Data from: Diversity effects on root length production and loss in an experimental grassland community

Advances in root ecology have revealed that root standing biomass is
higher in species-rich plant communities than in species-poor communities.
Currently, we do not know whether this below-ground diversity effect is
the result of enhanced root production or reduced root mortality or both,
which is essential information to understand ecosystem functioning, as it
determines C sequestration and N dynamics in soil. Minirhizotron
observations were combined with root coring in five different plant
communities (four monocultures and the respective mixture). Molecular
markers were used to quantitatively determine species abundance in mixed
root biomass samples in order to track shifts in below-ground species
composition. In addition, a litterbag experiment was performed to study
root decomposition independent of root mortality. Root length production
was greater and root length loss was lower in the mixture than expected
from monocultures in all years. Simulations suggest that at least two
species must have had reduced losses in mixture compared to monoculture.
However, the diversity effects on root mortality may partially be
explained by selection effects as the species with the longest root life
span became dominant in the mixtures. Root length loss from minirhizotrons
was very low; the combination of minirhizotron length measurements with
root biomass estimates from coring suggested underestimation of root loss
in minirhizotrons over time. Root decomposition was not affected by
diversity. Diversity enhanced root length production and decreased root
loss, resulting in below-ground overyielding. With decomposition
unaffected, our results suggest that root mortality is reduced with
increasing diversity. Future studies have to reveal the generality of our
observations in larger scale biodiversity experiments by using species
having a wider variety of root traits.