Winter climate controls soil carbon dynamics during summer in boreal forests

Abstract

Boreal forests, characterized by distinct winter seasons, store a large proportion of the global terrestrial carbon (C) pool. We studied summer soil C-dynamics in a boreal forest in northern Sweden using a seven-year experimental manipulation of soil frost. We found that winter soil climate conditions play a major role in controlling the dissolution/mineralization of soil organic-C in the following summer season. Intensified soil frost led to significantly higher concentrations of dissolved organic carbon (DOC). Intensified soil frost also led to higher rates of basal heterotrophic CO _2 production in surface soil samples. However, frost-induced decline in the in situ soil CO _2 concentrations in summer suggests a substantial decline in root and/or plant associated rhizosphere CO _2 production, which overrides the effects of increased heterotrophic CO _2 production. Thus, colder winter soils, as a result of reduced snow cover, can substantially alter C-dynamics in boreal forests by reducing summer soil CO _2 efflux, and increasing DOC losses.

Keywords

• summer season
• carbon dynamics
• boreal forest
• heterotrophic CO2 production
• dissolved organic carbon
• soil frost