Propuesta para la definición de un diámetro meta para los árboles futuro en renovales de roble (Nothofagus obliqua)

Los bosques de roble (Nothofagus obliqua), en el centro sur de Chile, constituyen masas forestales relativamente homogéneas, de fácil acceso, de buen crecimiento y madera de valor, razón por la cual son frecuentemente manejados con los incentivos mediante la ley de bosque nativo. El sistema silvícola que se ha implementado en estos bosques, por sobre otros métodos, es el del manejo de árbol futuro. En el presente estudio se entrega una propuesta para la decisión del momento de cosecha, a través de la definición de un diámetro meta para los árboles futuro que permita optimizar el beneficio económico. La metodología ocupada se basa en un modelo de cálculo de rentabilidad que propone que los ingresos adicionales por la madera, que se producen por el crecimiento del árbol, deben compararse con el interés adicional de esperar año a año para alcanzar un diámetro meta. Se aplicó este método en dos rodales de roble de la región de Los Ríos. Los resultados mostraron que el diámetro meta puede variar entre 34 y 46 cm, según la tasa de rentabilidad esperada y la condición inicial del rodal, expresada en la distribución diamétrica de los árboles futuro. Entre más alta era la rentabilidad esperada, más bajo el diámetro meta.

Crecimiento y supervivencia de un ensayo de procedencias y progenies de Roble (Nothofagus obliqua (Mirb.) Oerst.) de 21 años de edad en Pumillahue, Región de los Ríos, Chile

Se evalúa el desempeño en crecimiento (altura, diámetro y volumen), supervivencia y rectitud de fuste de 29 procedencias de roble, anidadas en 10 zonas de procedencia representativas de la distribución natural de la especie en Chile. Los datos de la evaluación provienen de un ensayo de procedencias y progenies de 21 años de edad establecido en el predio Pumillahue (18H 691753,9 m E; 5611422,86 m S). Se caracteriza el desempeño general del ensayo y se evalúa el efecto de las procedencias y zonas de procedencia mediante análisis de varianza no paramétrico. Se detectan diferencias estadísticamente significativas entre procedencias para la supervivencia y variables de crecimiento, no así para la rectitud de fuste. El ensayo presenta un desempeño inferior al observado en un ensayo de comparación, no obstante, las procedencias Cuesta Lastarria y Cruces, de la zona 4C, presentan un comportamiento sobresaliente en crecimiento y supervivencia, lo que permite sugerirlas como idóneas y recomendables para su uso en plantaciones. Se constata que la zona de procedencia y la procedencia individual de mejor desempeño son las correspondientes a la zona de establecimiento del ensayo, confirmando los postulados respecto al uso preferente de semilla local en las iniciativas de plantación.

Vegetation responses to past volcanic disturbances at the Araucaria araucana forest-steppe ecotone in northern Patagonia

Aims Volcanic eruptions play an important role in vegetation dynamics and its historical range of variability. However, large events are infrequent and eruptions with significant imprint in today vegetation occurred far in the past, limiting our understanding of ecological process. Volcanoes in southern Andes have been active during the last 10 ka, and support unique ecosystems such as the Araucaria-Nothofagus forest as part of the Valdivian Temperate Rainforest Hotspot. Araucaria is an endangered species, strongly fragmented and well adapted to disturbances. Yet it was suggested that volcanism might have increased the fragmentation of its populations. To provide an insight into the vegetation responses to past volcanic disturbances, a paleoecological study was conducted to assess the role of volcanic disturbance on the vegetation dynamics and if the current fragmentation has been caused by volcanism. Location Araucaria forest-steppe ecotone in northern Patagonia. Methods Pollen and tephra analysis from a sedimentary record. Results During the last 9 kyr, 39 tephrafall buried the vegetation around Lake Relem, more frequently between 4-2 ka. The vegetation was sensitive to small tephrafall but seldom caused significant changes. However, the large eruption of Sollipulli-Alpehue (~3 ka) might change the environmental conditions affecting severely the forest and grassland, as suggested by the pollen record. Ephedra dominated early successional stage, perhaps facilitating Nothofagus regeneration recovering original condition after ~500 years. Slight increase of pollen percentage from Araucaria and Nothofagus obliqua-type could be indicative of sparse biological legacies distributed in the landscape. The analysis showed that vegetation resisted without permanent changes, recovering relatively fast after the large eruption. Conclusion The relative stability of Araucaria pollen in the study area after several tephrafall suggests no change in its past geographical distribution at the current forest-steppe ecotone, thus I found no evidence that volcanic eruptions would have affected its current conservation status.

Estimation and spatial analysis of aerial biomass and carbon capture in native forests in the south of Chile: county of Valdivia

Introduction: Native forest reserves in southern Chile are the largest carbon sinks in the country, but the amount and level of grouping of the polygons that form these coverages is unknown.Objective: to estimate aerial biomass (AB) and carbon content in native forests in the county of Valdivia, Los Rios region, as well as the degree of grouping of polygons containing carbon in aerial biomass. Materials and methods: 21 land plots of 50 x 10 m were installed. Tree species were identified, and their diameter and height were measured. The AB was calculated using allometric equations, and the carbon content was calculated relating the AB to the factor 0.5. The degree of grouping of polygons with carbon content was calculated using the Getis-Ord G statistic.Results and discussion: The total carbon content in AB was estimated at 599.6 Mg C·ha-1. Carbon is concentrated in three forest types, Evergreen being the most important (63.3 %). The most abundant species was Nothofagus obliqua (Mirb.) Oerst. (18.34 %). There is a clustered spatial dependence on carbon-containing polygons in areas with forest reserves; the rest of the territory showed random distribution. Spatial dependence is related to the physiographic characteristics of the study area.Conclusions: The use of allometric functions for the estimation of aerial biomass and factors to obtain the carbon content is a valid methodology. The carbon polygons of the native forests in Valdivia have grouped spatial distribution.

Synergy in mixed Nothofagus spp. plantations: the effect of deciduous/evergreen neighbourhood on tree growth in the Chilean Andes

Background: The genus Nothofagus is a key component of the Valdivian temperate rainforests of South America, and several of its species have shown promising growth in plantations. Plantations with these species are an opportunity to diversify the Chilean forest sector, ideally through mixed-species arrangements, but the existing literature in this regard is scarce. This work aimed to evaluate individual tree growth for three Nothofagus species in a mixed plantation, considering two types of neighbourhoods. Methods: In a mid-elevation site in the foothills of the Andes ranges we evaluated growth of Nothofagus alpina (Poepp. & Endl.) Oerst, Nothofagus dombeyi (Mirb.) Oerst and Nothofagus obliqua (Mirb.) Oerst according to their neighbourhood, comprised of evergreen or deciduous tree species. We conducted stem analyses for 30 trees (10 per species, one-half with each type of neighbourhood; 370 cross-sections in total) and compared growth in diameter (d), height (h), and volume (v) for each of the 30 trees with nine nonlinear mixed-effects models. Results: Nothofagus alpina showed significantly greater cumulative growth in all variables when growing in an evergreen neighbourhood (EN) compared with a deciduous neigbourhood (DN): average diameter (± 1SD) of 15.3 ± 1.4 vs. 10.8 ± 2.0 cm; average height (± 1SD) of 15.5 ± 1.8 vs. 13.2 ±1.0 m; average volume (± 1SD) of 0.15 ± 0.05 vs. 0.06 ± 0.02 m3. Nothofagus dombeyi showed similar cumulative growth in both conditions for all variables, but there was less variability and greater cumulative volume in the evergreen neighbourhood condition. Finally, Nothofagus obliqua showed similar cumulative growth in both conditions, for average diameter (± 1SD) (14.7 ± 2.0 cm) and average volume (± 1SD) (0.01 ± 0.03 m3), but the average height (± 1SD) was significantly greater in the EN compared to DN (13.8 ± 0.8 vs. 11.2 ± 0.9 m). Conclusions: A suitable arrangement of mixed Nothofagus species plantations may deliver greater growth and productivity than pure plantations, or at least greater timber value considering that one species (N. dombeyi) usually surpasses the others in growth, but its timber is less valuable and its silviculture more costly. In these mixtures both facilitation and complementarity mechanisms occur, which was mostly expressed in the mid-tolerant N. alpina surrounded by the evergreen neighbourhood dominated by the shade-intolerant N. dombeyi. Our results provide new information relevant for the establishment of mixed plantations for production or restoration purposes. Both in Chile and Argentina, these three Nothofagus species cover extensive areas within the Valdivian Temperate Rainforests, so there is a great potential for these plantations in this or other regions with similar site conditions.

Soil Quality Changes within a (Nothofagus obliqua) Forest Under Silvopastoral Management in the Andes Mountain Range, South Central Chile

In Chile, 49.1% of the national territory is affected by soil degradation (including erosion and loss of soil organic matter), whereby of the 51.7 Mha that have been historically associated with agricultural-livestock and forestry activities, only 35.5 Mha are being used at the present. Consequently, soil degradation has resulted in the release of about 11.8 Gg yr−1 of carbon (C) equivalent (CO2eq) to the atmosphere. Silvopastoral systems (SPS), however, can increase soil organic C (SOC) through sequestration (C→SOC), improve ecosystem services, and have been internationally recommended for sustainable land use. Therefore, it was proposed to determine the effects of SPS on soils, over five years, in degraded sites that were located in the Ranchillo Alto (SPS-RA) (37°04′52″ S, 71°39′14″ W), Ñuble region. The sites were rated according to previous canopy disturbance levels (+) as follows: open (Op)+++, semi open (SOp)++, and semi closed (SC)+. The analysis was performed on different physical and chemical soil properties (0–5 and 5–20 cm depths), that were expressed as soil indicators (SIND) for chemical and physical properties, which were used to calculate a soil quality (SQ) index (SQI). The results indicated overall SQI values of 37.6 (SC) > 29.8 (Op) > 28.8 (SOp), but there were no significant variations (p < 0.05) in physical SQ, whereas chemical SQ varied in all conditions, mostly at 0–5 cm in Op and SOp. Increases of SOC were also observed (2015–2018 period) of 22.5, 14.5, and 4.8 Mg ha−1 for SOp, Op, and SC, respectively, showing that SPS promote the reclamation of Ranchillo Alto soils.

Crecimiento, desarrollo cualitativo y retorno financiero de una forestación con Roble (Nothofagus obliqua (Mirb.) Oerst.) al pie de monte andino del centro sur de Chile

En el año de 2002 una superficie de 3 ha de pastizales, situada al pie de monte andino en el Centro Sur de Chile, fue forestada con roble (Nothofagus obliqua (Mirb.) Oerst.). El crecimiento de este rodal plantado fue monitoreado durante 16 años. Se presentan los resultados de 3 inventarios consecutivos a las edades de 6; 11 y 16 años, incluyendo evaluaciones de la calidad exterior de los árboles. Se realizaron dos raleos, el primero a 11 años y el segundo a 16 años de edad. Además, se estudiaron los efectos de estas intervenciones sobre la calidad de los latizales.