Seasonal and annual variation of carbon fluxes in a young siberian larch (Larix sibirica) plantation in Iceland

This study reports 3-year measurements (2004-2006) of net ecosystem exchange (NEE) over a 12-15 year old Siberian larch forest in Iceland established on previously grazed heath land pasture that had been site-prepared prior to planting. The study evaluated interannual and seasonal variation of NEE and its component fluxes, gross primary production (GPP) and ecosystem respiration (Re), with the aim to clarify how meteorological factors controlled the site's carbon balance. The young plantation acted as a relatively strong sink for CO₂ during all of the three years, with a net sequestration of 375, 566 and 245 g CO₂ m^-2 for years 2004, 2005 and 2006, respectively. The annual carbon balance was strongly influenced by meteorological factors leading to a high interannual variability in NEE. This variation was more related to variation in carbon efflux (Re) than carbon uptake (GPP). The meteorological factors that showed the strongest correlation to R_e were air temperature during the growing season and soil water potential. The GPP mostly followed the seasonal pattern in irradiance, except in 2005, when the plantation experienced severe spring frost damage that set the GPP back to zero. It was not expected that the rather slow-growing Siberian larch plantation would be such a strong sink for atmospheric CO₂ only twelve years after site preparation and afforestation.