Global patterns in mycorrhizal types
Over the whole dataset, AM plants accounted for 71.3% of all plant species with an assigned mycorrhizal association, EcM plants accounted for 7.0%, ErM for 4.2%, NM for 15.8% and Orchid Mycorrhizas (OM) for 0.1%. These numbers are similar to the proportions per mycorrhizal type found by Soudzilovskaia et al., 2020 across the entire FungalRoot database (AM: 70%, EcM: 8%, ErM: 2%, OM: 1%, NM: 17%). The distribution of mycorrhizal types amongst native species in our data was likewise broadly similar to that of the FungalRoot database (AM: 79.3%, EcM: 6%, ErM: 3%, OM: 0.6%, NM: 10.3%). As expected, the majority of non-native species were found to associate with AM or to be non-mycorrhizal (AM: 85.6%, EcM: 0.3%, ErM: 0%, OM: 0%, NM: 14.1%). Mycorrhizal type distribution also varied with region (Fig. 1): AM plant species made up more than half of all vegetation in almost all regions except for Norway, where ErM vegetation was dominant. In Argentina, Armenia, Chile and India there was no or almost no EcM and ErM vegetation, with all plants being either AM or NM.
Globally, our models showed that both EcM and ErM vegetation cover decreased with increasing mean annual soil temperatures, while AM and NM vegetation cover increased (Table 1). This effect of temperature on EcM and ErM vegetation remained mostly consistent across regions while there was a high variability of responses for AM and NM vegetation (Table 2).