Greenhouse gas flux measurements in a forestry-drained peatland indicate a large carbon sink

Abstract

Abstract. Drainage for forestry purposes increases the depth of the oxic peat layer and leads to increased growth of shrubs and trees. Concurrently, the production and uptake of the greenhouse gases carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) change: due to the accelerated decomposition of peat in the presence of oxygen, drained peatlands are generally considered to lose peat carbon (C). We measured CO 2 exchange with the eddy covariance (EC) method above a drained nutrient-poor peatland forest in southern . Photosynthesis was detected throughout the year when the air temperature exceeded −3 • C. As the annual accumulation of C in the above and below ground tree biomass (175 ± 35 g C m −2 ) was significantly lower than the accumulation observed by the flux measurement (240 ± 30 g C m −2 ), about 65 g C m −2 yr −1 was likely to have accumulated as organic matter into the peat soil. This is a higher average accumulation rate than previously reported for natural northern peatlands, and the first time C accumulation has been shown by EC measurements to occur in a forestry-drained peatland. Our results suggest that forestry-drainage may significantly increase the CO 2 uptake rate of nutrient-poor peatland ecosystems.

Soil carbon stock changes in transitional mire drained for forestry in Latvia: a case study

“…Soil carbon stock increase after drainage is reported also by other researchers for the boreal region in Finland (Minkkinen & Laine, 1998b;Ojanen et al, 2010;Lohila et al, 2011). Although drainage accelerates organic matter decomposition, it can be compensated by higher aboveground and belowground litter production rates followed by an increased tree biomass growth.…”

“…This hypothesis is confirmed by an increased soil bulk density and increased total carbon stock in the soil. Carbon storage 54 years after drainage has increased Lohila et al, 2011). Although drainage accelerates organic matter decomposition, it can be compensated by higher aboveground and belowground litter production rates followed by an increased tree biomass growth.…”

Carbon dioxide flux and net primary production of a boreal treed bog: Responses to warming and water-table-lowering simulations of climate change

“…Tree root respiration (R r ) may account for a significant proportion of forest floor respiration (R ff ) in forested bogs (Lohila et al, 2011). Therefore, isolating R r from R ff is critical in attributing forest floor C to various sources of soil respiration and in filling knowledge gaps related to source-sink dynamics (Hanson et al, 2000;Janssens et al, 2001) of boreal treed bogs under a climate change scenario.…”

“…They found an increase in the net uptake and emission of 4.3 and 2.5 g C m −2 d −1 , respectively, coincident with an average increase in air and soil temperature from 0 • C (late April) to 27 • C (early June). Long-term drawdown of the water table in forested bogs significantly increased tree productivity of a Canadian (Lieffers and Rothwell, 1987) and a Finnish peatland (Heikurainen and Pakarinen, 1982;Lohila et al, 2011). For example, in a 35-year-old forestry drained (water level 40 cm below ground at the end of study) pine bog, a very high NEE of −871 ± 100 g C m −2 yr −1 and a tree productivity of 240 ± 30 g C m −2 yr −1 were reported by Lohila et al (2011).…”

“…Long-term drawdown of the water table in forested bogs significantly increased tree productivity of a Canadian (Lieffers and Rothwell, 1987) and a Finnish peatland (Heikurainen and Pakarinen, 1982;Lohila et al, 2011). For example, in a 35-year-old forestry drained (water level 40 cm below ground at the end of study) pine bog, a very high NEE of −871 ± 100 g C m −2 yr −1 and a tree productivity of 240 ± 30 g C m −2 yr −1 were reported by Lohila et al (2011). A sedge fen with a water table 25 cm below ground was reported to emit 8.21 g CO 2 m −2 d −1 (Aurela et al, 2007).…”