Agricultural and Forest Meteorology 198–199 (2014) 232–249 Contents lists available at ScienceDirect Agricultural and Forest Meteorology j o ur na l ho me pag e: www.elsevier.com/locate/agrformet Climatic sensitivity of the CO 2 flux in a cutaway boreal peatland cultivated with a perennial bioenergy crop (Phalaris arundinaceae, L.): Beyond diplotelmic modeling Jinnan Gong a,b,∗ , Seppo Kellomäki a , Narasinha J. Shurpali c , Kaiyun Wang a,b , Niina Hyvönen c , Chao Zhang a,b , Qicheng Zhong b , Pertti J. Martikainen c a School of Forest Sciences, University of Eastern Finland, PO Box 111, FIN-80101 Joensuu, Finland b Shanghai Key Laboratory for Urbanization and Ecological Restoration, East China Normal University, Shanghai 200062, China c Department of Environmental Sciences, University of Eastern Finland, Bioteknia 2, P.O. Box 1627, FIN-70211 Kuopio, Finland a r t i c l e i n f o Article history: Received 6 November 2013 Received in revised form 1 July 2014 Accepted 24 August 2014 Available online 18 September 2014 Keywords: Cutaway peatland Perennial agriculture Climate change CO2 sink a b s t r a c t In this study, a process-based model (RCG-C) was developed, parameterized and calibrated for studying the annual and seasonal dynamics of the ecosystem CO 2 exchange (NEE) in a cutaway peatland (Linnan- suo, eastern Finland) cultivated with a perennial bioenergy crop (Phalaris arundinaceae, L., RCG). Based on a number of prior studies and an environmentally controlled experiment, RCG-C emphasized sev- eral key processes beyond the generality of previous diplotelmic models for pristine peatlands. These processes included the effects of management (e.g., drainage, peat extraction, tilling, harvesting and fer- tilization) on the soil hydrology and the cycling of carbon and nitrogen, the influence of climatic factors on photosynthesis and the phenological cycle and phenological and soil-moisture controls on biomass production and canopy development. The model was validated based on continuous measurements of meteorological parameters, energy and CO 2 fluxes (eddy covariance system) performed at the site from 2005 to 2010, including variation associated with both wet and dry years. The results showed that the model captured the seasonal and annual trends of the latent heat flux and NEE during the six-year period. Moreover, the simulated values for the total C sink capacity, accumulation of rhizome biomass and peat formation from RCG obtained during the six-year period also agreed well with the field measurements. Based on the FINADAPT climate scenarios, a sensitivity analysis of the model showed that the potential increases in the atmospheric CO 2 concentration (Ca) and air temperature (Ta) could be the main forces driving the changes in NEE. The model simulation suggested that the effects of Ta tend to offset those of Ca and lead to a decrease in the total C sink capacity of the site during the main rotation period (4–15th year of cultivation). This decrease tends to become more intensive toward the end of the 21st century. During the period from 2060 to 2099, the total CO 2 sink capacity could decrease by 79% during the main rotation period at the Linnansuo site. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Peatlands serve as important CO 2 sinks, sequestering approxi- mately 30% of the soil carbon (C) in the world (Gorham, 1991). In the Baltic region, peatlands are widely distributed and are exten- sively drained for energy production, forestry and agricultural purposes (Turunen, 2008; Maljanen et al., 2010). Peatland drainage and the associated after-drainage practices (e.g., peat extraction, ∗ Corresponding author at: PO Box 111, FIN-80101 Room 287, Borealis Building Yliopisto 7, Joensuu, Finland. Tel.: +358 44 3284153. E-mail address: jinnang@student.uef.fi (J. Gong). tilling, liming and fertilization) are highly risky with respect to CO 2 sequestration in mire ecosystems. These disturbances usually cause significant CO 2 losses from peat to the atmosphere (Maljanen et al., 2010). In particular, cutaway peatlands act as large sources of CO 2 , potentially for decades after peat extraction ceases (e.g., Yli-Petäys et al., 2007). The area of such fields has been increasing by 20 km 2 annually in both Finland and Sweden (Maljanen et al., 2010). From 1970 to 2000, approximately 5.2 Tg of soil C was lost solely from cur- rent and abandoned peat extraction sites (approximately 630 km 2 ) in Finland (Turunen, 2008). For mitigating CO 2 emissions from cutaway peatlands, the culti- vation of reed canary grass (Phalaris arundinaceae, L.; RCG) provides a superior after-use option (Lewandowski et al., 2003; Alm et al., http://dx.doi.org/10.1016/j.agrformet.2014.08.011 0168-1923/© 2014 Elsevier B.V. All rights reserved.