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

MARTÍNEZ PASTUR, GUILLERMO; SOLER ESTEBAN, ROSINA MATILDE; LENCINAS, MARIA VANESSA; JUAN MANUEL CELLINI; PERI, PABLO LUIS

Campos de Jordão

Congreso; Latin American IALE Congress; 2009

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 sustainable forest management, knowledge of key aspects of these processes is required. The aim, here, was to determinate patterns of flowering, seeding and seedling establishment in primary and managed stands. Ten traps per stand (n=9) were collected monthly during 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. The production patterns at the landscape level were compared among the stands of the same treatment using multiple ANOVAs. The number of abscissions 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. Values were found to occur in descending order from PF to AR to 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 PF 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 attained up to 1.5% of the female flower production in PF, 0.8% in AR and 0.1% in DR. Greater differences were found at the landscape level when stands of same treatment were compared, varying their relevance according to the year considered. Seed masting years were observed in different stands in different years. The number of propagules produced was exceedingly large compared to the number of survivors. Our results showed a high percentage of pollinated flowers were successful in producing fruits. However, the main loss factors were associated with empty fruits, foraging and establishment and survivor of the seedlings. Finally, different flowering and seeding patterns were observed at the landscape level, independently of their forest structure or the analyzed year. Masting events were not coincident in all the stands and were not associated to the management treatment.