A user-friendly and affordable broad-band digital Near Infrared (NIR) camera (Canon PowerShot S110 NIR) was compared with a narrow-band reflectance spectrometer (USB2000, Ocean Optics) at leaf scale for monitoring changes in response to drought of three ecologically contrasting Quercus species (Q. robur, Q. pubescens, and Q. ilex). We aimed to (a) compare vegetation indices (VIs; that is: NDVI, Normalized Difference Vegetation Index; GNDVI, Green NDVI and NIRv, near-infrared reflectance of vegetation) retrieved by NIR-camera and spectrometer in order to test the reliability of a simple, low-cost, and rapid setup for widespread field applications; (b) to assess if NIR-camera VIs might be used to quantify water stress in oak seedlings; and (c) to track changes in leaf chlorophyll content. The study was carried out during a water stress test on 1-year-old seedlings in a greenhouse. The camera detected plant status in response to drought with results highly comparable to the visible/NIR (VIS/NIR) spectrometer (by calibration and standard geometry). Consistency between VIs and morpho-physiological traits was higher in Q. robur, the most drought-sensitive among the three species. Chlorophyll content was estimated with a high goodness-of-fit by VIs or reflectance bands in the visible range. Overall, NDVI performed better than GNDVI and NIRv, and VIs performed better than single bands. Looking forward, NIR-camera VIs are adequate for the early monitoring of drought stress in oak seedlings (or small trees) in the post-planting phase or in nursery settings, thus offering a new, reliable alternative for when costs are crucial, such as in the context of restoration programs.

在叶子尺度上，将一种用户友好且价格合理的宽带数字近红外（NIR）相机（佳能PowerShot S110 NIR）与窄带反射光谱仪（USB2000，Ocean Optics）进行了比较，以监测对三种生态干旱的响应对比栎种（Q. robur，Q. pubescens和Q. ilex）。我们的目的是（a）比较通过NIR相机和光谱仪获得的植被指数（VI;即NDVI，归一化植被指数; GNDVI，绿色NDVI和NIRv，植被的近红外反射率），以测试植被的可靠性。简单，低成本，快速的设置，适合广泛的现场应用；（b）评估是否可以将近红外相机VI用于量化橡树幼苗的水分胁迫；（c）跟踪叶片中叶绿素含量的变化。该研究是在温室中对1年龄幼苗进行的水分胁迫测试中进行的。摄像机检测到干旱情况下的植物状态，其结果与可见/近红外（VIS / NIR）光谱仪（通过校准和标准几何形状）高度可比。VI和形态生理性状之间的一致性是较高的Q.栎，是这三种物种中对干旱最敏感的。叶绿素含量通过可见光范围内的可见光或反射带估计具有很高的拟合优度。总体而言，NDVI的性能优于GNDVI和NIRv，VI的性能优于单频段。展望未来，NIR相机VI足以在种植后阶段或苗圃环境中早期监测橡树幼苗（或小树）中的干旱胁迫，从而为成本至关重要的情况提供了一种新的，可靠的替代方法，例如在恢复程序的范围内。