Browsing by Author "Gilabert, Horacio"

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    Allometric Models for Estimating Aboveground Biomass in Short Rotation Crops of Acacia Species in Two Different Sites in Chile
    (MDPI, 2021) Cabrera Ariza, Antonio; Valdes, Sara; Gilabert, Horacio; Santelices Moya, Romulo Eduardo; Alonso Valdes, Maximo
    We evaluated the ability of different allometric models to estimate the biomass production of short-rotation woody crops of Acacia dealbata, A. mearnsii and A. melanoxylon. Models considered the adjustment and validation of biomass functions and biological restrictions, such as the use of additive components of the biomass (stem, branches, and leaves). Adjustments of linear and nonlinear models of the three acacia species-established in two locations and of three densities in southern Chile-were utilized. Systems of equations were adjusted to guarantee the addition of the biomass components and the trees' total biomass. The selection of models was performed based on their goodness of fit and predictive quality. Methods that accounted for the correlation between biomass components granted an additively consistent equations system with efficient estimates and reliable prediction intervals.
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    An assessment of volume-ratio functions for Eucalyptus globulus and E. nitens in Chile
    (2010) Gilabert, Horacio; Paci, Carlos
    H. Gilabert, and C. Paci. 2010. An assessment of volume-ratio functions for Eucalyptus globulus and E. nitens in Chile. Cien. Inv. Agr. 37(1):5-15. Volume-ratio and total volume models for Eucalyptus nitens and E. globulus grown in southern Chile were fitted independently. The validation process considered the bias and the total error in the volume estimates, as well as the age classes close to thinning and harvesting operations. Volume estimates from the system of functions (volume and ratio) were compared to the volume estimates from a taper function (Bruce model) to estimate the volume at different top stem diameters. The results indicated that general (as opposed to local) logarithmic functions performed better in their estimation of the total volume for both species, while a unique polynomial model was the best model for the ratio estimates for both Eucalyptus species. The system of functions (total volume + ratio models) was an unbiased estimator for a top stem diameter of 5 and 10 cm for E. nitens, and was a slightly biased estimator for E. globulus. Estimates of the volume of top stems with 18 cm diameters had a large bias and a large total error for both species. These total errors were generally related to errors in the total volume function rather than to errors in the ratio estimates. When the volume estimates were compared with estimates from a taper function, the volumne-ratio system performed better for E. nit ens while the taper function performed better for E. globulus.
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    Demographic carrying capacity model: A tool for decision-making in Rapa Nui
    (2021) Bergamini, Kay; Moris, Roberto; Angel, Piroska; Zaviezo, Daniela; Gilabert, Horacio
    The increase of population in Rapa Nui (Easter Island) has fueled concerns within the community, given the uncertainty of its impacts. These concerns have driven a sociopolitical process that triggered the enactment of Law 21,070, which regulates the access and permanence of visitors in the territory as a way to cushion the pressure on different environmental, social, and infrastructure components that affect the local quality of life. However, for its application, this law requires technical foundations that allow restrictions to be applied and, therefore, knowledge about the demographic capacity of the territory is also needed. To this end, a dynamic model was built, which consists of different variables that are sensitive to population growth and also can be projected into the future, thus delivering timely information for decision-making. This paper describes the socio-political context for the creation of this instrument, as well as its elaboration process and main results.
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    Dinámica estacional y patrones de distribución de la avifauna asociada a humedales subantárticos de la Reserva de Biosfera Cabo de Hornos (54-55ºS), Chile
    (2009) Ibarra Eliessetch, José Tomás; Rozzi, Ricardo; Gilabert, Horacio; Anderson, Christoper B.; McGehee, Steven M.; Bonacic, Cristián
    El rol de las aves en la ecología de los ecosistemas subantárticos de la Reserva de Biosfera Cabo de Hornos (RBCH), Chile, ha sido poco estudiado. Se estudió el efecto de la altitud, distancia al borde costero, tamaño del espejo de agua, estación del año y cobertura vegetacional sobre la diversidad y abundancia de aves de humedales y de sus hábitats adyacentes en isla Navarino (54–55ºS, 67ºW) en la RBCH. Se cuantificó la composición específica, riqueza de especies y abundancias relativas de aves de humedales y de sus hábitats adyacentes, de manera estacional. Se registró un total de 56 especies pertenecientes a 10 órdenes y 25 familias, con una marcada estacionalidad en riqueza (P = 0,001) y número total de individuos (P < 0,01). De ellas, 33, 9% fueron residentes, 48,2% llegan en primavera-verano y para un 17,9% se desconoce su estacionalidad. La distancia a la costa marina es la variable que mejor explica tanto la riqueza (P < 0,01) como el número total de individuos (P < 0,05). Humedales a mayor distancia de la costa y altitud, presentaron menor diversidad de aves, a pesar de que los cambios en altitud fueron bajos (<300 m). Este trabajo muestra los patrones de estacionalidad y dinámica, así como los mecanismos subyacentes, de la avifauna de humedales y sus hábitats adyacentes en la RBCH. Aceptado el 20 de Mayo de 2009
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    Forest cover outside protected areas plays an important role in the conservation of the Vulnerable guina Leopardus guigna
    (2013) Galvez, Nicolas; Hernandez, Felipe; Laker, Jerry; Gilabert, Horacio; Petitpas, Robert; Bonacic Salas, Cristian; Gimona, Alessandro; Hester, Alison; Macdonald, David W.
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    Optimizing Inventory and Yield Data Collection for Forest Management Planning
    (OXFORD UNIV PRESS INC, 2010) Gilabert, Horacio; McDill, Marc E.
    This work uses a Cost+Loss approach to estimate the optimal investment in inventory information for forest planning A bootstrapping approach is used to simulate the impact of different inventory intensities on the quality of decisions in a linear programming harvest scheduling model Multiple formulations of the harvest model based on varying inventory intensities are used to calculate the value of a variable labeled Loss that measures the monetary losses resulting from the use of imperfect yield information in the harvest model The variable Loss and the cost of obtaining the inventory information are used to estimate empirical relationships between their expected value and the amount of inventory information (number of inventory plots and number of experimental plots) used in the harvest models These two relationships are combined to give an explicit estimate of the expected Cost+Loss as a function of the inventory intensity variables This Cost+Loss relationship is minimized to estimate optimal number of inventory plots and the optimal number of experimental plots An example is developed with radiata pine information from southern Chile Results for this example suggest that current practice uses too many experimental plots and too few inventory plots FOR SCI 56(6) 578-591
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    Temporal and spatial dissimilarities in an intertidal fish assemblage in the South Pacific Ocean: The role of the ENSO process and intrinsic habitat conditions in emerging patterns
    (2023) Espinoza, C. Valeria; Hernandez-Miranda, Eduardo; Gilabert, Horacio; Ojeda, F. Patricio
    An intertidal fish assemblage was studied in central Chile for 15 years in three localities: Isla Negra, El Tabo, and Las Cruces. Analyses of their multivariate dissimilarities were carried out considering temporal and spatial factors. Temporal factors included intra-annual and year-to-year variability. Spatial factors included locality, intertidal tidepool height, and each tidepool considered as a unique unit. Complementary to this, we tested the hypothesis that the El Nino Southern Oscillation (ENSO) would help explain year-to-year dissimilarities in the multivariate structure of this fish assemblage for the 15 years of data. To this end, the ENSO was regarded as a continuous inter-annual process as well as a set of discrete events. Additionally, dissimilarities in the temporal dynamics of the fish assemblage were evaluated considering each locality and tidepool unique units. Results indicated the following: (i) The most representative species for the whole area and period of the study were Scartichthys viridis (44 %), Helcogrammoides chilensis (17 %), Girella laevifrons (10 %), Graus nigra (7 %), Auchenionchus microcirrhis (5 %), and Helcogrammoides cunninghami (4 %); (ii) there is intra-annual (i.e., seasonality) and year-to-year multivariate variability in fish assemblage dissimilarities throughout the entire area of study, including all the tidepools and localities; (iii) when considering the spatial factor specifically, each tidepool unit, as well as their heights and localities, presented their own unique temporal yearto-year dynamics. The latter can be explained by the ENSO factor, also considering the intensity of the El Nino and La Nina events. In summary, the multivariate structure of the intertidal fish assemblage was statistically dissimilar when