3. Bryophytes
This group of primitive plants includes mosses and liverworts, both of which lack roots and have to absorb water directly from the substrate they are growing on. Because of this few species are found on bare rock, most preferring damp environments. No survey has been made of the species currently found in Independent Quarry, although the total is likely to be very low.
3a. Liverworts
Liverworts require a permanently damp environment and will not withstand exposure to drying wind and sun. Most will also not grow in areas permanently inundated with water. Only 7 species are known to occur on Portland (ref. 6). The most suitable habitats planned for Independent Quarry are the rocks around the pond and the most sheltered corners of the amphitheatre. If flowing water is provided it is quite possible that other species new to Portland could be found.
click here to view the list of Liverwort species already found on Portland in a new window
3b. Mosses
Limestone rocks and soils provide mosses with a ready supply of calcium and generally support a wide range of species. Mosses are less reliant on water than are liverworts and some species are able to survive on bare rock, often where water collects temporarily. They are amongst the first plant species to colonize newly exposed areas in quarries. Independent Quarry is likely to support many species in time, particularly if a wide range of habitats is provided, including damp, shaded areas as well as sunny calcareous grassland. The table below lists species that are suited to the sort of environments planned for Independent Quarry and any could be found there eventually. Not all are currently found on Portland.
click here to view the list of Mosses of grassy slopes and bunds in a new window
Relatively few species will be able to grow on the smooth faces of the dimensional stone exposed in the south-west corner of the quarry, but a variety of mosses will be found on stone giving a more varied substrate, such as the more fossiliferous strata. Another important habitat will be stacked stone, where specialist species will colonise the darkest clefts between blocks. More species will be found on north-facing rocks, but most will be in wet areas, particularly if made permanently wet by a constant supply of water. The pond will provide more habitats for different species of moss, with some species preferring areas that dry out regularly. Areas of wet moss provide niches for a range of microscopic invertebrates such as tardigrades and protozoa such as ciliates.
click here to view the list of Mosses of bare rock and Mosses of wet areas in a new window
References for Section 3.
1. Bowen, H. (2000) The Flora of Dorset, Pisces Publications
3. Dorset Environmental Records Centre web site, http://www.derc.org.uk
6. Bowen, H. (1995) A brief note on the botany of Portland, in Portland Bird Observatory and Field Centre Report for 1995