Carbon turnover in peatland mesocosms exposed to different water table levels

Abstract

Abstract. Changes of water table position influence carbon cycling in peatlands, but effects on the sources and sinks of carbon are difficult to isolate and quantify in field investigations due to seasonal dynamics and covariance of variables. We thus investigated carbon fluxes and dissolved carbon production in peatland mesocosms from two acidic and oligotrophic peatlands under steady state conditions at two different water table positions. Exchange rates and CO 2 , CH 4 and DOC production rates were simultaneously determined in the peat from diffusive-advective mass-balances of dissolved CO 2 , CH 4 and DOC in the pore water. Incubation experiments were used to quantify potential CO 2, CH 4 , and DOC production rates. The carbon turnover in the saturated peat was dominated by the production of DOC (10-15 mmol m −2 d −1 ) with lower rates of DIC (6.1-8.5 mmol m −2 d −1 ) and CH 4 (2.2-4.2 mmol m −2 d −1 ) production. All production rates strongly decreased with depth indicating the importance of fresh plant tissue for dissolved C release. A lower water table decreased area based rates of photosynthesis (24-42%), CH 4 production (factor 2.5-3.5) and emission, increased rates of soil respiration and microbial biomass C, and did not change DOC release. Due to the changes in process rates the C net balance of the mesocosms shifted by 36 mmol m −2 d −1 . According to our estimates the change in C mineralization contributed most to this change. Anaerobic rates of CO 2 production rates deeper in the peat increased significantly by a factor of 2-3.5 (DOC), 2.9-3.9 (CO 2 ), and 3-14 (CH 4 ) when the water table was lowered by 30 cm. This phenomenon might have been caused by easing an inhibiting effect by the accumulation of CO 2 and CH 4 when the water table was at the moss surface.

Fluorescence characteristics and biodegradability of dissolved organic matter in forest and wetland soils from coastal temperate watersheds in southeast Alaska

“…The organic C, N and P concentrations reported in this study fall within the range reported in other studies of forested (Qualls and Haines 1991;Michalzik et al 2001) and wetland soils (Fraser et al 2001;Blodau et al 2004), which supports the idea that DOM concentrations in wetland soils are signiWcantly greater than in upland forest soils. The organic forms of N and P dominated soil solution for all soil types and suggests that DON and DOP are an important component of nutrient cycling in coastal temperate soils.…”

Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production

“…Although this temperature is higher than those likely to occur at ∼10-cm depth in the field, it is common practice to incubate samples at a temperature higher than in situ to observe significant increases in gas production at the timescales used for laboratory experiments (21,(60)(61)(62)(63). The results thus represent potential CH 4 and CO 2 production rates (21), which are evaluated relative to one another to assess changes in organic matter lability along the thaw sequence.…”

Plant Litter Decomposition and Nutrient Release in Peatlands

“…Indeed, laboratory and field experiments have demonstrated that mass loss is higher under aerobic conditions than under anaerobic conditions [Belyea, 1996;Scanlon and Moore, 2000;Yavitt et al, 2000;Blodau et al, 2004;Laiho, 2006;Moore and Basiliko, 2006;Jaatinen et al, 2008;Wickland and Neff, 2008]. In Figure 3, mass losses from vascular plant litter and Sphagnum litter decomposing in parallel under aerobic and anaerobic conditions are compared.…”