Impact of harvest intensity on ectomycorrhizal and saprotrophic fungal communities in forest soils

Abstract Low‐intensity tree harvesting has been proposed as a sustainable forest management practice to balance and preserve forest productivity, carbon storage and resilience to climate extremes. Soil fungi play a central role in driving tree performance and soil carbon storage, but we have limited knowledge of how soil fungal communities respond to tree harvest intensity. Particularly, ectomycorrhizal fungal biomass and soil fungal community composition have been measured rarely for different tree harvest intensities. Here, we studied the impacts of different tree harvest intensities on the biomass and composition of soil fungal communities, explicitly disentangling effects on ectomycorrhizal and saprotrophic fungi. In a large‐scale forest management experiment covering 15 monospecific stands in the Netherlands, we sampled mineral topsoil near trees and stumps in plots without tree harvest, with 20% or 80% tree basal area reduction, or clearcutting. We determined soil fungal biomass and community composition, as well as ectomycorrhizal fungal biomass in fungal in‐growth bags. Soil fungal biomass near tree stumps in clear‐cut and 80% harvest plots was reduced compared with near trees in the no‐harvest control but did not differ between 20% harvest and no‐harvest control plots. Similarly, soil fungal community composition near stumps in clear‐cut and 80% harvest plots was most different from the no‐harvest control, while shifts in community composition between the 20% and no‐harvest plots were limited. We found larger changes in biomass and community composition for ectomycorrhizal fungi in response to harvesting treatments than for total and saprotrophic fungi. We conclude that responses of the soil fungal community to low‐intensity tree harvesting were relatively small, whereas high‐intensity harvesting and particularly clearcutting impacted fungal communities. High‐intensity harvesting, especially reduced ectomycorrhizal fungal biomass and diversity. Our findings suggest that low‐intensity tree harvesting can potentially provide a good balance between timber production and the preservation of fungal‐mediated soil functions. In addition, distances between remaining trees after harvesting should likely be small (<10 m) to preserve ectomycorrhizal fungi. Read the free Plain Language Summary for this article on the Journal blog.