Carbon content of below–ground biomass of young Scots pines in Latvia
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Forest ecosystems play crucial role in global carbon cycling, therefore, increasing afforestation of agricultural land in Europe has been recognized as important contribution of carbon sequestration. In carbon reporting systems, root carbon content (CC) default value has been set to 50%. The study aimed to estimate CC in below–ground biomass and in relation to tree age in young Scots pine stands on forest and former agricultural land. The below–ground CC of young (8 to 40 years) managed Scots pine (Pinus sylvestris L.) stands growing on nutrient poor mineral soils in Latvia was carried out. In total 62 sample trees (43 in forest land, 19 in former agricultural land) were randomly selected for destructive sampling to estimate the CC within below–ground biomass. Below–ground biomass weighted mean CC was 49.7 ± 0.4%, being slightly lower than the default CC value used to calculate carbon budgets. Root fractions stump, small roots (diameter 2–20 mm), coarse roots (diameter > 20 mm)) differed (p < 0.001) in their CC. Stumps (50.6 ± 0.6%) had highest (p < 0.001) CC in the below–ground biomass, followed by coarse (49.5 ± 0.4%) and small (49.1 ± 0.4%) roots, which did not differ from each other in their CC. Results demonstrated age–dependent increase of CC (p < 0.001) from 48.2 ± 0.3% to 51.7 ± 0.5%, indicating overestimation of the default value during the first two decades, but underestimation for older trees (24 to 40 years).