基于日光诱导叶绿素荧光的北半球森林物候研究

Vegetation phenology in the Northern Hemisphere based on the solar-induced chlorophyll fluorescence

植被物候是反映植被生长规律的重要指标,对气候的反馈具有重要意义。日光诱导叶绿素荧光(SIF)通过复杂的能量耗散机制与光合作用相关联,提供了从空间直接探测大范围植被物候的可能性。为了探究气候变化背景下SIF反演不同森林类型物候的适用性,该文以北半球35个全球通量网(FLUXNET)森林站点为研究对象,利用2007–2014年SIF值和总初级生产力(GPP)通过双逻辑生长模型和动态阈值法来估算3种典型森林类型的物候,并采用相关性分析等方法评价SIF在估算不同森林类型物候时的差异性。主要结果为:1) SIF对生长季开始时间(SOS)的估算精度高于生长季结束时间(EOS);2) SIF能够更准确地估算混交林(MF)的SOS,但是不能精确追踪落叶阔叶林(DBF)和常绿针叶林(ENF)的SOS;3)春季季前短波辐射是驱动SOS的主要气候因素。综上,建议在将来的研究中将SIF数据与其他遥感指数整合,应用于不同植物类型的物候监测。

Aims Vegetation phenology is an important indicator to reflect the stages of vegetation growth,which is of great significance to the feedback to climate.Solar-induced chlorophyll fluorescence(SIF)is a by-product of photosynthesis,which provides the possibility to directly detect vegetation phenology at the global scale.In order to reveal the accuracy of phenology estimated by SIF of different forest types,we estimated phenology of three forest types in the Northern Hemisphere.Methods Based on 35 eddy flux tower sites in the Northern Hemisphere during the period of 2007–2014,we estimated phenology of three typical forest types using SIF value and gross primary production(GPP)by double logistic growth model and dynamic threshold.Correlation analysis was used to evaluate the different potential of SIF in estimating phenology of different forest types.Important findings Results showed that:1)SIF was more suitable to estimate the timing of the start of growing season(SOS)than the timing of the end of growing season(EOS).2)SOS based on SIF had the highest correlation with SOS based on GPP in mixed forests(MF).However,the SOS of deciduous broadleaf forest(DBF)and evergreen needleleaf forest(ENF)could not be accurately tracked by SIF value.3)The preseason shortwave radiation(SR)was the primarily environmental factor of SOS.