Since the industrial revolution, human activities have significantly altered the energy fluxes as well as biogeochemical cycles of carbon (C) and nitrogen (N) in the Earth system, affecting climate by increasing atmospheric concentrations of carbon dioxide (CO₂), nitrous oxide (N₂O) or methane (CH₄). To mitigate global climate change and avoid its catastrophic consequences, countries have set targets to achieve net-zero greenhouse gas (GHG) emissions by the mid-21st century (van Soest et al., 2021). Forest-based practices (e.g., reforestation, forest management) are the most cost-effective and readily applicable climate solutions (Griscom et al., 2017). Assessing the spatially and temporally variable GHG fluxes in forests is therefore fundamental for accurate national inventories and effective management of GHGs.

Forests cover ~15% of the land area in Denmark. In 2022, forests absorbed ~3 million tons of CO₂ eqv., thus offsetting all the GHG emissions from other land cover types (Nielsen et al., 2024). Danish forest area has been increasing since 1990 as a result of the afforestation projects, and another 1 billion trees are expected to be planted in the next two decades (Ministeriet for Grønt Trepart, 2024). The carbon sequestration capacity of Danish forests is expected to increase further, although the spatiotemporal variations of GHG fluxes remain unclear.

In this project, we aim to derive spatially and temporally explicit estimates of GHG fluxes in Danish forests using the LandscapeDNDC model. LandscapeDNDC is a process-based model specialized in the simulation of biogeochemical cycles (Haas et al., 2013). Compiled C and N flux observations from global forests (Cen et al., 2024a; Cen et al., 2025; Cen et al., 2024b) will be used to calibrate and validate the model simulations. This study will contribute to a more accurate national GHG inventory in Denmark. The results, in combination with other ongoing projects in the Center (such as the farm modelling project), will have implications for localized GHG management strategies and for producing global GHG budgets.