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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    European journal of soil science 56 (2005), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Fires in boreal forests frequently convert organic matter in the organic layer to black carbon, but we know little of how changing fire frequency alters the amount, composition and distribution of black carbon and organic matter within soils, or affects podzolization. We compared black carbon and organic matter (organic carbon and nitrogen) in soils of three Siberian Scots pine forests with frequent, moderately frequent and infrequent fires.Black carbon did not significantly contribute to the storage of organic matter, most likely because it is consumed by intense fires. We found 99% of black carbon in the organic layer; maximum stocks were 72 g m−2. Less intense fires consumed only parts of the organic layer and converted some organic matter to black carbon (〉 5 g m−2), whereas more intense fires consumed almost the entire organic layer. In the upper 0.25 m of the mineral soil, black carbon stocks were 0.1 g m−2 in the infrequent fire regime.After fire, organic carbon and nitrogen in the organic layer accumulated with an estimated rate of 14.4 g C m−2 year−1 or 0.241 g N m−2 year−1. Maximum stocks 140 years after fire were 2190 g organic C m−2 and 40 g N m−2, with no differences among fire regimes. With increasing fire frequency, stocks of organic carbon increased from 600 to 1100 g m−2 (0–0.25 m). Stocks of nitrogen in the mineral soil were similar among the regimes (0.04 g m−2). We found that greater intensities of fire reduce amounts of organic matter in the organic layer but that the greater frequencies may slightly increase amounts in the mineral soil.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    European journal of soil science 56 (2005), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Soils and sediments contain only small amounts of organic matter, and large concentrations of paramagnetic metals can give poor solid-state nuclear magnetic resonance (NMR) spectra of organic matter. Pretreatment of samples with hydrofluoric acid (HF) dissolves significant proportions of the mineral matrix and extracts paramagnetic elements. We investigated the effects of 10% HF treatment on the stable isotope content of carbon (C) and nitrogen (N) of organic matter from soils, composts and shales. Additionally we inferred molecular and isotopic characteristics of lost materials from calculations of isotope mass balances. Treatment with HF enriched C and N in mineral samples substantially (factors 2.5–42.4), except for Podzol B horizons (1.1–1.7) and organic material (1.0–1.3). After treatment most of the C (59.7–91.7%) and N (53.7–86.6%) was recovered, although changing C/N ratios often indicated a preferential loss of N-rich material. Isotope ratios of C and N in the remaining material became more negative when net alterations exceeded 0.3‰. The isotope ratios of the lost material contained more 13C (1–2‰) and 15N (1–4‰) than the initial organic matter. Acid hydrolysis typically removes proteins, amino acids and polysaccharides, all of which are enriched in 13C, and in the case of proteins and amino acids, enriched in 15N as well. We conclude that HF treatment released fresh, soluble, probably microbial, biomass in addition to carbohydrates. Net changes of the bulk chemical composition of organic matter were small for most soils, size fractions and plant material, but not for samples containing little organic matter, or those rich in easily soluble organic matter associated with iron oxides, such as Podzol B horizons.
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