Linking diffuse radiation and ecosystem productivity of a desert steppe ecosystem

Cheng Li; Xin Jia; Jingyong Ma; Peng Liu; Ruizhi Yang; Yujie Bai; Muhammad Hayat; Jinglan Liu; Tianshan Zha

doi:10.7717/peerj.9043

Linking diffuse radiation and ecosystem productivity of a desert steppe ecosystem

PeerJ. 2020 May 5:8:e9043. doi: 10.7717/peerj.9043. eCollection 2020.

Authors

Cheng Li^{1

2}, Xin Jia^{1

2}, Jingyong Ma^{1

2}, Peng Liu^{1

2}, Ruizhi Yang^{1

2}, Yujie Bai^{1

2}, Muhammad Hayat^{1

2}, Jinglan Liu³, Tianshan Zha^{1

2}

Affiliations

¹ Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.
² Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China.
³ School of Ecology and Nature Conservation, Beijing Forestry University, Beijing, China.

Abstract

Radiation components have distinct effects on photosynthesis. In the desert steppe ecosystem, the influence of diffuse radiation on carbon fixation has not been thoroughly explored. We examined this diffusion and its effect on ecosystem productivity was examined during the growing season from 2014 to 2015 on the basis of eddy covariance measurements of CO₂ exchange in a desert steppe ecosystem in northwest China. Our results indicated that the gross ecosystem production (GEP) and diffuse photosynthetically active radiation (PAR_dif) peaked when the clearness index (CI) was around 0.5. The maximum canopy photosynthesis (P_max) under cloudy skies (CI < 0.7) was 23.7% greater than under clear skies (CI ≥ 0.7). When the skies became cloudy in the desert steppe ecosystem, PAR_dif had a greater effect on GEP. Additionally, lower vapor pressure deficits (VPD ≤ 1 kPa), lower air temperatures (T_a ≤ 20 °C), and non-stressed water conditions (REW ≥ 0.4) were more conducive for enhanced ecosystem photosynthesis under cloudy skies than under clear skies. This may be due to the comprehensive effects of VPD and T_a on stomatal conductance. We concluded that cloudiness can influence diffuse radiation components and that diffuse radiation can increase the ecosystem production of desert steppe ecosystems in northwest China.

Keywords: Clearness index; Desert steppe ecosystem; Diffuse radiation; Gross ecosystem production.

Grants and funding

This work was supported by the National Natural Science Foundation of China (NSFC; 31670710, 31670708), the Fundamental Research Funds for the Central Universities (Proj. No. 2015ZCQ-SB-02), and the Beijing Municipal Science & Technology Commission (Z161100001116084). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.