Flowering and seeding patterns in primary, secondary and silvopastoral managed Nothofagus antarctica forests in South Patagonia

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

New Zealand Journal of Botany

RSNZ PUBLISHING

Año: 2010 vol. 48 p. 63 - 73

0028-825X

The success of a reproductive process (flowers, seeds and seedlings) in trees depends on abiotic and biotic factors, which determines the final outcome of the natural regeneration. Silviculture impacts over the forest structure alter biotic and abiotic factors, and derive in secondary forest structures. To manage more effectively these forests, it is necessary to understand the bottlenecks of reproductive stages in a whole cycle approach study. The aim was to analyze flowering and seeding patterns in primary, secondary and silvopastoral managed Nothofagus antarctica forests, including the pre-dispersion foraging of insects and birds, as well as the abscised biomass production along one growing season. Forest structure in 12 stands was characterized through forest inventory plots and hemispherical photographs. Monthly biomass production was determined using 10 traps in each stand. Reproductive and litter components were classified and dried before weighted. Seeds quality was analyzed by manual opening and using the tetrazolium test. Instead there were evident in the forest structure between stands, the flowering and seeding patterns did not showed greatly differences.. Male flowers appeared first in secondary forests (November) compared to the other treatments (December). Seeding occurred in March before the mass litter-fall, and extended until May in the managed stands. A high percentage of female flowers produced fruits (95-96%), where the main loss factor before seeding was the abscission of immature fruits (11-14%). Seeding was greater in secondary forests (11.4 million.ha-1), but managed forests presented a higher percentage of flowers derived in seeds (82%). However, secondary forests had a better seed quality (17% of viable seeds), were the main loss factor was the presence of empty seeds in all treatments (39-50%). Biotic factors (foraging of insects and birds) were higher in managed than secondary than primary forests. N. antarctica produce large quantities of seeds, but abscised immature fruits and empty seeds due to self-incompatibility mechanisms, appeared as the major loss factors. More studies are necessary to explain these loss factors to quantify its influence in seeding.