Phytochemical Screening and Antioxidant Activity of Seven Native Species Growing in the Forests of Southern Chilean Patagonia

The genus Nothofagus is one of the most abundant in the subantarctic Patagonian forests. Five species inhabit these ecosystems, three evergreen (Nothofagus betuloides, Nothofagus dombeyi, and Nothofagus nitida) and two deciduous (Nothofagus pumilio and Nothofagus antarctica). This is the first report on the levels of secondary metabolites and the antioxidant capacity of Patagonian tree species growing in natural environments. The aim of this work was to carry out a phytochemical screening, to determine the antioxidant capacity, the sun protection factor, and the α-glucosidase and tyrosinase inhibitory activity of foliar extracts of the five previous species. Besides, Aristotelia chilensis and Berberis microphylla, two species of Patagonian shrubs growing in the same forests, were used as reference. N. dombeyi was the Nothofagus with the best antioxidant capacity. B. microphylla differed from all studied species. Moreover, the Nothofagus was split into two groups. N. betuloides and N. dombeyi are the most similar species to A. chilensis. The α-glucosidase was completely inhibited by all studied extracts. Furthermore, N. antarctica, N.pumilio, and N. nitida inhibited about 70% of the tyrosinase activity. All the results found in this study for the species of the genus Nothofagus support further research on their potential beneficial properties for human health.

Chronically Low Nutrient Concentrations in Tree Rings Are Linked to Greater Tree Vulnerability to Drought in Nothofagus dombeyi

Forest dieback and mortality episodes triggered by droughts are receiving increasing attention due to the projected increases in these extreme climate events. However, the role played by nutrient impairment in dieback is understudied, despite interactions among carbon-water balances and nutrition. Here, we followed a comparative analysis of long-term growth, intrinsic water-use efficiency (iWUE), oxygen isotopes (δ18O) and wood-nutrient composition patterns between living (L) and dead (D) trees of a Nothofagus dombeyi population, showing dieback in Argentina. The onset of the growth decline of D trees occurred ca. 40 years before death. These trees showed higher iWUE, pointing to higher drought stress. Their lower δ18O values, together with the uncoupling between δ18O and leaf-level processes, suggested a deeper source of water uptake for this vigor class. D trees showed a poorer nutritional status than L trees that likely amplified the dieback. This was supported by numerous positive associations of P- and K-concentrations in wood and related ratios with iWUE, δ18O and tree growth. Therefore, drought-related nutrient deterioration can significantly contribute to dieback and be an early warning signal of impending tree death.

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.

Growth and Silvicultural Potentiality of Lomatia hirsuta Forests from Stump Shoots in the Valley of El Manso/Patagonia/Argentina

Lomatia hirsuta (Lam.) Diels is a pioneer tree species that regenerates mostly after fire and is more frequently found as a secondary species in Patagonian forests dominated by Austrocedrus chilensis and Nothofagus dombeyi. However, in the El Manso Valley, Province of Río Negro in Western Argentina, L. hirsuta forms pure stands, originated from stump shoots. The wood is very attractive for its colourful appearance and beautiful grain, suitable for fine furniture. Nevertheless, these forests are not managed for timber production, they are mostly thinned for grazing, and the wood is mainly used as firewood. The objective of this study was to evaluate the possibility to improve quality wood production in stands through silvicultural interventions in a sustainable way. Samples have been carried out in dense stands of different ages and in one less dense stand with the traditional use for pastures. We evaluated the state and quality of the trees, and their growth has been studied by means of trunk analysis. The results indicate that there is a significant potential to improve the production of quality wood in dense stands through thinning oriented to crop trees. This should start in young stands, because in older stands, good form and sound trees are already considerably reduced. It also became apparent that forest management is necessary to stabilize these nearly unattended forests, which in old stands are very vulnerable to damages caused by wind and wet snow. In such stands, the extraction of trees could be combined with the planting of seed trees, with the expectation to improve the quality and vigour of the trees at maturity.

Individual-based dendrogenomic analysis of forest dieback driven by extreme droughts

Global change-driven droughts are triggering worldwide forest dieback which are predicted to increase even further. Here, we combined genome-wide single nucleotide polymorphisms (SNPs) and dendrochronological approaches to assess genetically-based individual tree vulnerability to past extreme droughts that caused massive mortality of Nothofagus dombeyi forests in northern Patagonia. We collected fresh leaves and wood cores from pairs of Healthy Crown (HC) and Partially Affected crown (PA) trees at four sites impacted by 1998, 2008 and 2014 droughts. We used dendrochronological techniques to estimate parameters in terms of growth trends due to drought and genomic analysis to assess its relationship with water stress. While 5,155 neutral loci did not discriminate PA from HC trees, a set of 33 adaptive SNPs did so, 8 of which were related to hydric stress. Association analysis between genomic variants and dendrophenotypic traits yielded 6 SNPs that were associated with a growth measure as resilience to cope with drought. Our preliminary results indicate that susceptibility to drought in N. dombeyi could be determined at the genomic level. The combination of both approaches provides a framework for the identification and analysis of candidate genes for stress response in non-model species.

Influencia del origen de las semillas en el desempeño de coigüe (Nothofagus dombeyi (Mirb.) Oerst.) en ensayos de 15 años en la costa y precordillera de la Región de Los Ríos

Se caracteriza el desempeño de coigüe, en términos de supervivencia, altura, diámetro y rectitud de fuste a los 14-15 años de edad en dos ensayos establecidos en costa y pre cordillera de la región de Los Ríos Chile (Huillilemu en San José de la Mariquina y Remeco en Panguipulli); se analiza también el efecto del origen de las semillas (zonas de procedencias) sobre las variables mencionadas.

The impact of recent land-use change in the Araucaria araucana forest in northern Patagonia

Land-use change in the form of extensive Pinus plantations is currently altering the natural vegetation cover at the forest–steppe ecotone in northern Patagonia. Providing recommendations for conservation efforts, with respect to this recent and earlier land-use changes, requires a longer time perspective. Using pollen analysis, we investigated to what degree the colonization of the area by Euro-American settlers changed the forest composition and the vegetation cover, and to explore the spread of the European weed Rumex acetosella. This study is based on short sediment cores from six lakes in the Araucaria araucana forest region, across the vegetation gradient from the forest to the steppe. Results document that although Araucaria araucana has been extensively logged elsewhere, near the investigated sites, populations were rather stable and other elements of the vegetation changed little with the initiation of Euro-American settlements. A reduction of Nothofagus dombeyi-type pollen occurred at some sites presumably due to logging Nothofagus dombeyi trees, while toward the steppe, Nothofagus antarctica shrubs may have been removed for pasture. The appearance of Rumex acetosella pollen is consistent with the initiation of land use by Euro-American settlers in all cores, probably indicating the onset of animal farming. The rise of the Rumex acetosella pollen curve during the 1950s marks more recent land-use change. These observations indicate that the spread and local expansion of the weed requires disturbance. Overall, the study shows that the initial colonization of the area by Euro-American settlers had little effect on the natural vegetation structure, while developments since the 1950s are strongly altering the natural vegetation cover.

Crecimiento de Austrocedrus chilensis y Nothofagus dombeyi en bosques mixtos y condiciones ambientales para el desarrollo de sus renovales: contribuciones al manejo de rodales afectados por el mal del ciprés

El ciprés de la cordillera (Austrocedrus chilensis (D. Don) Pic. Ser. et Bizzarri), es una conífera endémica de importancia forestal de los bosques Andino-patagónicos. El manejo silvícola de estos bosques se encuentra condicionado, en gran parte de su distribución natural, por el “mal del ciprés”, una enfermedad que produce mermas en su crecimiento y mortalidad. Los bosques enfermos pierden progresivamente su estructura y valor, siendo limitadas las posibilidades de aplicar en ellos un manejo forestal sustentable. En algunos rodales con mal del ciprés se ha observado que debido a la reducción de la cobertura del dosel que ocasiona la enfermedad, se impulsa el proceso de regeneración natural de la especie y, cuando existe una fuente de semillas cercana, también se incorpora la regeneración natural de coihue (Nothofagus dombeyi (Mirb.) Oerst.). El coihue es otra especie de valor con la cual el ciprés se combina naturalmente en parte de su distribución, formando bosques mixtos. El manejo de bosques mixtos es un tópico de creciente interés internacional debido a las ventajas productivas y ambientales que estos presentan en comparación con los mono-específicos. La productividad de los bosques mixtos está condicionada por la forma en que se distribuye el espacio de crecimiento entre los distintos componentes de la estructura forestal, como las especies y los estratos. En estructuras mixtas las variables forestales tradicionales (área basal, índices de densidad como el IDR, etc.) no permiten una buena representación del espacio de crecimiento ocupado. Un mejor indicador es el índice de área foliar (IAF). Esta tesis presenta información de base para diseñar propuestas para la conversión de bosques de ciprés enfermos y su manejo como bosques mixtos, a fin de aprovechar las ventajas productivas y ecosistémicas que esta conversión podría originar. El objetivo general de la tesis fue generar conocimientos para el manejo forestal de los bosques mixtos de ciprés de la cordillera y coihue, para las etapas de establecimiento y de conducción del rodal. Para la primera, acerca de la relación entre las condiciones ambientales (macro y micro) y el crecimiento de la regeneración de ambas especies, y para la segunda, cómo influye el espacio de crecimiento ocupado y su distribución sobre el incremento en volumen del rodal en distintas estructuras. Para cada especie se desarrollaron funciones de predicción del área foliar mediante relaciones alométricas y se evaluó su relación con el incremento corriente en volumen y la eficiencia de crecimiento. Los resultados muestran ajustes lineales satisfactorios para ambas especies. Las funciones ajustadas constituyen una herramienta fundamental para estudiar la distribución del crecimiento y formular pautas de manejo para bosques mixtos a través del control del espacio de crecimiento ocupado mediante el uso del IAF. En bosques mixtos naturales se determinó que las diferencias en el incremento corriente en volumen (ICV) del rodal de las estructuras estudiadas estuvieron más relacionadas a cómo se distribuye el IAF entre las especies que al IAF total del rodal. El coihue es la especie que aporta más al crecimiento del rodal en los bosques mixtos y muestra el doble de eficiencia para una misma unidad de área foliar. A su vez, el porcentaje de árboles eficientes del rodal está relacionado con el IAF del rodal, de manera que rodales con menores IAF muestran mayor eficiencia. Por otra parte, el crecimiento en altura de los renovales de ciprés y coihue tiene una relación inversa con el IAF del rodal. Sin embargo, el crecimiento en altura de coihue se ve favorecido en rodales con IAF menor a 4, mientras que el ciprés no presenta un umbral. A su vez, el crecimiento de los renovales se ve influenciado por la proporción de las especies en el IAF, evidenciando un efecto negativo de una mayor proporción de coihue en el dosel. Por lo tanto, para potenciar el crecimiento del rodal es recomendable aumentar la participación de IAF de coihue, mientras que para promover la regeneración es necesario disminuirla. En condiciones de vivero se determinó la respuesta en supervivencia y crecimiento de ciprés y coihue ante el efecto conjunto de distintos regímenes de luz y de humedad edáfica. En el campo a su vez, y en un sitio mésico y otro xérico, se determinó la respuesta de ambas especies a la cobertura del dosel, a la vegetación circundante y a la protección artificial. En vivero ambas especies mostraron respuestas similares a los factores estudiados en supervivencia e incremento en DAC, altura y volumen, y fueron susceptibles a la sequía. Aunque se observaron porcentajes de supervivencia similares al final de la temporada entre las especies, niveles de luz bajos y una mayor adaptación a la sequía retrasaron significativamente la mortalidad de las plantas de ciprés en comparación con las de coihue. En ambas especies una baja luminosidad puede afectar negativamente el crecimiento, al igual que una baja humedad. Los mayores crecimientos se registraron en los niveles intermedios de ambos factores y el coihue creció más que el ciprés. A campo se observó que ambas especies tienen buena supervivencia y crecimiento cuando la cobertura del dosel es de más de 30%. La remoción de la vegetación competidora es beneficiosa para ambas especies en ambos sitios. Para plantaciones sin cobertura del dosel se recomienda el uso de protección artificial. Ambas especies tienen el potencial para la restauración de rodales afectados por el mal del ciprés.