Gross primary production (GPP) and red solar induced fluorescence (SIF) respond differently to light and seasonal environmental conditions in a subalpine conifer forest
Gross primary production (GPP) and red solar induced fluorescence (SIF) respond differently to light and seasonal environmental conditions in a subalpine conifer forest
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DOI：
10.1016/j.agrformet.2022.108904
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发表时间：
2022-04
影响因子：
6.2
通讯作者：
Julia C. Yang;T. Magney;L. Albert;A. Richardson;C. Frankenberg;J. Stutz;K. Grossmann;S. Burns;B. Seyednasrollah;P. Blanken;D. Bowling
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作者：
Julia C. Yang;T. Magney;L. Albert;A. Richardson;C. Frankenberg;J. Stutz;K. Grossmann;S. Burns;B. Seyednasrollah;P. Blanken;D. Bowling
摘要(300字)山地针叶林的物候很可能会随着气候变化和光、温、湿度季节动态的变化而变化。太阳诱导荧光(SIF)有望为绘制常绿初级生产力(GPP)的时间变化地图提供实质性的改进，而不是基于绿度的遥感指数。SIF用于监测针叶树光合作用物候的季节性变化，取决于GPP和SIF对关键环境驱动因素的同步响应程度。然而，通过对光和其他环境条件的综合影响做出不同的反应，SIF和GPP在多大程度上变得脱钩仍是未知的。这项研究的目的是在半小时的时间尺度上描述GPP和SIF对一系列环境驱动因素的反应，并确定这些关系如何随季节变化。我们分析了来自科罗拉多州尼沃特岭一片针叶林的一年的基于塔式SIF和涡度协方差的GPP数据。我们比较了GPP和SIF在一年中的光反应，发现SIF在一年中对光的反应比GPP更早。GPP的光响应在春季具有正的温度依赖性，而在夏季由于蒸发需求的增加这种依赖性被逆转，而SIF的光响应对温度的依赖性较小。利用人工神经网络集成分析发现，从春季到夏季，SIF对GPP上的季节动态温湿度控制没有表现出平行的响应。夏季SIF与冠层导度不相关，说明SIF对气孔控制的敏感性低于GPP。我们的结果表明，在针叶林中，光系统在水分可用于光合作用之前就在春季开始激活，这对在针叶林中使用SIF作为物候学指标提出了挑战。
Abstract (300 words)The phenology of montane conifer forests is likely to shift in response to climate change and altered seasonal dynamics of light, temperature, and moisture. Solar-induced fluorescence (SIF) is expected to provide substantial improvement for mapping temporal changes in evergreen gross primary production (GPP) over greenness-based remote sensing indices. The utility of SIF to monitor seasonal changes in the phenology of conifer photosynthesis depends on the degree to which GPP and SIF respond in synchrony to key environmental drivers. However, to what extent SIF and GPP become decoupled by responding differently to the combined effects of light and other environmental conditions remains unknown. The goal of this study was to characterize the responses of GPP and SIFredto a suite of environmental drivers at the half-hour time scale and determine how these relationships change across seasons. We analyzed one year of tower-based SIFredand eddy covariance-derived GPP data from a conifer forest at Niwot Ridge, Colorado. We compared the light responses of GPP and SIFredacross the year, finding that SIFredincreased in response to light earlier in the year than did GPP. The light response of GPP had a positive temperature dependence in spring, and this dependency reversed in summer due to increased evaporative demand, while the light response of SIFredwas less temperature dependent. Using artificial neural network ensemble analysis, we found that from spring to summer, SIFreddid not exhibit a parallel response to the seasonally dynamic temperature and moisture controls on GPP. In summer SIFredwas not correlated with canopy conductance, suggesting that SIF is less sensitive to stomatal control than GPP. Our results suggest that, in conifers, photosystems begin to activate in spring prior to when water becomes available for photosynthesis, presenting a challenge for the use of SIF as a phenological indicator in conifer forests.