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）调控植物共存的路径多样，极大阻碍了学界对其影响植物间相互作用效应的认知。植物促进作用的结局可通过菌根共生受到间接影响，最终塑造生物多样性格局。本研究检验了菌根共生是否可增强植物促进作用，以及其效应在不同研究方法与生物学情境下是否具有一致性。我们针对215组案例开展了元分析（meta-analysis），涉及21种护聚物种与29种被促进植物物种，相关研究均测定了被促进植物物种在有、无菌根真菌条件下的生长表现。结果显示，菌根真菌主要通过提升植物地上生物量与养分含量，显著增强植物促进作用，但其效应因生物学情境而异：在半干旱环境中，菌根共生可显著增强植物促进作用，而在温带生态系统中其效应并不显著。此外，丛枝菌根真菌（arbuscular mycorrhizal fungi）可显著增强植物促进作用，而外生菌根真菌（ecto-mycorrhizal 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。本项元分析还发现了若干研究空白：除半干旱与温带森林外，菌根共生对植物促进作用的效应极少在其他生态系统中被评估；除养分供给外，真菌为植物提供的其他益处也鲜有被纳入考量。最后，我们仍未能充分理解整个真菌群落对植物间相互作用及植物物种共存的影响。