Abstract
Mapping biodiversity is essential for assessing conservation and ecosystem services in global terrestrial ecosystems. Compared with remotely sensed mapping of forest biodiversity, that of grassland plant diversity has been less studied, because of the small size of individual grass species and the inherent difficulty in identifying these species. The technological advances in unmanned aerial vehicle (UAV)-based or proximal imaging spectroscopy with high spatial resolution provide new approaches for mapping and assessing grassland plant diversity based on spectral diversity and functional trait diversity. However, relatively few studies have explored the relationships among spectral diversity, remote-sensing-estimated functional trait diversity, and species diversity in grassland ecosystems. In this study, we examined the links among spectral diversity, functional trait diversity, and species diversity in a semi-arid grassland monoculture experimental site. The results showed that (1) different grassland plant species harbored different functional traits or trait combinations (functional trait diversity), leading to different spectral patterns (spectral diversity). (2) The spectral diversity of grassland plant species increased gradually from the visible (VIR, 400–700 nm) to the near-infrared (NIR, 700–1100 nm) region, and to the short-wave infrared (SWIR, 1100–2400 nm) region. (3) As the species richness increased, the functional traits and spectral diversity increased in a nonlinear manner, finally tending to saturate. (4) Grassland plant species diversity could be accurately predicted using hyperspectral data (R2 = 0.73, p < 0.001) and remotely sensed functional traits (R2 = 0.66, p < 0.001) using cluster algorithms. This will enhance our understanding of the effect of biodiversity on ecosystem functions and support regional grassland biodiversity conservation.
Highlights
We examined the links among spectral diversity, functional trait diversity, and species diversity based on a semi-arid grassland monoculture experimental site, facilitating an in-depth integration of ecological knowledge and remote sensing principles
We found that different grassland plant species harbored different functional trait combinations, and the involvement of more functional traits could increase the functional trait diversity, but with a smaller contribution because of functional convergence
Our leaf-spectra-based analysis indicated that the spectral diversity of grassland plant species increased gradually from the visible region to the near-infrared region and to the short-wave infrared region
Summary
Licensee MDPI, Basel, Switzerland.Attribution (CC BY) license (https://creativecommons.org/licenses/by/ 4.0/).Grasslands, which cover a total area of 52.5 million km2 and account for approximately40.5% of the terrestrial area excluding Greenland and Antarctica, are the largest terrestrial ecosystems in the world [1]. However, serious losses in grassland plant diversity have been observed in the past decades owing to the combined effects of climate change and human activities, especially because of overgrazing, the conversion of grassland to crop agriculture, and habitat fragmentation [2,3]. Grassland plant diversity monitoring is a key issue for ecology and remote sensing sciences [4,5,6]. Traditional grassland plant diversity
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