Exploration of the Effect of Heatwave Temperatures on Traits of Soil Saprotrophic Fungi

Abstract

Soil fungi are key drivers of organic matter decomposition and nutrient cycling, yet their physiological responses to realistic soil heatwave temperatures remain poorly understood. Trait-based frameworks offer a promising approach to predict microbial responses to climate change, but their relevance for response of fungi to short-term heatwaves is unclear. We experimentally assessed how a subset of traits of six abundant, taxonomically diverse saprotrophic soil fungi responded to ambient (18 °C) and heatwave (25 °C) soil temperatures, reflecting realistic ambient and heatwave summer soil conditions in a European dry heathland. Taxa differed significantly in multivariate trait space at each temperature, with temperature itself producing a modest but significant shift in trait structure, driven mainly by taxon-specific responses. Furthermore, heatwave temperatures induced pronounced but taxon-specific changes in individual traits, while the responses of mean trait values across taxa were insignificant in most cases. Moreover, we did not detect trait pair covariation suggesting no coordination among fungal trait values. Changes in most traits did not predict intrinsic growth responses, although shifts in chitin decomposition capacity, mycelial density, and metabolic activity showed modest predictive power. We conclude that fungal trait responses to realistic warming conditions are multidimensional and highly taxon-specific, and as such they highlight how temperature can reshape individual fungal responses, independently of other environmental variables.