Second growth forests of Nothofagus obliqua (roble), N. alpina (raulí), and N. dombeyi (coihue), known locally as RORACO, are among the most important native mixed forests in Chile. To improve the sustainable management of these forests, managers need adequate information and models regarding not only existing forest conditions, but their future states with varying alternative silvicultural activities. In this study, an individual-tree diameter growth model was developed for the full geographical distribution of the RORACO forest type. This was achieved by fitting a complete model by comparing two variable selection procedures: cross-validation (CV), and least absolute shrinkage and selection operator (LASSO) regression. A small set of predictors successfully explained a large portion of the annual increment in diameter at breast height (DBH) growth, particularly variables associated with competition at both the tree-and stand-level. Goodness-of-fit statistics for this final model showed an empirical coefficient of correlation (R 2 emp) of 0.56, relative root mean square error of 44.49% and relative bias of −1.96% for annual DBH growth predictions, and R 2 emp of 0.98 and 0.97 for DBH projection at 6 and 12 years, respectively. This model constitutes a simple and useful tool to support management plans for these forest ecosystems.

While intact forests have intrinsic value in terms of conserving biodiversity, they are also important for associated ecosystem services of soil and water conservation, in addition to the biodiversity, function and geomorphology of stream and river ecosystems. In this latter context, the perspective of watershed is more relevant than forest patch, however we are unaware of any landscape assessments of intact forested watersheds (IFWs). We mapped the coverage of forested watersheds with limited intervention for southern Patagonia (Chile, Argentina) using existing forest stand mapping and high resolution stream/watershed delineation (patch size~0.4 km 2 ). Validation and adjusted IFW boundaries was performed using high resolution satellite imagery for three major inland basins representing the north-south range of the study area. For both scales we evaluated size distribution, conservation status, forest type (deciduous vs. evergreen temperate forest) and bio-climatic zones (precipitation range 500 to >6000 mm/year). For the coarse regional analysis potential IFWs covered over 40% of land surface, and included nearly 60% of all forest cover. These figures were significantly reduced following basin scale validation to 6-21% for IFWs and 5-14% of forest contribution to IFW. IFWs identified in the regional analysis were lower elevation (0-100 m) due to abundant coastal drainages, whereas the basin analyses were higher elevation headwaters systems (1000+ m), the largest over 80 km 2 . Total IFW cover was estimated between 50,000-132,000 km 2 , the range a reflection of disparate results across these two scales, further highlighting the need for comprehensive revision and field validation. At the same time the difference in areas, defined mostly by minor levels of intervention, indicate the vast potential for management or restoration. Taken together they represent a nationally and globally significant contribution to of intact temperate forests and IFWs. Interactions between forest and stream ecosystems, and their implications for IFW conservation, are discussed in these contexts, based on examples from the region. Finally we used Getis-Ord Gi* statistics to identify hot and cold spots for different attributes, providing an example of a combined index for prioritizing IFW conservation.

Second-growth forests of Nothofagus obliqua (roble), N. alpina (raulí) and N. dombeyi (coihue), known locally as RO-RA-CO forest type, are among the most important natural mixed forest types of Chile. Several studies have identified a wide range of factors that could influence both stand and tree variability found in these forests. To better characterize potential tree-and stand-level factors that are associated with RO-RA-CO variability, and that are available in typical forest inventories, several unsupervised multivariate statistical methods were evaluated: 1) non-metric multidimensional scaling (NMDS); 2) principal coordinates analysis (PCoA); and 3) principal component analysis (PCA). The data used in this study originated from a sample of 158 plots consisting of two plot networks that covered the full geographic area of the RO-RA-CO forest type in Chile. We found that site productivity and growth zones did not explain the differences within the sampled population. However, stand development stages, tree-to-tree competition, and tree-size attributes were critical variables with a high percentage of variance explained using PCA, ranging from 61 % to 67 %. In addition, for the PCoA analysis, the variable stand density is important, with ~78 % variance explained.

SUMMARYA total of ten individual tree taper models were fitted to felled raulí (Nothofagus alpina), roble (N. obliqua) and coigüe (N. dombeyi) trees, corresponding to total of 558 individuals (251, 180 and 127, respectively). They were selected from 108 sample plots of pure or mixed roble-raulí-coigüe second growth forests located between 36° and 42° S latitude in Chile. The taper models and a volume model were fitted to 12 fitting groups; these were defined according to the combinations of growth zone and specie together with three general groups representing each species. In all groups, the best taper models allowed to describe the profile with error values smaller than 15% in the estimation of the without bark section diameter. In all cases, the precision and bias in the volume predictions using taper models were similar to the individual volume model. At a general level, small differences among the best models were found with better results for Bruce and Kozak models where the latter showed slightly better performance.Key words: Nothofagus, tapering, volume, growth zones. RESUMENUn total de diez modelos fustales de árbol individual fueron ajustados para árboles volteados de raulí (Nothofagus alpina), roble (N. obliqua) y coigüe (N. dombeyi), correspondiendo a un total de 558 individuos (251, 180 y 127, respectivamente) provenientes de 108 parcelas de muestreo en rodales puros o mixtos de renovales de roble-raulí-coigüe localizados entre los 36° y 42° S en Chile. Los modelos fustales y un modelo de volumen fueron ajustados para 12 grupos, los que fueron definidos con base en la combinación de zona de crecimiento y especie, además de tres grupos generales que representan a cada especie. En todos los grupos, los mejores modelos fustales permitieron describir el perfil con valores de error menores al 15% en la estimación del diámetro de sección sin corteza. En todos los casos, la precisión y sesgo de las predicciones de volumen utilizando modelos fustales fueron similares al modelo de volumen individual. A nivel general, se encontraron leves diferencias entre los mejores modelos, destacando el de Bruce y Kozak con resultados ligeramente mejores para este último.Palabras clave: Nothofagus, ahusamiento, volumen, zonas de crecimiento.

1. Nonstructural carbohydrates (NSCs) mediate plant survival when the plant's carbon (C) balance is negative, suggesting that NSCs could predict plant survival under C stress. To examine this possibility, we exposed saplings of six temperate tree species to diverse levels of C stress created by the combination of two light conditions (full light availability and deep shade) and two defoliation levels (severe defoliation and nondefoliation). We then measured survival, biomass and total NSCs and soluble sugars (SSs) concentrations in different organs of both dead and live saplings.2. We estimated mean NSCs and SSs contents and concentrations per sapling and fitted logistic generalized mixed-effects models to determine if NSCs and SSs predict survival. Using inverse prediction modelling, we also determined whether there is a common NSCs and SSs threshold across species at the time of sapling's death. 3. Defoliation and shade reduced the mean sapling's NSCs and SSs contents, indicating C stress. Mean sapling NSCs and SSs contents and concentrations predicted survival and the robustness of the models improved with the inclusion of species. At death, saplings of the exotic deciduous tree species Acer pseudoplatanus exhibited significantly lower mean NSCs and SSs contents than saplings of the evergreen conifer species Podocarpus nubigenus and lower stem NSCs and SSs concentrations than the broadleaf evergreen species Drimys winteri. 4. The energetic role that NSCs and SSs play in plants under C stress was evidenced by the capacity of these compounds to predict sapling survival under C stress. No common threshold of NSCs and SSs contents or concentrations for sapling survival amongst species was found, indicating that the level of these compounds may not be good proxies for interspecific comparisons of tolerance to C stress. Presumably, there are species-specific limits for the mobilization and use of NSCs and SSs in metabolism. 5. Our results anticipate that the inclusion of NSCs and SSs in modelling will improve predictions regarding tree responses to ongoing climate change.