Novel strategies are required to reduce uncertainties in the assessment of ecosystem transpiration (T). A major problem in modelling T is related to the complexity of constraining canopy stomatal resistance (r_sc), accounting for the main biological controls on T besides non biological controls such as aerodynamic resistances or energy constraints. The novel Earth observation signal sun-induced chlorophyll fluorescence (SIF) is the most direct measure of plant photosynthesis and offers new pathways to advance estimates of T. The potential of using SIF to study ecosystem T either empirically or in combination with complex mechanistic models has already been demonstrated in recent studies. The diversity of environmental drivers determining diurnal and seasonal dynamics in T and SIF independently requires additional investigation to guide further developments towards robust SIF-informed T retrievals. This study consequently aims to identify relevant biotic and abiotic environmental drivers affecting the capability of SIF to inform estimates of ecosystem T. We used observational data from a temperate mixed forest during the leaf-on period and a Penman-Monteith (PM) based modelling framework, and observed varying sensitivities of SIF-informed approaches for diurnal and seasonal T dynamics (i.e. r² from 0.52 to 0.58 and rRMSD from 17 to 19%). We used the PM based modelling framework to investigate systematically the sensitivity of SIF to diurnal and seasonal variations in r_sc when empirically and mechanistically embedded in the models. We used observations and the Soil-Vegetation-Atmosphere-Transfer model SCOPE to study the dependence of SIF and T on abiotic and biotic environmental drivers including net radiation, air temperature, relative humidity, wind speed, and leaf area index. We conclude on the potential of SIF to advance estimates of T and suggest preferring more sophisticated modelling frameworks constrained with SIF and other Earth observation data over the single use of SIF to assess reliably ecosystem T across scales.

需要新的策略来减少评估生态系统蒸腾作用（T）的不确定性。建模T的主要问题与约束冠层气孔阻力（r _sc），除了非生物控制因素（如空气动力学阻力或能量限制）外，还应考虑到T的主要生物控制因素。新颖的地球观测信号太阳诱导的叶绿素荧光（SIF）是植物光合作用的最直接量度，并提供了新的途径来推进T的估算。利用SIF经验性地或结合复杂的机理模型研究生态系统T的潜力最近的研究已经证明了这一点。决定T和SIF的昼夜动态的环境驱动因素的多样性需要单独进行进一步的研究，以指导向SIF信息丰富的T检索的进一步发展。因此，本研究旨在确定影响SIF告知生态系统T估计能力的相关生物和非生物环境驱动因素。²从0.52到0.58，rRMSD从17到19％）。我们使用基于PM建模框架，系统地探讨SIF对昼夜变化和季节变化r中的敏感性_SC时凭经验和机械地嵌入模型。我们使用观测值和土壤-植被-大气-转移模型SCOPE来研究SIF和T对非生物和生物环境驱动因素的依赖性，包括净辐射，空气温度，相对湿度，风速和叶面积指数。我们总结了SIF在推算T值方面的潜力，并建议在使用SIF来跨尺度评估可靠的生态系统T时，更倾向于使用受SIF和其他地球观测数据约束的更复杂的建模框架。