Photosynthetic phenology has large effects on the land-atmosphere carbon exchange. Due to limited experimental assessments, a comprehensive understanding of the variations of photosynthetic phenology under future climate and its associated controlling factors is still missing, despite its high sensitivities to climate. Here, we develop an approach that uses cities as natural laboratories, since plants in urban areas are often exposed to higher temperatures and carbon dioxide (CO2) concentrations, which reflect expected future environmental conditions. Using more than 880 urban-rural gradients across the Northern Hemisphere (>= 30 degrees N), combined with concurrent satellite retrievals of Sun-induced chlorophyll fluorescence (SIF) and atmospheric CO2, we investigated the combined impacts of elevated CO2 and temperature on photosynthetic phenology at the large scale. The results showed that, under urban conditions of elevated CO2 and temperature, vegetation photosynthetic activity began earlier (-5.6 +/- 0.7 d), peaked earlier (-4.9 +/- 0.9 d) and ended later (4.6 +/- 0.8 d) than in neighbouring rural areas, with a striking two- to fourfold higher climate sensitivity than greenness phenology. The earlier start and peak of season were sensitive to both the enhancements of CO2 and temperature, whereas the delayed end of season was mainly attributed to CO2 enrichments. We used these sensitivities to project phenology shifts under four Representative Concentration Pathway climate scenarios, predicting that vegetation will have prolonged photosynthetic seasons in the coming two decades. This observation-driven study indicates that realistic urban environments, together with SIF observations, provide a promising method for studying vegetation physiology under future climate change.
1.Nanjing Univ, Int Inst Earth Syst Sci, Nanjing, Jiangsu, Peoples R China 2.Jiangsu Ctr Collaborat Innovat Geog Informat Reso, Nanjing, Jiangsu, Peoples R China 3.Collaborat Innovat Ctr Novel Software Technol & I, Nanjing, Jiangsu, Peoples R China 4.UAB, CSIC, CREAF, Global Ecol Unit, Barcelona, Spain 5.CREAF, Barcelona, Spain 6.European Commiss, Joint Res Ctr, Directorate Sustainable Resources, Ispra, Italy 7.Iowa State Univ, Dept Geol & Atmospher Sci, Ames, IA USA 8.Beijing Normal Univ, Coll Water Sci, Beijing, Peoples R China 9.Univ Technol Sydney, Sch Life Sci, Sydney, NSW, Australia 10.East China Normal Univ, Sch Ecol & Environm Sci, Shanghai Key Lab Urban Ecol Proc & Ecorestorat, Shanghai, Peoples R China 11.Inst Ecochongming, Shanghai, Peoples R China
Recommended Citation:
Wang, Songhan,Ju, Weimin,Penuelas, Josep,et al. Urban-rural gradients reveal joint control of elevated CO2 and temperature on extended photosynthetic seasons[J]. NATURE ECOLOGY & EVOLUTION,2019-01-01,3(7):1076-1085