Impact of stockpiling on soil fungal communities and their functions

Fungal communities are important components of soil biology and play crucial roles in multiple ecosystem functions and services; therefore, they can be used as effective indicators of soil function in stockpiled reclamation soils. We profiled the fungal communities of seven stockpiles of different ages (0.5, 1.5, 2, 5, 7, 11, and 28 years old) at various soil depths (0–300 cm) in two oil sand extraction locations in northern Alberta. Fungal communities of the stockpiles differed from the communities in the nearby undisturbed reference soils. The differences with the reference soils were more pronounced for the oldest and some of the younger stockpiled soils. Similar to previous studies, there was a decrease in fungal richness and overall diversity with increasing stockpile depth. Furthermore, soil stockpiling generated a shift in the functional composition based on inferred fungal guilds and trophic modes. Ectomycorrhizal fungi decreased and saprotrophic fungi increased in the stockpiles relative to the reference soils. Such a shift may have important implications for ecosystem functions and services associated with fungal communities, such as litter decomposition and plant growth promotion, when these stockpiles are used to reclaim ecosystems. Our results align with previous research identifying the negative effects of stockpiling on soil microbial communities, shed light on the soil functions that may be affected by this disturbance and their consequences for ecosystem functioning, and reflect the high sensitivity of fungal communities to soil disturbances like stockpiling.