A study of the competitive relationship between Calluna vulgaris (L) Hull and Deschampsia flexuosa (L) Trin. in North-East Scotland
Recent changes in nutrient inputs to heathland have occurred in the Netherlands and this, together with disturbances to the vegetation, has resulted in dramatic changes from heathland communities to grassland communities. A study was undertaken to consider the influence of increased nutrient availability and grazing disturbance on the competitive relationship between Calluna vulgaris and Deschampsia flexuosa in North-east Scotland. Both Calluna vulgaris and Deschampsia flexuosa responded positively to increased nutrient availability when growing separately. When growing together Calluna vulgaris responds negatively to nutrients, while Deschampsia flexuosa responds positively, although the overall dominance of Calluna vulgaris in the community remained. Calluna vulgaris is adversely affected by grazing and benefits in situations where grazing animals are excluded. The opposite is true for Deschampsia flexuosa. In combination the effects of increased nutrients and grazing are compounded. A number of Replacement Series Competition Experiments were undertaken. In nutrient experiments there was a general suppression of Calluna vulgaris in the presence of Deschampsia flexuosa. Generally the performance of D.flexuosa is enhanced when Calluna vulgaris is suppressed, but not always and this appears to depend on how intimately the roots of the two species are associated. Both species are found to be sensitive to reductions in temperature when the plants are growing in monocultures. In mixtures Calluna vulgaris is relatively insensitive to temperature and Deschampsia flexuosa is less able to compete gainst Calluna vulgaris at lower temperatures. The competitive relationship was more favourable to Calluna vulgaris when grown in peat compared to sand; this was probably due to differences in the moisture retention properties of the two soils.