Potential and efficiency of seed production of Pinus engelmannii Carr., in three seed stands of the state of Durango, Mexico

The potential and efficiency of seed production of Pinus engelmannii Carr. it was determined in three seed stands in the state of Durango (El Encinal and Las Cumbres, municipality of Durango, and La Florida, municipality of San Dimas). In each stand, 10 trees were selected, separated by a minimum distance of 50 m; from each tree 10 cones were collected, they were air-dried to loosen the scales and then quantify: Productive potential, developed seeds, ovule abortion in the first and second year of development and, infertile upper and lower scales. In each stand, 400 seeds were randomly chosen and then X-ray tested, to measure: full seed, vain and damaged by insects. Moreover, through germination tests, speed and capacity of germination were determined. It was found that at the stand El Encinal existed the highest potential production with 171.9 seeds per cone and also the best seed developed with 143.7 seeds per cone. At Las Cumbres, the best values of filled seed (77,2%) and germination (98,1%) were found. The largest ovule abortion in the first year occurred in La Florida with 38,2 seeds per cone, reflecting autopollination or damage by Leptoglossus occidentalis Heidemann in the early stages of seed development. The most intense insect damage was observed at El Encinal with 7,0% of affected seed. The largest seed production efficiency was found at Las Cumbres with 66,9%, while in El Encinal and La Florida the percentage was lower than 41,0%.