Competition constrains the resistance and recovery of fungi to heat stress under low nutrient concentration

Soil fungi contribute to several ecosystem functions, such as nutrient cycling and plant productivity. Yet, we know little about how biotic interactions among fungi, such as competition, may influence fungal stability against environmental stresses. For instance, a significant challenge is understanding the roles of competition in driving resistance (immediate response to stress) and recovery (response after the stress is over) of fungi under climate extremes, such as heat waves, particularly under variable resource availability. Here, we investigated how competitive interactions between fungi affect their resistance and recovery to a heat event. Four saprotrophic fungal strains were cultivated as monocultures or in pairwise cultures on agar at low or high nutrient concentrations. The cultures were exposed to heat (+10°C compared to the control temperature of 20°C) for 48 hours, followed by a recovery time of 48 hours at 20°C. Our results show that the competition between Morchella elata (a fungus showing a relatively high radial growth rate) and Trichoderma atroviride (a fungus showing a relatively low radial growth rate) shifted both the resistance and recovery of their respective radial growth rates to heat stress. Specifically, competition decreased the recovery of M. elata and the resistance of T. atroviride under low nutrient concentration. Our experiment highlights that competition among fungi may reduce stability of certain fungal species under heat extremes, particularly in low nutrient conditions.