The impact of phenological shifts on carbon uptake across major terrestrial biomes

Abstract

Changes in climate are altering plant growth patterns and associated phenological events like the Start of Season (SOS), End of Season (EOS), and Length of the Growing Season (LGS). However, there is limited research quantifying the impact of these changes on key vegetation-atmospheric interaction processes such as the carbon and water cycles. This study uses 914 site years of data across 132 flux tower sites in the FLUXNET2015 dataset to explore the relationships between carbon sequestration, expressed by Gross Primary Productivity (GPP), and multiple phenological variables, including LGS, changes in SOS (ΔSOS), and changes in EOS (ΔEOS). LGS explains 23% of the variability in GPP across all sites. Significant correlations were found in deciduous broadleaf forests (R² = 0.5) and evergreen needleleaf forests (R² = 0.44), while ecosystems such as shrublands, savannas, and wetlands displayed weaker connections. Changes in the SOS also affected GPP, with an earlier SOS increasing the total annual GPP. Deciduous Broadleaf Forests (R² = 0.54), Evergreen Needleleaf Forests (R² = 0.5), Grasslands (R² = 0.47) showed a significant negative association between ΔSOS and ΔGPP, whereas Croplands showed weaker correlations. Conversely, EOS variations had little impact on GPP. Upscaled to global vegetated land area these relationships suggest that each additional day in the growing season could increase carbon uptake by 1.035 Gt C yr-1, while an earlier SOS by 0.93 Gt C yr-1 and a one-day delay in EOS by approximately 0.65 Gt C yr-1. These findings underscore the need to account for seasonal shifts and phenological changes in global carbon models.

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Identifiers

ORCID for Getachew Mulualem: orcid.org/0000-0002-6488-4402

ORCID for Jadu Dash: orcid.org/0000-0002-5444-2109

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