Allelopathic effect of Salix caprea litter on late successional plants at different substrates of post-mining sites: pot experiment studies

The willow Salix caprea L. is a common colonizer of post-mining sites including those in the Sokolov coal mining district (Czech Republic) where this study was conducted. In one bioassay and two pot experiments, we investigated the effect of S. caprea litter on three plant species ( Arrhenatherum elatius (L.) P. Beauv. ex J. Presl & C. Presl, Plantago lanceolata L., and Lotus corniculatus L.) that commonly grow in late successional stages on these sites. In a sandy soil, leachate from fresh S. caprea litter reduced the number of germinated individuals (experiment 1) and shoot and root growth (experiment 2). In the clayey substrate originally unaffected by the S. caprea (experiment 3) leachate suppressed germination of all three species, but no reduction of biomass (both aboveground and belowground) was observed. Biomass was enhanced, however, in substrate that was naturally enriched with S. caprea litter (i.e., substrate collected on the same locality as previously mentioned substrate but beneath the S. caprea shrubs). Salix caprea therefore can suppress the establishment of new plants that arrive as seeds, but this suppression may only occur with seeds that directly contact the litter. When S. caprea litter is incorporated into the substrate, it can considerably improve substrate quality and the growth of successional plants.