Recording and Mapping
 
 
The British Bryological Society (BBS) has a network of Recorders across Britain who are responsible for collecting and collating records of bryophytes and submitting them to the BBS Recording Secretary, and the moss and liverwort recorders of the BBS. The records are eventually passed to the national Biological Records Centre, where they are stored in a computer database. This recording effort resulted in the publication in the early 1990s of a three volume "Atlas of the Bryophytes of Britain and Ireland" (see booklist).

Each Recorder is assigned a vice-county, of which there are 112 in the UK, including 13 in Wales. The vice-counties were originally defined by H C Watson in 1852 (and hence are often referred to as Watsonian vice-counties). The vice-county boundaries have remained independent of changes in administrative county boundaries, which can sometimes lead to confusion since a vice-county and and an administrative county may sometimes have the same name, but different boundaries. However, for the purposes of biological recording it is preferable to have geographical units with fixed boundaries.

The vice-counties have a number as well as a name, with Cornwall being vc 1, and Shetland vc 112. (In Ireland there are 40 vice-counties, and their numbers are prefixed with an "H" - so West Donegal, for instance, is vc H35).

The Welsh vice-counties are as follows:

VCMAP 35 Monmouthshire
41 Glamorgan
42 Brecknockshire
43 Radnorshire
44 Carmarthenshire
45 Pembrokeshire
46 Cardiganshire
47 Montgomeryshire
48 Merioneth
49 Caernarvonshire
50 Denbighshire
51 Flintshire
52 Anglesey


(The numbered ticks marked on the map border mark the boundaries of 100 km squares of the National Grid).

In 1981, the BBS published the "Distribution of Bryophytes in the British Isles - A Census Catalogue of their Occurrence in the Vice-Counties". As the title implies, this is a list of the bryophytes recorded in the British Isles with, for each species, the vice-counties in which they occur. Each year additions to the vice-county lists are published in the Bulletin of the British Bryological Society.

In addition to the vice-county scheme, BBS members have been involved in a project to map bryophyte distribution in Britain by 10 kilometre squares of the National Grid - the BBS Mapping Scheme. This was begun in 1960 and involved the participation of the UK Biological Records Centre (BRC), who computerised the records and produced "dot-maps" for each species (eventually published in the "Atlas of the Bryophytes of Britain and Ireland" (see booklist).

Other projects have been undertaken to record and map bryophytes at a regional level. M O Hill in 1988 published a "Bryophyte Flora of North Wales" (Journal of Bryology, 1988 15:377-491). This includes few maps, but is a useful record of the distribution and habitats of individual bryophytes in North Wales. Some mapping projects have been undertaken at vice-county level. For example, Ray Woods in his "Flora of Radnorshire" (National Museum of Wales, 1993) maps of the distribution of a number of bryophyte species in the vice-county, at a resolution of 5 km squares.

Dot maps are a useful and immediate way of conveying the frequency and distribution pattern of a species across a geographical unit, and of detecting relationships with topographical, geological, climatic or other factors. Note that they do not give an indication of the abundance of a species within the grid unit specified - a dot in a 10km square could indicate a single individual or population of a species or a thousand individuals or populations - there is no way of knowing from the map information alone.

Petalophyllum_map The example map on the left shows the 10km square distribution in Wales of the Red Data Book liverwort Petalophyllum ralfsii. Straightaway it can be seen from the map that this species has a coastal distribution. In fact, it is associated with major sand-dune systems in Wales - such as Aberffraw on Anglesey; Kenfig in Glamorgan, and Ynyslas in Cardiganshire.

Zygodon__map The map on the right shows the distribution of the epiphytic moss Zygodon viridissimus in the vice-county of Cardiganshire. The records here are plotted at a finer scale - 2km squares, or "tetrads". (Note that the numbered squares drawn on the map are of side 10km).

Caution has to be exercised in drawing conclusions from distribution maps if the coverage is not complete, or at least good (as is the case in Cardiganshire). On the other hand, incomplete maps can at least illustrate where coverage is lacking, and which squares might be worth searching for particular species.

 

More distribution maps for bryophytes in Wales can be found on the Photos and Maps page.

 

 

This page was created by Alan Hale. Please email your comments or queries.
Maps produced with DMAP.