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Forest ecosystems play a crucial role in mitigating climate change through carbon (C) sequestration (i. e. , photosynthesis). However, the increasing frequency and intensity of climate extremes, especially heatwaves and drought events, are affecting the balance between C uptake and C loss in terrestrial ecosystem, resulting in decreasing CO2 sequestration from the atmosphere and storage as plant biomass. Reaching the ecosystem tipping point, with the consequent transition from carbon sinks to carbon sources, is a concrete risk. Climate change has the potential to alter different forest processes in complex ways, showing high variability across space and time, and impacting ecological processes at different spatial scales, from the individual trees to the whole ecosystem. The structure of forests and the diversity in vegetation distribution may act as a form of insurance against these environmental changes, but the understanding of the mechanisms behind forest resistance and resilience to climate change require further investigation. The primary objective of the present study is to establish a quantitative link between the functional and structural properties of a European larch forest located in the Western Alps, within the Aosta Valley (Italy) at an altitude of around 2100 meters a. s. l. (Larix decidua Mill. , IT-Trf, LTER site: LTEREUIT₀78). To achieve this goal, the study take advantage of different methods. The main approach is represented by the eddy covariance method to measure C fluxes at two levels: 1) whole forest ecosystem and 2) understory vegetation. Biometric measurements of tree growth, performed in 2020, aimed at quantifying the carbon allocated to the wood biomass as structural carbohydrates. Additionally, satellite and UAV-based LiDAR observations were used to analyse the structure and composition of various vegetation layers. Results revealed that only a small fraction of the total CO2 sequestered by the ecosystem contributes to tree stem growth. Furthermore, due to the openness of the larch forest stand, the understory vegetation accounts for approximately 30% of the total ecosystem's gross primary productivity. These findings underscore the intricate relationship between forest structure, overall ecosystem function, and the specific roles played by various vegetation components.
Oddi et al. (Mon,) studied this question.