Climate and growth of Podocarpus salignus in Valdivia, Chile

Abstract: Little dendroclimatic research has been conducted on species of Podocarpus, in response to inherent difficulties associated with tree-ring differentiation and cross-dating. We sampled complete stem cross sections from a plantation of Podocarpus salignus trees in Valdivia, Chile, near the southern edge of the species' range. We measured earlywood, latewood, and total ring widths avoiding ring wedging, and we calculated the corresponding chronologies. The relationship of these chronologies with maximum temperature, precipitation, and sea level pressure was addressed using correlation and redundancy analyses. All chronologies showed a similar response to climate that was consistent with the cloudy, rainy, and temperate conditions of the study area. That is, warm and dry conditions during previous late springs were beneficial, while warm and rainy winters under low atmospheric pressures were detrimental for growth. The observed climatic responses are in contrast to those of conifers from mountainous areas of southern South America. Limitation of carbohydrates available for growth in the following active season was a possible cause for the observed responses to climate. That is, high winter temperatures may deplete stored carbohydrates by increasing respiration, and a high degree of cloud cover reduces the radiation received by the trees in the active season, which may hamper photosynthesis. Our work highlights the dendroclimatological value of Podocarpus salignus to investigate the influence of climatic variation on tree growth and forest productivity

3D-CMCC-FEM (Coupled Model Carbon Cycle) BioGeoChemical and Biophysical Forest Ecosystem Model

This is the 3D-CMCC-FEM (Three Dimensional - Coupled Model Carbon Cycle - Forest Ecosystem Model) user guide for the version 5.5-ISIMIP and 5.6. The 3D-CMCC-FEM is a biochemical, biophysical process-based model and is basically a research tool which is freely available only for non-commercial use. This user guide describes the essential steps for input data creation, model parameterization and for running the model code on different IDEs but even on R environment using different wrappers for pre- and post-processing for3D-CMCC-FEM (both versions: Light Use Efficiency and the fully BioGeoChemical version). We have developed the 3D-CMCC-FEM code relying solely on open source components, in order to facilitate its use and further development by others. The 3D-CMCC-FEM code is released under the GNU General Public Licence v3.0 (GPL)

Modelo De Apoyo AcadéMico Al Estudiante Ufro Como Aporte A La RetencióN De Los Estudiantes De Primer AñO

El Programa de Apoyo Académico al Estudiante UFRO corresponde a un conjunto de servicios para estudiantes de primer año, que trabaja sobre una metodología de intervención basada en el Tutorías, Mentorías y Talleres. Aquí se aborda el factor académico asociado a la retención, teniendo como objetivo: fortalecer el potencial académico de los estudiantes de primer año en pos de favorecer su aprobación, rendimiento y retención. Este Programa se inserta en una universidad donde más del 75% de la población pertenece a los 5 primeros deciles, y el 90% de los estudiantes estudia con beca y/o crédito universitario; por tanto, focaliza sus esfuerzos en estudiantes académicamente vulnerables. El sistema de apoyos se nutre de los antecedentes obtenidos del perfil socioacadémico del estudiante, identificado a partir de un modelo predictivo de “vulnerabilidad académica”, con el cual se elabora un plan de intervención centrado en aquellos estudiantes que reúnen mayores probabilidades de reprobar y/o desertar. Este plan de intervención incluye Tutorías académicas, Talleres de Apoyo a la adaptación universitaria y/o Mentorias. El acceso a estos servicios es voluntario, o por solicitud de docentes y/o directores de carrera, o sugerido por el mismo Programa, según el nivel de vulnerabilidad académica de cada estudiante. Los resultados obtenidos muestran que la retención presenta avances, partiendo por debajo de la retención UFRO en el año 2012, hasta superarla el año 2014 por 4 puntos porcentuales. Además, se identifica alta satisfacción de los estudiantes con las actividades y con el programa en general, catalogándolo como un buen apoyo para adaptarse a la universidad y enfrentar sus desafíos académicos. Así, el modelo aquí presentado comprende un aporte a la retención, mostrando la importancia de abordar el factor académico como eje al apoyo de los estudiantes, en un contexto altamente vulnerable

Diagnóstico De Estrategias De Aprendizaje Para La Orientación Y Focalización De Los Apoyos Académicos Que Favorecen La Permanencia De Estudiantes De Primer Año En La Universidad De La Frontera

Para la adecuada focalización de las acciones de apoyo académico tendientes a propiciar la permanencia de los estudiantes en la Universidad es necesario contar con un diagnóstico certero y preciso de las condiciones de entrada de los estudiantes. Es en este contexto que el Programa de Apoyo Académico al Estudiante de la Universidad de La Frontera ha implementado la construcción de un perfil académico de ingreso de los estudiantes de primer año, utilizando información académica y socioeconómica de ingreso, a lo cual se ha decido adicionar información sobre la motiviación y habilidades de aprendizaje de los estudiantes, que según la literatura es otro factor a considerar al analizar la permanencia y el abandono. Para este último propósito se ha disponiendo la aplicación de un diagnóstico llamado “Motivación hacia el Aprendizaje” (traducción propia de Motivated Strategies for Leraning Questionnaire – MSLQ, disponible en Pintrich, R. R. y DeGroot, E. V., 1990). Desde la aplicación piloto el año 2014, se obtuvo un nivel de confiabilidad de 0.88 (Alpha de Cronbach) y se observó una consistencia interna para cada ítem que varía entre 0.88 y 0.89; a partir de lo cual se realizaron algunos ajustes y se implementó durante el año 2016 como parte de los diagnósticos de ingreso para conocer el perfil de los estudiantes de primer año. La aplicación fue realizada a 1.588 estudiantes de primer año, obteniéndose información para complementar el perfil de ingreso de los estudiantes y siendo un importante insumo para los encargados de nivelar y acompañar el proceso de adaptación da los estudiantes de primer año, favoreciendo su permanencia, aprobación y rendimiento académico (Programa de Apoyo Académico al Estudiante UFRO – PAAU). Al analizar la relación entre las distintas dimensiones que constituyen la motivación hacia el aprendizaje y otras condiciones académicas de entrada (puntaje en pruebas de acceso y rendimiento en enseñanza media), se observa una correlación positiva, indicando que el grupo de estudiantes que ingresa a la universidad con menores aprendizajes previos, además tiene asociado menores estrategias de aprendizaje. Con este resultado se ha ajustado la estructura de apoyos a los estudiantes de primer año: es necesario reforzar las estrategias de aprendizaje y en algunos casos generar en temáticas de tipo motivacional y de habilidades. Además, estos resultados refuerzan el modelo de apoyo académico del Pregrado, centrado en los aprendizajes de los contenidos de las asignaturas e integrando también temáticas de hábitos de estudios y otras habilidades de aprendizaje

Wood anatomical traits reveal water constraints on black spruce xylem formation in the boreal ecosystem

One of the most evident effects of the rapid warming occurring recently in cold and high-latitude forests is the lengthening of the growing season, with the concurrent extension of the period of wood formation. In addition, the increase of evapotranspiration demand is starting to induce drought-stress conditions. By selecting the same black spruce (Picea mariana) trees (20 trees in 4 sites along a latitudinal gradient in Quebec, Canada) where xylogenesis analyses were performed in the last years, we investigated long-term series of wood anatomical traits and compare them to previous short-term findings. Time series of wood anatomical traits were correlated to chronologies of daily temperature, VPD and precipitation during the period 1936-2010. In all sites, tracheid area correlated negatively with June-September temperature and VPD, and positively with precipitation. Meanwhile, cell-wall thickness and the number of cells per ring in the northernmost site were positively affected by spring and summer temperature. While previous monitoring studies evidenced temperature as the key climate variable influencing the timing of xylogenesis phases, our results show that water availability plays a central role in shaping xylem cell features in boreal black spruce. This stresses the importance of an integrate approach to better understand the relationships between wood formation and climate variability at both intra-annual and long (decadal) time scales. This approach will hopefully reduce the uncertainties and skewed interpretations of models on how boreal forest will perform in the future

Using Wood-Anatomical Traits to Clarify Araucaria Araucana Decline in Northern Patagonia

Araucaria araucana is an endemic species of the temperate rainforest in Chile and Argentina, declared a natural monument in 1990 and classified as Endangered by the IUCN in 2013. In recent years mega-drought and warming have been inducing decline and mortality phenomena in many stands. These enduring extreme conditions are challenging the potential of these ecosystems to recover. The aim of this research is to determine the effective drivers of tree decline by applying cutting edge techniques and analyzing wood anatomical traits (tracheid size and cell wall thickness) in A. araucana trees across its natural distribution range

Climate and growth of Podocarpus salignus in Valdivia, Chile

Little dendroclimatic research has been conducted on species of Podocarpus, in response to inherent difficulties associated with tree-ring differentiation and cross-dating. We sampled complete stem cross sections from a plantation of Podocarpus salignus trees in Valdivia, Chile, near the southern edge of the species’ range. We measured earlywood, latewood, and total ring widths avoiding ring wedging, and we calculated the corresponding chronologies. The relationship of these chronologies with maximum temperature, precipitation, and sea level pressure was addressed using correlation and redundancy analyses. All chronologies showed a similar response to climate that was consistent with the cloudy, rainy, and temperate conditions of the study area. That is, warm and dry conditions during previous late springs were beneficial, while warm and rainy winters under low atmospheric pressures were detrimental for growth. The observed climatic responses are in contrast to those of conifers from mountainous areas of southern South America. Limitation of carbohydrates available for growth in the following active season was a possible cause for the observed responses to climate. That is, high winter temperatures may deplete stored carbohydrates by increasing respiration, and a high degree of cloud cover reduces the radiation received by the trees in the active season, which may hamper photosynthesis. Our work highlights the dendroclimatological value of Podocarpus salignus to investigate the influence of climatic variation on tree growth and forest productivity

Effect of climate on tree-ring growth in subtropical Southeastern South America: the first chronologies for Uruguay

Tree-ring research in the highland tropics and subtropics represents a major frontier for understanding climate-growth relationships. Nonetheless, there are many lowland regions \u2013 including the South American Pampa biome \u2013 with scarce tree ring data. We present the first two tree-ring chronologies for Scutia buxifolia in subtropical Southeastern South America (SESA), using 54 series from 29 trees in two sites in northern and southern Uruguay. We cross-dated annual rings and compared tree growth from 1950 to 2012 with regional climate variability, including rainfall, temperature and the Palmer Drought Severity Index \u2013 PDSI, the El Ni\uf1o Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). Overall, ring width variability was highly responsive to climate signals linked to water availability. For example, tree growth was positively correlated with accumulated rainfall in the summer-fall prior to ring formation for both chronologies. Summer climate conditions were key for tree growth, as shown by a negative effect of hot summer temperatures and a positive correlation with PDSI in late austral summer. The El Ni\uf1o phase in late spring/early summer favored an increase in rainfall and annual tree growth, while the La Ni\uf1a phase was associated with less rainfall and reduced tree growth. Extratropical climate factors such as SAM had an equally relevant effect on tree growth, whereby the positive phase of SAM had a negative effect over radial growth. These findings demonstrate the potential for dendroclimatic research and climate reconstruction in a region with scarce tree-ring data. They also improve the understanding of how climate variability may affect woody growth in native forests \u2013 an extremely limited ecosystem in the Pampa biome

Long-term eddy covariance fluxes and xylem anatomy for understanding carbon fixation in white pine woody biomass

Improving our understanding of the carbon cycle is key to addressing the challenges of climate change. In this study, we investigated the relationships between intra and inter-annual climate variations, carbon fluxes, and the xylem biomass in an 80-year plantation of Pinus strobus at Turkey Point, Ontario, Canada. From eddy covariance tower, we obtained daily Gross Primary Production (GPP), precipitation and air temperature for the period 2003-2018. To determine inter-and intra-annual xylem biomass we selected 12 trees and built wood anatomical trait chronologies (cell lumen area, cell wall thickness, cell number, cell wall area and ring wall area) over the past 50 years. Using moving windows, we correlated all chronologies with daily climate data and GPP to analyse their associations at intra-annual scale. The analysis showed that cell lumen area and cell wall thickness were strongly influenced by spring and summer temperature and precipitation. For the first time, we observed strong positive and significant correlations between GPP in the growing season and the cell wall area (which estimates the amount of carbon in each xylem cell) both in earlywood (May 10 - Aug 4, r = 0.685) and latewood (Jul 3 – Sep 3, r = 0.885). Strong positive correlations were also found between GPP and cell number and ring wall area. These results suggest a direct linkage between CO2 fluxes and the accumulation of carbon in woody biomass. This work will help to reconcile two important techniques that are widely used to study carbon sequestration in forests. It will help to reduce uncertainty in woody carbon accumulation and will open new perspectives in the study of the forest carbon cycle