Li Cheng, Jia Xin, Ma Jingyong, Liu Peng, Yang Ruizhi, Bai Yujie, Hayat Muhammad, Liu Jinglan, Zha Tianshan
Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.
Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China.
PeerJ. 2020 May 5;8:e9043. doi: 10.7717/peerj.9043. eCollection 2020.
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 CO exchange in a desert steppe ecosystem in northwest China. Our results indicated that the gross ecosystem production (GEP) and diffuse photosynthetically active radiation (PAR) peaked when the clearness index (CI) was around 0.5. The maximum canopy photosynthesis (P) 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 had a greater effect on GEP. Additionally, lower vapor pressure deficits (VPD ≤ 1 kPa), lower air temperatures (T ≤ 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 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.
辐射成分对光合作用有不同的影响。在荒漠草原生态系统中，漫射辐射对碳固定的影响尚未得到充分研究。基于对中国西北荒漠草原生态系统中CO交换的涡度相关测量，我们在2014年至2015年生长季研究了这种漫射及其对生态系统生产力的影响。我们的结果表明，当晴空指数（CI）约为0.5时，生态系统总生产力（GEP）和漫射光合有效辐射（PAR）达到峰值。阴天（CI < 0.7）时的最大冠层光合作用（P）比晴天（CI≥0.7）时高23.7%。在荒漠草原生态系统中，当天空变阴时，PAR对GEP的影响更大。此外，较低的水汽压差（VPD≤1 kPa）、较低的气温（T≤20°C）以及非胁迫水分条件（REW≥0.4）在阴天比晴天更有利于增强生态系统光合作用。这可能是由于VPD和T对气孔导度的综合影响。我们得出结论，云量会影响漫射辐射成分，并且漫射辐射可以增加中国西北荒漠草原生态系统的生态系统生产力。
