Forest Dynamics, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland.
PLoS One. 2012;7(4):e35275. doi: 10.1371/journal.pone.0035275. Epub 2012 Apr 5.
Many trees species form symbiotic associations with ectomycorrhizal (ECM) fungi, which improve nutrient and water acquisition of their host. Until now it is unclear whether the species richness of ECM fungi is beneficial for tree seedling performance, be it during moist conditions or drought. We performed a pot experiment using Pinus sylvestris seedlings inoculated with four selected ECM fungi (Cenococcum geophilum, Paxillus involutus, Rhizopogon roseolus and Suillus granulatus) to investigate (i) whether these four ECM fungi, in monoculture or in species mixtures, affect growth of P. sylvestris seedlings, and (ii) whether this effect can be attributed to species number per se or to species identity. Two different watering regimes (moist vs. dry) were applied to examine the context-dependency of the results. Additionally, we assessed the activity of eight extracellular enzymes in the root tips. Shoot growth was enhanced in the presence of S. granulatus, but not by any other ECM fungal species. The positive effect of S. granulatus on shoot growth was more pronounced under moist (threefold increase) than under dry conditions (twofold increase), indicating that the investigated ECM fungi did not provide additional support during drought stress. The activity of secreted extracellular enzymes was higher in S. granulatus than in any other species. In conclusion, our findings suggest that ECM fungal species composition may affect seedling performance in terms of aboveground biomass.
许多树种与外生菌根（ECM）真菌形成共生关系，这有助于提高宿主的养分和水分吸收。到目前为止，还不清楚 ECM 真菌的物种丰富度是否有利于树木幼苗的表现，无论是在湿润条件下还是干旱条件下。我们使用接种了四种选定的 ECM 真菌（Cenococcum geophilum、Paxillus involutus、Rhizopogon roseolus 和 Suillus granulatus）的欧洲赤松幼苗进行了盆栽实验，以调查：（i）这四种 ECM 真菌在单一培养或物种混合培养中是否会影响欧洲赤松幼苗的生长；（ii）这种影响是归因于每个物种的数量本身还是物种的身份。我们采用了两种不同的浇水方式（湿润与干旱）来检验结果的上下文依赖性。此外，我们还评估了根尖的八种胞外酶的活性。在 S. granulatus 的存在下，幼苗的生长得到了促进，但其他任何 ECM 真菌物种都没有。在湿润条件下（增加三倍），S. granulatus 对幼苗生长的积极影响比干旱条件下（增加两倍）更为明显，这表明所研究的 ECM 真菌在干旱胁迫下并没有提供额外的支持。分泌的胞外酶的活性在 S. granulatus 中比任何其他物种都高。总之，我们的研究结果表明，ECM 真菌的物种组成可能会影响幼苗的地上生物量表现。
