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Biochar has been widely researched as an important technology for climate smart agriculture, yet work is still necessary to identify the magnitude of potential greenhouse gas (GHG) mitigation and mechanisms involved. This study measured slow-pyrolysis wood-derived biochar's impact on GHG efflux, mineral N dynamics, and soil organic C in a series of two incubations across fertilized and unfertilized agricultural soils and soil moisture regimes. This research explored the magnitude of biochar's full GHG mitigation potential and drivers of such impacts. Results of this incubation indicate slow-pyrolysis wood-derived biochar has potential to provide annual emission reductions of 0.58-1.72 Mg CO 2 -eq ha À1 at a 25 Mg ha À1 biochar application rate. The greatest GHG mitigation potential was from C sequestration and nitrous oxide (N 2 O) reduction in mineral N fertilized soils, with minimal impacts on N 2 O emissions in unfertilized soils, carbon dioxide (CO 2 ) emissions, and methane (CH 4 ) uptake. Analysis of mineral N dynamics in the bulk soil and on biochar isolates indicated that neither biochar impacts on net mineralization and nitrification nor retention of ammonium (NH þ 4 ) on biochar isolates could explain biochar's N 2 O reduction. Instead, biochar amendments exhibited consistent N 2 O emission reductions relative to the N 2 O emission in the control soil regardless of soil type and fertilization. Results across a soil moisture gradient suggest that woody biochar may aerate soils shifting redox conditions and subsequent N 2 O production. Understanding the magnitude of biochar's GHG reduction potential and the mechanisms driving these effects can help inform biochar modeling efforts, explain field results and identify agricultural applications that maximize biochar's full GHG mitigation potential.

Germany, as an Annex I Party is expected to prepare and submit annual Greenhouse Gas (GHG) Inventories of emissions and removals, including Land Use, Land-Use Change, and Forestry (LULUCF) sector. Uganda, a non-Annex 1 party, is institutionalizing a sustainable national GHG inventory system. The LULUCF sector is a key emission source and plays a vital role in these two countries’ GHG inventories. This research analyzes the differences between applied LULUCF methodologies in Uganda as a developing country and Germany as a developed country with a particular focus on the forestry sector. It further analyzes the root cause factors for the different approaches, existing gaps and gives recommendations for future inventory improvement. The intricate institutional, policy framework, expertise, and applied methodological approaches for carbon change estimations in biomass pools are analyzed. Uncertainty analysis and time-series consistency process is reviewed with regard to how the countries’ quality assurance/control (QA/QC) and verification approaches adhere to the transparency framework. Resource limitations and data collection challenges dictate that Uganda uses the tier 1 methodological approach for emissions inventory. Consolidation and institutionalization of the GHG process will improve inventory accuracy while enhancing adherence to climate commitments. Germany uses higher tiers. Besides, government support for planned improvements using the recently developed country-specific biomass functions for estimating belowground biomass of silver birch, oak, and Scotch pine tree species will be essential for improving inventory quality. Operationalization of the inventory plan (IP) will be critical in driving inventory improvements geared towards time-series consistency, comparability, and transparency.