Journal of Plant Ecology ›› 2022, Vol. 15 ›› Issue (5): 961-976.DOI: 10.1093/jpe/rtac065

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  • 收稿日期:2021-12-15 修回日期:2022-02-04 接受日期:2022-05-10 出版日期:2022-09-01 发布日期:2022-09-30

Seasonal and interannual variations of ecosystem photosynthetic characteristics in a semi-arid grassland of Northern China

Cuihai You1,2, Yanbing Wang1,2, Xingru Tan1,2, Bingwei Zhang1,3, Tingting Ren1, Boyu Chen1,2, Mengzhen Xu1,2 and Shiping Chen1,2,*   

  1. 1 State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China, 2 University of Chinese Academy of Sciences, Beijing 100049, China, 3 Zhuhai Branch of State Key Laboratory of Earth Surface Processes and Resource Ecology, Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai 519087, China

    *Corresponding author. E-mail: spchen@ibcas.ac.cn
  • Received:2021-12-15 Revised:2022-02-04 Accepted:2022-05-10 Online:2022-09-01 Published:2022-09-30

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摘要： 北方半干旱草原生态系统光合参数的季节和年际变异
生态系统表观量子效率(α)、最大光合速率(Pmax)和暗呼吸速率(Rd)不仅反映了生态系统水平 光合生理特征，同时也是碳循环模型中光合过程模拟的关键参数。气候和植被因子都会影 响光合参数的季节和年际变异，但二者在光合参数调控过程中的相对贡献和作用途径尚不清晰。本研究基于连续12年(2006–2017)的涡度相关观测数据，分析了内蒙古半干旱典型草原光合参数的季节和年际变化规律；利用回归分析和结构方程模型(SEM)方法明晰了环境和生理调控的作用途径及相对贡献。结果发现，光合参数(α、Pmax和Rd)均表现出单峰的季节变化趋势，并呈现明显的年际波动。温度(Ta)和土壤含水量(SWC)的变化共同影响光合参数的季节变化，而SWC主导了其年际变异。α和Rd的变化主要由Ta决定，而Pmax的变化主要受SWC的影响。SEM模型分析表明，除了直接作用外，环境因子主要通过影响冠层水平气孔导度(gc)对光合参数和碳同化生理过程进行调控。此外，叶面积指数对光合参数特别是Pmax的季节和年际变异起主要调控作用。以上结果明确了环境和植被共同决定了生态系统水平光合参数的季节和年际变异，并强调了在水分受限的草原生态系统中，植被生理调控在光合碳同化能力和碳汇功能评估中的重要作用。


关键词: 光合参数, 半干旱草原, 涡度相关法, 碳通量, 生理调控

Abstract:

The ecosystem apparent quantum yield (α), maximum rate of gross CO2 assimilation (Pmax) and daytime ecosystem respiration rate (Rd), reflecting the physiological functioning of ecosystem, are vital photosynthetic parameters for the estimation of ecosystem carbon budget. Climatic drivers may affect photosynthetic parameters both directly and indirectly by altering the response of vegetation. However, the relative contribution and regulation pathway of environmental and physiological controls remain unclear, especially in semi-arid grasslands. We analyzed seasonal and interannual variations of photosynthetic parameters derived from eddy-covariance observation in a typical semi-arid grassland in Inner Mongolia, Northern China, over 12 years from 2006 to 2017. Regression analyses and a structural equation model (SEM) were adopted to separate the contributions of environmental and physiological effects. The photosynthetic parameters showed unimodal seasonal patterns and significantly interannual variations. Variations of air temperature (Ta) and soil water content (SWC) drove the seasonal patterns of photosynthetic parameters, while SWC predominated their interannual variations. Moreover, contrasting with the predominant roles of Ta on α and Rd, SWC explained more variance of Pmax than Ta. Results of SEM revealed that environmental factors impacted photosynthetic parameters both directly and indirectly through regulating physiological responses reflected by stomatal conductance at the canopy level. Moreover, leaf area index (LAI) directly affected α, Pmax and Rd and dominated the variation of Pmax. On the other hand, SWC influenced photosynthetic parameters indirectly through LAI and canopy surface conductance (gc). Our findings highlight the importance of physiological regulation on the photosynthetic parameters and carbon assimilation capacity, especially in water-limited grassland ecosystems.

Key words: photosynthetic parameter, water-limited grasslands, eddy covariance, carbon flux, physiological regulation

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