Abstract
Old unmanaged forests are commonly assumed to be carbon neutral; however, there is still a lack of reference studies available to increase the recognition of carbon stock changes in these forests. Studies of old forest carbon storage from hemiboreal regions are very rare compared to temperate and boreal forests in Europe; therefore, the aim of this study was to quantify the carbon stock in hemiboreal over-mature (167–213 years) Norway spruce (Picea abies (L.) Karst.) stands. To explore the total ecosystem carbon pool, the carbon stock of tree biomass, deadwood, and soil in unmanaged (for at least the last 40 years) spruce stands was calculated and compared between different forest site types on dry, wet, and drained mineral soils. Total carbon stock of hemiboreal over-mature spruce stands ranged from 164.8 Mg C ha−1 to 386.7 Mg C ha−1, and 238.5 Mg C ha−1 on average, with no significant differences (p > 0.05) between the forest site types. The carbon stock of tree biomass was significantly affected by the basal area of the upper tree layer (p < 0.0001) and the interaction between the forest site type and proportion of spruce in the stand composition (p = 0.002). Tree biomass was the dominant carbon pool, followed by soil and deadwood in over-mature spruce stands.
Highlights
Framework Convention on Climate Change (UNFCCC), Kyoto Protocol, and Paris Agreement [1].Boreal forests are one of the biggest terrestrial carbon pools on Earth [2,3], storing carbon in the tree biomass and releasing it through decomposition, playing a significant role in global climate change mitigation [4,5]
The tree biomass was the dominant carbon pool in over-mature spruce forests, ranging greatly between the stands from 41% to 74% of total carbon stock. This corresponds with the results found in other old-growth forest studies [2,17]
Some significant differences were observed in tree and deadwood carbon pools due to variations in stand structure between the stands
Summary
Framework Convention on Climate Change (UNFCCC), Kyoto Protocol, and Paris Agreement [1]. Boreal forests are one of the biggest terrestrial carbon pools on Earth [2,3], storing carbon in the tree biomass and releasing it through decomposition, playing a significant role in global climate change mitigation [4,5]. Under unmanaged conditions, ageing forests slowly develop stand structures that are typical for old-growth forests [11]. In these conditions, species and age composition as well as the occurrence of natural disturbances play a key role in the formation of carbon stock and carbon fluxes [12,13,14]
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