SEED-SHEDDING IN A SCOTTISH HEATH COMMUNITY

For a 28-week period in late 1987 and early 1988, a study of seed-shedding by several heath species was carried out at the Muir of Dinnet in northeastern Scotland. The dominant species in the heath is Calluna vulgaris. Seed-shedding in Calluna began in early September 1987 and was completed in April 1988, with the period of maximum shedding falling between early November and late December 1987. The total numbers of seeds/m2 deposited in stands of Calluna in its four growth-phases were: pioneer, 18 910; building, 169 010; mature, 198 580; degenerate, 33 900. Substantial loss of potential seeds results from the shedding of immature flowers. A control area close to, but outside the area of Calluna dominance had a deposition rate of 770 Calluna seedS/M2, indicating sufficient seed to colonise nearby available habitats. Seed rain was also recorded for several other heathland species: Erica cinerea, E. tetralix, Carex spp. and Betula pendula. Seeds of Erica cinerea were deposited in all the Calluna stands, 32 670/m2 in the pioneer stand, 17 600/M2 in building, 3720/M2 in mature, 210/M2 in degenerate (120/M2 in the control area). Numbers were greatest at the start of the sampling period, declining thereafter. This applied also to Betula seeds. Erica tetralix occurred in the degenerate Calluna stand and yielded 640 seedS/M2 (400/M2 in the control area). Seeds of Carex spp. were obtained in the control: 4110/M2. The method of sampling has a significant effect on the figures obtained. A method using tube collectors, emptied frequently, is recommended.