Ecosystem controls on nitrogen fixation in boreal feather moss communities

Area of Science:

• Ecology
• Forest Science
• Biogeochemistry

Background:

• Nitrogen (N) fixation in feather moss carpets is crucial for boreal forest ecosystems.
• Understanding the factors influencing cyanobacterial N fixation across forest successional stages is limited.

Purpose of the Study:

• To investigate ecosystem factors controlling nitrogen fixation in feather moss carpets (*Pleurozium schreberi*) at different forest successional stages.
• To assess the role of cyanobacteria in nitrogen fixation within these successional gradients.

Main Methods:

• A reciprocal transplant experiment using intact moss microplots between early and late successional boreal forests.
• Monitoring of nitrogen fixation rates via acetylene reduction assays.
• Microscopic analysis of cyanobacteria presence on moss shoots.
• Measurement of forest nutrient status using ionic resin capsules.

Main Results:

• Late successional forests demonstrated high nitrogen fixation rates and abundant cyanobacteria, coupled with low available nitrogen.
• Early successional forests exhibited lower nitrogen fixation rates and limited cyanobacteria, but higher nitrogen availability.
• Transplanted moss carpets showed significant shifts in cyanobacteria presence and activity within one year, indicating a response to forest nutrient fertility.

Conclusions:

• Forest successional stage significantly influences nitrogen fixation rates in feather moss carpets.
• Nutrient availability, particularly nitrogen, is a key driver of cyanobacterial abundance and nitrogen fixation activity.
• Moss carpets are dynamic and responsive to the successional changes in their surrounding forest environment.