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- Bolinder, Martin, et al.
(author)
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Implementing a new version of ICBM in NIR
- 2019
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Reports (other academic/artistic)abstract
- In the sector Land Use, Land-Use Change and Forestry (LULUCF, CRF sector 4) within the national greenhouse gas inventory (NIR), Sweden is applying a Tier 3 method for estimating the loss or gain of soil organic carbon (SOC) stocks for cropland on mineral soils to a depth of 0.25 m. The Introductory Carbon Balance Model (ICBM) is used for calculating stock change rates in eight agricultural production regions and results are aggregated to the national level. Calculations involves yearly agricultural census data and daily weather records, as well as results from a national soil-monitoring program (SMP) on soil carbon contents. Initially, only data from the first sampling of the national SMP were used for initializing ICBM. Since the first soil inventory, two additional samplings within the SMP have become available. Simultaneously, we have also gained more knowledge about SOC dynamics. In a development project last year, we were re-analyzing the complete records of data from the last two decades of the SMP confirming that SOC stocks are increasing, and we were starting to calibrate a new version of ICBM. The purpose of the project this year was to implement the new ICBM version in the NIR system.The results show that the new version of ICBM simulates increasing SOC stocks for the period 1990 to 2018, which is thereby more consistent with estimates from the national SMP data than results obtained using the previous ICBM version. The ICBM and SMP assessment methods of SOC stock changes are complementing each other, and both have their inherent limitations. Our analysis with both methodologies are still not fully completed. There remain some fine-tuning in the new ICBM version. Furthermore, we are continuously working on improving the interpretation regarding SOC stocks in the current database from the national SMP. Maintaining the latter and repeating the sampling at least once more would also substantially improve the value of this database.
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