Litter decomposition generates overyielding when local adaptation of
saprotrophic microbes is the underlying driver
Decomposition facilitates the recycling of often limiting resources,
which may promote plant productivity responses to diversity, i.e.
overyielding. However, the direct relationship between decomposition and
overyielding remains underexplored in grassland diversity manipulations.
We test whether local adaptation of microbes, i.e. home-field advantage
(HFA), N-priming from plant inputs, or precipitation drive decomposition
and whether decomposition generates overyielding in an established
rainfall and diversity manipulation. Precipitation was a strong,
independent driver of decomposition. Grass diversity stimulates
decomposition, which decreased with phylogenetic dissimilarity from and
densities of the ‘home’ species, providing strong evidence HFA drives
decomposition through closely related neighbors, rather than
conspecifics. Legumes stimulate decomposition of litter carbon,
suggesting N-priming stimulates decomposition. However, decomposition
and overyielding were unrelated in legume communities and positively
related in grass communities. Combined this suggest diversity stimulates
decomposition through multiple mechanisms, but only HFA generates
overyielding through resource recycling, linking diversity with
ecosystem processes directly facilitating overyielding.