Abstract
In polar regions, vegetation is especially sensitive to climate dynamics and thus can be used as an indicator of the global and regional environmental change. However, in Antarctica, there is very little information on vegetation distribution and growth status. To fill this gap, we evaluated the ability of both linear and nonlinear spectral mixture analysis (SMA) models, including a group of newly developed modified Nascimento’s models for Antarctic vegetated areas (MNM-AVs), in estimating the abundance of major Antarctic vegetation types, i.e., mosses and lichens. The study was conducted using WorldView-2 satellite data and field measurements over the Fildes Peninsula and its surroundings, which are representative vegetated areas in Antarctica. In MNM-AVs, we introduced secondary scattering components for vegetation and its background to account for the sparsity of vegetation cover and reassigned their coefficients. The new models achieved improved performances, among which MNM-AV3 achieved the lowest error for mosses (lichens) abundance estimation with RMSE = 0.202 (0.213). Compared with MNM-AVs, the linear model performed particularly poor for lichens (RMSE = 0.322), which is in contrast to the case of mosses (RMSE = 0.212), demonstrating that spectral signals of lichens are more prone to mix with their backgrounds. Abundance maps of mosses and lichens, as well as a map of moss health status for the entire study area, were then obtained based on MNM-AV3 with around 80% overall accuracy. Moss areas account for 0.7695 km2 in Fildes and 0.3259 km2 in Ardley Island; unhealthy mosses amounted to 40% (49%) of the area in the summer of 2018 (2019), indicating considerable environmental stress.
Highlights
The Antarctic ecosystem is unique and fragile
To facilitate the dynamic monitoring of Antarctic vegetation, this study evaluated the ability of Very high resolution (VHR) satellite images for vegetation abundance estimating and mosses health monitoring
Results are denoted as MNM-AV1, MNM-AV2, and MNM-AV3, representing only corrected water abundance and “virtual abundance” reassigned with assumptions (1) and
Summary
The Antarctic ecosystem is unique and fragile. Vascular plants are very rare, while mosses and lichens dominate and are distributed in small patches [1,2,3,4,5]. To determine the most important spectral ranges for Antarctica vegetation discrimination, Calviño-Cancela et al [37] adopted the linear discriminant analysis (LDA) method This method was applied in a similar environment of North Alaska based on field spectroscopy and multispectral satellite data to map dominant vegetation distributions [38]. [43] explored the possibility of using near-distance imaging spectroscopy in the moss-bed health assessment, i.e., water-deficient (stressed) and well-watered (unstressed), and mentioned that the method could provide quantitative maps for Antarctic moss-bed health once applied to remotely-sensed hyperspectral images These studies focused on digital photographs and UAV data, while few studies have addressed such monitoring based on satellite images. The model performance and the variation of moss heath status in two consecutive years were analyzed
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