The Influence of Soil Conditions on the Course of Succession on the Chalk of Southern England

• Published in: The Journal of ecology 1967-03, Vol.55 (1), p.137-146
• Main Authors: Lloyd, P. S., Pigott, C. D.
• Format: Article
• Language: English
• Subjects: Grasses; Grassland soils; Nitrogen; Phosphorus; Plants; Pulpits; Seedlings; Shrubs; Soil nutrients; Vegetation
• ISSN: 0022-0477; 1365-2745
• DOI: 10.2307/2257722

Vegetation developed on sites of former cultivation on chalk soils in south-east England retains a distinctive character for many years after cultivation has ceased. The mechanism of the succession on such sites has not previously been examined. A field at Pulpit Hill in the Chilterns was studied as a typical example of these sites. The field had been ploughed in 1941 and now bears an open species-rich herbaceous vegetation with many young plants of Thelycrania sanguinea and other shrub species. The characteristic feature of the vegetation is the low contribution of grass species to the total plant cover. The growth from seed and the nutritional requirements of two shrub species and two grass species were compared. Shrubs seedlings hardly responded to additions of nitrogen and phosphorus to the soil, whereas grass seedlings responded vigorously in glasshouse experiments. In the field, addition of either water or nitrogen to the soil caused phosphorus to become a limiting factor for grass growth, and it is concluded that under natural conditions an inadequate water supply causes a nitrogen deficiency in the soil, which severely restricts the growth of small-seeded grasses. Shrub species, with larger seed reserves than the grasses, are initially relatively independent of the nutrient status of the soil but successful germination and establishment is affected by the percentage cover and the vigour of the herbaceous vegetation. Long-term experiments would be necessary to indicate the eventual importance of nutrient status for the shrub species.