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

MARTÍNEZ PASTUR, G; SOLER ESTEBAN, R; LENCINAS, MV; CELLINI, JM; PERI, P

Campos do Jordao, Brazil

Conferencia; Latin American IALE Conference; 2009

IALE

Introduction: Forest management in South Patagonian Nothofagus forests are based in their own natural regeneration. Nothofagus pumilio was harvested through shelterwood cuts with variable retention, which can impact over biotic and abiotic processes and influence over the whole cycle of natural regeneration. To attain a sustainable forest management it was requires knowledge of key aspects of these processes. The aim was determine patterns of flowering, seeding and seedling establishment in primary and managed stands.Methods: 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 followed in nine permanent plots. Data were compared using multiple ANOVAs.Results: 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. Greater values were found for BP than AR than DR. When the year production was compared there were no differences for all variables, except for reproductive biomass. The main losses during the whole cycle were due to: 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.Discussion: The number of propagules produced is exceedingly large compared to the number of successful survivors. This allows trees to adjust the numbers of survivors to that which is optimal under current environmental conditions. 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.