[A-CG35] Global Carbon Cycle Observation and Analysis

[ACG35-02] The role of plant regrowth in recent enhancement of terrestrial carbon uptake

*Masayuki Kondo¹, Kazuhito Ichii^1,2, Prabir K Patra³, Benjamin Poulter^4,5, Leonardo Calle⁵ (1. Center for Environmental Remote Sensing, Chiba University, 2.National Institute for Environmental Studies, 3.Japan Agency for Marine-Earth Science and Technology,, 4.NASA Goddard Space Flight Center, 5.Montana State University)

Keywords:carbon budget, plant regrowth, land use change

Attributing drivers of net carbon uptake in detail leads to clarification of causes for the recent enhancement of carbon dioxide (CO₂) uptake by the terrestrial biosphere. The increasing strength of the land uptake in the 2000s has been attributed so far to a stimulating effect of rising atmospheric CO₂ on photosynthesis (CO₂ fertilization). However, it is still arguable whether the CO₂ fertilization is a dominant cause for the recent enhancement of CO₂ uptake because, in addition to the level of atmospheric CO₂, the terrestrial biosphere has undergone historical changes through land use and management. CO₂ emissions resulting from LUC activities account for ~9% of the total global anthropogenic CO₂ emissions, therefore changes in LUC could affect the course of the net sink-source pattern of CO₂ over time.

Here using an ensemble of biosphere models, we show a decadal-scale carbon uptake enhancement is induced not only by CO₂ fertilization, but also an increasing uptake by plant regrowth from past land use changes (LUC), with its effect most pronounced in eastern North America, southern and eastern Europe, and southeastern temperate Eurasia. Our analysis indicates that ecosystems in North America and Europe have established the current productive state through regrowth over a half-century, and those in temperate Eurasia are still in a recovering stage from active LUC in the 1980s. As the strength of model representation of CO₂ fertilization is still in debate, plant regrowth might have a greater potential to sequester carbon than indicated by this study.