DENSITY EFFECT ON THE FRUIT-SET, SEED CROP VIABILITY AND SEEDLING VIGOR OF ABIES PINSAPO

Variation in fruit-set. cone crop, seed viability and seedling vigour of Abies pinsapo Boiss. were recorded at two different stand densities during four consecutive years (1990-1993). In this period only two co ne crops were observed (1991 and 1992). Extreme differences were found in response to density. In the low density stand trees had a greater seed-cone production and fruit-set in each of the two crop years. Also , significant differences were recorded in the seed crop viability: in the low density zone average seed viability was only 21% whereas in t he high density one it was 82%. Other important differences such as co ne size, number of seeds per cone and seedling vigour were recorded at different densities. The results suggest that both pollen availabilit y and pollen origin in low density stands influence the frequency and quality of filled seeds. The results have practical implications for t he management of A. pinsapo for seed production and subsequent refores tation. (C) 1996 Annals of Botany Company