Compound soil and atmospheric drought (CSAD) events and CO 2 fluxes of a mixed deciduous forest: the occurrence, impact, and temporal contribution of main drivers

作者：Liliana Scapucci, Ankit Shekhar, Sergio Aranda-Barranco, Anastasiia Bolshakova, Lukas Hörtnagl, Mana Gharun, Nina Buchmann · 发表于：Biogeosciences · 年份：2024 · DOI：10.5194/bg-21-3571-2024 · 被引用次数：17 · 研究领域：Plant Water Relations and Carbon Dynamics、Forest ecology and management、Plant responses to elevated CO2

Abstract. With global warming, forests are increasingly exposed to “compound soil and atmospheric drought” (CSAD) events, characterized by low soil water content (SWC) and high vapour pressure deficit (VPD). Such CSAD events trigger responses in both ecosystem and forest-floor CO2 fluxes, which we know little about. In this study, we used multi-year daily and daytime above-canopy (18 years; 2005–2022) and daily forest-floor (5 years; 2018–2022) eddy covariance CO2 fluxes from a Swiss forest site by the name of CH-Lae (a mixed deciduous montane forest). The objectives were (1) to characterize CSAD events at CH-Lae, (2) to quantify the impact of CSAD events on ecosystem and forest-floor CO2 fluxes, and (3) to identify the major drivers and their temporal contributions to changing ecosystem and forest-floor CO2 fluxes during CSAD events and CSAD growing seasons. Our results showed that the growing seasons of 2015, 2018, and 2022 were the three driest at CH-Lae since 2005 (referred to as the CSAD years), exhibiting similar intensity and duration of the CSAD events but considerably different pre-drought conditions. The CSAD events reduced daily mean net ecosystem productivity (NEP) in all 3 CSAD years by about 38 % compared to the long-term mean, with the highest reduction observed during 2022 (41 %). This reduction in daily mean NEP was largely due to decreased gross primary productivity (GPP; > 16 % below the long-term mean) rather than increased ecosystem respiration (Reco) ...