Litter leachate as a potential selector of woody species germination at alpine treeline

The advancement of upper forest limits is driven by environmental conditions, but our current understanding overlooks the attributes of habitats and germination ability of woody species. Habitats, through plant litter, impact the competitive relation of germination and seedling growth. The aims of this study were to identify the selective effect of six litter leachates on the germination of indigenous Norway spruce (Picea abies) and nonindigenous dwarf pine (Pinus mugo) and compare the germination rates of the species. We collected plant litter and seeds from the (sub)alpine belt of the Hrubý Jeseník Mts. (the Eastern Sudetes Mts.; the Czech Republic). We evaluated the effect of plant litter leachates from alpine heathlands, wind-swept alpine grasslands, subalpine tall-herb plants, Pinus mugo scrub, subalpine Vaccinium vegetation, and Norway spruce clonal groups on germination process under standard light and temperature conditions. The germination of Norway spruce was inhibited by the litter leachate from subalpine tall-herb vegetation mainly dominated by Calamagrostis villosa, whereas that of dwarf pine was not. The other five litter leachates had no significant effect on the both. Under standard conditions, the germination time of dwarf pine is on average one day faster. These results suggest that most of the litter leachates examined may have small impacts on the germinability and germination time of Norway spruce and dwarf pine, but litter from the subalpine tall-herb vegetation can act as a filter that influences the seedling composition of the woody species.</p