Interactions between silicate weathering and ectomycorrhiza in severely acidified forests

Abstract

Soil acidification driven by anthropogenic nitrogen (N) deposition is a growing global threat to forest health. Aside from direct nutrient-related effects, as forest soils acidify, severe reductions in ectomycorrhizal (EcM) fungi abundance and diversity follow. This is worrisome, as EcM fungi are essential for tree nutrient acquisition and are important catalysts of mineral weathering and soil formation. Conventional remediation techniques such as dolomite liming often increase buffering too rapidly, leading to disturbed EcM fungal communities. Enhanced silicate weathering (ESW), the application of finely ground rock dust, has emerged as a more gradual, slow-release antacid. However, interactions and feedback processes between ESW and EcM remain poorly understood. ESW may improve EcM conditions, with outcomes depending on fungal community composition and mineralogy of the applied rock dust. Because EcM also accelerates mineral weathering, we postulate a positive feedback between ESW, EcM recovery and silicate dissolution. This synergy could restore nutrient cycling and tree vitality, while stabilising soil organic carbon (SOC) through complexation onto secondary minerals. Key knowledge gaps include genetic and biogeochemical pathways underlying fungal-mineral interaction, SOC sequestration effects, and the scalability across forest types and soil conditions. Tackling these unknowns will be crucial to safeguarding forest resilience under ongoing acidification.