Assessing plant trait diversity as an indicators of species α and β-diversity in a subalpine grassland of the Italian Alps

As the need for ecosystem biodiversity assessment increases within the climatecrisis framework, more and more studies using spectral variation hypothesis(SVH) are proposed to assess biodiversity at various scales. The SVH impliesoptical diversity (also called spectral diversity) is driven by light absorptiondynamics associated with plant traits (PTs) variability (which is an indicator offunctional diversity) which is, in turn, determined by biodiversity. In this study,we examined the relationship between PTs variability, optical diversity andα-andβ-diversity at different taxonomic ranks at the Monte Bondone grasslands,Trentino province, Italy. The results of the study showed that the PTs variabil-ity, at theαscale, was not correlated with biodiversity. On the other hand, theresults observed at the community scale (β-diversity) showed that the variationof some of the investigated biochemical and biophysical PTs was associatedwith theβ-diversity. We used the Mantel test to analyse the relationshipbetween the PTs variability and speciesβ-diversity. The results showed a corre-lation coefficient of up to 0.50 between PTs variability and speciesβ-diversity.For higher taxonomic ranks such as family and functional groups, a slightlyhigher Spearman’s correlation coefficient of up to 0.64 and 0.61 was observed,respectively. The SVH approach was also tested to estimateβ-diversity and wefound that spectral diversity calculated by Spectral Angle Mapper showed to bea better proxy of biodiversity in the same ecosystem where the spectral diversityapproach failed to estimateα-diversity. These findings suggest that optical andPTs diversity approaches can be used to predict species diversity in the grass-lands ecosystem where the species turnover is high.