Data from: Root traits and soil legacies drive species competition outcomes

Plant competition can be affected by plant functional traits but also by
differences in fitness mediated by soil microbes. Climatic conditions such
as drought further influence plant competition. Yet little is known about
how soil microbes and drought interact with species with distinct root
traits differences and how this influences plant competition outcomes. We
grew three plant species that co-occur in temperate grasslands in China
(Stipa krylovii, Artemisia frigida, Agropyron cristatum) in monocultures
and mixtures and subjected the plant combinations to five soil inocula
(root-associated soil of S.krylovii, A.frigida, A.cristatum, an equal
mixture of the three root zone soils, and sterilized soil) as well as to a
drought treatment. The relative change in plant biomass was used to
determine plant competition outcomes. The three species exhibited clear
differences in competitive abilities with A.cristatum > S.krylovii
> A.frigida, and soil inocula or the drought treatment did not
change the order. The relative yield (RY) of plants was affected by soil
inocula, drought and plant arrangement. The strongest competitor,
A.cristatum, with high total root length, root surface area, and root
volume experienced more negative biotic feedback, and drought enhanced the
magnitude of these negative effects. On the contrary, the most inferior
competitor, A.frigida, with high specific root length tended to have
neutral or positive biotic feedback, and drought had no effect. Further,
the RY and fitness difference (reflected as the competitive ability in the
mixture) of the three species was differentially influenced by root traits
and plant-soil feedback. RY of A.cristatum could be predicted by the
feedback effect in the mixture, and the fitness difference was mainly
related to root traits. Both RY and fitness differences of A.frigida (the
weakest competitor) could be predicted by root trait differences and
feedback effects. Differences in root traits were the best predictors of
the intermediate competitor S.krylovii. Our study shows that competition
outcomes of co-existing species depend on root traits and species-specific
PSF effects in mixture. Future work should examine the mechanisms that
explain how plant competition and soil microbial heterogeneity act in
conjunction with climate change in influencing plant coexistence.