25 Jul 2022
25 Jul 2022
Status: this preprint is currently under review for the journal BG.

Impact of sky conditions on net ecosystem productivity of a “floating blanket” wetland in southwest China

Yamei Shao1,2, Huizhi Liu1,2, Qun Du1,2, Yang Liu1,2, Jihua Sun3, and Yaohui Li4 Yamei Shao et al.
  • 1State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
  • 2University of Chinese Academy of Sciences, Beijing 100029, China
  • 3Yunnan Meteorological Observatory, Kunming 530100, China
  • 4College of Aviation Meteorology, Civil Aviation Flight University of China, Guanghan 618307, China

Abstract. Based on eddy covariance (EC) measurements from 2016 to 2020, the impact of sky conditions on net ecosystem productivity (NEP) over Beihai wetland was examined. Sky conditions were classified into sunny, cloudy and overcast skies. On half-hourly timescale, the daytime NEP responds to the changing total photosynthetically active radiation (PARt) more efficiently under cloudy and overcast conditions than sunny conditions across seasons. Compared with sunny conditions, the apparent quantum yield (α) under overcast (cloudy) conditions increased 342.9 % (271.4 %) in spring, 17.6 % (20.6 %) in summer, 280.0 % (230.0 %) in autumn and 125.0 % (25.0 %) in winter, respectively. Unlike the patterns of half-hourly NEP, the daily NEP was significantly lower under overcast conditions than that under cloudy and sunny conditions. And the daily NEP peaked under cloudy skies when the clearness index (CI) fluctuated around 0.3–0.6. Additionally, the ecosystem light use efficiency (LUE) and water use efficiency (WUE) also changed with the variations in sky conditions. The daily LUE and WUE reached their maximum values under overcast (CI: 0–0.2) and cloudy conditions (CI: 0.2–0.4), respectively. NEP was mainly controlled by the diffuse photosynthetically active radiation (PARd) and air temperature (Ta), and the direct photosynthetically active radiation (PARb) had a secondary effect on NEP from half-hourly to monthly timescales. Path analysis revealed that PARb and Ta were the main controls affecting NEP under sunny conditions. While under cloudy and overcast conditions, PARd was the most responsible for the variations of NEP.

Yamei Shao et al.

Status: open (until 05 Sep 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-131', Anonymous Referee #1, 26 Jul 2022 reply
  • RC2: 'Comment on bg-2022-131', Anonymous Referee #2, 05 Aug 2022 reply

Yamei Shao et al.

Yamei Shao et al.


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Short summary
The effects of sky conditions on ecosystem productivity over wetlands received little attention. Based on eddy covariance measurements during 2016–2020, we explored the impact of sky conditions on net ecosystem productivity (NEP) over an alpine marsh wetland in southwest China. We found diffuse radiation played a critical role in the variations of NEP, and gloomier sky condition was conducive to increasing apparent quantum yield and NEP.