Effects of altitude and seed size on germination and seedling survival of heathland plants in North Spain

The effects of altitude and seed size on germination and seedling survival were studied in Calluna vulgaris, Erica cinerea and Erica vagans. Experiments were carried out in the laboratory over a one year period. Seeds collected from heathlands of different altitudes were divided in two size classes. They were sowed on moist filter paper inside Petri dishes which were placed in chambers at 20 degrees C and a photoperiod of 12 h light/12 h darkeness. The seeds of Calluna vulgaris were the first to begin germination and had the highest rate and percentage of germination. The germination of Erica vagans was moderate, while seeds of Erica cinerea germinated later and the germination was very low. Seeds of Calluna vulgaris and E. cinerea collected at the highest altitudes had the highest germination percentages. Seed size in Calluna vulgaris and E. cinerea did not affect germination. However, large seeds of Erica vagans had higher germination rates and percentages than small seeds. The large seed size of Calluna vulgaris contributes to a better survival and growth of its seedlings.