Continuous canopy and understory spectral reflectance measurements of a sparse black spruce forest at Poker Flat Research Range (PFRR), interior Alaska (Year 2017)

Plant phenology timings, such as spring green-up and autumn senescence, are essential state information characterizing biological responses and terrestrial carbon cycles. Current efforts for the in-situ reflectance measurements are not enough to obtain the exact interpretation of how seasonal spectral signature responds to phenological stages in boreal evergreen needleleaf forests. This data set shows the in situ continuous measurements of spectral reflectance in a boreal forest in interior Alaska. We deployed two field-based spectroradiometer systems in an open black spruce forest. These two spectroradiometer systems were used to obtain canopy scale (overstory + understory) and understory reflectances. The data set includes the overstory and understory incoming and reflected hemispherical spectral irradiance data (Level 1), and spectral reflectance computed by the in- and out-going spectral data (Level 2). Because the reflected hemispherical irradiance contains the reflection from tower structure for overstory measurements. The further reflectance correction was applied for the measurements at the tower top level (Level 3).植物物候时序（plant phenology timings），如春季返青（spring green-up）与秋季衰老（autumn senescence），是表征生物响应与陆地碳循环（terrestrial carbon cycles）的核心状态信息。当前原位反射率测量（in-situ reflectance measurements）工作尚不足以精准阐释北方常绿针叶林（boreal evergreen needleleaf forests）的季节性光谱特征如何响应物候阶段。本数据集呈现了阿拉斯加内陆一处北方森林的原位连续光谱反射率测量结果。我们在一片开阔黑云杉林（black spruce forest）中部署了两套野外光谱辐射计（spectroradiometer）系统，分别获取冠层尺度（上层林冠（overstory）+下层植被（understory））与下层植被的反射率数据。数据集包含上层林冠与下层植被的入射及反射半球光谱辐照度（hemispherical spectral irradiance）数据（Level 1，一级），以及由入射与出射光谱数据计算得到的光谱反射率数据（Level 2，二级）。由于上层林冠测量所用的反射半球光谱辐照度包含塔架结构（tower structure）产生的反射信号，我们对塔顶测点的测量数据开展了额外的反射率校正，最终得到三级数据（Level 3）。