Old growth forests: A blueprint for restoring mycorrhizal fungi in second-growth and thinned coast redwood (Sequoia sempervirens) stands

Second-growth coast redwood (Sequoia sempervirens) stands, particularly those with encroaching Pinaceae species like Sitka spruce and Douglas-fir, exhibit significantly reduced richness and abundance of arbuscular mycorrhizal fungi (AMF) compared to old-growth forests. This study, conducted in Redwood National and State Parks, found that while ectomycorrhizal fungi (EMF) prevalence did not differ between old- and second-growth stands, AMF were nearly absent in the latter due to the dominance of EMF-dependent Pinaceae species. Thinning efforts failed to restore AMF communities, which remained closer to unthinned second-growth levels rather than old-growth benchmarks. The broader fungal community showed only marginal differences across stand types, underscoring the need for targeted restoration strategies—such as inoculum introduction—to recover mycorrhizal diversity to pre-logged conditions.

Bañuelas, D. C., Bellier-Igasaki, S. A., Guzman, D. J., Esquivel, A., Le, N. H. D., Nguyen, D. M., Franco, C. A., Giampietro, J. R., & Treseder, K. K. (2025). Old growth forests: A blueprint for restoring mycorrhizal fungi in second-growth and thinned coast redwood (Sequoia sempervirens) stands. Biological Conservation, 305, 111036. https://doi.org/10.1016/j.biocon.2025.111036