Browsing by Author "Medina, Alex"

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    Changes in leaf physiology for eucalyptus genotypes with increase in integral water stress and its consequence for initial growth in central Chile
    (2022) Goncalves de Oliveira, Thiago Wendling; Rubilar, Rafael; Sanquetta, Carlos Roberto; Dalla Corte, Ana Paula; Bozo, Daniel; Medina, Alex; Mardones, Oscar; Emhart, Veronica; Quiroga, Juan Jose; Valenzuela, Hector
    Limited information exists on how small changes in soil water affect the physiological responses of eucalyptus and their relationship with productivity. This experiment evaluated physiological traits during decreased soil water and compared them with growth and water stress integral (WSI) of 22 eucalyptus genotypes with 1.5 years old. The experiment was conducted in sandy soil with low water holding capacity in Chile. Selected genotypes were Eucalyptus globulus, E. nitens, and E. nitens x E. globulus hybrids (E. gloni). Seasonal predawn leaf water potential (psi(pd)) was evaluated under well-irrigated conditions and after 40 days without irrigation. Subsequently, two sampling instances were considered for analysis, well-irrigated conditions M-0 (470 days after planting) and 40 days without irrigation M-final (510 days after planting). During that period, we measured midday leaf water potential (psi(pd)), leaf area index (LAI), diurnal changes in photosynthesis (A(n)) and stomatal conductance (g(s)). The broad range of WSI among genotypes indicated contrasting levels of accumulated water stress during early development. In fact, E. globulus presented 30% more water stress than E. nitens, and genotypes with the highest WSI showed the lowest growth. Between M-0 and M-final, there was a reduction in A(n) and g(s) in the morning and midday with small changes in the afternoon, and consequently, values of the intrinsic water use efficiency (iWUE) increased. The psi(pd) showed small changes and we observed a large LAI increment for all genotypes. Changes in iWUE were more pronounced for genotypes with lower WSI, which suggested that these genotypes with lower accumulated water stress were more sensitive to changes in soil water, such as E. gloni genotypes allowing them to maintain high productivity.
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    Differences in rainfall interception among Eucalyptus genotypes
    (2023) Valverde, Juan Carlos; Rubilar, Rafael; Barrientos, Guillermo; Medina, Alex; Pincheira, Matias; Emhart, Veronica; Zapata, Alvaro; Bozo, Daniel; Espinoza, Yosselin; Campoe, Otavio C.
    Key messageHydrological indicators such as rainfall interception of Eucalyptus genotypes are essential to guarantee the water sustainability of forest plantations under climate change scenarios.Rainfall interception is a critical component of water balance in Eucalyptus plantations and may provide better water sustainability by reducing potential adverse effects under drought scenarios. This study evaluated rainfall interception of Eucalyptus globulus and E. nitens x globulus (high and low yield), E. nitens, E. badjensis, E. smithii, and E. camaldulensis x globulus. Rainfall, stemflow, throughfall, and interception (calculated as rainfall-stemflow-throughfall) were measured for 2 years (2020-2022) and correlated with plantation characteristics [diameter at breast height, total height, stem growth, and leaf area index (LAI)]. Our results showed an average rainfall of 1063.6 mm year(-1); only stemflow did not show differences among genotypes with an average value of 193.4 mm year(-1) (18.2% of annual rain). In contrast, throughfall and interception presented significant differences among genotypes, and both parameters showed a strong relationship with LAI. Therefore, three independent groups were obtained: E. badjensis and E. smithii showed the highest LAI (average 5.7 m(2) m(-2)) with 517.0 mm year(-1) of average interception and 427.6 mm year(-1) of average throughfall (48.6% and 40.2% respectively). For E. globulus (low-yield), E. nitens x globulus (low-yield), and E. nitens, that showed the lowest LAI (average 3.3 m(2) m(-2)), average throughfall reached 730.8 mm year(-1) (68.7%), and average interception reached 197.3 mm year(-1) (18.5%). Finally, E. globulus (high-yield), E. nitens x globulus (high-yield), and E. camaldulensis x globulus with an average LAI of 4.5 m(2) m(-2), average interception reached 345.2 mm year(-1) (32.5%), and average throughfall reached 602.7 mm year(-1) (56.7%). Our results suggest that understanding differences between taxas/genotypes may contribute to developing hydrological indicators that may improve estimates of plantation water sustainability under water scarcity climate change scenarios.
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    Morphological, physiological and carbon balance response of Eucalyptus genotypes under water stress
    (2024) Garcia, Luz Yeidy; Rubilar, Rafael; Valverde, Juan Carlos; Emhart, Veronica; Bascunan, Luisa; Medina, Alex; Bozo, Daniel
    Water stress is considered one of the main environmental factors that limit survival and productivity of Eucalyptus plantations. Identifying genotypes traits that provide evidence of tolerance to water stress may allow sustained productivity and secure better resilience of forest plantations under climate change in Mediterranean environments. Our study analyzed morphological, physiological, and carbon (C) balance responses of ten Eucalyptus genotypes under contrasting water regimes under nursery conditions. One-year-old cuttings of Eucalyptus nitens (En1 and En2), E. smithii (Es), E. badjensis (Eb), E. nitens x globulus (Eng1, Eng2, Eng3, and Eng4), E. globulus (Eg), and E. camaldulensis x globulus (Ecg) were evaluated under progressive drought from well-watered (soil water potential close to 0 MPa) to severe water stress (soil water potential close to - 2.5 MPa) conditions. Absolute growth rate (root collar diameter, height, shoot: root biomass ratio), net photosynthesis, stomatal conductance, transpiration, intrinsic water use efficiency (iWUE), predawn water potential (Psi(pd)) and C balance (flux and partitioning) were evaluated. As expected, water stress significantly reduced growth and physiological activity for all genotypes. Of all evaluated parameters iWUE and Psi(pd) were the key grouping physiological and growth response variables among genotypes. Genotypes En1, Eng3, and Eng4 were considered tolerant genotypes, with the smallest physiological change and larger morphological growth. Genotypes En2, Es, Eng1 and Eng2 were moderately tolerant showing intermediate responses compared to other groups. In contrast, Eg, Eb, and Ecg were considered highly sensitive, with major changes in morphology and physiological variables over time. Our results suggest that nursery stage physiological evaluation of genotypes may allow selection for sites with water resource availability risks and may allow to reduce mortality and early establishment productivity losses under drier climate change scenarios.
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    Taper and individual tree volume equations of Eucalyptus varieties under contrasting irrigation regimes
    (2022) Valverde, Juan Carlos; Rubilar, Rafael; Medina, Alex; Mardones, Oscar; Emhart, Veronica; Bozo, Daniel; Espinoza, Yosselin; Campoe, Otavio
    Background: Compatible taper and volume equations are key for traditional growth and yield and current process-based or hybrid models. However, most equations do not consider variables such as genotype, water regime and their interaction, limiting the development of general equations for species or regions. Our research investigated taper and individual tree volume equations for eight Eucalyptus genotypes (E. nitens, E. badjensis, E. smithii, E. camaldulensis x globulus and two varieties of low and high productivity of E. globulus and E. nitens x globulus), all materials are growing under summer irrigated vs. no irrigated conditions.
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    Wood Basic Density Assessment of Eucalyptus Genotypes Growing under Contrasting Water Availability Conditions
    (2024) Elissetche, Juan Pedro; Alzamora, Rosa M.; Espinoza, Yosselin; Emhart, Veronica; Pincheira, Matias; Medina, Alex; Rubilar, Rafael
    Limited research exists on wood properties in E. nitens x E. globulus hybrid genotypes grown in water-limited conditions generated by the climate change influence in Mediterranean areas. The EUCAHYDRO project aimed to assess environmental stress impacts on eucalyptus genotypes, including responses to reduced water availability, and to evaluate wood density and resistance using the non-destructive drill resistance technique. This study focused on 10-year-old E. nitens x E. globulus hybrids and Eucalyptus badjensis Beuzev. & Welch, revealing that low irrigation led to a 13% (p < 0.05) decrease in diameter and a 6.5% (p > 0.05) increase in wood density for the hybrids. On the contrary, E. badjensis demonstrated a noteworthy 22% increase in wood density (p < 0.05), while showing a corresponding 0.6% growth increase (p > 0.05), as measured by the diameter at breast height. Drill resistance measurement results indicated that E. nitens x E. globulus' amplitude ranged from 20.1% to 26.6%, while E. badjensis' ranged from 20.8% to 27.2%. The study revealed a high correlation between resistance amplitude and wood density, with coefficients of 0.97 observed for E. nitens x E. globulus and 0.84 for E. badjensis (p < 0.05). These findings fall within the range reported in similar studies involving Eucalyptus spp. The primary focus of the research was to assess the growth potential and wood quality of novel Eucalyptus spp. under conditions of water limitation. The study also explored the utility of drill resistance as a predictive measure for evaluating wood density as an indicator of wood quality.