Abstract

Usually mature stands were considered as forests withhigher conservation values, despite their tree agestructure. However, natural stands presented a rangeof stand conditions, from even-aged at differentdevelopment phases (OG = optimum growth stages,MD = mature and decaying stages) to uneven-agedcombining 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 andcover of even and uneven-aged stands of Nothofagusantarctica in Tierra del Fuego, and relate them withforest structure variables. A total of 75 stands weresampled across the natural range distribution, whereunderstory (point intercept method) and foreststructure (angle count sampling and eye-fish photos)variables were measured. Seventeen one-way ANOVAswere conducted using Tukey test at p<0.05. Amongforest 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 generalwith a positive or negative trend across the MD-UMDUOG-OGgradient. Regeneration not presentsignificant 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 speciesrichness not present significant differences (4-5species). Cover also not significantly change (total,dicots, ferns and inferior plants), however monocotssignificantly differs among treatments (F=3.9,p=0.012), where UMD>MD>UOG>OG. Finally, thecover of indicator plant for environmental degradationnot present significant differences (F=2.1, p=0.106),but was positive related to mature stages. We canconclude that uneven-aged presented some highconservation values compared to even-aged stands,and with a direct relationship with the developmentstage of the trees, where mature have better valuesthan optimum growth stages. These findings can beused for better silviculture practices that combinesilvopastoral and conservation strategies.