Plant spectral diversity as a surrogate for species, functional and phylogenetic diversity across a hyper‐diverse biogeographic region

Abstract

Aim With plant biodiversity under global threat, there is an urgent need to monitor the spatial distribution of multiple axes of biodiversity. Remote sensing is a critical tool in this endeavour. One remote sensing approach for detecting biodiversity is based on the hypothesis that the spectral diversity of plant communities is a surrogate of multiple dimensions of biodiversity. We investigated the generality of this ‘surrogacy’ for spectral, species, functional and phylogenetic diversity across 1,267 plots in the Greater Cape Floristic Region (GCFR), a hyper‐diverse region comprising several biomes and two adjacent global biodiversity hotspots. Location The GCFR centred in south‐western and western South Africa. Time period All data were collected between 1978–2014. Major taxa studied Vascular plants within the GCFR. Methods Spectral diversity was calculated using leaf reflectance spectra (450–950 nm) and was related to other dimensions of biodiversity via linear models. The accuracy of different spectral diversity metrics was compared using 10‐fold cross‐validation. Results We found that a distance‐based spectral diversity metric was a robust predictor of species, functional and phylogenetic biodiversity. This result serves as a proof‐of‐concept that spectral diversity is a potential surrogate of biodiversity across a hyper‐diverse biogeographic region. While our results support the generality of spectral diversity as a biodiversity surrogate, we also find that relationships vary between different geographic subregions and biomes, suggesting that differences in broad‐scale community composition can affect these relationships. Main conclusions Spectral diversity was shown to be a robust surrogate of multiple dimensions of biodiversity across biomes and a widely varying biogeographic region. We also extend these surrogacy relationships to ecological redundancy to demonstrate the potential for additional insights into community structure based on spectral reflectance.

Flexible estimation of biodiversity with short-range multispectral imaging in a temperate grassland

“…The coefficient of variation in spectral reflectance was positively associated with the Shannon-Weiner and Simpsons indices, and in particular the green and red bands of the electromagnetic (EM) spectrum were most indicative of grassland biodiversity. Our results build on extensive work in grassland ecosystems exploring the use of spectral diversity as a surrogate for biodiversity (Frye et al, 2021;Gholizadeh et al, 2019;Villoslada et al, 2020) and species composition (Lopatin et al, 2017).…”

“…Increases in cost-effectiveness may also be increased by automated flight paths over survey locations, for which unsupervised spectral reflectance data could be collected. Furthermore, while rapid advancements have been made on spectral diversity, previous studies have utilised high-resolution multi/hyperspectral sensors that are either immobile, high-cost, or both (Frye et al, 2021; Gholizadeh et al, 2019; Imran et al, 2021; Lopatin et al, 2017). The current complete monitoring system is available for purchase for < 10,000 USD, relative to >50,000 USD for many hyperspectral sensors.…”

“…While this negative relationship was insufficient to influence species-diversity relationships in the current study below 10 m in recording height, this finding suggests that at greater recording heights associations with high-resolution measures of species diversity may breakdown. Previous studies have either focussed on short-range/destructive sampling (Frye et al, 2021; Lopatin et al, 2017) or long-range multispectral imaging (Gholizadeh et al, 2019), and therefore there is a need to explore species-spectral diversity associations across spatial scales. Recently, novel dissimilarity approaches have been applied to satellite imaging data at a range of spatial scales (Rossi et al, 2021).…”

“…However, biodiversity metrics are not the only ecological indicators, and functional traits are also widely used as ecological indicators of environmental change ( e.g., Bjorkman et al, 2018). Because spectral reflectance is related to functional form (Gamon et al, 1997), the applicability of sensing technology is not limited to biodiversity, and can also act as a proxy for functional diversity (Frye et al, 2021). In the current study site, incorporating UAV monitoring to long-term experimental manipulations will enable the investigation of how environmental disturbances such as drought and nutrient addition influence biodiversity, functional diversity and community structure.…”

A spectral analysis of stem bark for boreal and temperate tree species

“…However, to date, the majority of studies interested in phylogenetic relatedness and taxonomic diversity have analyzed leaf optical properties Asner et al, 2009Asner et al, , 2014Frye et al, 2021;McManus et al, 2016;Meireles et al, 2020;Schweiger et al, 2018). Woody structures, such as bark, have not been utilized as widely (Lang et al, 2017), and therefore it remains unknown if taxonomic relatedness of species could be determined from bark spectra.…”