Significance of Over-Mature and Decaying Trees for Carbon Stocks in a Central European Natural Spruce Forest

Abstract

Old-growth forests are important stores for carbon as they may accumulate C for centuries. The alteration of biomass and soil carbon pools across the development stages of a forest dynamics cycle has rarely been quantified. We studied the above- and belowground C stocks in the five forest development stages (regeneration to decay stage) of a montane spruce (Picea abies) forest of the northern German Harz Mountains, one of Central Europe’s few forests where the natural forest dynamics have not been disturbed by man for several centuries. The over-mature and decay stages had the largest total (up to 480 Mg C ha−1) and aboveground biomass carbon pools (200 Mg C ha−1) with biomass C stored in dead wood in the decay stage. The soil C pool (220–275 Mg C ha−1, 0–60 cm) was two to three times larger than in temperate lowland spruce forests and remained invariant across the forest dynamics cycle. On the landscape level, taking into account the frequency of the five forest development stages, the total carbon pool was approximately 420 Mg C ha−1. The results evidence the high significance of over-mature and decaying stages of temperate mountain forests not only for conserving specialized forest organisms but also for their large carbon storage potential.