A Theoretical Approach to a Study of Chalk Grassland

In the early days the emphasis was on floristics; in more recent years this has developed into a study of the distribution of species (Lousley 1950) and discussion of the origin of the various elements in the flora and the influence of historical factors on distribution problems (Pigott & Walters 1954). 2. In the 1920s investigations turned to seral relationships of the community and it has been shown that it should be regarded as a plagioclimax which probably originated by man's direct and indirect activity and is only maintained by his continued interference (Tansley & Adamson 1925). In his absence, and with the recent reduction in rabbit population, the community would rapidly disappear under scrub and finally woodland. This work has been amplified by the observations of later ecologists (Hope-Simpson 1940, Locket 1946). 3. The characteristic species of the ideal plagioclimax community have been described and listed with estimates of their frequency (Tansley & Adamson 1926). The figures, however, have been based largely on work in one area, the South Downs, and may be criticized on the grounds that there was bias in favour of sites on northern aspects which led to an over-representation of higher humiditytolerant species whilst species confined to drier aspects were under-represented. Little attempt has been made to recognize associations and sub-associations within the community though comments have been passed on the different types of grassland which occur on grazed and ungrazed sites, northand south-facing slopes. However, the comments have been concerned mainly with physiognomy whilst the associated distribution of smaller and less obvious members of the community has not been studied. Descriptions of chalk grassland in other parts of the country have been published (Dony 1953, Godwin 1938, Grose 1957, Pigott 1955) but so far no comparative studies have been made in any detail. The relationship to similar vegetation in Europe has only been briefly mentioned and awaits detailed investigation. 4. The physiological problems of chalk grassland have received considerable attention. The water relations were studied admirably over thirty years ago (Anderson 1927) but it would be of value to have observations from other types of chalk soils than those investigated. A study of the calcicole-calcifuge problem started with field observations and