Vegetation phenology, the cycle sequence of the vital activities, is a highly sensitive indicator of the climate impacts on terrestrial ecosystems. Most recent studies focus on the structural changes of plants, such as using the growth process of leaves represented by the greenness indicators. However, these indices work well for capturing the variations in chlorophyll content or structural changes but are less sensitive to physiological changes in vegetation photosynthesis. Therefore, the inaccurate estimation of vegetation greenness-based phenology can lead to substantial uncertainties in estimating plant productivity and carbon sequestration.

Researchers of the Global Change Ecology Group at Wuhan Botanical Garden developed a method combining a smoothing filter and change-point detection to retrieve photosynthetic phenology from a recently developed satellite-based solar-induced chlorophyll fluorescence (SIF)-based gross primary productivity (GPP) product (GOSIF-GPP: 2001-2020) with a 0.05° spatial resolution.

Several phenology metrics have been considered, including the state-transition dates of photosynthesis (SOS), the end state-transition dates of photosynthesis (EOS), and the duration length of photosynthesis (LOS) for terrestrial ecosystems above 30° N latitude (Northern Biomes, including forests, shrublands, savannas, grasslands, wetlands and croplands).

The dataset contains single-season and double-growing season phenology time, and the corresponding thresholds extracted by 10%, 25%, and 50%. Each data is compared to other vegetation indices or GPP data, and using the flux dataset to validate it.

This phenology product enables us to acquire multiple photosynthesis activity of vegetation, and helps for monitoring the climate change impacts on terrestrial ecosystems.

This work was supported by the National Natural Science Foundation of China, which has been published in Scientific Data entitled “Vegetation photosynthetic phenology dataset in northern terrestrial ecosystems”. (Published: 19 May 2023)

The spatial distribution of the mean photosynthetic phenology metrics (first growing season) in the Northern Biomes of 2001-2020 (0.05° spatial resolution). DOY: day of the year. The right parts are the latitudinal pattern. (Image by WBG)