Effects of Spontaneous Colonization by Eriophorum vaginatum on Belowground C and N Mobilization and Greenhouse Gas Emissions in a Restored Boreal Peatland
Abstract
Peatland restoration aims at recovering the ecological function of these ecosystems as active C sinks by re-establishing Sphagnum-dominated vegetation. In addition, restoration encourages the establishment of naturally occurring vascular plant species from the local seed bank. Whereas these plants could contribute to a substantial short-term increase in C sequestration due to their large biomass accumulation, their impacts on peat biogeochemistry are complex and belowground C and N mobilization could be substantial, leading to increased greenhouse gas emissions. We investigated the effects of cottongrass (Eriophorum vaginatum), a common vascular plant species colonizing extracted peatlands, on porewater dissolved organic C (DOC) and total dissolved N (TDN) as well as CO2, CH4 and N2O fluxes in a cutover boreal bog in Alberta (Canada), restored three years prior to the study. We hypothesized that cottongrass would increase the concentration of DOC and TDN in porewater as well as net N2O and CH4 emission from peat compared to areas of bare peat or moss. We studied porewater chemistry and net gas exchange for CO2, CH4, and N2O, using static chambers, over one growing season (May-September 2015) and we compared between plots containing cottongrass and plots lacking vascular plants. Plots were located along a transect of increasing water table, to discriminate between the effects of cottongrass and the prevailing hydrological conditions on porewater chemistry and gas fluxes. Cottongrass presence had contrasting effects on porewater DOC chemistry depending on wetness of the site, reducing DOC concentration in dry sites but increasing it at wet sites as compared with bare plots. This suggests that DOC mobilization is primarily controlled by hydrological conditions rather than cottongrass presence. However, cottongrass significantly increased CH4 emissions independently of the plot moisture. Cottongrass presence reduced net emission of N2O in the later part of the growing season, with cottongrass plots frequently acting as net consumers in July and August. Porewater TDN was significantly higher under cottongrass at the wettest area of the site than under either bare or cottongrass plots at the drier area, suggesting nitrogen mobilization from peat by an interaction between cottongrass roots and water.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.B51G0491L
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0452 Instruments and techniques;
- BIOGEOSCIENCESDE: 0476 Plant ecology;
- BIOGEOSCIENCESDE: 1865 Soils;
- HYDROLOGY