Asymmetric Diurnal and Monthly Responses of Ecosystem Carbon Fluxes to Experimental Warming

• Published in: Clean : soil, air, water air, water, 2017-03, Vol.45 (3), p.np-n/a
• Main Authors: Chen, Ji, Zhou, Xuhui, Hruska, Tracy, Cao, Junji, Zhang, Baocheng, Liu, Chen, Liu, Min, Shelton, Shelby, Guo, Liang, Wei, Yonglin, Wang, Junfeng, Xiao, Shun, Wang, Ping
• Format: Article
• Language: English
• Subjects: Climate change; Ecosystem respiration; Ecosystems; Gross primary productivity; Net ecosystem exchange; Temperature sensitivity
• ISSN: 1863-0650; 1863-0669
• DOI: 10.1002/clen.201600557

Quantifying the diurnal and monthly responses of ecosystem carbon (C) fluxes is critical to accurately understand the feedback between global climate change and ecosystem C dynamics. However, the diurnal and monthly responses of ecosystem C fluxes to climate warming remain unclear. In this study, a field simulated warming experiment was conducted by using open top chambers to explore the diurnal and monthly responses of ecosystem C fluxes during one growing season (GS) in a Tibetan Plateau grassland. The results showed that ecosystem C fluxes responded unevenly to the simulated warming during one GS. Warming significantly increased C uptake (gross primary production) and sequestration (net ecosystem exchange) during the start (May to June) and peak (July to August) of the GS, but promoted ecosystem respiration (ER) during the peak and end (September to October) of the GS. Warming also had more pronounced positive effects on ER during night than during day. In addition, although warming significantly decreased the temperature sensitivity (Q10) of ER over the whole GS, Q10 also responded positively to warming during the start and end of GS as well as during the night. These results highlight the hypothesis that asymmetrical responses of the diurnal and monthly variations of ecosystem C fluxes and Q10 should be taken into consideration to project the C‐climate feedback, especially under future non‐uniform warming scenarios. Warming by open top chambers significantly increases carbon uptake during start and peak of growing season, but warming also promotes ecosystem respiration during peak and end of growing season. Moreover, warming has more pronounced positive effects on ecosystem respiration during night than during day. These results suggest that warming has asymmetrical impacts on diurnal and monthly variations of ecosystem CO2 exchange.