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

Microtopographical differences in peatland-atmosphere carbon exchange following water table drawdown.

Strack, Maria ^*,1, Waddington, J.M.¹, ¹ McMaster University, Hamilton, ON, Canada

ABSTRACT- Northern peatlands are expected to experience lowered water table position in response to climate change and this may have important consequences for their rates of carbon exchange. Predictions regarding the impact of this lowered water table on peatland-atmosphere carbon exchange are often based on simple empirical relationships and do not account for site heterogeneity or ecological succession. In order to investigate peatland response to a shift in water table, CO₂ and CH₄ fluxes along a poor fen microtopographic gradient (ridge, lawn, hollow) were compared between a control site and one which experienced a 20 cm water table drawdown approximately eight years prior to the study (drained). Following the water table drawdown, ecological succession led to the invasion of low lying areas by Sphagnum and sedges resulting in enhanced gross ecosystem photosynthesis (GEP) at hollows and lawns relative to the control site. In contrast, vegetation desiccation on ridges reduced GEP in these zones. Meanwhile, the water table drawdown resulted in increased ecosystem respiration throughout the site. Despite this, the observed vegetation shift has maintained rates of net ecosystem CO₂ exchange and CH₄ flux at topographic lows. This reveals that the effect of water table drawdown on peatland carbon emissions is dependent on the antecedent wetness of the peatland.

Key words: peatland, carbon exchange, ecological succession, climate change