Patterns of pedoturbation by tree uprooting in forest soils


The fall of a tree accompanied by its uprooting is the most common natural end of the tree life. To understand how soil is affected by treefalls, it is necessary to recognize their signs in soil profiles, even when their surface features (pit-and-mound topography) are erased. The paper reviews these signs of treefalls in soil profiles, which can be used to distinguish the patterns of old treefall-related pedoturbations. The paper is based on a literature analysis and results of authors’ long-term studies of forest soil in the European part of Russia and in the Western Siberia. Two main types of uprooting of a falling tree (hinge and rotational treefalls) are considered. The paper presents data on the sizes of 424 pit-and-mound soil complexes for nine tree species (Tilia cordata, Acer platanoides, Fraxinus excelsior, Ulmus glabra, Quercus robur, Betula pendula, Populus tremula, Picea abies and Pinus sylvestris) and describes peculiarities of soil relocation in the process of different treefalls, which is necessary to recognize old treefall complexes in soil profiles. The following soil-profile signs of treefalls are considered: (1) treefall pits (cauldrons); (2) spotty or streaky structures of different degrees of contrast; (3) blocks of «buried material» from the upper soil layers; (4) washed (bleached) material depositing at the bottom of pits and filling soil pores and channels of various origins; (5) signs of hydrogenous changes of soil material resulting from water stagnation in the pits; (6) root channels at the bottom of the pit and (7) inclusions of litter and charcoal. As shown by our studies, treefall-related pedoturbations affect soil profiles at a depth larger than the depth usually described by the soil horizons A, E, Bhs, etc. A conclusion is made that in most forest soils, the middle and lower parts of profiles have patterns originating from the transfer of soil material upon treefalls.