accepted

Limited tree richness effects on herb layer composition, richness and productivity in experimental forest stands

2016-11-03

2016-11-03

Journal of Plant Ecology

2016-11-03

Aims In forests, the herbaceous understory vegetation plays an important role for ecosystem functioning as it represents a significant component of total aboveground productivity. In addition, the herb layer contributes to overall forest species richness and controls tree species regeneration. Vice versa, trees in the overstory control understory herb and shrub growth through competition for resources. Using an experimental forest plantation with manipulated tree richness we asked to which degree tree species richness and identity affect herb layer composition, richness and productivity and how these relationships across strata change with abiotic environmental conditions and competition intensity. Methods In the context of the Biodiversity-Ecosystem Functioning project in subtropical China (BEF-China), we made use of the integrated BEFmod experiment arranged along a tree species richness gradient at two sites, with additional subplot treatments of phosphorus addition, herb layer weeding and no weeding. We recorded the understory vegetation and determined herb layer biomass production on a total of 201 subplots. Important Findings While tree layer richness influenced herb layer species composition, there was only a weak effect on herb layer richness and no effect yet on productivity. Furthermore, there were strong tree layer identity effects on all response variables, which were partly explained by differences in leaf area index (LAI) and by a high share of woody species both in total herb layer species richness and biomass. There were strong treatment effects, which were largest in the “no weeding” treatment but we did not find any treatment × tree layer richness interaction in herb layer responses. Thus, these effects are mainly explained by increased competition intensity within the herb layer in the absence of weeding. Despite the young age of the experiment, the interactions between tree species identity, tree richness and the herb layer did already emerge and can be expected to become stronger with ongoing runtime of the experiment.

Markus Germany, Helge Bruelheide, Prof., Alexandra Erfmeier