Transformation of soil organic matter in connection with the intensity of peat fire (on the example of the swamp spruce forest of the Kuznetsk Alatau)
T. T. Efremova, A. V. Pimenov, S. P. Efremov, A. F. Avrova
Sukachev Institute of Forest (department of FIC KSC SB RAS) Siberian Branch Russian Academy of Sciences, Krasnoyarsk, Russia
Keywords: humic acids, fulvic acids, fractional composition, pyrogenesis, soil clusters, underground focal smoldering, open fire, multivariate statistical analysis
Abstract
Within the ecological direction of studying humus using traditional methods and terms, the peculiarities of the transformation of organic matter of peat eutrophic soils (Hypereutric Sapric Histosols) and peaty gleezems (Eutric Histic Gleysols) 20 years after a forest-peat fire are discussed. The object of the study was the green moss-hypnum spruce forests (Picea obovata Ledeb.) of eastern slope of the Kuznetsk Alatau (absolute height 622 m). The composition of organic matter of pyrogenic soils (0-30 cm) is characterized by high variability (coefficient of variation 12-92 %). According to the factor analysis, 76 % of the total variance is due to a combination of humic substances, 24 % - polysaccharides. Using the cluster analysis procedure, we identified two groups of objects whose statistical reliability was confirmed by discriminant analysis. Soil clusters reflect the peculiarities of pyrogenic processes - underground focal smoldering, below the point of ignition, and open intense and medium strength fire. Relative to the background carbon content of 41 % (peats not covered by fire), its amount decreases to 26.5 and 13.4 %, respectively. At the same time, there is an almost equal formation of humification products (∑GC + ∑FC) - 55.4 and 53.7 % due mainly to fulvic acids (Cgc/Cfc 0.2-0.6). The peculiarities of the thermal effect are occurred mainly at the fractional level. The specificity of underground smoldering is an increased yield of fulvic acids of the first fraction, free and loosely bound to R2O3. An open fire is accompanied by the predominant formation of humic and fulvic acids associated with calcium. According to standardized coefficients of canonical analysis, the first and second fractions of humic and fulvic acids make the greatest cumulative contribution to cluster discrimination, the maximum personal weight is HC-2, FC-1 and FC-2. Based on previously obtained information about the group composition of buried peats and the important role of anaerobiosis in the formation of humic acids, which are more correspond with the restored nature of the substance compared to fulvic acids, it can be assumed that peat genesis continuing in the area of the fire can cause the transformation of fulvate humus into fulvate-humate and/or humate. In the case of burial of a pyrogenic peat layer of 0-30 cm, this can happen in about 270 years, based on the rate of linear growth of peat in the spruce forests of the Kuznetsk Alatau - 1.12 mm/ year. The research results confirm the validity of the traditional division of humic acids into fractions.
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