Structure and growth in coastal evergreen forests as the bases for uneven-aged silviculture in Chile

Sampling of three undisturbed, three 4- to 6-year-old selectively cut and one 15 year-old patch-cut old-growth stands was undertaken in Evergreen forests between 39 and 41°S lat. in the Coastal Cordillera and mid elevations of the mountains of the central valley of Chile. Tepa (Laureliopsis philippiana (Looser) Schodde or Laurelia philippiana Looser)), followed by ulmo (Eucryphia cordifolia Cav., Eucryphiaceae) were the most important species in these stands. Olivillo (Aextoxicon punctatum R.et Pav., Aextocicaceae) was also important in the two stands sampled at lower elevations. Plots 1000 m2 in size were used to characterize the diameter structure of the stands, and 2 m2 plots used to characterize regeneration and understory vegetation. Also approximately 100 trees were sampled in each stand for assessment of diameter growth. Several variables allowed determination of poorer site quality in the western side of the Coastal Cordillera. In stands dominated by shade-tolerant species, diameter distributions had a reverse-J shape and good fits to the negative exponential model. In stands with ≥50 percent of the basal area in shade-intolerant species, diameter structures resembled a rotated-S shape, and they had their best fits to polynomial models. Regeneration of commercial species was affected in poor and good sites by one understory species and some indicator of canopy cover. On average regeneration was more abundant in good sites (17,994 vs. 6,230 seedlings 5–200 cm tall per ha). Diameter growth of tepa increased with tree diameter (up to about 50 cm in good sites and 40 cm in poor sites), with lower basal area, after cutting (especially trees <40 cm dbh), and was higher in plots with >50 percent of the trees from 5 to 25 cm dbh. Better regeneration and growth were observed in plots with a lower canopy cover, and were it was balanced among broad diameter (age) classes. The study shows the suitability of these forests to the use of selection system, some basic ecological knowledge and guidelines for its application, and supports the idea of balancing canopy area among diameter classes in order to attain better growth and regeneration of the desired species.