Light limitation regulates the response of autumn terrestrial carbon uptake to warming
Abstract
Global warming is projected to shift the phenology and increase the productivity of northern ecosystems. Both changes will further feedback to climate through biophysical and biogeochemical processes, and are critical for the prediction of future climate. However, whether warming and the extended growing season, especially in autumn, would lead to increased net ecosystem carbon uptake remains unclear. Here we analyze satellite observations, field measurements, and model simulations and show a prevalent radiation limitation on carbon uptake in northern ecosystems, especially in autumn. By comparing the start and end of growing season estimated from vegetation indices and solar induced chlorophyll fluorescence (a proxy for gross primary production, GPP), we find a greater change in greenness-based start and end of season than that from GPP, which is mostly caused by the radiation limitation on photosynthesis. This radiation limitation further explains the either positive or negative response of autumn net carbon exchanges to warming, using both eddy covariance measurements and model simulations from CMIP5. Regions with weak radiation limitation benefit more from warming and enhanced vegetation greenness in autumn, where GPP increases can outweigh the warming-induced respiration carbon losses. With continued warming, radiation limitation will increase and exert a strong upper bound on northern ecosystems to act as carbon sinks.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B11G2339Z
- Keywords:
-
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0480 Remote sensing;
- BIOGEOSCIENCES;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE