Braunton Burrows: The Effects on the Vegetation of the Addition of Mineral Nutrients to the Dune Soils

Abstract

The influence of the levels of various mineral nutrients on the growth and floristic composition of the natural vegetation of a number of habitats of the sand-dune system of Braunton Burrows, N. Devon, England, was investigated. In addition, the effects on turf transplants from the Burrows of treatment with mineral nutrients in different combinations were studied under greenhouse conditions. When mixtures of salts containing all the essential plant nutrients were added to the turf, the vegetation of the dry areas became dominated by Festuca rubra and Poa pratensis ssp. subcaerulae, and of the wetter areas by Agrostis stolonifera. The variety of species was highly re-duced, many small and low-growing plants, e.g. rosette forms, bryo-phytes, being stifled by the tall, dense growth made by the grasses. In one dune slack after treatment for 2 years there was a 15-fold increase in height of the vegetation and a 7-fold increase in fresh weight The most severe deficiencies were of N and P, although K also limited growth. No deficiencies of trace elements were detected. The importance of N-deficiency was overriding, as addition of nutrients complete except for N had little effect on the vegetation which remained sparse and short Addition of nutrients complete except for P, however, resulted in distinctive changes in floristic composition, Carex flacca and Juncus gerardii being especially favored; Carex flacca may have a low requirement The results suggest that the stunted and open character of the vegetation of many parts of the Burrows is largely attributable to the deficiencies of N and P in the soil.