Abstract :
[en] Forests, as vital carbon sinks, face mounting challenges due to the increasing frequency of extreme events. These events, particularly heatwaves, storms and droughts, highlight the need of understanding how forests respond to environmental stresses. To tackle this challenge, long-term studies provide a unique lens through which we can unravel the intricate dynamics of forest ecosystems and their relationship with climatic fluctuations. In this context, our research focuses on a 24-year dataset of continuous CO2 measurements from the recently ICOS-labelled Hesse site, a beech-dominated forest under temperate conditions in north-eastern France. We introduce a novel approach using the continuous wavelet transform, a time-frequency analysis tool, to define indicators of gross primary productivity (GPP) intra-annual dynamics. Our study uncovers critical temporal windows during which current or previous year meteorological conditions significantly impact beech photosynthetic activity and eco-physiological behavior. Notably, precipitations during a 1–2 week period in July-August emerges as a pivotal phase for next year’s GPP dynamics. Furthermore, radiation, air temperature, vapor pressure deficit, precipitations and soil water availability exhibit both short and long-term effects on GPP. Our proposed approach disentangles these influences, identifying dominant periods for each variable and their localized impact on GPP dynamics. By unraveling these correlations, our study provides insights supporting a comprehensive understanding of forest resilience and yields critical information for developing sustainable forest management strategies in response to shifting climate patterns.
