Stratification and dynamics of bait-lamina perforation in three forest soils along a north–south gradient in Russia

Abstract

The bait-lamina test was developed for estimating soil biotic activity in arable and contaminated soils. To investigate the utility of the test in unpolluted soils under various climatic and soil conditions, three plots along a north–south gradient in the European part of Russia were chosen. They are: (i) a pine forest at the White Sea coast on poorly developed podzolic soils (Karelia Region); (ii) a spruce forest near Borovsk (Kaluga Region) on podzolic soils; and (iii) oak-beech forest near Novorossiysk, on the Black Sea coast with brown soils (Krasnodar Region). Forty bait-laminas were used at each plot and checked at various times of exposure. Parallel sampling to investigate soil macrofaunal diversity was carried out. Litter and small stone mass, water-holding capacity (WHC), loss on ignition (LOI) and pH were determined in every soil sample in the laboratory. Differences in bait-lamina perforation over time were observed and it was concluded that a 10-day exposure is appropriate under most conditions. Great differences in bait-lamina perforation were found between soil types. An optimal combination of climatic factors (Borovsk plot) reflected by Budyko’s drought index corresponded with the highest feeding activity (65% of pierced apertures), although the abundance of soil macrofauna was only 287 individuals m −2. The Novorossiysk plot had higher densities of soil invertebrates (1380 individuals m −2), but they showed a lower trophic activity (27%), comparable to that of the White Sea cost plot (14%). The depth distribution of bait-lamina perforation varied from plot to plot, but maximal activity was always observed at a depth 0–4 cm from the soil surface, which was supported by a proposed index of average depth of tropic activity. Vertical distribution of bait-lamina perforation depended mostly on soil profile structure and climatic conditions.