Timber management with variable retention in Nothofagus pumilio forests of Southern Patagonia

MARTINEZ PASTUR G.; LENCINAS M.V.; CELLINI J.M.; PERI P.L.; SOLER ESTEBAN R.

FOREST ECOLOGY AND MANAGEMENT

ELSEVIER SCIENCE BV

Año: 2009 vol. 258 p. 436 - 443

0378-1127

Silviculture management proposals which use ecological and social variables have been replacing forestry practices based only on economic variables. Traditional silviculture as shelterwood cuts transforms uneven-aged original stands to an even-aged managed forest. Recently, other silvicultural methods have proposed to conserve some of the original heterogeneity of the old-growth forests. This leaves 30% of the timber quality forest area as aggregated retention and 20% basal area as dispersed retention. The aim was to analyze the feasibility of timber management with aggregated and dispersed retention in Nothofagus pumilio old-growth forests by analyzing timber and harvesting yield potential compared with traditional regeneration systems. Also, remnant tree stability of aggregated retention was analyzed. Timber yield potential of old-growth forests varied from 136 to 479 m3 ha-1 across a site quality gradient. High grading cutting improved yield index (timber volume and harvested basal area ratio of 7.9 m3 m-²). In contrast, this index decreased in clear cuts (4.7 m3 m-²), and shelterwood cuts (4.9 m3 m-²). The index also decreased in the aggregated and dispersed retention treatment (5.1 m3 m-²) but with higher timber harvested volumes. Windthrown of remaining trees in aggregated retention was related to time, being significantly higher during the first year after harvesting. Windthrown was affected by crown class and position into the aggregates of the remnant trees as well as site quality of the stand. Regeneration methods with aggregated retention were feasible to be applied across the entire site quality gradient, where economic value losses were not significant when it was compared to shelterwood cuts. Stability of remnant overstory maintained the ecological conditions to ensure biodiversity conservation and continuity of harvested stands.