Study site
The data come from the Orchamp long-term biodiversity observatory
(www.orchamp.osug.fr, Appendix
1). It encompasses 24 elevation gradients (at the time of this study)
across the French Alps sampled between 2016 and 2020 (Fig.1a). These
gradients represent diverse climatic, vegetation and soil conditions.
Each gradient consists of four to nine 30 x 30 m permanent plots, spaced
approximately 200 m apart in altitude. We thus worked with 127 plots
ranging from 280 m and 2780 m above sea level.
Habitat type (forest, grassland, shrubland) was determined on-site.
Plant species abundances were estimated at the peak of the vegetation
along a linear transect traversing each plot, using the pin-point method
(Jonasson 1988). Soil sampling was performed at the end of the summer
season in three subplots (2 x 2 m) located along a separate 4 m wide
transect within each plot. In each subplot, we collected ten soil cores,
5 cm in diameter and ~15 cm in depth (excluding litter),
pooled together to a biological sample. Some elevational gradients (37
plots) were sampled twice (i.e., in different years).