Diversity and habitat relationships of hypogeous fungi. III. Factors influencing the occurrence of fire-adapted species

Among the huge array of hypogeous ectomycorrhizal fungi so far documented from Australia, six genera and more than 30 species occur within the family Mesophelliaceae, all of which show various adaptations for surviving in fire-prone landscapes. These mostly endemic fungi are critical to postfire reestablishment of regenerating vegetation, and their fruit-bodies provide essential food resources for diverse ground-dwelling fauna. We developed habitat models for five common representatives of the Mesophelliaceae based on repeat collections of their fruit-bodies from 136 study plots situated along a series of environmental gradients across the south-eastern mainland of Australia. At a meso- or landscape scale, temperature influenced the occurrence of Castoreum radicatum, Mesophellia clelandii and Nothocastoreum cretaceum, with the type of response varying. Below a threshold, C. radicatum preferred sites with cooler mean annual temperatures. In contrast, M. clelandii and N. cretaceum had optimal ranges of temperature, above and below which the probability of detecting them dropped. Also at a landscape scale, C. radicatum was more likely to be detected at sites with lower levels of precipitation during the driest quarter of the year. At a micro-site scale, M. clelandii and N. cretaceum were more likely to occur in stands with an intermediate number of host eucalypt stems, likely relating to successional age of the stand. Sites with a higher number of large fallen trees were more likely to have N. cretaceum, while sites with intermediate litter depths were more likely to have C. radicatum and M. clelandii. Mesophellia glauca and M. trabalis showed no consistent patterns. They are apparently the most broadly adaptable in terms of the independent variables tested. Although fire has been previously suggested to be heavily implicated in the life cycle of several members of the Mesophelliaceae, we found no relationship between time since disturbance by fire and other factors and likelihood of occurrence. Instead, other habitat attributes appeared to be more important in explaining their distribution. The complex and differing responses of the species of Mesophelliaceae studied here, to features of their environment, reinforce the need to manage multiple-use forest landscapes across the region for a diversity of attributes.