Growth responses after a future crop tree thinning and a thinning from below in a second-growth Nothofagus pumilio forest in Tierra del Fuego, Chile

Abstract

G.E. Cruz, F.A. Rodríguez, P.A. Tapia, and H.E. Bown. 2018. Growth responses after a

future crop tree thinning and a thinning from below in a second-growth Nothofagus pumilio

forest in Tierra del Fuego, Chile. Cien. Inv. Agr. 45(3): 263-276. Nothofagus pumilio (lenga)

is the most important native species for timber production in southern Patagonia both in Chile

and Argentina. Thinning application to second-growth N. pumilio forests has been limited in

Patagonia, probably because of the long time necessary for the investment to be recovered. In

addition, experimental trials have focused mostly on thinnings from below, leaving a high residual

stand density, which has led to a modest growth response. Using measurements (1995–2014)

obtained from a thinning trial carried out in a second-growth N. pumilio forest located in Tierra

del Fuego (Chile), the objective of this case study was to analyze whether selective thinnings with

future crop trees (in the sense of Z-Bäumen thinning) promote greater growth responses than

those from a thinning from below. In addition, we explored the associations between climatic

factors and age on N. pumilio tree growth. Trial treatments comprised a control, a thinning from

below and a future crop tree thinning. The growth response after a future crop tree thinning was

greater and lasted for a longer period (10 yrs) than did the thinning from below (4 yrs). The tree

basal area and diameter at breast height (dbh) growth increased with dbh and annual absolute

minimum temperature and decreased with age for the unthinned treatment during the period from

1977–2014 (~70–110 yrs old). Our results suggest that the future crop thinning might be a better

alternative than the thinning from below for secondary N. pumilio forests in Patagonia due to the

greater growth response while being a less intensive silvicultural method.