This investigation quantitatively links chlorophyll a+b (chl a+b) concentration, a physiological indicator of forest health condition, to hyperspectral observations of Jack Pine (Pings banksiana), a dominant Boreal forest species. Between June and September of 2001, four field campaigns of data collection were conducted over forested areas near Sudbury, Ontario, Canada. Using the Compact Airborne Spectrographic Imager (CASI), optical image data were collected, in the visible-near infrared domain, over eight selected Jack Pine sites. Supplementing the airborne campaigns was simultaneous on-site collection of foliage samples for laboratory spectral and chemical measurements. The study first linked needle-level optical properties and pigment concentration through the inversion of radiative transfer models, PROSPECT and LIBERTY. Next, a chlorophyll sensitive optical index (R750/R710), was "scaled-up" to the canopy level using turbid medium canopy models and infinite reflectance formulae, which approximate the canopy as an optically thick vegetative medium. However, due to the potential confounding effects of open canopy structure and foliage clumping, such a simple approach requires careful validation. Accordingly, the analysis focused on high spatial resolution CASI imagery (1 meter) to visually target tree crowns, while accounting for shadows, and open (sun-lit) understory areas. Estimating needle-level chl a+b concentration using coupled leaf and canopy models were shown to be feasible with root mean square errors ranging from 4.5 to 6.5 mug/cm2, 16% of typical needle pigment values. Effectively eliminating the confounding variables will permit the prediction of needle pigment content at large spatial scales to highlight regions of potential stress for prospective management strategies.
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机译:这项研究将森林健康状况的生理指标叶绿素a + b(chl a + b)的浓度定量地与北方森林的主要树种Jack Pine(Pings bankiana)的高光谱观测结果联系起来。在2001年6月至9月之间,在加拿大安大略省萨德伯里附近的林区进行了四次数据收集的野外活动。使用紧凑型机载光谱成像仪(CASI),在8个选定的Jack Pine站点上,在可见近红外域中收集了光学图像数据。作为对空降战役的补充,是在现场同时采集树叶样本以进行实验室光谱和化学测量。该研究首先通过辐射传递模型PROSPECT和LIBERTY的反演将针级光学特性和颜料浓度联系起来。接下来,使用浑浊的介质冠层模型和无限反射公式将叶绿素敏感的光学指数(R750 / R710)“按比例放大”到冠层水平,该模型将冠层近似为光学上较厚的营养介质。但是,由于开放冠层结构和树叶结块的潜在混杂影响,这种简单方法需要仔细验证。因此,分析着眼于空间分辨率高的CASI图像(1米),以目视目标树冠为目标,同时考虑了阴影和林下开放区域(阳光直射)。使用叶和冠层耦合模型估算针头水平chl a + b浓度是可行的,均方根误差范围为4.5至6.5杯/ cm2,是典型针头色素值的16%。有效消除混淆变量将允许在较大的空间尺度上预测针状色素的含量,以突出潜在的潜在压力区域,以进行前瞻性管理策略。
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