Annual and geographic variation in seed traits of Argentinean populations of southern beech Nothofagus nervosa (Phil.) Dim. et Mil.

MARCHELLI, P; GALLO, L

FOREST ECOLOGY AND MANAGEMENT

Año: 1999 vol. 131 p. 239 - 250

0378-1127

Nothofagus nervosa (ˆN. alpina) is one of the most important native forest tree species of Argentina, with a very small naturaldistribution area, fast growth and a high wood quality. Its overexploitation in the past seriously affected some populations andmade others disappear, making it necessary to implement conservation policies and breeding programs.In order to study the genetic and geographic variation of the species, seeds from a total of 29 populations from the entirenatural distribution area in Argentina were harvested, 11 of them during four consecutive years. Annual and geographiccovariation of seed production, seed weight and proportion of seeds damaged by insects were analyzed.Signi®cant differences among populations and among years for all studied traits were found. Seed production was highlyvariable, both among populations and among years. `Partial mast years' seem to occur every two years, whereas the occurrenceof `full mast years' has a lower frequency. A signi®cant population  year interaction was found both for the proportion ofdamaged seeds and for the seed weight. The proportion of seeds damaged by insects was very important, reaching >80% of thetotal seed produced in some populations. The differences in the quantity of attacked seeds among years are discussed in relationto seed production, insect's life cycle and climatic factors. Seed weight was also variable among populations and years, despitethe small natural distribution area of the species in Argentina. Best seed quality, according to lower proportion of damaged seedsand higher seed weight, was observed in the analyzed `full mast year'. This would also imply a better genetic representation ofpopulations with seed samples harvested during these years. A lower proportion of damaged seeds as well as the heaviest seedswere also found among those seeds fallen during the ®rst part of the seed-fall period.The found covariation is discussed in relation to patterns of genetic variation previously found in this species and to theimplementation of genetic studies and conservation and breeding programs.#1999 Elsevier Science B.V. All rights reserved.