title: Temperature sensitivity of soil carbon fractions in boreal forest soil.
abstract: Feedback to climate warming from the carbon balance of terrestrial ecosystems depends critically on the temperature sensitivity of soil organic carbon (SOC) decomposition. Still, the temperature sensitivity is not known for the majority of the SOC, which is tens or hundreds of years old. This old fraction is paradoxically concluded to be more, less, or equally sensitive compared to the younger fraction. Here, we present results that explain these inconsistencies. We show that the temperature sensitivity of decomposition increases remarkably from the youngest annually cycling fraction (Q10 < 2) to a decadally cycling one (Q10 = 4.2-6.9) but decreases again to a centennially cycling fraction (Q10 = 2.4-2.8) in boreal forest soil. Compared to the method used for current global estimates (temperature sensitivity of all SOC equal to that of the total heterotrophic soil respiration), the soils studied will lose 30-45% more carbon in response to climate warming during the next few decades, if there is no change in carbon input. Carbon input, derivative of plant productivity, would have to increase by 100-120%, as compared to the earlier estimated 70-80%, in order to compensate for the accelerated decomposition.
authors.affiliation: Finnish Environment Institute, Research Programme for Global Change, P.O. Box 140, FI-00251 Helsinki, Finland.
authors.forename: Kristiina
authors.initials: K
authors.lastname: Karhu
authors.forename: Hannu
authors.initials: H
authors.lastname: Fritze
authors.forename: Kai
authors.initials: K
authors.lastname: Hämäläinen
authors.forename: Pekka
authors.initials: P
authors.lastname: Vanhala
authors.forename: Högne
authors.initials: H
authors.lastname: Jungner
authors.forename: Markku
authors.initials: M
authors.lastname: Oinonen
authors.forename: Eloni
authors.initials: E
authors.lastname: Sonninen
authors.forename: Mikko
authors.initials: M
authors.lastname: Tuomi
authors.forename: Peter
authors.initials: P
authors.lastname: Spetz
authors.forename: Veikko
authors.initials: V
authors.lastname: Kitunen
authors.forename: Jari
authors.initials: J
authors.lastname: Liski
mesh_terms: D001110:Arctic Regions; D002244:Carbon / Q000737:chemistry*; D008954:Models, Biological; D012987:Soil / Q000032:analysis*; D013696:Temperature; D014197:Trees
chemical_list: D012987:Soil; D002244:Carbon