Density effect on the fruit-set, seed crop viability and seedling vigour 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 cone 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 the high density one it was 82%. Other important differences such as cone size, number of seeds per cone and seedling vigour were recorded at different densities. The results suggest that both pollen availability and pollen origin in low density stands influence the frequency and quality of filled seeds. The results have practical implications for the management of A. pinsapo for seed production and subsequent reforestation. (C) 1996 Annals of Botany Company