native forest and grass for agricultural production in Australia.

4. Most forest and grassland soils of the U.S. are estimated to have lost from 20-50% of their original SOC pool in the first 40–50 years of cultivation (Rasmussen and Collins, 1991; Camberdella and Elliott, 1992).

4. Cultivation may increase decomposition rates by exposing SOM occluded in soil aggregates to microbial degradation, because both disruption of soil structure leads to changes in porosity that create a more favorable decomposition environment. In addition, cultivation, especially when followed by fallow, creates favorable conditions for both wind and water erosion (Packer et al., 1992).

4. The depletion of SOC stored has created a great potential for agricultural soils to return soil C from the present to pre-conversion soil organic C level (IPCC, 2000),

4. ... and could significantly change current atmospheric CO2 concentrations (Wang et al., 1999)

5

5. A SOC concentration of less than 2% (or 3.4% SOM) is considered to be the threshold value below which soil function is impaired (Greenland et al., 1975; Lal, 2004c).

5. Although there is little quantitative evidence for such a threshold (Loveland and Webb, 2003), ...

5. Janzen (2006) proposed that the bioavailability of SOM is the major influence on soil properties.

5. However, the general responses of soil organic C stocks in terrestrial ecosystems to changes in environmental conditions remains unclear, especially temperature and precipitation, and their combined effect (Wu et al., 2011).

5. In contrast, in addition to leading to increased atmospheric CO2 concentrations, losses of SOM could have adverse impacts on soil quality, agricultural production, and the environment. The adverse impacts [listed] (Lal, 2004c, Whitbread et al., 1998)

6 Soil organic matter fractions

6. SOM is partitioned into different pools with varying decomposition rates or turnover times (Adair et al., 2008). The term “pool” is used to refer to theoretically separated, kinetically delineated components of SOM which share similar turnover times within the soil (Davidson and Janssens, 2006; Paustian et al., 1992).

6. The best known biogeochemical model of soil C dynamics – the CENTURY (Parton et al., 1987) model divides SOM into three pools in the mineral soils (from the most labile to the most recalcitrant to decomposition): [fast pool, slow pool, passive pool]

6. The proportion of total soil C in each pool can vary widely, but is assumed to be in the range of 10% for the fast pool, 40-80% for the slow pool, and 10-50% to for the passive pool (Biala, 2011).

Biala 2011

Biala, J. 2011. The benefits of using compost for mitigating climate change. Department of Environment, Climate Change and Water NSW (New South Wales). Sydney South, Australia.

https://www.epa.nsw.gov.au/resources/waste/110171-compost-climate-change.pdf

Supports but it is complicated by the biochar statement: In addition to the above three soil carbon pools, the FullCAM model refers also to recalcitrant carbon, but in that case it represents charred carbon. The proportion of total soil carbon in each pool can vary widely, but is assumed to be in the range of 10% for the fast pool, 40% to 80% for the slow pool, and 10% to 50% for the passive pool.

7 Fast Pool

7. The fractions of this pool also include simple sugars, amino acids, proteins, polysaccharides, and carbohydrate (Hopkins and Dungait, 2010),

7. which may derive from microbes due to exudation and excretions, cell death, and decay (Hofman and Dusek, 2003).

7. Some compounds (e.g. simple sugar) in the soil can decompose very quickly, with a less than one hour of half-life turnover time, because they are rich in energy, readily accessible to organisms, and rapidly assimilated (Boddy et al., 2007; Hill et al., 2008).

7. Cellulose and hemicelluloses polysaccharides are the most abundant substrates in plant litter (Dungait et al., 2005; Jia et al., 2008).

7. It has been determined 60% of cellulose is mineralized in soil after one month, with an additional 7% decomposed within three months (Derrien et al., 2007),

7. ... and the remainder persisting in soils long-term (Gleixner et al., 2002). It has been suggested soil polysaccharides play an important role in stabilization of soil microaggregates, (<250 µm) as their length and linear structure allow them to bridge the space between soil particles (Martens, 2000)

7. ... and intact polysaccharides may become occluded within soil aggregates as components of intra-aggregate particulate SOM (Six et al., 2000a, b). Other compounds decompose relatively slowly, with a half-life (turnover) time from less than one hour to a few years.

Slow Pool Passive Pool

7. The recalcitrant SOM pool has decades to centuries of a half-life turnover time. The decomposition of lignin and its derivatives is often regarded as the rate limiting step in biological C cycling (Zhang et al., 2008; St. John et al., 2011).

7. It is reported about 92% of total lignin extracted from soils decompose within one year (Rasse et al., 2006; Dungait et al., 2010),

7. ... with the remainder decomposing within decades (Digac et al., 2005; Heim and Schmidt, 2007).

7. A recent review concluded the literature is contradictory with regard to decomposition rates, but agreed most decompose within five years (Thevenot et al., 2010).

Supporting Link - Laird 2008

The Charcoal Vision: A Win–Win–Win Scenario for Simultaneously Producing Bioenergy, Permanently Sequestering Carbon, while Improving Soil and Water Quality http://chargrow.org/sites/default/files/LAIRD.pdf

Reports vary, but our best guess is that 5 to 15% of the C in Midwestern prairie soils is charcoal, a legacy of 10,000 yr of prairie fi res.

Supporting Link - Skjemstad 2002

Charcoal Carbon in U.S. Agricultural Soils Jan O. Skjemstad, Donald C. Reicosky, Alan R. Wilts, and Janine A. McGowan Soil Sci. Soc. Am. J. 66:1249–1255 (2002). http://pubag.nal.usda.gov/pubag/downloadPDF.xhtml?id=13040&content=PDF

The charcoal was determined as a portion of the TOC

Charcoal can constitute a large proportion of recalcitrant C pools in agricultural soils and can greatly impact soil C dynamics (Skjemstad et al., 2001)

Skjemstad 2001

Skjemstad, J.O., R.C. Dalal, L.J. Janik, and J.A. McGowan. 2001. Changes in chemical nature of soil organic carbon in Vertisols under wheat in southeastern Queensland. Aust. J. Soil Res. 39: 343–359 http://www.thefreelibrary.com/Changes+in+chemical+nature+of+soil+organic+carbon+in+Vertisols+under...-a073023635 and https://www.researchgate.net/publication/245637093_Changes_in_chemical_nature_of_soil_organic_carbon_in_Vertisols_under_wheat_in_southeastern_Queensland_Aust_J_Soil_Res

Changes in chemical nature of soil organic carbon in Vertisols under wheat in southeastern Queensland. Aust J Soil Res

ARTICLE in AUSTRALIAN JOURNAL OF SOIL RESEARCH 39(2) · MARCH 2001

J. O. Skjemstad, R. C. Dalal, L. J. Janik, and J. A. McGowan

A CSIRO Land and Water, PMB 2, Glen Osmond, SA 5064 Australia. B Department of Natural Resources, RSK, Natural Sciences Precinct, 80 Meiers Road, Indooroopilly, Qld 4068, Australia.

supports char as the inert fraction

supports char C at 30% of SOC "the dominant soil C pool in the Waco soil, after about 20 years of cultivation, is char C."

"Recently, Skjemstad et al. (1999b) showed that a Waco soil (Pellustert) contained a significant proportion (30%) of its soil organic C as char C"

Skjemstad 1999

Skjemstad JO, Taylor JA, Smernik RJ (1999) Estimation of charcoal (char) in soils. Communications in Soil Science and Plant Analysis 30, 2283-2298.

8. Soil char

8. Black C is the charred remains of plant material which appears in soils as a result of human activity and natural fires (Dungait et al., 2012).

Dungait 2012

Dungait, J.A.J., Hopkins, D.W., Andrew, S., Gregory, A.S., Whitmore, A.P. 2012. Soil organic matter turnover is governed by accessibility not recalcitrance. Global Change Biology. 18:1781-1796. http://kaikkeus.dy.fi/a/soil/Soil%20organic%20matter%20turnover%20is%20governed%20by%20accessibility%20not%20recalcitrance.pdf Table 1, p 1783, supports placing biochar in the inert class for modelling.

See also Dungait, J.A.J., Bol, R., Evershed, R.P. 2005. Quantification of dung C incorporation in a temperate grassland soil following spring application using bulk stable C isotope determinations. Isotopes in Environmental and Health Studies. 41:3-11.

Dungait, J.A.J., Bol, R., Lopez-Capel, E., Bull, E.D., Chadwick, D., Amelung, W., Granger, S.J., Manning, D.A.C., Evershed, R.P. 2010. Applications of stable isotope ratio mass spectrometry in cattle dung C cycling studies. Rapid Communications in Mass Spectrometry. 24:495–500.

8. 5-50%

8. Black C derived from biomass consists of a substantial component (5-50%) of organic C in some soils, with a much slower decomposition rate than SOM due to its highly condensed aromatic structure (Schmidt et al., 2001).

resonates with " “Biomass-derived black C comprises a substantial component (5–50%) of organic C in some soils, and is assumed to decompose at a much slower rate than SOM due to its highly condensed aromatic structure (Schmidt et al., 2001)." at American Carbon Registry

Schmidt 2001

Schmidt, M.W.I.; Skjemstad, J.O.; Czimczik, C.I.; Glaser, B.; Prentice, K.M.; Gelinas, Y.; Kuhlbusch, T.A.J. (2001). "Comparative analysis of black C in soils" (PDF). Global Biogeochemical Cycles. 15: 163–168. doi:10.1029/2000GB001284. S2CID 54976103.

(Data on page 164 gives a wide range - multiple secondary sources summarize this table saying 5-50% citing Schmidt 2001: Laird powerpoint useds 5-50 without citation)

supporting link on 50% - Skjemstad 2001

Skjemstad, J.O., R.C. Dalal, L.J. Janik, and J.A. McGowan. 2001. Changes in chemical nature of soil organic carbon in Vertisols under wheat in southeastern Queensland. Aust. J. Soil Res. 39: 343–359 http://www.thefreelibrary.com/Changes+in+chemical+nature+of+soil+organic+carbon+in+Vertisols+under...-a073023635 and https://www.researchgate.net/publication/245637093_Changes_in_chemical_nature_of_soil_organic_carbon_in_Vertisols_under_wheat_in_southeastern_Queensland_Aust_J_Soil_Res

supports char at 50% of SOC "the dominant soil C pool in the Waco soil, after about 20 years of cultivation, is char C."

8 cont.

8. Large charcoal particles originating from forest wildfires can remain in soils for thousands of years (Major et al., 2010).

8. Lemann et al. (2006) suggested that conversion of biomass C to biochar sequesters about 50% of the initial C yielding more stable soil C than burning or direct land application of biomass.

8. However, biochar is not completely inert since it can be used as a substrate by soil microorganisms (Wengel et al., 2006).

8. Experimental results are contradictory, and both rapid (Bird et al., 1999)

8. ... and slow (Shindo, 1991) decomposition of biochar were reported.

8. Black C has been C dated in soils in excess of 2500 years. “Notwithstanding the remaining uncertainty about its precise turnover, black C has been found to be the oldest fraction of C in soil, older than the most protected C in soil aggregates and organo-mineral complexes (Pessenda et al., 2001),

https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/3890/3315 Pessenda, L.C.R., Gouveia, S.E.M. and Aravena, R.: 2001, ‘Radiocarbon dating of total soil organic matter and humin fraction and its comparison with 14C ages of fossil charcoal’, Radiocarbon 43, 595-601.

8. which is commonly the most stable C in soil. This indicates that in quantitative terms biochar is stable, with decomposition leading to subtle, and possibly important changes in the bio-chemical form of the material rather than to significant mass loss.”

Lehmann, J; Gaunt, J; Rondon, M (2006), "Biochar sequestration in terrestrial ecosystems: a review" (PDF), Mitigation and Adaptation Strategies for Global Change, 11 (2), Springer: 403–427, doi:10.1007/s11027-005-9006-5, S2CID 4696862

9

9. SOC, a major source of system stability in agroecosystems, is controlled by many factors that have complex interactions (Burke et al., 1989).

9. These factors include soil properties, climate conditions (temperature and precipitation), and land use and management practices (Baldock and SKjemstad, 1999)

9. Major C losses are from mineralization of organic materials and soil erosion (De Jong and Kachanoski, 1988; Paustian et al. 1997).

9. Erosion has been a major loss mechanism for SOC from agro-ecosystems, which accounts for an estimated 20-50% of historic C losses (Lal, 2004b).

9. Eroded SOC can be a net sink for or a net source of CO2 depending both on the frame of reference and on the fate of this eroded material (Stallard, 1998; Yoo et al., 2005).

9. Conventional cultivation practices promote the mineralization and losses as CO2 of the more labile SOC fractions. Soil management practices such as conservation farming are designed to increase C inputs and minimize the C losses that are characteristics of traditional cultivation practices.

11

11. Along with the combination of texture and clay content, total soil porosity or soil bulk density determines relative soil aeration, which controls soil microbial respiration. Native prairie soils have bulk densities of about 1.0, which tends to be too well aerated for optimal microbial 12 respiration. This aids the accumulation of SOC. Soil bulk density of approximately 1.2 is ideal for microbial mineralization of soil organic matter, which results in decreases in soil C storage (Hudson, 1994)

Recalcitrance

from http://biochar.pbworks.com/w/page/9748048/Recalcitrance

Campfire Lessons

Breaking Down the Combustion Process to Understand Biochar Production and Characterization from www.biochar-journal.org/en/ct/47

Cite as: Fuchs M, Garcia-Perez M, Small P, Flora G: Campfire Lessons - breaking down the combustion process to understand biochar production, the Biochar Journal 2014, Arbaz, Switzerland. ISSN 2297-1114, http://www.biochar-journal.org/en/ct/47, Version of 31 th December 2014, Accessed: [date]

Resource to track down

Batjes 1996

Batjes, N.H. (1996). "Total carbon and nitrogen in the soils of the world". Soil Science 47 (2): 151-163. doi:10.1111/j.1365-2389.1996.tb01386.x Batjes, N.H.: 1996, ‘Total carbon and nitrogen in soils of the world’, European J. Soil Sci. 47, 151-163.

https://library.wur.nl/isric/fulltext/isricu_t47d6414d_001.pdf

Batjes 1992

Batjes, N.H., 1992. Organic matter and carbon dioxide. In: A Review of Soil Factors and Processes that Control Fluxes of Heat, Moisture and Greenhouse Gases, pp. 97–148 (eds N.H. Batjes & E.M. Bridges). Technical Paper 23, International Soil Reference and Information Centre, Wageningen.

http://www.isric.org/isric/webdocs/docs/ISRIC_TP23.pdf

Soil is the largest terrestrial pool of organic carbon, 1115 to 2200 Pg of C (see Batjes, 1992)

p. 138. gives a range of soil that includes the 1115 (Adams 1990), the 2200 (Bohn 1982), but also down to 1061 (Kimble 1990) and up to 3000 (Bohn 1976).

p. 136. The present carbon reserve, as calculated by Adams 1990b is 924 Pg C for vegetation, 1115 pg C for soils and 280 pg C for peat, accounting for a total of 2319 Pg C.

Adams 1990

Adams, J. M., H. Faure, L. Faure-Denard, J. M. McGlade & F. I. Woodward, 1990, Increases in terrestrial carbon storage from the Last Glacial Maximum to the present. Nature 348, 711 - 714 (27 December 1990); doi:10.1038/348711a0

https://www.researchgate.net/publication/242874564_Increases_in_terrestrial_carbon_storage_from_the_Last_Glacial_Maximum_to_the_Present

P 713 Fig 2 924 Pg C for vegetation, 1115 pg C for soils and 280 pg C for peat, accounting for a total of 2319 Pg C.

Eswaran, 1995

Eswaran, H., Van den Berg, E. & Reich, P. 1993. Organic carbon in soils of the world. Soil Science Society of America Journal, 57, 192-194

1576 Pg of C (Eswaran, 1995)

Skjemstad, 1990

Skjemstad, J.O., LeFeuvre, R.P. & Prebble, R.E. 1990. Turnover of soil organic matter under pasture determined by 13C natural abundance. Australian Journal of Soil Research, 28, 267-276. Skjemstad JO, Lefeuvre RP, Prebble RE (1990) Turnover of soil organic matter under pasture as determined by 13C natural abundance. Australian Journal of Soil Research 28 , 267–276.

http://www.publish.csiro.au/paper/SR9900267.htm https://www.researchgate.net/publication/240506018_Turnover_of_soil_organic_matter_under_pasture_as_determined_by_13C_natural_abundance_Australian_Journal_of_Soil_Research_28_267-276

UNCONFIRMED AT THIS POINT Most methods for determining soil organic carbon do not account for resistant forms such as charcoal (Skjemstad, 1990, Sanford 1985) thus it remains difficult to quantify this source of organic carbon in global budgets.

Sanford 1985

Sanford, R.L., Saldarriaga, J., Clark, K.E., Uhe, C. & Herrera, R. 1985. Amazon rainforest fires. Science, 227, 53-55.

UNCONFIRMED AT THIS POINT Most methods for determining soil organic carbon do not account for resistant forms such as charcoal (Skjemstad, 1990, Sanford 1985) thus it remains difficult to quantify this source of organic carbon in global budgets.

Schlesinger 1982

Schlesinger, W.H. 1982. Carbon storage in the caliche of the arid world: a case study from Arizona. Soil Science, 133, 247-255

Inorganic carbon as carbonates stored in soils estimated at 780-930 Pg of C (Schlesinger, 1982)

Biofuel Watch Response: Changes to Methodology

American Carbon Registry

one

A 2011 scientific review by 14 authors (one of them the Chair of the Board of the International Biochar Initiative, Johannes Lehmann) [speaks to the complexity of biochar persistence. The article, Persistence of Soil Organic Matter as an Ecosystems Property, Michael W.I. Schmidt et al, Nature, 6 October 2011, summarises recent soil science findings as proving that “the persistence of soil organic carbon is primarily not a molecular property, but an ecosystem property”. This means that the actual stability of soil carbon depends largely on ecosystems functions, such as soil types and properties, climate, microbial diversity and distribution, etc. The article explains: “The molecular structure of biomass and organic material has long been thought to determine long-term decomposition rates in the mineral soil. However, using compound-specific isotopic analysis, molecules predicted to persist in soils (such as lignins or plant lipids) have been shown to turn over more rapidly than the bulk of the organic matter. Furthermore, other potentially labile compounds, such as sugars, can persist not for weeks but for decades. We therefore cannot extrapolate the initial stages of litter decomposition to explain the persistence of organic compounds in soils for centuries to millennia - other mechanisms protect against decomposition. Perhaps certain compounds require cometabolism with another (missing) compound, or microenvironmental conditions restrict the access (or activity) of decomposer enzymes (for example, hydrophobicity, soil acidity, or sorption to surfaces).”

The authors make it clear that those findings also apply to black carbon (biochar): “[Black carbon] is not inert, but its decomposition pathways remain a mystery. Fire derived carbon was suspected to be more stable in soil than other organic matter because of its fused aromatic ring structures and the old radiocarbon ages of fire residues isolated from soil. However, fire-derived carbon does undergo oxidation and transport, as we now know from archaeological settings, soils and from breakdown products in river and ocean water. In a field experiment, fire-derived residues were even observed to decompose faster than the remaining bulk organic matter, with 25% lost over 100 years (ref. 29). Spectroscopic characterization shows that combustion temperature affects the degree of aromaticity and the size of aromatic sheets, which in turn determine short-term mineralization rates… Certain types of biochar can degrade relatively rapidly in some soils, probably depending on the conditions under which they were produced, which suggests that pyrolysis could be optimized to generate a more stable biochar. But as with natural fire residues, persistence over the long term may also be affected by interaction with minerals and by soil conditions (for microorganisms capable of char oxidation and for abiotic oxidation). Whether interactions of fire derived carbon with soil minerals may be manipulated to enhance stability, and what the trade-offs might be with fertility benefits, are not known.”

two

accessibility not recalcitrance

Another soil science review comes to similar conclusions: Soil organic matter turnover is governed by accessibility not recalcitrance, Jennifer A.J. Dungait et al, Global Change Biology, 2012.

The authors also point out that testing for ‘carbon recalcitrance’ in a laboratory cannot accurately predict the fate of different types of soil carbon: “An apparently obvious method to increase C stocks in soils is to augment the soil C pools with the longest mean residence times (MRT). Computer simulation models of soil C dynamics, e.g. RothC and Century, partition these refractory constituents into slow and passive pools with MRTs of centuries to millennia…However, contemporary analytical approaches suggest that the chemical composition of these pools is not necessarily predictable because, despite considerable progress with understanding decomposition processes and the role of decomposer organisms, along with refinements in simulation models, little progress has been made in reconciling biochemical properties with the kinetically defined pools.”

According to this article, the main factors that control all soil carbon decomposition are substrate quality, soil organisms and their enzymatic repertoire and environmental conditions - not the apparent ‘recalcitrance’ of soil carbon that can be determined in a laboratory.

The article specifically discusses the implications for biomass-derived black carbon (biochar):

“Biomass-derived black C comprises a substantial component (5-50%) of organic C in some soils, and is assumed to decompose at a much slower rate than SOM due to its highly condensed aromatic structure (Schmidt et al., 2001).

Large charcoal particles originating from forest wildfires can remain in soils for thousands of years (Major et al., 2010),

although smaller particles derived from grassland burning can hardly be detected in steppe and prairie soils (Forbes et al., 2006).

Lehmann et al. (2006) suggested that conversion of biomass C to biochar leads to sequestration of about 50% of the initial C yielding more stable soil C than burning or direct land application of biomass.

However, biochar can be used as a substrate by soil microorganisms (Wengel et al., 2006) and is therefore not completely inert…

After application to soils, biochar decomposition rates vary under different soil conditions, e.g. water regime (Nguyen & Lehmann, 2009),

native SOM concentrations (Kimetu & Lehmann, 2010)

and pH (Luo et al., 2011)

Overall, the use of biochar as a robust strategy to increase soil C stocks as described by Lovelock (2009) requires additional investigation.”

The ‘stability’ of the carbon from the same type of biochar is heavily affected by different soil properties and that biochars predicted to remain ‘stable’ in one soil for many centuries would be decomposed within a few decades in other soil samples: Biochar carbon stability in four contrasting soils, Y Fang et al, European Journal of Soil Science, 2013.

“The physical movement of Biochar away from the point of soil application appears to occur at a similar rate to or possibly faster than for other organic carbon in soil (Rumpel et al., 2005; Guggenberger et al., 2008; Major et al., 2010b).

Eroded Biochar C is considered to remain sequestered as it is typically buried in lower horizons of soil or in lake or ocean sediments (France‐Lanord and Derry, 1997; Galy et al., 2007; Van Oost et al., 2007).”

There is no doubt that a considerable proportion of black carbon (most of it black carbon from wildfires) is regularly transported to lake or ocean sediments and that it can remain there for very long periods. But there is no evidence that all black carbon transported from soils is sequestered elsewhere rather than being decomposed biotically or abiotically. To the contrary: Researchers who have looked at the global black carbon budget have found that the overall amount of black carbon sequestered in marine in freshwater sediments and in soils combined is far smaller than it would be if the black carbon produced annually was as recalcitrant as many assume it to be.

A 2004 study (New Directions in Black Carbon Organic Chemistry, C.A. Masiello, Marine Chemistry 92, 2004) highlights those discrepancies: “Measurements of BC production and loss processes are not balanced… The lower end of the BC production rate, 0.05 Gt/year, would mean that BC was 30% of sedimentary organic carbon and although it is possible that this could be the case in some abyssal sediments, the vast majority of sedimentary organic carbon is stored in deltas, shelves, and slopes (Hedges and Keil, 1995). [apparently the 2004 source cited the 1995 source, as well as all the following]

Measurements of BC in these regions suggest that BC is only 3- 10% of sedimentary organic carbon (Table 1)… If BC has been produced since the last glacial maximum via biomass burning at the same rate as it is now produced, BC should account for 25- 125% of the total soil organic carbon pool (Masiello and Druffel, 2003).

Although a few measurements of soil BC/SOC are as large as 25%, even this lower bound is unrealistic for the entire soil carbon pool. Some of this BC may be lost to erosion, but as Dickens et al. (2004) have shown that less is stored in sediments, erosion cannot solve this BC pool size problem (Schmidt, 2004)

… even a labile BC loss process with a timescale of thousands of years is too slow to account for environmental observations.”

priming

We are not aware of any recent scientific discovery that would change this conclusion, nor of any stud that ‘balances’ the global black carbon budget by using the International Biochar Initiative’s assumptions about carbon stability. The second hypothesis on which the methodology is based, closely coupled to the first, is that negative priming is assumed to exceed positive priming - another argument used to justify the lack of proposed soil carbon measurements. ‘Priming’ refers to the effect which the addition of new soil carbon has on existing soil carbon pools. ‘Positive priming’ means that adding new sources of carbon results in an accelerated decomposition of existing soil carbon. ‘Negative priming’ means the opposite, i.e. that adding a new source of carbon results in existing soil carbon pools becoming more stable. Net carbon sequestration does not just depend on the added biochar carbon remaining stable, but on the overall soil carbon pool being increased. Biochar studies – mostly laboratory ones – show that biochar additions can cause either positive or negative priming. The authors of the draft Methodology cite a single peer -reviewed study as evidence that negative priming can be assumed for outweigh positive priming: Modelling the long -term response to positive and negative priming of soil organic carbon by black carbon, Dominic Woolf and Johannes Lehmann, Biogeochemistry 2012. We believe that it is wholly inappropriate to cite this single article as ‘conclusive evidence’. As the title suggests, this is a modelling study, not a biochar trial, nor review of data gained from field trials. It relies on a version of the RothC soil carbon model, a model which relies on predicting the fate of soil carbon from its chemical structures and properties, i.e. on defining ‘recalcitrance’ from incubation studies. This is precisely the approach which, as the two soil science reviews discussed above (one of which had Johannes Lehmann as a co-author) show, do not reflect current soil science knowledge and cannot adequately predict the fate of soil carbon. The article by Dominic Woolf and Johannes Lehmann cited in the draft Methodology cautions: “Given the paucity and variability of existing data on priming effects by BC, together with the challenges inherent in extrapolating from short-term laboratory incubations to long-term effects in a natural environment, some caution needs to be exercised in how these results should be interpreted… It is clear from this modeling study that an improved understanding of the mechanisms underlying SOC stabilization should be a research priority in determining how incorporation of BC into soil would impact long-term npSOC levels.”

CSIRO Soil C

CSIRO-soil-C-review.pdf http://www.mla.com.au/files/847771fc-b6cc-4abf-a1c6-9d8f00cdca04/csiro-soil-c-review.pdf.

At the Rodale Institute Farming Systems Trial in Pennsylvania, USA, 22 years of manure based and legume-based organic farming system accumulated SOC at a rate 0.7 and 0.3 Mg C ha-1 yr-1 higher, respectively, than their conventional counterpart (Pimentel et al. 2005). However, a more detailed investigation of the SOM in these treatments indicated that the new SOC primarily accumulated in biologically active fractions (Wander and Traina 1996; Wander et al. 1994) that may have little permanence if the new inputs ceased. Currently, most organic farming systems rely on multiple tillage operations to control weeds and incorporate manure and cover crop residues. Due to this tillage requirement, it is unclear whether organic farming systems will improve SOC levels more than conventional no-tillage systems. In one of the few studies that directly addressed this issue, Teasdale et al. (2007) found in a corn-soybean-wheat rotation that, despite depressed corn yields, the organic systems had increased SOC levels ~20% over 9 years when compared to the conventional no-tillage system. Overall, anecdotal evidence is strong that these systems can capture and store more SOC than their traditional counterparts; however, with a few notable exceptions (i.e. Clark et al. 1998; Pimentel et al. 2005; Wells et al. 2000), detailed and replicated studies are currently lacking. Another potentially troubling, but also scientifically intriguing, issue is that there is no readily apparent mechanistic explanation for some of the very large SOC gains being anecdotally reported.

Wiki source

Organic and inorganic carbon Jutta Laine-Ylijoki, Päivi Kauppila, Markku Juvankoski, Tommi Kaartinen, Elina Merta, Ulla-Maija Mroueh, Jarno Mäkinen, Emma Niemeläinen, Henna Punkkinen & Margareta Wahlström; 1VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, FI-02044 VTT, Finland, Geological Survey of Finland, P.O. BOX 1237, FI-70211 Kuopio, FINLAND http://wiki.gtk.fi/pt_PT/web/mine-closedure/wiki/-/wiki/Wiki/Organic+and+inorganic+carbon

Elemental carbon forms include charcoal, soot graphite, and coal. The primary sources for elemental carbon in soils and sediments are incomplete combustion products of organic matter (i.e. charcoal, graphite, and soot), geologic sources (i.e., graphite and coal), or dispersion of these carbon forms during mining, processing, or combustion of these materials. In soils, wastes and sediments, there are three basic forms of carbon that may be present. They are: (1) elemental C, (2) inorganic C, and (3) organic C. The quality of organic matter in a certain matrix is critical to the environmental behaviour of many elements and contaminants. (Schumacher 2002)

SOM fractions

Michelle Wander 2004 Soil Organic Matter Fractions and Their Relevance to Soil Function in Soil Organic Matter in Sustainable Agriculture, Fred Magdoff, Ray R. Weil

ISBN 978-0849312946

ISBN 0849312949

http://www.planta.cn/forum/files_planta/soil_organic_matter_fractions_and_their_relevance_to_soil_function_380.pdf

Skjemstad 1999

Skjemstad JO, Taylor JA (1999) Does the Walkley and Black method determine soil charcoal? Communications in Soil Science and Plant Analysis 30, 2299-2310.

(Note: with hot dichromate, yes)

Parent 2015

Open Journal of Soil Science, 2015, 5, 135-143 Published Online June 2015 in SciRes. www.scirp.org/journal/ojss^{[predatory publisher]} http://dx.doi.org/10.4236/ojss.2015.56013 How to cite this paper: Parent, S.-É. and Parent, L.E. (2015) Biochemical Fractionation of Soil Organic Matter after Incorporation of Organic Residues. Open Journal of Soil Science, 5, 135-143. http://dx.doi.org/10.4236/ojss.2015.56013 Biochemical Fractionation of Soil Organic Matter after Incorporation of Organic Residues Serge-Étienne Parent, Léon E. Parent* Department of Soils and Agrifood Engineering, Université Laval, Québec, Canada Email: *leon-etienne.parent@fsaa.ulaval.ca Received 13 May 2015; accepted 12 June 2015; published 15 June 2015

Soil organic carbon (SOC) is the primary soil quality indicator driving soil chemical, biological, and physical functions [1]-[3]. The SOC decomposition rate depends on physical, chemical and biochemical protection mechanisms [4]. The physical protection to SOC against decomposition is provided by soil micro-aggregates (<250 µm in size) that are compact assemblages of mineral and organic matter [5]. The SOC models generally consider two or three biochemical C pools [6] [7]. The most labile SOC pools are sensitive indicators of soil biological activity [8] and structural stability [9] [10] resulting from agro-ecosystem management [11]-[14]. Labile and recalcitrant soil organic matter (SOM) fractions can be separated by size [15]. The particulate organic matter (POM) fraction is 53 to 2000 µm in size and provides an estimate of labile C [16]. The POM often has a bulk density less than one [17] [18], hence facilitating densimetric separation, is high in C [19], and contains plant debris [20], hyphae, spores, seeds, faunal skeletons, microbial biomass and partially humified materials [21] that can be separated by sieving. The biochemical composition of POM requires analyzing POM using a biochemical fractionation procedure.

[1]Doran, J.W. and Parkin, T.B. (1994) Defining and Assessing Soil Quality. In: Doran, J.W., Coleman, D.C., Bezdicek, D.F.and Stewart, B.A., Eds., Defining Soil Quality for a Sustainable Environment, Soil Science Society of America Journal, Madison, 3-21. http://dx.doi.org/10.2136/sssaspecpub35.c1

[2] Louwagie, G., Gay, S.H. and Burrell, A. (2009) Addressing Soil Degradation in EU Agriculture: Relevant Processes, Practices and Policies. Report on the Project Sustainable Agriculture and Soil Conservation (SoCo), European Communities. http://eusoils.jrc.ec.europa.eu/esdb_archive/eusoils_docs/other/EUR23767.pdf

[3] Weil, R.R. and Magdoff, F. (2004) Significance of Soil Organic Matter to Soil Quality and Health. In: Magdoff, F. and Weil, R.R., Eds., Soil Organic Matter in Sustainable Agriculture, CRC Press, Boca Raton, 1-43. http://dx.doi.org/10.1201/9780203496374.ch1

[4] Stewart, C.E., Paustian, K., Conant, R.T., Plante, A.F. and Six, J. (2007) Soil Carbon Saturation: Concept, Evidence and Evaluation. Biogeochemistry, 86, 19-31. http://dx.doi.org/10.1007/s10533-007-9140-0

[5] Tisdall, J.M. and Oades, J.M. (1982) Organic Matter and Water-Stable Aggregates in Soils. Journal of Soil Science, 33, 141-163. http://dx.doi.org/10.1111/j.1365-2389.1982.tb01755.x

[6] Andrén, O. and Kätterer, T. (1997) ICBM: The Introductory Carbon Balance Model for Exploration of Soil Carbon Balances. Ecological Applications, 7, 1226-1236. http://dx.doi.org/10.1890/1051-0761(1997)007[1226:ITICBM]2.0.CO;2

[7] Thuriès, L., Pansu, M., Feller, C., Herrmann, P. and Rémy, J.C. (2001) Kinetics of Added Organic Matter Decomposition in a Mediterranean Sandy Soil. Soil Biology and Biochemistry, 33, 997-1010. http://dx.doi.org/10.1016/S0038-0717(01)00003-7qrqer

[8] Gregorich, E.G. and Janzen, H.H. (1996) Storage of Soil Carbon in the Light Fraction and Macro-Organic Matter. In: Carter, M.R. and Stewart, B.A., Eds., Structure and Soil Organic Matter Storage in Agricultural Soils, CRC Press, Boca Raton, 167-190.

[9] Haynes, R.J. and Beare, M.H. (1996) Aggregation and Organic Matter Storage in Mesothermal, Humid Soils. In: Carter, M.R. and Stewart, B.A., Eds., Structure and Soil Organic Matter Storage in Agricultural Soils, CRC Press, Boca Raton, 213-262.

[10] Janzen, H.H., Campbell, C.A., Ellert, B.H. and Bremer, E. (1997) Soil Organic Matter Dynamics and Their Relationship to Soil Quality. In: Gregorich, E.G. and Carter, M.R., Eds., Soil Quality for Crop Production and Ecosystem Health, Elsevier Science, Amsterdam, 277-291. http://dx.doi.org/10.1016/s0166-2481(97)80039-6

[11] Cambardella, C.A. and Elliott, E.T. (1992) Particulate Soil Organic-Matter Changes across a Grassland Cultivation Sequence. Soil Science Society of America Journal, 56, 777-783. http://dx.doi.org/10.2136/sssaj1992.03615995005600030017x

[12] Campbell, C.A., Biederbeck, V.O., Wen, G., Zentner, R.P., Schoenau, J. and Hahn, D. (1999) Seasonal Trends in Selected Soil Biochemical Attributes: Effects of Crop Rotation in the Semiarid Prairie. Canadian Journal of Soil Science, 79, 73-84. http://dx.doi.org/10.4141/S98-008

[13] Graham, M.H., Haynes, R.J. and Meyer, J.H. (2002) Soil Organic Matter Content and Quality: Effects of Fertilizer Applications, Burning and Trash Retention on a Long-Term Sugarcane Experiment in South Africa. Soil Biology and Biochemistry, 34, 93-102. http://dx.doi.org/10.1016/S0038-0717(01)00160-2

[14] Wander, M. and Nissen, T. (2004) Value of Soil Organic Carbon in Agricultural Lands. Mitigation and Adaptation Strategies for Global Change, 9, 417-431. http://dx.doi.org/10.1023/B:MITI.0000038847.30124.77

[15] Balesdent, J. (1996) Un point sur l’évolution des réserves organiques des sols de France. Étude et Gestion des Sols, 3, 245-260.

[16] Cambardella, C.A., Gajda, A.M., Doran, J.W., Wienhold, B.J. and Kettler, T.A. (2001) Estimation of Particulate and Total Organic Matter by Weight Loss-on-Ignition. In: Lal, R., Kimble, J.M., Follett, R.F. and Stewart, B.A., Eds., Assessment Methods for Soil Carbon, Advances in Soil Science, CRC Press, Boca Raton, 349-359.

[17] Guggenberger, G. and Zech, W. (1999) Soil Organic Matter Composition under Primary Forest, Pasture, and Secondary Forest Succession, Region Huetar Norte, Costa Rica. Forest Ecology and Management, 124, 93-104. http://dx.doi.org/10.1016/S0378-1127(99)00055-9

[18] Six, J., Elliott, E.T., Paustian, K. and Doran, J.W. (1998) Aggregation and Soil Organic Matter Accumulation in Cultivated and Native Grassland Soils. Soil Science Society of America Journal, 62, 1367-1377. http://dx.doi.org/10.2136/sssaj1998.03615995006200050032x

[19] Carter, M.R., Gregorich, E.G., Angers, D.A., Donald, R.G. and Bolinder, M.A. (1998) Organic C and N Storage, and Organic C Fractions, in Adjacent Cultivated and Forested Soils of Eastern Canada. Soil and Tillage Research, 47, 253- 261. http://dx.doi.org/10.1016/S0167-1987(98)00114-7

[20] Skjemstad, J.O., Lefeuvre, R.P. and Prebble, R.E. (1990) Turnover of Soil Organic Matter under Pasture as Determined by 13C Natural Abundance. Australian Journal of Soil Research, 28, 267-276. http://dx.doi.org/10.1071/SR9900267

[21] Baldock, J.A., Oades, J.M., Waters, A.G., Peng, X., Vassallo, A.M. and Wilson, M.A. (1992) Aspects of the Chemical Structure of Soil Organic Materials as Revealed by Solid-State Carbon-13 NMR Spectroscopy. Biogeochemistry, 16, 1- 42. http://dx.doi.org/10.1007/BF02402261

[22] Lashermes, G., Nicolardot, B., Parnaudeau, V., Thuriès, L., Chaussod, R., Guillotin, M.L., Linères, M., Mary, B., Metzger, L., Morvan, T., Tricaud, A., Villette, C. and Houot, S. (2009) Indicator of Potential Residual Carbon in Soils after Exogenous Organic Matter Application. European Journal of Soil Science, 60, 297-310. http://dx.doi.org/10.1111/j.1365-2389.2008.01110.x

[23] Van Soest, P.J. and Wine, R.H. (1967) Use of Detergents in the Analysis of Fibrous Feeds. IV. Determination of Plant Cell-Wall Constituents. Journal of the Association of Official Analytical Chemists, 50, 50-55.

[24] Van Soest, P.J. and Wine, R.H. (1968) Determination of Lignin and Cellulose in Acid-Detergent Fiber with Permanganate. Journal of the Association of Official Analytical Chemists, 51, 780-785.

[25] Gabrielle, B., Da-Silveira, J., Houot, S. and Francou, C. (2004) Simulating Urban Waste Compost Effects on Carbon and Nitrogen Dynamics Using a Biochemical Index. Journal of Environmental Quality, 33, 2333-2342. http://dx.doi.org/10.2134/jeq2004.2333

[26] Soil Classification Working Group (1998) The Canadian System of Soil Classification. 3rd Edition, Agriculture and Agri-Food Canada Publications, Ottawa, 1646.

[27] Gregorich, E.G. and Beare, M.H. (2007) Physically Uncomplexed Organic Matter. In: Carter, M.R. and Gregorich, E.G., Eds., Soil Sampling and Methods of Analysis, 2nd Edition, CRC Press, Boca Raton, 1262.

Skjemstad 2002

Charcoal carbon in U.S. agricultural soils Skjemstad, Jan O; Reicosky, Donald C; Wilts, Alan R; McGowan, Janine A. Soil Science Society of America Journal 66.4 (Jul/Aug 2002): 1249-1255. Vol. 66 No. 4, p. 1249-1255 doi:10.2136/sssaj2002.1249

{{cite journal |last=Skjemstad|first=Jan O.|date=2002 |title=Charcoal carbon in U.S. agricultural soils|journal=Soil Science Society of America Journal |volume=66 |issue=4 |pages=1249-1255 |doi=10.2136/sssaj2002.1249|access-date= 16 January 2016}}

Mergel 1998

{{cite conference |conference=Proceedings of the 5th Symposium of the International Society of Root Research |year=1998 |book-title=Root Demographics and Their Efficiencies in Sustainable Agriculture, Grasslands and Forest Ecosystems |editor-last=Box, Jr. |editor-first=J. |series=82 |page=43-54 |title=Role of plant root exudates in soil carbon and nitrogen transformation |first=A. |last=Mergel |doi=10.1007/978-94-011-5270-9_3 |isbn=978-94-010-6218-3 |access-date= 16 January 2016 |publisher=Springer Netherlands |location=Madren Conference Center, Clemson University, Clemson, South Carolina, USA }}

Hockaday 2006

Hockaday WC (2006) The organic geochemistry of charcoal black carbon in the soils of the University of Michigan Biological Station. PhD Thesis, Ohio State University, Columbus, OH https://etd.ohiolink.edu/!etd.send_file?accession=osu1141850676&disposition=inline

Lehmann 2006

Lehmann 2006 has a nice chart of relative persistence. Lehmann, J; Gaunt, J; Rondon, M (2006), "Biochar sequestration in terrestrial ecosystems: a review" (PDF), Mitigation and Adaptation Strategies for Global Change, 11 (2), Springer: 403–427, doi:10.1007/s11027-005-9006-5, S2CID 4696862

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