Understanding the exchange processes between terrestrial ecosystems and the atmosphere above is crucial for mitigating climate change and promoting ecosystem resilience. Over the past decade, I have investigated the land-atmosphere interactions with regard to energy, water vapor, and CO₂ fluxes in various ecosystems, including forests, croplands, and grasslands, at different spatial and temporal scales. In this lecture, I will present recent results of a near-natural mixed-beech forest in the National Park Hainich in central Germany. Based on a comprehensive long-term dataset of eddy covariance flux observations, we conducted statistical time series analysis to investigate the exchange processes of this diverse, near-natural ecosystem. Furthermore, in collaborations with various partner institutions additional observations are being obtained at this flux study site, such as drone imagery, terrestrial laser scans, vegetation optical depth, forest biomass inventory, phenological photos, and on tree-scale records of stem growth, sapflow and leaf water potential. Using this multi-scale dataset, we aim to improve our understanding of the link between forest exchange processes and tree response dynamics, as well as the impact of extreme weather events (e.g., droughts).

The Hainich forest represents a large carbon sink prevailing throughout the past 26 years. However, the ongoing warming trend is altering the start and duration of the growing season of trees and the herbal layer. Tree vitality is being impacted by diseases and recent drought events such as in 2018-2020 have changed the forest’s processes and dynamics. We observed an increase in the canopy gap fraction in 2021 indicating a significant increase in tree mortality. Surviving trees were affected differently by the droughts depending on their species, age, and competition. In particular, the growth of older and larger trees (mostly ash), was impaired during and after the drought period, resulting in a reduction of the overall CO₂ uptake strength of the forest ecosystem between 2018 and 2022. However, about half of the observed trees, mostly suppressed, vital beech trees, showed a positive growth trend during and after the drought period. The given structural diversity influences the responses and resilience of individual trees and the entire ecosystem. The comprehensive dataset further provides an opportunity to investigate the influence of climate and soil characteristics and of forest management on flux exchange processes within multi-site comparison studies.

How to cite: Klosterhalfen, A.: Flux exchange of a near-natural temperate deciduous forest under drought stress, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12627, https://doi.org/10.5194/egusphere-egu26-12627, 2026.

EGU26-12627

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Roughly 90% of the organic carbon (OC) buried in the global ocean is stored in muddy sediments along continental margins. Estuarine "hotspots" are especially important, with deltas accounting for about 40% of this burial and fjords for around 12%. To understand the sources and fate of OC in aquatic systems, researchers have widely applied molecular biomarkers and bulk geochemical proxies. In my work, I will explore the application of both bulk analytical techniques and molecular biomarkers to investigate how environmental changes across the land–to-ocean aquatic continuum (LOAC) are influencing OC burial and long-term carbon sequestration.  These muds produced by rock weathering play a critical role in the global carbon cycle by binding and shielding OC from degradation. The quantity and characteristics of OC stored in these muds influence the extent, duration, and mechanisms of carbon sequestration.

Human activities, including dam construction, levee building, and climate change, have profoundly reshaped patterns of mud accumulation and organic carbon (OC) storage across diverse environments. I demonstrate that climate warming has generally increased mud–OC fluxes through processes such as glacier melt, enhanced erosion, and dam-driven sediment burial, although these effects vary regionally. From 1950 to 2010, dams reduced global riverine sediment delivery to the oceans by approximately 49%, despite rising upstream sediment loads, trapping an estimated ~60 TgC yr⁻¹ of organic carbon. At the same time, global coastal wetlands experienced a net loss of about 4,000 km² between 1999 and 2019, yet they continue to sequester substantial amounts of carbon (up to ~60 TgC yr⁻¹). In the Arctic, warming has accelerated permafrost erosion, mobilizing roughly 14 TgC yr⁻¹. Together, these examples highlight the complex and often competing influences of human activity and climate change on river systems and the global carbon cycle, with coastal zones emerging as both highly vulnerable and critically important for carbon sequestration. However, whether these changes ultimately enhance or diminish long-term OC storage remains uncertain, given the complexity and variability of the processes and timescales involved.

How to cite: Bianchi, T.: Carbon Processing in the Land-to-Ocean Aquatic Continuum (LOAC): Challenges in the 21st Century, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12722, https://doi.org/10.5194/egusphere-egu26-12722, 2026.

EGU26-12722

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