Post-pyrogenic Evolution of Sandy Soils under Pine Forests in the Baikal Region

Abstract

The development of sandy soils under pine forests and the influence of forest fires on the soil properties have been studied in the Baikal region, The profile of background soils consists of a litter layer and a thin humus-accumulative horizon with features of grain bleaching in the lower part. In the WRB system, such soils are classified as Eutric Arenosols (Ochric). They have an acid reaction, fulvate humus, and slightly developed features of the Al–Fe-humus process. Post-pyrogenic soil successions depend on the type of fire. In fifteen years after the ground fire, a soil with specific pyrogenic horizons in the upper part of the profile was formed. It had a high content of carbonaceous matter and humus, a slightly acid reaction, and a relatively high content of exchangeable and total calcium. The soil humus was of the fulvate–humate type, and the humus pool considerably increased. These changes were related to the presence of charcoal microparticles adsorbing dispersed substances on their surface and detected in thin sections. After the crown fire with the destruction of the tree stand and activation of wind erosion, the features of pyrogenesis were poorly expressed in the soils. In this case, post-pyrogenic soils had a weakly developed immature profile, acid reaction, and a low content of humus of the humate–fulvate type. The properties of the background soils allow us to classify them as podzolized humic psammozems (Eutric Arenosols (Ochric)); the soils of post-pyrogenic successions after the ground fire can be classified as post-pyrogenic humic psammozems; after the crown fire, as humic psammozems.