Sanitation Logging Against Spruce Bark Beetles Raises Boreal Soil Carbon Loss in Finnish Study

A decade-long field study in southeastern Finland finds that clear-cut sanitation logging against the European spruce bark beetle can increase soil carbon loss in Norway spruce stands. Logged plots had higher soil temperatures, lower carbon and nitrogen in the humus layer, and faster breakdown of resistant organic material than undisturbed forests. Beetle-killed stands left unmanaged kept more organic matter, suggesting the standard pest response may worsen the boreal soil carbon balance. The study compared undisturbed mature stands, unmanaged beetle-killed stands, and sanitation-logged clear-cuts about ten years after a storm triggered an Ips typographus outbreak. Soil sampling and tea bag decomposition tests showed that removing the canopy warmed the soil and accelerated organic matter decay. For forest managers and carbon accounting, this is a concrete reminder that pest control actions have below-ground climate consequences that need to be weighed alongside timber protection.