Abstract

Usually mature stands were considered as forests with higher conservation values, despite their tree age structure. However, natural stands presented a range of stand conditions, from even-aged at different development phases (OG = optimum growth stages, MD = mature and decaying stages) to uneven-aged combining different different development phases (UMD = uneven-aged combining both stages of MD, UOG = uneven-aged combining OG and MD stages). The aim was to determine the understory richness and cover of even and uneven-aged stands of Nothofagusantarctica in Tierra del Fuego, and relate them with forest structure variables. A total of 75 stands were sampled across the natural range distribution, whereunderstory (point intercept method) and forest structure (angle count sampling and eye-fish photos) variables were measured. Seventeen one-way ANOVAs were conducted using Tukey test at p<0.05. Among forest structure variables, cover (F=4.3, p=0.007), radiation (F=4.4, p=0.006), density (F=10.3, p<0.001), diameter (F=10.3, p<0.001) and growth (F=4.9, p=0.004) presented significant values, and in general with a positive or negative trend across the MD-UMDUOG-OGgradient. Regeneration not present significant differences among treatments. Total (F=6.5, p<0.001) and native species (F=7.2, p<0.001) richness were significant, where UMD>UOG>MD>OG (17-28, and 13-24 species, respectively). Exotic species richness not present significant differences (4-5 species). Cover also not significantly change (total, dicots, ferns and inferior plants), however monocots significantly differs among treatments (F=3.9, p=0.012), where UMD>MD>UOG>OG. Finally, the cover of indicator plant for environmental degradation not present significant differences (F=2.1, p=0.106), but was positive related to mature stages. We can conclude that uneven-aged presented some high conservation values compared to even-aged stands, and with a direct relationship with the development stage of the trees, where mature have better values than optimum growth stages. These findings can be used for better silviculture practices that combine silvopastoral and conservation strategies.