This study assesses changes to resource acquisition with stand age and informs our understanding of the role of ectomycorrhizal fungi in age-related forest decline.

Wasyliw J, Karst J. Shifts in ectomycorrhizal exploration types parallel leaf and fine root area with forest age. J Ecol. 2020; 108: 2270–2282.

This study shows that connections among Douglas-fir trees through individual mycorrhizal fungal genets are positively correlated with the growth of mature trees.  

Birch JD, Simard SW, Beiler KJ, Karst J. Beyond seedlings: Ectomycorrhizal fungal networks and growth of mature Pseudotsuga menziesii. J Ecol. 2021; 109: 806–818. 

 This research supports the use of dendrochemistry to investigate, and potentially monitor, tree rooting at depth in substrates with signature metals.

La Flèche M, Cuss CW, Noernberg T, Shotyk W, Karst J. Trace metals as indicators of tree rooting in bituminous soils. Land Degrad Dev. 2021; 32: 1970–1980.

We applied nitrogen (30 kg ha−1 year−1) for 13 years to stands dominated by aspen (Populus tremuloides Michx.) and hypothesized that tree stem radial growth would increase, ectomycorrhizal fungal biomass would decrease, ectomycorrhizal fungal community composition would shift, and the abundance of arbuscular mycorrhizal (AM) fungi would increase. Nitrogen addition initially increased stem radial growth of aspen, but it was not sustained at the time we characterized their mycorrhizas. After 13 years, the abundance of fungi possessing extramatrical hyphae, or “high-biomass” ectomycorrhizas, doubled. No changes occurred in ectomycorrhizal and AM fungal community composition, or in ecto- and AM abundance measured as root colonization. This dual-mycorrhizal tree species did not shift away from ectomycorrhizal fungal dominance with long-term nitrogen input. The unexpected increase in high-biomass ectomycorrhizal fungi with nitrogen addition may be due to increased carbon allocation to their fungal partners by growth-limited trees. 

Karst, J., Wasyliw, J., Birch, J. D., Franklin, J., Chang, S. X., & Erbilgin, N. (2021). Long-term nitrogen addition does not sustain host tree stem radial growth but doubles the abundance of high-biomass ectomycorrhizal fungi. Global Change Biology, 27, 4125–4138.