Radial growth response of Nothofagus betuloides to different thinning intensity levels in Tierra del Fuego, Argentina

MG FRANCO; IA MUNDO; G MARTÍNEZ PASTUR; MD BARRERA

Mendoza

Conferencia; Third American Dendrochronology Conference; 2016

IANIGLA

Silvicultural proposals for different forest types are crucial toimprove management practices and to adjust them to naturaldynamics. Forest management proposals for Nothofagusbetuloides (guindo) are scarce and tree ring analysis, which canbe a powerful tool to perform high precision analysis for slowgrowing species, have not been included in silviculturalproposals. The objective of this study was to determine the radialgrowth response of N. betuloides to different thinning intensitylevels using dendrochronological techniques. Thinnings frombellow were conducted in 1993 (four thinning levels) and 2000(two thinning levels), resulting in eight thinning combinations,which were compared with a control treatment. Growthdifferences were evaluated both through visual and statisticalanalysis, considering ring widths, basal area increments,percentage of growth change and periodic annual increments.Thinning intensities showed differential effects on radial growth,where heavy thinning treatments resulted in higher individualgrowth rates (3.31 mm.year-1 and 10.73 cm2year-1) than thecontrol treatment (0.68 mm.year-1 and 1.64 cm2year-1). Besidethis, low density plots showed higher growth increments,suggesting that growth is not only determined by thinningintensity but also by post-intervention plot density. Thedifferentiated effect of the first thinning was masked by thesecond intervention, indicating that this species responds tointense interventions. These results indicate that it is possible toreduce the number of non-commercial thinning and, inconsequence, the cost of application of the silvicultural system.However, no significant differences in stem diameter weredetected among treatments twelve years after the secondintervention. Thus, recommendations about the most convenientthinning intensity cannot be made based on these results, beingnecessary long-term studies. Further studies should be carriedout to determine the optimal thinning density, includingeconomic aspects, and to evaluate managed stands stability andcrown development that can have influence in further individualgrowth and commercial timber products.