Mapping Vegetation Change on Limestone Pavements
Based: Lancaster University
Limestone pavements occur in several upland regions of Britain principally located upon Carboniferous and Cambrian limestones. The species rich vegetation of limestone pavements is unusual, combining floristic elements of woodland (in the shaded humid grikes), rocky habitats and calcareous grasslands. There are several rare species associated with Limestone pavement including rigid buckler-fern (Dryopteris submontana), dark-red helleborine (Epipactis atrorubens), and baneberry (Actaea spicata).
Limestone pavement is an internationally important habitat, globally they are rare and occur in a very restricted region, centred on Europe. The most extensive examples of the habitat in Europe are found in Ireland with 2100 ha of limestone pavement found within the UK. Within the UK the majority of pavements are found in northern England, from Morecambe bay to the Pennines. There are also examples in north and west Scotland and in Wales. Limestone pavement is a UK BAP priority habitat and many sites are protected as SSSIs or National Nature Reserves. Many pavements have been heavily damaged by quarrying or rock collection but are not most threatened by undergrazing.
Despite the rarity of the habitat and their botanical importance there has not been a recent assessment of limestone pavement habitat quality at a national scale. An assessment was conducted in 1976 by Ward and Evans assessing the extent and vegetation of British limestone pavements but has not been repeated since. Fieldwork to address this has already begun but an assessment of changes in areal tree cover needs to be undertaken to complement the survey. This project will address this using aerial images taken in 1976 and modern remotely sensed images.
- To define polygons of surveyed areas using maps created in the original limestone pavement survey in 1976.
- To geolocate aerial images of limestone pavements taken in 1976 using historic and modern maps.
- To estimate tree cover on the limestone pavements and analyse how it has changed between the two surveys.
- To produce a short report on the results of the analysis and the methods used.
This project has been very successful. This student has catalogued and scanned all the areal images, overcome difficulties in aligning them with modern images and maps and used them to map tree cover for all of the sites for which we have images. This is incredibly useful as a research output making it possible for me to compare this data with species data collected as part of the project and assess how the limestone pavements have changed over time. Ultimately, using these two sources of data I will be able to make management recommendations and assess what has driven vegetation changes.
The student has done an excellent job of reporting on his approaches used and providing details of his procedures.
The student has benefited through experience of working as part of a research team, by learning ARC GIS and imaging software and by learning about limestone pavement ecology.