Soil organic carbon (SOC) is a mandatory pool in national inventory reports on greenhouse gas (GHG) emissions and removals to the UNFCCC. Hence, its accurate assessment is important. Modelling SOC changes for national GHG reports is encouraged, but the uncertainty related to this pool still presents a significant challenge; thus, verifying modelling results with field observations is essential. We used the process-based model Biome-BGCMuSo and assessed its suitability for use in Croatia’s GHG reporting. We modelled SOC stocks in the top 30 cm of the mineral soil layer (SOC₃₀) for four different land-use (LU) categories (Deciduous/Coniferous Forest, Grassland and Annual Cropland) distributed in three biogeographical regions (Alpine, Continental and Mediterranean) and compared them with results of a national soil survey. A total of 573 plot level simulations were undertaken and results were evaluated at three stratification levels (LU, LU × biogeographical region, and plot). The model reproduced the overall country mean of SOC₃₀ with no overall bias, and showed good performance at the LU level with no significant (p < 0.05) difference for all LUs except Deciduous Forest (11% overestimation). At finer stratifications, the model performance considerably worsened. Further model calibration, improvement and testing, as well as repeated soil survey are needed in order to assess the changes in SOC₃₀ and to evaluate the potential of the Biome-BGCMuSo model for use in GHG reporting.

中文翻译：

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陆地生态系统模型Biome-BGCMuSo在不同土地利用下模拟土壤有机碳的评价

土壤有机碳 (SOC) 是向 UNFCCC 提交的关于温室气体 (GHG) 排放和清除的国家清单报告中的强制性集合。因此，其准确的评估很重要。鼓励为国家温室气体报告模拟 SOC 变化，但与此池相关的不确定性仍然是一个重大挑战；因此，必须通过实地观察来验证建模结果。我们使用了基于流程的模型 Biome-BGCMuSo 并评估了其在克罗地亚温室气体报告中的适用性。我们模拟了矿质土壤层前 30 厘米 (SOC ₃₀) 分布在三个生物地理区域（高山、大陆和地中海）的四种不同土地利用 (LU) 类别（落叶/针叶林、草地和一年生农田），并将它们与国家土壤调查的结果进行比较。总共进行了 573 个地块级模拟，并在三个分层级别（LU、LU × 生物地理区域和地块）评估结果。该模型在没有总体偏差的情况下再现了 SOC ₃₀的总体国家平均值，并且在 LU 水平上表现良好，没有显着性（p< 0.05) 除落叶林外的所有 LU 的差异（高估 11%）。在更精细的分层中，模型性能显着恶化。需要进一步的模型校准、改进和测试以及重复的土壤调查，以评估 SOC ₃₀的变化并评估 Biome-BGCMuSo 模型用于温室气体报告的潜力。