Charcoal Carbon in U.S. Agricultural Soils

Abstract

Despite few workers recording black C or charcoal in soils from the USA, historically fire has been extensive High levels of charcoal C resulting from repeated historical burning in the North American grasslands. For example, Collins of grasslands, open woodlands, and agricultural crop residues have (1990) reported that because of "periodic droughts, high been reported in soils from Australia and Germany. In this study, temperatures, and strong winds, the North American five U.S. soils were selected from long-term research plots in widely different agricultural areas. The charcoal C content was estimated on grasslands provide an ideal environment for ignition each soil using a combination of physical separation, high energy photoand perpetuation of fire." Collins (1990) also concluded oxidation and solid-state 13 C nuclear magnetic resonance (NMR) specthat "most evidence suggests that Indians frequently troscopy. These analyses showed that all five soils contained measurstarted grassland fires to modify habitat and either drive able amounts of charcoal C, Ͻ53 m in size and ranging from 1.8 to or attract wild game" and that "fires, caused by human 13.6 g C kg Ϫ1 soil and constituted up to 35% of the soil total organic C activity or otherwise, were historically a frequent com-(TOC). Scanning electron microscopy showed that the charcoal mateponent of the disturbance regime in grasslands." It might rial had a plant-like morphology but were blocky and had fractured be expected therefore that a legacy of this frequent edges. These particles were similar in morphology to those separated burning would be the presence of significant quantities from Australian and German soils. The implications of this material, of charcoal in the soil profiles under this activity. which must be highly resistant to microbiological decomposition, to the soil C cycle are discussed.

Abundant and Stable Char Residues in Soils: Implications for Soil Fertility and Carbon Sequestration

“…32 The spectral pattern of COO − and CO substituted aromatic rings revealed in 13 C NMR of Terra Preta organic carbon can also be recognized in the spectra of organic matter of temperate-region grassland soils, though with a larger background of nonchar organic carbon. 16,22,33,34 This is exemplified in Figure 1c, which shows the 13 C NMR spectrum of a humic acid extract from the surface horizon of an Iowa Mollisol (Zook, a Cumulic Vertic Endoaquoll). 22 Counting the nonprotonated cores and the substituted or protonated edges of the aromatic clusters, as well as the COO and CO groups bonded to them, oxidized char residues represent 67 ± 9% of all carbon in the Mollisol humic acid extract (see Table S1, Supporting Information).…”

Investigation of growth responses in saprophytic fungi to charred biomass

“…The importance of charcoal to global biogeochemical cycles is highlighted by the fact that at present, total global production of pyrogenically altered carbon (including charcoal) from biomass burning has been estimated at 50-270 Gt yr -1 [3]. Therefore, the products of biomass pyrolysis, including charcoal, make up an important proportion of many soils, comprising up to 35% of total organic content [4].…”

Probing the pH Dependent Optical Properties of Aquatic, Terrestrial and Microbial Humic Substances by Sodium Borohydride Reduction

“…Formation of micelles is unlikely due to the Beer Lambert behavior seen in all HS in this study (Table 2) but other forms of protection such as encapsulation or association with cations or clays is known to provide protection from enzymatic attack (Heighton et al, 2008;Hedges et al 2000;Baldock & Skjemstad, 2000). The soil humic acids EHA and LHA have a higher percentage of black carbon or conjugated cyclic carbon (Skjemstad et al, 2002). The carbon content of LHA is potentially high when compared to other humic acids as this HA is derived from lignite a precursor of coal.…”