The relationship between species and spectral diversity in grassland communities is mediated by their vertical complexity
Abstract
Aims
The link between spectral diversity and in-situ plant biodiversity is one promising approach for using remote sensing for biodiversity assessment. Nevertheless, there is little evidence to whether this link is maintained at fine scales, as well as to how it is influenced by vegetation’s vertical complexity. Here we test, at community level in grasslands, the link between diversity of the spectral signal (SDiv) and taxonomic diversity (TDiv), and the influence of vertical complexity.
Methods
We used 196 1.5×1.5 m experimental communities with different biodiversity levels. To measure vertical complexity, we quantified height diversity (HDiv) of the most abundant species in the community. TDiv was calculated using Shannon index based on species cover. Canopy spectral information was gathered using an UAV mounted with a multi-spectral sensor providing spectral information via six 10 nm bands covering the visible and near-infrared region at 3 cm spatial resolution. We measured SDiv in a core area of 1×1 m within the communities as mean Euclidean distance of all pixels in a feature space spanned between the two first components of a PCA calculated for the complete raster stack. We modelled SDiv through mixed effect linear models, using TDiv, HDiv, and their interaction as fixed effect predictors.
Results
Contrarily to our expectations, TDiv was negatively linked to SDiv. The diversity in plant height was positively related to SDiv. More importantly, diversity in plant height and TDiv had a significant negative interaction, meaning the more complex the vegetation was in terms of height, the more the SDiv-TDiv relationship became negative.
Conclusions
Our results suggest that in order to exploit the SDiv-TDiv link for monitoring purposes, it needs to be contextualized. Moreover, they highlight that communities’ functional characteristics (i.e. plant height) mediate such link, calling for new insights on the relation between SDiv and functional diversity.
https://onlinelibrary.wiley.com/doi/abs/10.1111/avsc.12600