Arnkil, Sini

Bubier, Jill

Humphreys, Elyn

Juutinen, Sari

Larmola, Tuula

Moore, Tim

Roy, Cameron

Jukuri

Geophysical Research AbstractsVol. 18, EGU2016-12050, 2016EGU General Assembly 2016© Author(s) 2016. CC Attribution 3.0 License.Nutrient load can lead to enhanced CH4 fluxes through changes invegetation, peat surface elevation and water table depth in ombrotrophicbogSari Juutinen (1,2), Jill Bubier (3), Tuula Larmola (1,4), Elyn Humphreys (5), Sini Arnkil (1), Cameron Roy (6),and Tim Moore (6)(1) Department of Forest Sciences, University of Helsinki, Helsinki, Finland (sari.juutinen@helsinki.fi;sini.arnkil@helsinki.fi), (2) Department of Environmental Sciences, University of Helsinki, Finland(sari.juutinen@helsinki.fi), (3) Environmetal Studies Department, Mount Holyoke College, South Hadley, USA(jbubier@mtholyoke.edu), (4) Natural Resources Institute Finland, Vantaa, Finland (tuula.larmola@luke.fi), (5) Department ofGeography and Environmetal Studies, Carleton University, Ottawa, Canada (elyn.humphreys@carleton.ca), (6) Department ofGeography, McGill University, Montreal, Canada (cameron.roy@mail.mcgill.ca; tim.moore@mcgill.ca)Atmospheric nitrogen (N) deposition has led to nutrient enrichment in wetlands, particularly in temperate areas,affecting plant community composition, carbon (C) cycling, and microbial dynamics. It is vital to understandthe temporal scales and mechanisms of the changes, because peatlands are long-term sinks of C, but sources ofmethane (CH4), an important greenhouse gas. Rainwater fed (ombrotrophic) bogs are considered to be vulnerableto nutrient loading due to their natural nutrient poor status. We fertilized Mer Bleue Bog, a Sphagnum moss andevergreen shrub-dominated ombrotrophic bog near Ottawa, Ontario, now for 11-16 years with N (NO3 NH4) at0.6, 3.2, and 6.4 g N m-2 y-1 (∼5, 10 and 20 times ambient N deposition during summer months) with and withoutphosphorus (P) and potassium (K). Treatments were applied to triplicate plots (3 x 3 m) from May – August 2000-2015 and control plots received distilled water. We measured CH4 fluxes with static chambers weekly from Mayto September 2015 and peat samples were incubated in laboratory to measure CH4 production and consumptionpotentials. Methane fluxes at the site were generally low, but after 16 years, mean CH4 emissions have increasedand more than doubled in high nitrogen addition treatments if P and K input was also increased (3.2 and 6.4 gN m-2yr-1 with PK), owing to drastic changes in vegetation and soil moisture. Vegetation changes include a lossof Sphagnum moss and introduction of new species, typical to minerogenic mires, which together with increaseddecomposition have led to decreased surface elevation and to higher water table level relative to the surface. Thetrajectories indicate that the N only treatments may result in similar responses, but only over longer time scales.Elevated atmospheric deposition of nutrients to peatlands may increase loss of C not only due to changes inCO2 exchange but also due to enhanced CH4 emissions in peatlands through a complex suite of feedbacks andinteractions among vegetation, microclimate, and microbial processes. It is uncertain, however, how the vegetationchange continues due to collapsing surface and higher water table levels, and how that will affect future CH4emissions and C balance.

Nutrient load can lead to enhanced CH4 fluxes through changes in vegetation, peat surface elevation and water table depth in ombrotrophic bog

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