Can niche plasticity promote biodiversity-productivity relationships through increased complementarity?
Created at: 2016-08-17
Initial title: Interspecific niche differences in pilot experiment
Envisaged journal: Ecology
Envisaged date: 2017-01-27
Most experimental biodiversity-ecosystem functioning research to date has addressed
herbaceous plant communities. Comparably little is known about how forest communities
will respond to species losses, despite their importance for global biogeochemical cycling.
We studied tree species interactions in experimental subtropical tree communities with 33
distinct tree species mixtures and one, two or four species. Plots were either exposed to
natural light levels or shaded. Trees grew rapidly and were intensely competing above ground
after 1.5 growing seasons when plots were thinned and the vertical distribution of leaves and
wood determined by separating the biomass of harvested trees into 50 cm height increments.
Our aim was to analyze effects of species richness in relation to the vertical allocation of leaf
biomass and wood, with an emphasis on bipartite competitive interactions among species.
Aboveground productivity increased with species richness. The community-level vertical
leaf and wood distribution depended on the species composition of communities. Mean
height and breadth of species-level vertical leaf and wood distributions did not change with
species richness. However, the extra biomass produced by mixtures compared to
monocultures of the component species increased when vertical leaf distributions of
monocultures were more different.
Decomposition of biodiversity effects with the additive partitioning scheme indicated
positive complementarity effects that were higher in light than in shade. Selection effects did
not deviate from zero, irrespective of light levels. Vertical leaf distributions shifted apart in
mixed stands as consequence of competition-driven phenotypic plasticity, promoting realized
complementarity. Structural equation models showed that this effect was larger for species
that differed more in growth strategies that were characterized by functional traits.
In 13 of the 18 investigated two species-mixtures, both species benefitted 49 relative to
intraspecific competition in monoculture. In the remaining 5 pairwise mixtures, the relative
yield gain of one species exceeded the relative yield loss of the other species, resulting in a
relative yield total (RYT) exceeding one.
Overall, our analysis indicates that richness-productivity relationships are promoted by
interspecific niche complementarity at early stages of stand development, and that this effect
is enhanced by architectural plasticity.