Carbon and Phosphorus Dynamics in Restored Minnesota Peatlands

Abstract

While many peatlands have been drained for anthropogenic purposes across the world, there is currently high interest in restoring peatlands for carbon and nutrient cycling benefits. Peat holds a disproportionate amount of the world’s soil carbon, making peatlands promising ecosystems for mitigating greenhouse gas emissions and climate change. Additionally, peatlands can sequester phosphorus (P) and prevent it from causing eutrophication in downstream waters, but they can also act as a P source under high runoff conditions. This study aimed to investigate the factors impacting 1) peat carbon dioxide (CO2) flux and 2) mobilization of peat P to porewater in a restored bog and fen in Minnesota. Peat CO2 flux was monitored in-situ throughout the growing season in conjunction with peat type, water table depth, and temperature. Peat columns from each site were saturated and subjected to controlled laboratory incubations to relate porewater ortho-P content to temperature and porewater aluminum (Al), calcium (Ca), and iron (Fe) content. A higher water table was significantly related to lower peat CO2 flux in the fen, and peat CO2 flux across both sites was higher in regions with more decomposed peat. During the peak of the growing season, CO2 flux was much higher in the fen than the bog, but both sites had similarly low CO2 flux at the end of the growing season. It is important that restoration ecologists consider a peatland’s water table when restoring a site’s hydrological, ecological, and biogeochemical functioning in order to achieve the greatest carbon benefit. Higher porewater ortho-P corresponded to higher dissolved porewater Al, Ca, and Fe. Additionally, higher initial peat Ca was significantly related to lower porewater P. These ions play a role in binding and mobilizing P, and their dynamics can help researchers predict and mitigate P release and subsequent export.