The effect of earthworms and other saprophagous macrofauna on soil microstructure in reclaimed and un-reclaimed post-mining sites in Central Europe

Soil macrofauna density and the distribution of macrofauna faeces and other structures in topsoil were studied in two chronosequences of post-mining sites, the first overgrown by spontaneously developed vegetation and the second reclaimed by planting alder. Each chronosequence consisted of three plots of the respective age of 15, 23 and 40 years since heaping. Density of all macrofauna groups, and earthworms in particular, was higher in reclaimed than in un-reclaimed sites. Soil microstructure formation was closely related to soil fauna density and activity. Faster earthworm colonization resulted in more rapid accumulation of earthworm coprolites in topsoil and consequent formation of humus layer in reclaimed than in un-reclaimed sites. Low density of earthworms in intermediate succession stages of un-reclaimed sites resulted in low soil mixing and in accumulation of litter fragments and macrofauna faecal pellets in soil surface, where they formed a massive fermentation layer. The study showed that besides plant establishment, successful colonization of post-mining sites by soil fauna seems to be critical for soil development as the substantial part of newly formed soils consisted of soil macrofauna faeces.