Relations Between Soil Nutrients and Vegetation in Wet-Heaths: II. Nutrient Uptake by the Major Species in the Field and in Controlled Conditions

Abstract

Seedlings or tillers of Molinia caerulaa, Calluna vulgar is and Erica tetralix were planted at widely-spaced intervals in cleared plots of 3 sites, representative of the different facies of wet-heath. At harvest, yields and nutrient contents were lowest in the valley bog site. Only 39% of the original Calluna seedlings survived there, and E. tetralix, in spite of its relative abundance in the natural plant cover of this site, showed there a greater reduction in dry weight relative to its weight in the Molinietum site, than either of the other 2 species. In the Molinietum site, the heath species grew well when competition from Molinia was eliminated and had slightly higher nutrient contents than plants grown in the central associes of wet-heath. A glasshouse experiment confirmed that the Molinietum soil had the highest, and the valley bog the lowest nutrient status. Growth in all soils was improved by P additions and to a lesser extent by N and K. Draining the valley bog soil failed to improve growth, but the central associes and Molinietum soils supported better Molinia growth when drained, though nutrient concentrations within the plants were only slightly affected. Although differences in the nutrient status of the sites may play a contributory role in influencing the composition of the natural plant cover, other factors such as inter-specific competition and soil aeration are important.