Supplementary material: Fundamental watersheds and altitudinal tripartition of the mountain cloud forests from Northwestern Argentina (Yungas)

Vegetation zonation along the slopes of a mountain, from low to high
altitude, is a well-known pattern in landscape ecology. A similar
picture is also described in the field of freshwater ecology.
Rivers and streams show different types of habitats between
upland and downland site locations. We studied both segmentations
of altitudinal gradient in a subtropical hotspot of biodiversity, namely
the mountainous rainforest of Yungas from
Northwestern Argentina. We assessed the agreement between
vegetation stratification (fog grasslands, cloud montane forest and low
montane rainforest) and the tripartition of assemblages of mayflies (an
ancient group of aquatic insects). The products we offer
here accompany the paper of Biotropica entitled The
inter-forest line could be the master key to track biocoenotic effects of
climate change in a subtropical forest. We established a pair of
altitudinal cutoffs in each of the watersheds from Argentinean Yungas.
They correspond to the upper and lower limits of the middle
layer, and they were obtained through an optimization task. The
objective function was to maximize the overlap between the extent of such
a middle layer and the area classified as cloud montane forest. The upper
limit approaches to the treeline, whereas the lower limit is expected to
fit the inter-forest line. Interestingly enough, assemblages of
aquatic insects can be ordinated along altitudinal transects, but the main
distinction occurs at either side of the hypothetical inter-forest line
rather than the treeline. This finding is consistent throughout
the study area. Map of the three altitudinal floors, as
well as the different watersheds, are available
as raster
files.