This study was designed to estimate the variation in non-volatile carbon (C) content in different above- and belowground tree parts (stem, living branches, dead branches, stumps, coarse roots and small roots) and to develop country-specific weighted mean C content values for the major tree species in hemiboreal forests in Latvia: Norway spruce (Picea abies (L.) H. Karst.), Scots pine (Pinus sylvestris L.), birch spp. (Betula spp.) and European aspen (Populus tremula L.). In total, 372 sample trees from 124 forest stands were selected and destructively sampled. As the tree samples were pre-treated by oven-drying before elemental analysis, the results of this study represent the non-volatile C fraction. Our findings indicate a significant variation in C content among the tree parts and studied species with a range of 504.6 ± 3.4 g·kg⁻¹ (European aspen, coarse roots) to 550.6 ± 2.4 g·kg⁻¹ (Scots pine, dead branches). The weighted mean C content values for whole trees ranged from 509.0 ± 1.6 g·kg⁻¹ for European aspen to 533.2 ± 1.6 g·kg⁻¹ for Scots pine. Only in Norway spruce was the whole tree C content significantly influenced by tree age and size. Our analysis revealed that the use of the Intergovernmental Panel on Climate Change (IPCC) default C content values recommended for temperate and boreal ecological zones leads to a 5.1% underestimation of C stock in living tree biomass in Latvia’s forests. Thus, the country-specific weighted mean C content values for major tree species we provide may improve the accuracy of National Greenhouse Gas Inventory estimates.

中文翻译：

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拉脱维亚半球森林主要树种碳含量的变化

本研究旨在估计不同地上和地下树木部分（茎、活枝、枯枝、树桩、粗根和小根）的非挥发性碳 (C) 含量的变化，并制定国家特定的加权平均值拉脱维亚半北方森林中主要树种的 C 含量值：挪威云杉 ( Picea abies (L.) H. Karst.)、苏格兰松 ( Pinus sylvestris L.)、桦树 spp. ( Betula spp.) 和欧洲白杨 ( Populus tremula L.）。总共从 124 个林分中选择了 372 棵样本树并进行了破坏性采样。由于在元素分析之前通过烘箱干燥对树木样品进行了预处理，因此本研究的结果代表了非挥发性 C 部分。我们的研究结果表明，树木部分和研究物种之间的 C 含量存在显着差异，范围为 504.6 ± 3.4 g·kg ^-1（欧洲白杨，粗根）至 550.6 ± 2.4 g·kg ^-1（苏格兰松、枯枝） ）。整棵树的加权平均 C 含量值范围从欧洲白杨的509.0 ± 1.6 g·kg ^-1到 533.2 ± 1.6 g·kg ^-1对于苏格兰松。只有在挪威云杉中，整棵树的 C 含量受树龄和大小的显着影响。我们的分析表明，使用政府间气候变化专门委员会 (IPCC) 为温带和北方生态区推荐的默认碳含量值导致拉脱维亚森林中活树生物量的碳储量被低估了 5.1%。因此，我们提供的主要树种的特定国家加权平均 C 含量值可能会提高国家温室气体清单估计的准确性。