Nitrogen deposition changes ectomycorrhizal communities in Swiss beech forests

Area of Science:

• Forest Ecology
• Environmental Science
• Mycology

Background:

• Atmospheric pollution, particularly nitrogen (N) deposition, significantly impacts temperate forest health and biodiversity in Central Europe.
• Elevated N deposition shifts forest ecosystems from N-limited to other nutrient limitations, affecting tree health and ectomycorrhizal fungi (EMF) crucial for nutrient uptake.
• The consequences of altered EMF communities on tree health under high N deposition remain unclear.

Purpose of the Study:

• To investigate changes in EMF communities in beech forests along a nitrogen deposition gradient.
• To understand the relationship between N deposition, EMF community composition, and forest health indicators.
• To assess the impact of EMF community shifts on nutrient uptake and belowground processes.

Main Methods:

• Studied EMF communities on root tips and in soil within beech forests experiencing N deposition from 16 to 33 kg N ha⁻¹ yr⁻¹.
• Analyzed variations in EMF community composition in relation to N deposition, base saturation, temperature, and precipitation.
• Quantified fine root length, EMF root colonization, EMF diversity, and extramatrical mycelium production.

Main Results:

• Increased N deposition significantly decreased fine root length, EMF root colonization, EMF diversity, and extramatrical mycelium production.
• EMF community composition was strongly influenced by N deposition, base saturation, temperature, and precipitation.
• Foliar phosphorus (P) and potassium (K) levels were positively associated with EMF diversity; EMF community composition correlated with foliar P and N:P ratio.

Conclusions:

• Decreased EMF colonization and diversity under high N deposition suggest impaired nutrient uptake in European beech forests.
• Changes in EMF communities, including reduced abundance of key species like Cenococcum geophilum, impact belowground carbon allocation.
• Continued high N deposition alters soil carbon and nutrient cycles, negatively affecting overall forest ecosystem health and potentially optimizing P uptake via specific EMF adaptations.