Abstract
Detailed monitoring of vegetation changes in ice-free areas of Antarctica is crucial to determine the effects of climate warming and increasing human presence in this vulnerable ecosystem. Remote sensing techniques are especially suitable in this distant and rough environment, with high spectral and spatial resolutions needed owing to the patchiness and similarity between vegetation elements. We analyze the reflectance spectra of the most representative vegetation elements in ice-free areas of Antarctica to assess the potential for discrimination. This research is aimed as a basis for future aircraft/satellite research for long-term vegetation monitoring. The study was conducted in the Barton Peninsula, King George Island. The reflectance of ground patches of different types of vegetation or bare ground (c. 0.25 m 2 , n = 30 patches per class) was recorded with a spectrophotometer measuring between 340 nm to 1025 nm at a resolution of 0.38 n m . We used Linear Discriminant Analysis (LDA) to classify the cover classes according to reflectance spectra, after reduction of the number of bands using Principal Component Analysis (PCA). The first five principal components explained an accumulated 99.4% of the total variance and were added to the discriminant function. The LDA classification resulted in c. 92% of cases correctly classified (a hit ratio 11.9 times greater than chance). The most important region for discrimination was the visible and near ultraviolet (UV), with the relative importance of spectral bands steeply decreasing in the Near Infra-Red (NIR) region. Our study shows the feasibility of discriminating among representative taxa of Antarctic vegetation using their spectral patterns in the near UV, visible and NIR. The results are encouraging for hyperspectral vegetation mapping in Antarctica, which could greatly facilitate monitoring vegetation changes in response to a changing environment, reducing the costs and environmental impacts of field surveys.
Highlights
Antarctic terrestrial ecosystems are changing rapidly in response to global threats, such as climate warming [1] and the introduction of alien species [2,3], and to local impacts due to increasing human presence [4]
The results are encouraging in regard to the use of hyperspectral imagery to map the distribution of different vegetation types in the ice-free areas of Antarctica, which could greatly facilitate monitoring of changes along time in response to environmental changes such as global warming and increasing human disturbance
Our results suggest that in order to increase the accuracy and reliability of detailed vegetation mapping in Antarctica, the spectral characteristics of all representative taxa in the region must be taken into account
Summary
Antarctic terrestrial ecosystems are changing rapidly in response to global threats, such as climate warming [1] and the introduction of alien species [2,3], and to local impacts due to increasing human presence [4]. Increasing temperatures result in the recession of glaciers and snow, exposing new bare ground for colonization by pioneer vegetation [6,7]. They involve longer summer-growing seasons and higher water availability, ameliorating the harsh conditions prevailing in Antarctica. This leads to an increase in the Remote Sens. Increasing competition may lead to the loss of some native species Changes in both structure and floristic composition of communities are expected in the short-, medium- and long-term timescales [11]
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