Abstract
The soil organic matter (SOM) is searched for the biomarkers and specific features associated with the effect of wildfires by the case study of peat soil, Rheic Hemic Histosol (Lignic), in the south of the middle taiga of the Komi Republic. It is shown that fires considerably influence the peat organic matter. Pyrogenic activity is assessed according to the content of charcoal particles. SOM is examined using solid-state 13C-NMR spectroscopy to determine the concentrations of polycyclic aromatic hydrocarbons (PAHs) and benzene polycarboxylic acids (BPCAs). The used methods allow for diagnosing the effects of wildfires on the SOM composition. In the horizons with the signs of pyrogenesis, the share of carbon represented by aromatic fragments increases as well as the PAH concentration, mainly at the expense of naphthalene, phenanthrene, and chrysene. The carbon stock of pyrogenically modified compounds, amounting to 4.4 kg/m2, is for the first time assessed in the European north based on the BPCA content. The characteristics of pyrogenically changed organic compounds and their fragments obtained by different methods correlate well: the Pearson coefficient for the correlation of the carbon content in aromatic compounds (Caryl) with total BPCA content is R = 0.84 (p < 0.05) and with individual BPCAs, R = 0.81–0.90 (p < 0.05).
Highlights
Wildfires are among the major factors that change the terrestrial ecosystems of the globe [28, 32, 34, 57]
Note that this peatland repeatedly experienced wildfires both during the Holocene and in modern times
A comparison of the NMR spectroscopy data and polycyclic aromatic hydrocarbons (PAHs) contents has shown that these methods make it possible to diagnose the input of pyrogenically modified organic compounds
Summary
Wildfires are among the major factors that change the terrestrial ecosystems of the globe [28, 32, 34, 57]. The carbon of pyrogenically modified organic compounds (PyC) is regarded as one of the most stable pools of soil carbon resistant to microbiological decomposition [10, 54, 55]. 110 120 Depth, cm (third and fourth fractions) in the studied soil profile (Table 2). Note that the role of carbon content in the water-soluble compounds and individual amphiphilic fractions is less important as an indicator when studying the effects of the wildfires of the past as compared with the current wildfires in the forest ecosystems on mineral soils [6]. Under stagnant moistening in bog ecosystems, hydrophilic fractions accumulate only in the upper horizon of peat soils. An increase in the content of hydrophobic fractions, represented by high-molecular weight structural components, including those of aromatic nature, can indirectly reflect a pyrogenic influence. Any significant effect of pyrogenesis on the composition of alkali-soluble organic matter and the content of amphiphilic fractions is unobservable
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