Postpyrogenic mosaicism of physicochemical properties and carbon losses in forest soils of the swampy valley of the Kuznetsk Alatau

Abstract

Eutrophic peat(y) (Hypereutric Sapric Histosols) pyrogenic soils on the hammock and hollow of phytogenic microrelief were studied 20 years after a large fire in the swamp spruce forest (Picea obovata Ledeb.) of the eastern macroslope of the Kuznetsk Alatau. Currently, the burned area occupied by dense shrub-sedge-green moss birch forest (Betula pubescens Ehrh.). Pyrogenic peat soils (mechanical and chemical underburning), differentiated by elements (groups) of the microrelief, are characterized by a pronounced intra-group spatial heterogeneity of physical and chemical properties (CV 21–39 %). However, according to the average indicators of most characteristics, except for moisture of peat, the soils of hammock and hollow do not significantly differ from each other. The content of ash substances is in the range of 52.5–53.5 %, carbon – 20.4–21.2 %, the bulk density is 0.29–0.31 g/cm3, the moisture of peat soil bulk is 49–60.8 %, the soil reaction is mainly slightly alkaline. The process of passive smoldering (below the ignition point) of a peat deposit is accompanied by an additional loss of carbon, which was calculated directly from the element using a natural experiment before and after the fire. The loss value is characterized by high variability (CV 34–42 %) due to a variety of thermal effects caused by environmental factors and fire features. Lower level of carbon loss and its weak mosaicity have been objectively identified for the hammock relative to the hollow. Additional carbon loss – limit, average (standard deviation) is: in pyrogenic soils of hammock 1.4–4.4, 2.98 ± 1.05, in the hollow – 0.4–5.7, 3.71 ± 1.57 kg/m2. On average, this corresponds to 33.5 t/ha in the burned area, which is equivalent to 122.9 t/ha of CO2 released into the atmosphere. The intensity of carbon losses in the process of passive smoldering is approximately 3–4 times lower compared to the burning of a peat deposit.

Keywords

• eutrophic pyrogenic soils
• passive smoldering
• co2 emissions
• soil clusters
• multivariate statistical analysis