Alternative silvicultural practices with variable retention to improve understory plant diversity conservation in southern Patagonian forests

Thin trees within forests: effects on understory plants

A controlled study in 2001-2005 in temperate Nothofagus pumilio forest in Argentina (Lencinas et al. 2011) found that thinning increased plant cover, biomass and species richness. Cover (thinned: 36-40%; unthinned: 20%) and biomass (thinned: 1,000-1,251 kg/ha; unthinned: 200 kg/ha) of understory plants were higher in the three thinning treatments. Numbers of plant species/1 m² was higher in aggregated retention plots (8.2) than in unthinned plots (6.1), and similar to both in dispersed (7.1) and combined retention plots (7.0). In 2001, three thinning treatments (11-24 ha): dispersed retention (20–30% of green tree retention); aggregated retention (28% of trees retained, one aggregate of forest/ha); combined retention (40–50% of retention, one aggregate/ha and dispersed retention among them), and unthinned (9 ha) were established within a 61 ha area. Data were repeatedly collected 1-4 years after treatments in 10 permanent plots (1 m²) in each treatment.