Microbial community composition and function beneath temperate trees exposed to elevated atmospheric carbon dioxide...

Area of Science:

• Soil Science
• Microbial Ecology
• Plant Ecology

Background:

• Atmospheric CO2 and O3 enrichment can alter plant growth and carbon allocation.
• Soil food webs play a crucial role in nutrient cycling and carbon sequestration.
• Understanding how these atmospheric changes impact soil microbial communities is vital for predicting ecosystem responses.

Purpose of the Study:

• To investigate the impact of elevated atmospheric CO2 and O3 on carbon flow through soil food webs.
• To determine if these effects vary among different temperate tree species.
• To assess the role of microbial metabolism in response to altered atmospheric conditions.

Main Methods:

• Utilized soils from a free-air CO2 and O3 enrichment site.
• Applied 13C-labeled cellobiose or N-acetylglucosamine to soils under factorial CO2 and O3 treatments.
• Analyzed 13C recovery in microbial respiration and phospholipid fatty acids (PLFAs).

Main Results:

• Elevated CO2 increased microbial respiration of 13C by 29% compared to ambient conditions; elevated O3 negated this effect.
• Soils under aspen and aspen-birch showed greater 13C-CO2 production than those under aspen-maple.
• Elevated CO2 enhanced microbial metabolism of 13C-cellobiose, with increased fungal activity indicated by 13C-PLFAs.
• N-acetylglucosamine amendment resulted in an order of magnitude greater 13C recovery in PLFAs than cellobiose.

Conclusions:

• Elevated CO2 significantly alters carbon flow in soil food webs, primarily by increasing microbial respiration and fungal activity.
• The impact of CO2 and O3 enrichment on soil microbial processes is species-specific, with early-successional trees (aspen, birch) exhibiting stronger responses than late-successional species (maple).
• Substrate availability (cellobiose vs. N-acetylglucosamine) influences the extent of microbial metabolism and soil carbon cycling under altered atmospheric conditions.