Flowering, seeding and natural regeneration in unmanaged and managed Nothofagus pumilio forests in south Patagonia

MARTÍNEZ PASTUR G.; SOLER ESTEBAN R.; LENCINAS M.V.; CELLINI J.M.; PERI P.L.

Campos do Jordão (Brazil)

Conferencia; Latin American Landscape Ecology Conference (IALE); 2009

IALE

Forest management in South Patagonian Nothofagus forests are based on natural regeneration. Nothofagus pumilio forests have been harvested through shelterwood cuts with variable retention, which can impact biotic and abiotic processes and therefore influence the natural regeneration cycle. To attain a sustainable forest management it was requires knowledge of key aspects of these processes. The aim was to determine patterns of flowering, seeding and seedling establishment in primary and managed stands. Ten traps per stand (n=9) were monthly collected along two seasons analyzing flower and seed production in primary (PF) and managed forests (aggregated retention-AR and dispersed retention-DR). Bird, insect and mouse foraging, as well as seed quality and viability were analyzed. Natural regeneration was measured in nine permanent plots. Data were compared using multiple ANOVAs. Abscission of number of male and female flowers, immature fruits, seeds, as well as reproductive and non-reproductive biomass presented differences when stand type and month were analyzed. Higher values were found for BP than AR than DR. There were no differences in all variables when annual production was compared, except for reproductive biomass. The main losses during the whole cycle were: in BP quality loss in seeds (39%), abscission (27%) and foraging (18%); in AR quality loss in seeds (41%), abscission (26%) and germination during establishment (19%); and in DR quality loss in seeds (41%), foraging (20%) and germination during establishment (20%). Seedling effective establishment during the first season attain to 1.5% of the female flower production in BP, 0.8% in AR and 0.1% in DR. Greater differences were found at landscape level when stands of same treatment were compared, varying their relevance according to the year considered. Mast seeding years were observed in different stands in different years. The number of propagules produced was exceedingly large compared to the number of successful survivors. Our results showed a high percentage of pollinated flowers success in produced fruits, with main loss factors associated to empty fruits, foraging and establishment and survivor of the seedlings. Finally, different flowering and seeding patterns were observed at landscape level, independently of their forest structure or the analyzed year