Seasonality in photosynthetic activity is a critical component of seasonal carbon, water, and energy cycles in the Earth system. This characteristic is a consequence of plant's adaptive evolutionary processes to a given set of environmental conditions. Changing climate in northern lands (> 30 degrees N) alters the state of climatic constraints on plant growth, and therefore, changes in the seasonality and carbon accumulation are anticipated. However, how photosynthetic seasonality evolved to its current state, and what role climatic constraints and their variability played in this process and ultimately in carbon cycle is still poorly understood due to its complexity. Here, we take the "laws of minimum" as a basis and introduce a new framework where the timing (day of year) of peak photosynthetic activity (DOYPmax) acts as a proxy for plant's adaptive state to climatic constraints on its growth. Our analyses confirm that spatial variations in DOYPmax reflect spatial gradients in climatic constraints as well as seasonal maximum and total productivity. We find a widespread warming-induced advance in DOYPmax (-1.66 +/- 0.30 days/decade, p < 0.001) across northern lands, indicating a spatiotemporal dynamism of climatic constraints to plant growth. We show that the observed changes in DOYPmax are associated with an increase in total gross primary productivity through enhanced carbon assimilation early in the growing season, which leads to an earlier phase shift in land-atmosphere carbon fluxes and an increase in their amplitude. Such changes are expected to continue in the future based on our analysis of earth system model projections. Our study provides a simplified, yet realistic framework based on first principles for the complex mechanisms by which various climatic factors constrain plant growth in northern ecosystems.
1.Boston Univ, Dept Earth & Environm, Boston, MA 02215 USA 2.Univ Oxford, Sch Geog & Environm, Oxford, England 3.Norwegian Inst Nat Res, FRAM High North Res Ctr Climate & Environm, Tromso, Norway 4.Rhombus Power Inc, NASA Ames Res Pk, Moffett Field, CA USA 5.Max Planck Inst Meteorol, Hamburg, Germany 6.Int Max Planck Res Sch Earth Syst Modeling, Hamburg, Germany 7.Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA 8.Univ Alaska, Inst Arctic Biol, Fairbanks, AK 99775 USA 9.Peking Univ, Coll Urban & Environm Sci, Beijing, Peoples R China 10.NASA, Ames Res Ctr, Moffett Field, CA 94035 USA
Recommended Citation:
Park, Taejin,Chen, Chi,Macias-Fauria, Marc,et al. Changes in timing of seasonal peak photosynthetic activity in northern ecosystems[J]. GLOBAL CHANGE BIOLOGY,2019-01-01,25(7):2382-2395