& Introduction Silviculture systems applied in Nothofagus pumilio forests are based on opening the canopy to stimulate natural regeneration by modifying light and soil moisture. The objective is to evaluate regeneration dynamics of N. pumilio along different forest canopy and solar radiation gradients. & Materials and methods Regeneration data and seed production were obtained in 98 permanent plots established in old-growth and harvested stands along a crown cover gradient (19-93%). Volumetric soil water content and basal area were also measured, while crown cover and solar radiation transmission were estimated using hemispherical photographs. Sapling height was modeled using plant age, crown cover, and solar radiation transmission of the stands as explanatory variables. & Results Natural regeneration dynamics were closely related to crown cover values, which determined seed production and the successful establishment and subsequent regeneration growth. Height growth was found to be related to crown cover and solar radiation transmission, where N. pumilio regeneration is optimized at intermediate crown cover levels (45% crown cover, 0.5 effective leaf area index, 26 W m 2 global radiation, and 65% percentage of global radiation). & Conclusion These findings can be used to develop new silvicultural methods or to adjust the current practices to ensure regeneration establishment and maximize height growth at the stand level.

Modelos forzados y no forzados para el cálculo del índice de sitio en bosques deNothofagus antarctica en Patagonia Sur SUMMARYYield potential of a stand can be defined through site quality. One way to measure site quality is using site index equations, being available different equation types (constrained and non-constrained). The objective of this study was to compare the fitness of site index equations using different base ages, and validate them along site quality and age classes in Nothofagus antarctica forests of South Patagonia. Four height growth equations were fitted using two constrained and two non-constrained models. The equations were fitted using three base ages (30, 40 and 50 years). Self-validation was done using gradients of age and site quality. Lower errors were obtained when a base age of 50 years was used for all the equations. Besides this, the best fitting along the age and site quality gradients were obtained with Weibull, Richards and Newnham equations. The self-validation values of the selected equation were comparable to the fitting presented by other authors, who worked with site index models in Nothofagus spp. forests. Newnham equation better described the height dominant growth in N. antarctica, which presented great biological significance according to the shape of the obtained curves. Hence, this model can be recommended to be used as a prediction tool for forest management planning in N. antarctica forests.

Foliar anatomy and morphology are strongly related to physiological performance; therefore, phenotypic plasticity in leaves to variations in environmental conditions, such as irradiance and soil moisture availability, can be related to growth rate and survivorship, mainly during critical growth phases, such as establishment. The aim of this work was to analyze changes in the foliar internal anatomy (tissue proportions and cell dimensions) and external morphology (leaf length, width and area) of Nothofagus pumilio (Poepp. et Endl.) Krasser seedlings growing in a greenhouse under controlled irradiance (three levels) and soil moisture (two levels) during one growing season (measured three times), and to relate them to physiological traits. Three irradiance levels (4, 26 and 64% of the natural incident light) and two soil moisture levels (40 and 80% soil capacity) were evaluated during November, January and March. Internal foliar anatomy of seedlings was analyzed using digital photographs of histological cuttings, while leaf gross morphology was measured using digital calipers and image analysis software. Most internal anatomical variables presented significant differences under different irradiance levels during the growing season, but differences were not detected between soil moisture levels. Palisade parenchyma was the tissue most sensitive to irradiance levels, and high irradiance levels (64% natural incident light) produced greater values in most of the internal anatomical variables than lower irradiance levels (4-24% natural incident light). Complementarily, larger leaves were observed in medium and low irradiance levels, as well as under low soil moisture levels (40% soil capacity). The relationship of main results with some eco-physiological traits was discussed. Foliar internal anatomical and external morphological plasticity allows quick acclimation of seedlings to environmental changes (e.g., during harvesting). These results can be used to propose new forest practices that consider soil moisture and light availability changes to maintain high physiological performance of seedlings.