Stand structure and regeneration of harvested Araucaria araucana–Nothofagus stands in central Chile

Abstract

In this study we examined the current structure and regeneration status of mixed Araucaria araucana–Nothofagus spp. stands that had been logged 20 years ago. We measured stand density of saplings, juvenile and adult trees, as well as stand basal area of A. araucana and Nothofagus spp. in 69 plots distributed in five sites in order to characterise diameter distributions using a Weibull function. Araucaria araucana represented 23–75% of total stand density (69–197 trees ha⁻¹) and total basal area (17.5–54.9 m² ha⁻¹), and the remaining tree species were Nothofagus pumilio, N. dombeyi and N. obliqua. Stand density of A. araucana juveniles ranged from 106 to 1 422 plants ha⁻¹, whereas juveniles of Nothofagus spp. ranged from 4 to 495 plants ha⁻¹. Based on the fitted Weibull distribution function, the shape of the diameter distribution for A. araucana individuals &#8805 10 cm dbh was dominated by the reverse-J (c = 1.0) and mound-shaped (c = 1.26) forms. The Weibull shape parameter of N. pumilio indicated that the diameter distributions were positively skewed. These results are indicative of a good regeneration status for A. araucana and a medium one for N. pumilio. Stand characteristics were used to predict regeneration of A. araucana on the study sites using a principal component analysis (PCA). The PCA showed that regeneration, including seedlings and saplings, was higher in those stands including high values of density of A. araucana. Stand density of juvenile trees in stands where A. araucana had been previously logged suggests that harvesting during the 1980s may have provided occasional recruitment sites where shading may have otherwise precluded regeneration. The results of the study improve our understanding of the ecology, dynamics and succession of mixed A. araucana–Nothofagus forests in southern South America.

Keywords: forest stand dynamics, forest stand structure, Nothofagus pumilio, silviculture, sustainable forest management, Weibull

Southern Forests 2014, 76(1): 11–19