Impact of heat and water stress on SIF: from tower-based observation at a temperate forest

Abstract:

Rising air temperature (T_a) and atmospheric dryness (vapor pressure deficit, VPD) are major phenomena predicted to occur in many regions as a part of climate change, which will intensify the drought impact. Both environmental drivers are closely related to plant carbon uptake by influencing stomatal regulation and other metabolic processes. They can act as stressors to plants if they are outside the optimal range for plants, which can result in reduced carbon uptake. Meanwhile, measurements of solar-induced chlorophyll florescence (SIF) has gained its popularity for its ecophysiological link with GPP, although how SIF responds to rising T_a and VPD has not rarely been studied. In this study, we address this question based on continuous canopy-scale tower-based measurement of SIF (Fluospec2 system) at a temperate forest located in Virginia from 2019 to 2020. Specifically, we show directional change in SIF-PAR relationship with changing T_a and VPD, suggesting significantly sensitive florescence yield to increasing heat and water stress. This work provides evidence that SIF could be used to monitor vegetation response to changing T_a and VPD.