The Incidence of Lime-Chlorosis in the Natural Vegetation of England

Abstract

Lime-chlorosis is a well-known feature of vegetation on calcareous soils throughout the world. The symptoms closely resemble those caused by iron-deficiency and are characteristic of the younger, actively growing leaves. During the onset of chlorosis the interveinal areas of the leaf are yellow whilst the cells adjacent to the veins usually remain green (Phot. 1). In severe cases, bleaching of the laminae is followed by the death of the shoot apices and by the appearance of brown patches in the marginal regions of the leaves. Crops which are afflicted may suffer a serious reduction in yield (Stewart & Leonard 1952). Citrus, apples and grapes are particularly susceptible and in countries such as the United States, Israel, Spain and France lime-chlorosis is a serious economic problem. In Britain, however, the condition is of little economic consequence (Delap 1964). Despite its low incidence in farmland, lime-chlorosis is a familiar feature of the natural vegetation of calcareous localities such as the valley sides of the Derbyshire dales. Experiments have shown that soils collected from both chalk and limestone areas in England are capable of inducing chlorosis (Grime 1959, 1965). Marked differences in chlorosis-susceptibility have been recorded between species in laboratory experiments (Grime 1959, 1965; Hutchinson 1967a). Species restricted in the field to acidic soils are, in general, more susceptible to lime-chlorosis than those confined to calcareous sites. Ecotypic differences in chlorosis-susceptibility have also been described by Snaydon (1962) and Hutchinson (1966). It is of interest to know how frequently high potentials for lime-chlorosis occur in situ, and what effect, if any, these have in determining the flora over calcareous substrata. Some information on these points may be obtained by recording the frequency of chlorosis in naturally occurring vegetation in areas of chalk and limestone. This paper is an account of a survey of lime-chlorosis in England carried out during the period 1958-65.