Carbon fluxes controlled by land management and disturbances at a cluster of long-term ecosystem monitoring sites in Central Europe

Terrestrial ecosystems play a crucial role in carbon sequestration and provide vital ecosystem services such as food, energy, and raw materials. Climate change, through rising temperatures, altered precipitation patterns, and extreme events, threatens the carbon sink potential of these ecosystems, with forests and grasslands particularly at risk. Long-term data from flux tower networks offer valuable insights into how different ecosystems respond to climate change and management interventions, helping to develop strategies to mitigate greenhouse gas emissions and maintain ecosystem resilience. In this study, we present such data from a <10 km cluster of long-term FLUXNET/ICOS sites in Central Europe, comprising an old spruce forest (DE-Tha), a young oak plantation after a cleared windthrow (DE-Hzd), a permanent grassland site (DE-Gri), and an agricultural site with a crop rotation typical for this region (DE-Kli). By analysing decades of data from these four eddy covariance measurement sites, the research highlights the influence of drought, management, and land cover changes on CO₂ and H₂O fluxes. The interannual variability of evapotranspiration depends less on land use than the CO₂ exchange. Our findings show that  forests without terminal disturbances can act as larger carbon sinks than previously estimated. DE-Tha is a consistent carbon sink, with thinning helping to maintain the CO₂ sequestration at a stable level of 350 gC m⁻² a⁻¹. In contrast, disturbances like clear cutting or windthrow can cause ecosystems to become carbon sources for several years, with recovery delayed due to soil carbon losses from increased respiration (DE-Hzd). While DE-Hzd was resilient to drought, the carbon uptake of DE-Tha was significantly reduced by around 50% during dry years compared to wet years. Furthermore, sustainable management maintains carbon sequestration and land-use practices, such as crop selection, significantly impact net ecosystem productivity. These insights are valuable for optimizing land management strategies to enhance carbon sinks in similar regions.