DOI: 10.5061/dryad.p6646
title: Data from: Belowground complementarity effects in a grassland biodiversity experiment are related to deep-rooting species

description: 1. Belowground resource partitioning is often proposed as the underlying
 mechanism for the positive relationship between plant species richness and
 productivity. For example, if species have different root distributions, a
 mixture of plant species may be able to use the available resources more
 completely than the individual species in a monoculture. However, there is
 little experimental evidence for differentiation in vertical root
 distributions among species and its contribution to biodiversity effects.
 2. We determined species-specific root standing biomass over depth using
 molecular techniques (real time-qPCR) in a large grassland biodiversity
 experiment (1-8 plant species mixtures), in two years. Species-specific
 root biomass data were used to disentangle the effects of positive
 interactions between species (complementarity effects) and effects due to
 dominance of productive species (selection effects) on root biomass in
 mixtures. In a next step, these biodiversity effects were linked to the
 diversity of rooting depths and the averaged rooting depth of the
 community. 3. Root biomass increased with species richness. This was
 mainly due to positive interactions (the complementarity effect), which
 increased with species richness belowground. In contrast, the selection
 effect decreased with species richness. Although there was considerable
 variation in vertical root distribution between species in monocultures,
 the diversity of rooting strategies did not explain the complementarity
 effect. Rather, the abundance of deep-rooting species in mixtures (i.e.
 high community weighted mean) was significantly related to the
 complementarity effect. Comparing the ‘predicted’ root distribution (based
 on monocultures) to the actual distribution in mixtures, we found that
 mixtures rooted deeper than expected, but this did not better explain the
 complementarity effect. 4. Synthesis: This study demonstrates that
 vertical root distributions of species provide only subtle evidence for
 resource partitioning. We found no evidence that functional diversity in
 vertical rooting patterns was important for the complementarity effect, in
 contrast to our expectation that the enhancement of productivity was due
 to resource partitioning. Alternatively, we found significant but weak
 relationships between the complementarity effect and deep-rooting
 communities, based on the community weighted mean root distribution. This
 suggests that factors other than belowground resource partitioning alone
 may drive the biodiversity-productivity relationship.
description: root biomass per plot
 per layer in 2012 and 2014Root biomass was sampled
 to a depth of 40 cm and separated into five depth layers in the
 Trait-based biodiversity experiment in Jena, Germany, in 2012 and 2014.
 This file contains total root biomass per soil layer per plot per year. A
 description of each variable is included on a separate sheet called
 ‘metadata’ in the file.rootbiomass-plot-layer.xlsxspecies-specific root biomass per plot per layer in 2012 and 2014Root biomass was sampled to a depth of 40 cm and separated into five depth layers in the Trait-based biodiversity experiment in Jena, Germany, in 2012 and 2014. This file contains root biomass per species per layer per plot per year. A description of each variable is included on a separate sheet called ‘metadata’ in each file.rootbiomass-species-plot-layer.xlsxPlot-level data of root biomass and variables derived thereofRoot biomass was sampled to a depth of 40 cm and separated into five depth layers in the Trait-based biodiversity experiment in Jena, Germany, in 2012 and 2014. This data file contains plot-level data of root biomass (averaged over the five depth layers) and calculated variables based on root biomass. A description of each variable is included on a separate sheet called ‘metadata’ in each file.community-plot-year.xlsx