Data from: Mycorrhizal symbiosis increases the benefits of plant facilitative interactions

The diversity of pathways through which mycorrhizal fungi alter plant coexistence hinders the understanding of their effects on plant-plant interactions. The outcome of plant facilitative interactions can be indirectly affected by mycorrhizal symbiosis, ultimately shaping biodiversity patterns. We tested whether mycorrhizal symbiosis enhances plant facilitative interactions and whether its effect is consistent across different methodological approaches and biological scenarios. We conducted a meta-analysis of 215 cases (involving 21 nurse and 29 facilitated species), in which the performance of a facilitated plant species is measured in the presence or absence of mycorrhizal fungi. We show that mycorrhizal fungi significantly enhance plant facilitative interactions mainly through an increment in plant biomass (aboveground) and nutrient content, although their effects differ across biological contexts. In semiarid environments mycorrhizal symbiosis enhances plant facilitation, while its effect is non-significant in temperate ecosystems. In addition, arbuscular but not ecto-mycorrhizal (EMF) fungi significantly enhances plant facilitation, particularly increasing the P content of the plants more than EMF. Some knowledge gaps regarding the importance of this phenomenon have been detected in this meta-analysis. The effect of mycorrhizal symbiosis on plant facilitation has rarely been assessed in other ecosystems different from semiarid and temperate forests, and rarely considering other fungal benefits provided to plants besides nutrients. Finally, we are still far from understanding the effects of the whole fungal community on plant-plant interactions, and on plant species coexistence.

菌根真菌（mycorrhizal fungi）调控植物共存的通路多样，这一特性阻碍了学界对其在植物间互作中作用的认知。植物促进互作的结果可受菌根共生的间接调控，最终塑造生物多样性格局。本研究旨在探究菌根共生是否可强化植物促进互作，且其作用效果在不同研究方法与生物学情境下是否保持一致。我们针对215组案例开展了元分析（meta-analysis），共涉及21种护育物种与29种被促进物种；该分析中，研究者分别在有、无菌根真菌存在的条件下测定了被促进植物的生长表现。研究结果表明，菌根真菌主要通过提升植物地上生物量与养分含量，显著强化植物促进互作，不过其作用效果会随生物学情境的不同而存在差异。在半干旱环境中，菌根共生可强化植物促进作用，但在温带生态系统中其作用并不显著。此外，丛枝菌根真菌可显著强化植物促进作用，而外生菌根真菌（ectomycorrhizal fungi, EMF）则无此效果；相较于外生菌根真菌，丛枝菌根真菌对植物磷（P）含量的提升作用更为突出。本次元分析亦揭示了该研究领域尚存的若干认知空白：目前针对菌根共生调控植物促进作用的研究，极少涉及半干旱与温带森林之外的其他生态系统，且大多未考量真菌除提供养分外的其他植物获益途径。最终，学界仍未能充分解析整个真菌群落对植物间互作以及植物物种共存的影响。