Weathering-driven fungal adaptations in boreal forest biomass degradation and biomineralization.

Forest biomass photodegradation and subsequent fungal biodegradation are crucial to the carbon cycle in ecosystems. Meanwhile, fungal biomineralization significantly contributes to the biogeochemical mineral cycle. However, the interplay between these processes, where fungi play a specific role as co-protagonists, particularly under weathering conditions, remains poorly understood. Here, we investigated the fungal biodegradation of weathered forest biomass components, examining mycelium morphology, metabolic activity, biomass chemistry, hyphal biomineralization, and survival strategies. Our findings indicated that fungi exhibit stress-induced growth variations when exposed to different biomass photodegradation products, highlighting their adaptive or evasive responses to environmental changes. In boreal forests, brown-rot fungi consumed cellulose and hemicellulose as nutrient sources, with calcium detoxification during biomineralization facilitating adaptation to weathered biomass. Conversely, weathered lignin and antifungal extracts impeded fungal growth, causing calcium poisoning and stress from biomineralization products (CaOx). In response, hyphae regenerated, enhanced non-enzymatic degradation, and formed enzyme-producing mycelial clusters, allowing them to sustain growth and overcome antifungal barriers to exploit new nutrients. This research highlights the pivotal role of fungi in perpetuating biological carbon and biogeological mineral cycles, offering insights into their positive contributions to natural evolutionary processes. This study provides a foundation for understanding how fungal adaptation and resilience influence ecosystem evolution and the long-term cycling of carbon and minerals in natural environments.