Soil respiration across a managed forest chronosequence in southern Sweden

Soil respiration is a major pathway by which terrestrial carbon returns to the atmosphere, although knowledge about its variation across forest stand age classes is limited. Forest stand age is considered a key factor influencing forest-floor CO₂ fluxes, however, previous studies report contrasting patterns for heterotrophic respiration – ranging from no effect to increases with age. Improving our understanding of these dynamics is essential for reducing uncertainties in forest carbon balance and informing sustainable management strategies.

We present ongoing work based on manual chamber measurements of CO₂ efflux across ten managed Norway spruce forest stands in northeastern Skåne, Sweden, spanning a chronosequence from recent clear-cut to mature stands (0 to ~120 years). Monthly measurements began in summer 2024 to capture seasonal cycles across all stands, providing a unique dataset to explore how forest development influences soil respiration. Each stand includes untreated reference plots and root-exclusion treatments, enabling future partitioning of autotrophic and heterotrophic respiration. Preliminary results indicate differences among age classes, with younger stands exhibiting higher summer CO₂ fluxes compared to older stands, although variability remains high. These patterns may reflect differences in root contribution, soil organic matter pools and microclimatic conditions across the chronosequence.

This study is part of a larger research effort aimed at identifying the stand age at which optimum carbon uptake occurs and evaluating rotation forestry against alternative management practices, such as continuous cover forestry. By contributing empirical observations from a managed forest landscape, this study also aims to reduce uncertainties in carbon flux estimates and support improved parameterization of vegetation models. Ultimately, these findings will inform assessments of forest carbon balance and, in turn, support policy and climate mitigation strategies and offer insights relevant to harvest planning and stand rotation decisions.