PARENT SESSION
Organized Oral Session 21: Implications of disturbance on boreal peatland carbon cycling: From sites to to landscape-scale carbon budgets
Organizer(s): RK Wieder, KD Scott, and DH Vitt
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 511a, Level 5, Palais des congrès de Montréal

Carbon fluxes from drought-stressed fens in boreal, western, continental Canada.

Vile, Melanie¹, Wieder, R. Kelman², Vitt, Dale³, Scott, Kimberli², Kamminga, Katherine², ¹ Patrick Center for Environmental Research, Philadelphia, PA, USA² Department of Biology, Villanova, PA, USA³ Department of Plant Biology, Carbondale, IL, USA

ABSTRACT- Boreal regions of the northern hemisphere are expected to undergo dramatic changes in climate. Boreal peatlands store large quantities of C (455 Pg globally; 48 Pg in continental, western Canada alone), a testament to their long-term functioning as a sink for atmospheric C. Soil surfaces of boreal peatlands typically have close to 100% cover of mosses. These nonvascular plants, without true stomates and with narrow tolerances to precipitation and temperature, may respond with exceptional sensitivity to changing climate. Boreal, continental, western Canada has been experiencing prolonged drought conditions since 1996, and in 2003 we observed moss decline on southward facing hummocks in our fen sites. With continued drought conditions predicted, understanding the carbon balance of dying and dead fens is timely and important. Our goal was to quantify carbon fluxes from peat deposits in fen microenvironments where mosses have recently died. We established 10 replicate plots per site (two stressed fens with dead and dying mosses and two control sites). Flux measurements were made once or twice monthly throughout the field season. Monthly CO₂ fluxes from dying fens represented either a small net source or small net sink for C, while fluxes from control sites always represented net sinks for atmospheric C, consuming 18 times more C than dying fen sites (2.539 vs. 0.141 mol m² CO₂ sec¹, respectively; field season mean). Our observations of dead fens throughout north-central Alberta may indicate fens as harbingers of ecosystem responses to climate change.

Key words: peatlands, fens, carbon, drought