Models for estimating leaf pigments and relative water content in three vertical canopy levels of Norway spruce based on laboratory spectroscopy

Unique set of data was obtained during the field campaign in the Krušné hory Mts. (the western part of the Czech Republic) in August 2013. From fifty five representative 80-year-old trees of Norway Spruce (Picea abies L. Karst.) equally distributed on eleven study sites, branches were taken in three vertical canopy levels (sunlit productive upper and lower parts of a tree crown, shaded saturated part of a tree crown) and first three needle age classes were analysed. Spectral reflectance of these spruce foliage samples was measured in the range between 350 and 2,500 nm using an ASD FieldSpec 4 Wide-Res spectrometer in combination with the fibre optic contact probe. Some samples were also measured in the integrating sphere. Photosynthetic pigment (total chlorophylls, total carotenoids) contents and relative water content were determined in laboratory for all samples. The results of analysis of variance (ANOVA) show that the contents of pigments and relative water content are significantly different not only between the needle age classes (what is widely known) but also in the vertical canopy levels. There are only few studies dealing with vertical heterogeneity in Norway spruce canopy. Thus, the main goal of this study is to build and compare the statistically based prediction models for photosynthetic pigments and water content estimation for three vertical canopy levels of Norway Spruce. These results in classifications of biochemical and biophysical properties of Norway Spruce stands using hyperspectral remote sensing data.

2013年8月，于捷克共和国西部克鲁什内山脉（Krušné hory Mts.）野外调查期间，获取了这套独特数据集。研究选取分布于11个研究样地的55株代表性80年生挪威云杉（Picea abies L. Karst.），从树冠三个垂直冠层（受光的树冠上部、下部光合有效层，以及遮阴的树冠饱和光合层）采集枝条，并对前三个树龄级的针叶开展分析。采用ASD FieldSpec 4 Wide-Res光谱仪搭配光纤接触探头（fibre optic contact probe），在350~2500 nm波段范围内测定了上述云杉针叶样本的光谱反射率；部分样本还通过积分球（integrating sphere）完成了测量。所有样本均在实验室完成了光合色素（photosynthetic pigment）、总叶绿素（total chlorophylls）与总类胡萝卜素（total carotenoids）含量及相对含水量的测定。方差分析（ANOVA）结果表明，色素含量与相对含水量的显著差异不仅存在于不同针叶树龄级间（该现象已为学界广泛认知），在不同垂直冠层间同样显著。目前针对挪威云杉冠层垂直异质性的研究较为少见，因此本研究的核心目标为构建并对比基于统计方法的预测模型，以实现挪威云杉三个垂直冠层的光合色素与含水量估算。本研究结果可为利用高光谱遥感（hyperspectral remote sensing）数据开展挪威云杉林生化与生物物理特性分类工作提供助力。