摘要:叶绿素荧光技术能够快速、灵敏、无损地测定植物光合功能对环境变化的响应，已成为当前植物光合能力测定的重要技术手段之一，但是探讨亚热带森林叶绿素荧光参数在不同季节日变化特征受环境因子影响的研究较少，更缺乏与植被生产力关系的研究。以亚热带人工针叶林为研究对象，利用2016年叶绿素荧光测量和涡度相关通量观测数据，分析了不同季节湿地松和马尾松叶片荧光参数实际光化学效率（Photochemical efficiency of PSⅡ，Φ_PSⅡ）和非光化学淬灭（Non-photochemical quenching，NPQ）的日变化特征，并结合增强回归树等统计方法，定量化环境因子对其影响，最后探讨了荧光参数与总初级生产力（Gross primary productivity，GPP）和光能利用率（Light use efficiency，LUE）的关系。结果表明，Φ_PSⅡ日变化总体上呈现"U型"，早晚高午间低，而NPQ先升后降，午间达到峰值，与Φ_PSⅡ的日变化显著负相关。研究发现，光照是影响亚热带人工针叶林Φ_PSⅡ日变化最主要的环境因子，Φ_PSⅡ随着光合有效辐射（Photosynthetically active radiation，PAR）的升高而降低，PAR对湿地松和马尾松叶片Φ_PSⅡ的相对贡献率分别为83.0%和51.1%。PAR对湿地松叶片NPQ日变化的相对贡献率也最高（77.2%），但马尾松的NPQ主要受叶片温度（Leaf temperature，T_leaf）的影响（59.6%）。此外，GPP与Φ_PSⅡ显著负相关，而与NPQ有显著的正相关关系。LUE随着Φ_PSⅡ增长，但存在Φ_PSⅡ高而LUE低的情况，LUE与NPQ显著负相关，热耗散的比例越高，光能利用效率也相应降低。



Abstract:Chlorophyll fluorescence has become a very powerful technique to estimate the photosynthetic capacities of different plants in a rapid and non-invasive way. However, the effect of environmental factors on the diurnal variations in chlorophyll fluorescence parameters in different seasons has been less studied, and their relation to vegetation productivity has hardly been discussed. In this study, we characterized the diurnal changes in fluorescence parameters (photochemical efficiency of PSⅡ and non-photochemical quenching (NPQ)), and quantified the influence of the three environmental factors (photosynthetically active radiation (PAR), leaf temperature (T_leaf), and relative humidity (RH) using Boosted Regression Trees (BRT) and Pearson correlation analysis). In addition, the relationships between the fluorescence parameters and vegetation productivity (gross primary productivity (GPP) and light use efficiency (LUE)) were explored. We conducted in situ chlorophyll fluorescence measurements on Slash Pine (Pinus elliottii Engelm.) and Masson Pine (Pinus massoniana Lamb.) in the Qianyanzhou (QYZ) subtropical coniferous plantation, Jiangxi province, China, during 2016. Our results showed that Φ_PSⅡ decreased to a minimum at midday and subsequently progressively rose, whereas NPQ was highest at midday, significantly contrary to Φ_PSⅡ. Among the three environmental factors, PAR played the strongest role in determining the diurnal changes of Φ_PSⅡ (83.0% in Slash Pine and 51.1% in Masson Pine). Φ_PSⅡ decreased with PAR. PAR also had an important influence on NPQ in Slash Pine (77.2%). However, NPQ in Masson Pine was mainly affected by T_leaf (59.6%). In addition, we obtained the synchronous LUE and GPP from the eddy covariance flux observation in QYZ and found that GPP had a significantly negative correlation with Φ_PSⅡ, but a positive correlation with NPQ. LUE increased with Φ_PSⅡ, but sometimes high Φ_PSⅡ was accompanied by low LUE. LUE decreased with NPQ, indicating that higher proportion of heat dissipation resulting in lower light use efficiency.





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