Elevated atmospheric CO₂ alters root symbiont community structure in forest trees

Area of Science:

• Forest Ecology
• Mycology
• Climate Change Biology

Background:

• Ectomycorrhizal (ECM) fungi form vital symbiotic relationships with forest trees, influencing nutrient uptake and carbon cycling.
• Understanding how ECM communities respond to environmental changes like elevated atmospheric carbon dioxide (CO2) is crucial for predicting forest ecosystem dynamics.

Purpose of the Study:

• To investigate the impact of elevated CO2 and nutrient addition on the below-ground ECM fungal community structure in a Norway spruce (Picea abies) forest.
• To compare the effects of short-term elevated CO2 exposure with long-term fertilization on ECM community composition.

Main Methods:

• Experimental manipulation of Norway spruce trees using whole-tree chambers to simulate ambient and elevated CO2 (700 ppm) conditions.
• Factorial design including balanced nutrient addition (+/-).
• ECM fungal community structure assessed using morphotyping and molecular analyses in 1997 and 2000.

Main Results:

• Elevated CO2 significantly affected ECM community structure, with effects comparable in magnitude to 15 years of fertilization after only 3 years.
• Neither elevated CO2 nor fertilization altered ECM species richness.
• Considerable variation among samples may have masked treatment effects on individual species.

Conclusions:

• Increasing atmospheric CO2 concentrations demonstrably alter the community structure of ECM root symbionts in forest trees.
• Altered ECM community structure has potential implications for carbon and nutrient allocation and turnover within forest ecosystems.