Belowground biomass, production, and carbon cycling in mature Norway spruce, Maine, U.S.A.

Abstract

Two 55-year-old stands of Norway spruce (Picea abies (L.) Karst.) were sampled to determine belowground biomass, production and decomposition of fine and small roots, litterfall and litter decay rates, soil respiration rates, and carbon cycling patterns. Mean biomass of live fine (<1 mm) Norway spruce roots to a soil depth of 40 cm was 359 ash-free dry g·m–2, whereas biomass of live fine + small roots ([Formula: see text]3 mm) amounted to 561 g·m–2. Mean root production averaged 297 g·m–2·year–1 for roots <1 mm and 418 g·m–2·year–1 for roots [Formula: see text]3 mm. By comparison, needle litter production was 205 g·m–2·year–1. Norway spruce roots [Formula: see text]3 mm decomposed at a rate of 9.5% of total root mass per month during the growing season, compared with a needle litter annual decay rate of 22.3%·year–1. A partial carbon budget for Norway spruce indicated that annual needle litterfall mass was 98 g C·m–2·year–1, and annual carbon release from fresh litter decay was approximately 22 g·C·m–2·year–1. During the growing season, monthly CO2 flux from soil respiration was 69 g C·m–2·month–1, belowground C allocation to net production of roots [Formula: see text]3 mm was 33.5 g C·m–2·month–1, and C release from decomposition of roots [Formula: see text]3 mm was 31 g C·m–2·month–1. These values were also extrapolated to annual estimates of C fluxes.