Further Changes in Vegetation since the Advent of Myxomatosis

Abstract

A report on the studies of changes in vegetation between 1954 and 1958 included references to the history of rabbits in Britain, to past studies of their effects on vegetation, as well as brief descriptions of the sites and methods in this recording (Thomas 1960a). In 1954, 1955 and 1956, the work was done with the assistance of permanent staff, and records were made along the more important transects twice a year. From 1957 onwards the work was done on contract with the help of parties of students from Reading University to carry out the bulk of point-quadrat recording. As the field work had to be fitted into the university vacations, recording along each transect could be done only once a year, although notes and photographs were taken along the major transects twice a year. As mentioned in the previous report, when point-quadrat recording was repeated both in the spring and in the autumn of 1954, 1955 and 1956, the total numbers of contacts with grasses and forbs were greater in the autumn than in the spring; but the records of mosses and bare ground were greater in the spring. These seasonal differences had a great bearing on the reliability of results and made it essential that the records on any one transect should be repeated at the same season each year. Therefore, the work was planned so that the recording along each transect should be repeated near the season of the first recording in 1954 or 1955, for most of those first records were made before or during the periods when the rabbits were almost exterminated by myxomatosis. Lullington, Kingley Vale and Old Winchester Hill transects have been recorded during the Easter vacations; Broomhill Burrows, Skomer, Hod Hill, Dungeness and Crundale transects have usually been recorded at the end of June or early July; Aston Rowant and Horn Heath transects during the second half of August. Visits at other times to the transects for the purpose of making notes and photographs have been fitted into periods when no point-quadrat recording was being done. The repetition of colour photographs, taken at exactly the same places once or twice a year, has been a most important part of the work and has often been greatly hampered by bad weather; it was sometimes necessary to make four or five visits to a transect in order to secure reasonable conditions for the series of routine photographs. Point-quadrat records, photographs and field notes of the heights and extents of the different plant associations along the transects, all have been combined to give a detailed, accurate and objective picture of the vegetation. Eight seasons of point-quadrat recording have proved the value of the method when it is done conscientiously. Students worked in pairs, one lying down to name the plants which touched each point, only the first contact of each species being mentioned, and the other student recording them on sheets of graph paper. Any interesting plants within 1 ft (30 cm) of the frame were also recorded. This seemed advisable to prevent keen