Abstract
Abstract. This paper focuses on spectral separability of closed alpine grasslands dominated with Nardus stricta and competitive grasses Calamagrostis villosa and Molinia caerulea in the relict arctic-alpine tundra located in the Krkonoše Mountains National Park, Czech Republic. The spectral data were acquired and compared at three levels: spectra of a single layer of leaves measured with the ASD FieldSpec4 Wide-Res spectroradiometer coupled with a contact probe in a laboratory (leaf level), canopy spectra measured in a field with the same spectroradiometer using the fiber optic cable with a pistol grip (canopy level), and hyperspectral image data acquired by Nano-Hyperspec® fastened to the DJI Matrice 600 Pro drone (image level). All the measurements were repeated three times during the 2019 vegetation season – in June, July and August. Using the methods of analysis of variance and Welch's (unpaired) t-test, it was proven that there were differences in the results for all three spectra sources. But in general, for each combination of species and each data source a suitable date and intervals of the spectral bands for species separation exist. The most suitable term for data acquisition in order to differentiate all the species is July. At the leaf level, the best species separability was observed in the near-infrared and shortwave infrared spectral ranges. At the canopy and image levels, the visible bands are of higher importance for discriminating the species.
Highlights
The relict arctic-alpine tundra located in the Krkonoše Mountains National Park, the Czech Republic (51°N, 16°E, altitude above 1,350 m a. s. l.) is a unique ecosystem combining arctic, alpine and middle European flora and fauna
This paper focuses on spectral separability of closed alpine grasslands dominated with Nardus stricta and competitive grass species Calamagrostis villosa and Molinia caerulea
Analysis of variance (Figure 3) shows that the best separability among all studied species was reached on the image level (Nano-Hyperspec®) – at least one species reflectance significantly differs from others at all the wavelengths from 400 to 1,000 nm in all three phenology phases
Summary
The relict arctic-alpine tundra located in the Krkonoše Mountains National Park, the Czech Republic (51°N, 16°E, altitude above 1,350 m a. s. l.) is a unique ecosystem combining arctic, alpine and middle European flora and fauna. The relict arctic-alpine tundra located in the Krkonoše Mountains National Park, the Czech Republic Due to that as well as due to the climate change, some developments in vegetation composition are being recorded: closed alpine grassland dominated with Nardus stricta are threatened by the spread of competitive grasses Calamagrostis villosa (Hejcman et al, 2009) and Molinia caerulea (Hejcman et al, 2010). Remote sensing – laboratory and image spectroscopy – proved to be an effective tool for detailed mapping and for differentiating tundra vegetation species or communities. It was successfully used in arctic tundra regions In order to carry out effective monitoring, i.e. to minimise time for data acquisition and processing and maximise the classification accuracy, it is necessary i) to find the most suitable phenology phase when the spectra of the observed species differ the most and ii) to identify wavelengths which are crucial for the species separability and
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