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BlackBridge imagery is one of the new means of information used in forest condition analysis. Rapid Eye satellite data with a 5 m spatial resolution register spectral information from 440 to 850 nm through 5 spectral bands. This range of electromagnetic spectrum provides information on plant chlorophyll content as well as cell structure. Such data allows to monitor vegetation condition. This paper focuses on a research conducted in the Sudety and Western Beskidy mountains (southern Poland). The aim of the research was to verify whether high resolution satellite imagery is applicable in detection of the damages caused by Ips typographus and acid rain in Norway spruce dominated stands through supervised classification. BlackBridge Rapid Eye satellite images from 2012 and 2013 were analysed. Various modifications of classification methods were tested, including change in combination of spectral bands. Each method resulted in different classification accuracy. Best results were observed in case of the Maximum Likelihood classification method applied on all spectral bands. The analysis showed that the time of the image registration has a significant impact on classification results. The average classification accuracy for 2012 images was 0.53, whereas for 2013 – 0.69. Moreover, information gathered from 5 m pixels is too general to classify individual dead trees in a precise manner. Tested methods are applicable only in detection of clusters of dead trees.
Remote sensing, which is based on a reflected electromagnetic spectrum, offers a wide range of research methods. It allows for the identification of plant properties, e.g., chlorophyll, but a registered signal not only comes from green parts but also from dry shoots, soil, and other objects located next to the plants. It is, thus, important to identify the most applicable remote-acquired indices for chlorophyll detection in polar regions, which play a primary role in global monitoring systems but consist of areas with high and low accessibility. This study focuses on an analysis of in situ-acquired hyperspectral properties, which was verified by simultaneously measuring the chlorophyll concentration in three representative arctic plant species, i.e., the prostrate deciduous shrub Salix polaris, the herb Bistorta vivipara, and the prostrate semievergreen shrub Dryas octopetala. This study was conducted at the high Arctic archipelago of Svalbard, Norway. Of the 23 analyzed candidate vegetation and chlorophyll indices, the following showed the best statistical correlations with the optical measurements of chlorophyll concentration: Vogelmann red edge index 1, 2, 3 (VOG 1, 2, 3), Zarco-Tejada and Miller index (ZMI), modified normalized difference vegetation index 705 (mNDVI 705), modified normalized difference index (mND), red edge normalized difference vegetation index (NDVI 705), and Gitelson and Merzlyak index 2 (GM 2). An assessment of the results from this analysis indicates that S. polaris and B. vivipara were in good health, while the health status of D. octopetala was reduced. This is consistent with other studies from the same area. There were also differences between study sites, probably as a result of local variation in environmental conditions. All these indices may be extracted from future satellite missions like EnMAP (Environmental Mapping and Analysis Program) and FLEX (Fluorescence Explorer), thus, enabling the efficient monitoring of vegetation condition in vast and inaccessible polar areas.
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