Ponencia
Above-ground seedling responses to canopy gaps, removal of root competition and addition of fertilizer of evergreen and deciduous Nothofagus species in Tierra del Fuego, Chile
Autor
Promis-Baeza, Alvaro
Allen, Robert Bruce
Bown, Horacio
Institución
Resumen
Pure evergreen Nothofagus betuloides forests are found on nutrient poor sites in Tierra del
Fuego, whereas the deciduous N. pumilio species on nutrient richer sites. Soil resources
and root competition can affect seedling performances in infertile soils, whereas light can
limit seedling growths on fertile soils. The research objective was to analyse the aboveground
responses of N. betuloides and N. pumilio seedlings to the removal of root
competition and the addition of fertiliser in canopy gaps and beneath undisturbed forests.
The research was conducted in an uneven-aged mixed N. betuloides-N. pumilio forest (17
ha, 730 trees/ha, 96.2 m2/ha) in Tierra del Fuego (53º45’S, 69º58’W).
Eight canopy gaps were selected (63-207 m2). Four 4 m2 plots were established in each
canopy gap (CG) and beneath its undisturbed forest (UF). In November 2011 (beginning
growing season) one treatment (control, fertiliser, root trenching and fertiliser + root
trenching) was applied to each of the four plots in both canopy conditions. The fertiliser
was applied as 348 g of urea (equivalent to 400 kg/ha of N), 45 g of triple super phosphate
(52 kg/ha of P), 89 g of sulphate potash magnesia (40 kg/ha of Mg), 8 g of lime (40 kg/ha
of Ca) and 21 g of muriate of potash (80 kg/ha of K). The boundary of root trenched plots
was cut to a 30 cm depth using a spade. The height and root collar diameter (RCD) of all
seedlings were measured at the beginning and re-measured in March 2012 to determine
mortality, height and RCD growth.
The density of N. betuloides and N. pumilio seedlings, at the beginning and end of the
growing season were not statistical different, in both CG and UF. The RCD growth of N.
pumilio was significantly higher than N. betuloides in CG for the control, fertiliser and root
trenching treatments. N. betuloides showed similar RCD growth to N. pumilio in the
fertiliser + root trenching treatment. The height growth of N. pumilio was also significantly
higher than N. betuloides in CG for the control treatment. However, N. betuloides showed
similar height growths to N. pumilio in all other treatments. In UF N. pumilio and N.
betuloides did not show differences in RCD growths. The height growth of N. pumilio was
statistically higher than N. betuloides for the root trenching treatment.
CGs can influence growth differences among both species. These growth differences
reflect soil resource availability.