Bryophytes

With 22,000 species worldwide, bryophytes, which include mosses and liverworts, are a group of terrestrial plants whose diversification coincides with that of the massive development of forests of flowering plants (angiosperms) around 100 million years ago, and for which the tree ecosystem is therefore essential. The advent of the great angiosperm forests in the Upper Cretaceous played a key role in the diversification of bryophytes by offering them a wide variety of habitats, from the base of the trunk to the canopy, in a forest climate that was much less subject to major fluctuations in temperature and humidity than open environments, an essential characteristic for these organisms whose water supply comes exclusively from precipitation.

These non-vascular plants colonise virtually every part of the tree and, in terms of number of species and individuals, form the majority group of plants associated with the tree. It is obviously impossible to carry out an exhaustive inventory of these plants, so we assess their species richness by sampling small areas in pre-defined zones. The tree is arbitrarily divided into six height classes, which more or less reflect different ecological habitats and the different micro-environments it offers for the growth of living organisms. The mosses and liverworts were collected from randomly distributed quadrats in each of the six zones.

In the field, the mosses and liverworts collected from the trees are sorted using a binocular magnifying glass. This stage is essential, because on a single leaf measuring just a few square centimetres, up to fifteen species of epiphyllous bryophytes can be found, ranging in size from 1/5 of a mm to a few mm. The second step is to identify each species. This involves microscopic examination of each specimen and identification using Flora. For very diverse groups where taxonomy is still insufficiently known, samples are sent to experts for identification.