Photoperiodic regulation of the seasonal pattern of photosynthetic capacity and the implications for carbon cycling

Abstract

Although temperature is an important driver of seasonal changes in photosynthetic physiology, photoperiod also regulates leaf activity. Climate change will extend growing seasons if temperature cues predominate, but photoperiod-controlled species will show limited responsiveness to warming. We show that photoperiod explains more seasonal variation in photosynthetic activity across 23 tree species than temperature. Although leaves remain green, photosynthetic capacity peaks just after summer solstice and declines with decreasing photoperiod, before air temperatures peak. In support of these findings, saplings grown at constant temperature but exposed to an extended photoperiod maintained high photosynthetic capacity, but photosynthetic activity declined in saplings experiencing a naturally shortening photoperiod; leaves remained equally green in both treatments. Incorporating a photoperiodic correction of photosynthetic physiology into a global-scale terrestrial carbon-cycle model significantly improves predictions of seasonal atmospheric CO2 cycling, demonstrating the benefit of such a function in coupled climate system models. Accounting for photo-period-induced seasonality in photosynthetic parameters reduces modeled global gross primary production 2.5% (similar to 4 PgC y(-1)), resulting in a >3% (similar to 2 PgC y(-1)) decrease of net primary production. Such a correction is also needed in models estimating current carbon uptake based on remotely sensed greenness. Photoperiod-associated declines in photosynthetic capacity could limit autumn carbon gain in forests, even if warming delays leaf senescence.

Keywords

day length; gross primary productivity; carbon sequestration; leaf area index; evapotranspiration

Published in

Proceedings of the National Academy of Sciences
2012, Volume: 109, number: 22, pages: 8612-8617 Publisher: NATL ACAD SCIENCES

SLU Authors

• Oren, Ram

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

SDG13 Climate action


UKÄ Subject classification

Forest Science


Publication identifier

DOI: https://doi.org/10.1073/pnas.1119131109

Permanent link to this page (URI)

https://res.slu.se/id/publ/41096