PYROGENIC-EXTREME SOILS OF THE NORTHERN AND MIDDLE TAIGA OF RUSSIA

Abstract

With the rise in the number of fi res, the proportion of pyrogenic soils in Russia is constantly increasing. The objective of this study is to determine how contrasting environmental conditions can trigger wildfires and affect post-fi re recovery scenarios. Post-pyrogenic Arenosols, Podzols and Fluvisols have been studied in the taiga subzones: in the Pinezhsky and Pechoro-Ilychsky nature reserves at the European territory of Russia and in the basin of Sukhoi Polui river in the north of Western Siberia. We employed soil morphology description, analysis of anthracomass concentration (calculated as the sum of charcoal particles >0,5 mm) and a set of chemical methods. We demonstrate that some fi res dramatically change the direction of soil formation, causing: 1) loss of organic horizon(s); 2) partial loss of mineral horizon(s); 3) restart of soil formation if the soil stratum has been completely degraded. We propose to distinguish such varieties as pyro-extreme soils. Both weakly transformed full-profile soils (para-extreme) and strongly degraded soils (ortho-extreme) can coexist in the fi re-damaged areas. Ecosystems whose properties (e.g. climate, topography, fire-return intervals) predetermine severe fi re damage to vegetation and soil cover are proposed as pyrogenically vulnerable. Among studied factors, the post-fi re erosion has proven to be a predominant control over long-term changes in the direction of soil formation. We propose a concept of «fi re centers» for description of spatial heterogeneity in burning, which can be tracked by changes in the anthracomass concentration.