Boyu Ren

Accurate monitoring of vegetation phenology is vital for understanding climate change impacts on terrestrial ecosystems. While global vegetation greenness phenology (VGP) products are widely available, vegetation productivity phenology (VPP), which better reflects ecosystems’ carbon dynamics, remains largely inaccessible. This study introduces a novel global 500 m VPP dataset (GLASS VPP) from 2001 to 2020, derived from the GLASS gross primary productivity (GPP) product. Validation against three ground-based datasets—Fluxnet 2015, PhenoCam V2.0, and PEP725—demonstrated the dataset’s superior accuracy. Compared to the widely used MCD12Q2 VGP product, GLASS VPP reduced RMSE and bias by 35% and 63%, respectively, when validated against Fluxnet data. It also showed stronger correlations than MCD12Q2 when compared with PhenoCam (195 sites) and PEP725 (99 sites) observations, and it captured spatial and altitudinal phenology patterns more effectively. Overall, GLASS VPP exhibits a higher spatial integrity, stronger ecological interpretability, and improved consistency with ground observations, making it a valuable dataset for phenology modeling, carbon cycle research, and ecological forecasting under climate change.

Rapid Arctic warming is driving significant changes in boreal vegetation phenology and productivity. The potentially asynchronous response of these processes could substantially alter the relative impacts of phenological shifts on variations in gross primary productivity (GPP), but this remains poorly understood. The objective of this study is to quantify the impact of phenology extension on boreal ecosystem GPP changes across different periods from 1982 to 2018. To achieve this, we developed a statistical model that integrates vegetation phenology and physiology, and introduced a new metric, the Relative Increment Effect (RIE), to assess the contribution of phenology extension to GPP increase. Our analysis revealed that phenology extension became the dominant driver of GPP increment over time. Specifically, the overall RIE for boreal vegetation increased by 22% from the earlier period (P1: 1982–2000, 3.2) to the more recent period (P2: 2001–2018, 3.93). This increase was more pronounced for grass and shrub ecosystems. Spatial patterns showed that RIE increases were particularly concentrated at high latitudes, especially in northern Siberia. These findings suggested that phenology extension was playing an increasing role in regulating boreal ecosystem productivity, with significant implications for the boreal carbon budget under future warming scenarios.