Accurate characterization of gross primary productivity (GPP) is critically important in assessing mangrove carbon budgets, but the current knowledge of the temporal variations of GPP in evergreen mangroves is very limited. Remote sensing of sun‐induced chlorophyll fluorescence (SIF) has emerged as a promising approach to approximating GPP across ecosystems, but its capability for tracking GPP in evergreen mangroves has not been assessed. The SIF‐GPP link at a subtropical mangrove and its environmental controls are explored using 1‐year time‐series measurements from tower‐based hyperspectral and eddy covariance systems. Both the relationship between SIF and GPP as well as that between SIF_y (SIF yield: the ratio of SIF over absorbed photosynthetically active radiation [APAR]) and LUE (light use efficiency: the ratio of GPP over APAR) at diurnal and seasonal time scales are analyzed. The temporal variations of SIF and GPP shared overall similar changing patterns, but their functional relationship tended to be time scale‐dependent. Midday depressions in SIF were observed when environmental stresses occurred around noon (including excess light and high VPD), and the strength of the SIF‐GPP link was affected by changing environmental conditions. The SIF_y‐LUE relationship was temporally more dynamic, tending to match during midday hours but diverge from each other during morning and afternoon hours. These findings confirm SIF can serve as a potential remotely sensed indicator of mangrove canopy photosynthesis. This paper provides the first, high temporal‐resolution, continuous SIF measurements in mangroves, and highlights the importance of the impacts of environmental conditions on the SIF‐GPP relationship.

中文翻译：

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太阳诱导的叶绿素荧光指示红树林冠层光合作用的潜力

总初级生产力（GPP）的准确表征对于评估红树林碳预算至关重要，但是目前关于常绿红树林中GPP随时间变化的知识非常有限。对太阳诱导的叶绿素荧光（SIF）进行遥感已成为一种有希望的方法，可以在整个生态系统中逼近GPP，但尚未评估其在常绿红树林中跟踪GPP的能力。利用基于塔的高光谱和涡度协方差系统的1年时间序列测量，探索了亚热带红树林的SIF-GPP链接及其环境控制。SIF和GPP之间的关系以及SIF _y之间的关系（SIF产量：SIF对吸收的光合有效辐射[APAR]的比率）和LUE（光利用效率：GPP对APAR的比率）在昼夜和季节尺度上进行分析。SIF和GPP的时间变化总体上共享相似的变化模式，但是它们的功能关系倾向于与时间尺度相关。当中午左右发生环境压力（包括过多的光照和高VPD）时，会观察到SIF的午休低落，并且SIF-GPP链路的强度受到环境条件变化的影响。SIF _y‐LUE关系在时间上更具动态性，倾向于在中午时分匹配，但在早晨和下午时分彼此不同。这些发现证实了SIF可以作为红树林冠层光合作用的潜在遥感指标。本文提供了红树林中首次的高时间分辨率连续SIF测量，并强调了环境条件对SIF-GPP关系的影响的重要性。