Vegetation phenology in the northern hemisphere based on the solar-induced chlorophyll fluorescence

Abstract

Aims Vegetation phenology is an important indicator to reflect the stages of vegetation growth, which is of great significance to the feedback to climate. Solar-induced chlorophyll fluorescence (SIF) is a by-product of photosynthesis, which provides the possibility to directly detect vegetation phenology at the global scale. In order to reveal the accuracy of phenology estimated by SIF of different forest types, we estimated phenology of three forest types in the Northern Hemisphere. Methods Based on 35 eddy flux tower sites in the Northern Hemisphere during the period of 2007-2014, we estimated phenology of three typical forest types using SIF value and gross primary production (GPP) by double logistic growth model and dynamic threshold. Correlation analysis was used to evaluate the different potential of SIF in estimating phenology of different forest types. Important findings Results showed that: (1) SIF was more suitable to estimate the timing of the start of growing season (SOS) than the timing of the end of growing seasons (EOS). (2) SOS based on SIF had the highest correlation with SOS based on GPP in mixed forests (MF). However, the SOS of deciduous broadleaf forest (DBF) and Evergreen Needleleaf forest (ENF) could not be accurately tracked by SIF value. (3) The preseason shortwave radiation (SR) was the primarily environmental factor of SOS.