Limits to Sphagnum Growth in an Abandoned Mined Peatland

Abstract

<p> The net ecosystem CO2 exchange and Sphagnum net primary production of an abandoned block-cut bog were measured in the field and in the laboratory using gas exchange techniques. Environmental variables were measured concurrently. Seasonal Sphagnum growth and decomposition were determined using crank wires and litter bags.</p> <p> The bog was a net source of CO2 during the summer months. While, Sphagnum did grow over the study period, the Sphagnum net primary production was offset by peat respiration. Sphagnum net primary production and net ecosystem CO2 exchange at the abandoned block-cut bog are within the ranges found for natural peatlands.</p> <p> Sphagnum photosynthesis was greatest at wet sites and at the start and end of the study period when the water table was higher and the temperature was cooler. Ericaceous shrub cover strongly affected Sphagnum growth. Sites with vascular plant cover photosynthesized at approximately twice the rate of sites where cover was removed.</p> <p> Laboratory results indicate that drying and wetting cycles negatively affect Sphagnum net primary production and net ecosystem CO2 exchange. Sphagnum and peat respiration increased 4 to 14 fold upon rewetting whereas Sphagnum photosynthesis did not recover until 20 days of saturation.</p> <p> The results emphasize the importance of stable moisture availability for the development of a new acrotelm. The peatland will likely remain a source of CO2 until the acrotelm is able to counterbalance the peat respiration.</p>