Browsing by Author "Salas-Eljatib, Christian"

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    Control of invasive conifers in temperate Andean forests promotes native vegetation restoration, but requires continuous management
    (2024) Fuentes-Ramirez, Andres; Vargas-Gaete, Rodrigo; Toy-Opazo, Octavio; Munoz-Gomez, Nayadeth; Salas-Eljatib, Christian; Pauchard, Anibal
    Non -native conifers have been planted widely because of their growth potential and wood quality. However, many of them have become invasive in the introduced ranges. In Chile, the initial introduction of non -native conifers helped the recovery of degraded land, but today some pine species present a high invasion risk when they are not properly managed, leading to detrimental impacts on natural ecosystems and biodiversity. Such is the case of Douglas fir ( Pseudotsuga menziesii ), a species listed as invasive in south -central Chile, as well as in many other countries, when it establishes beyond the original plantation range. The main goal of this research was to characterize the invasion pattern of P. menziesii within a recently-declared protected area nearby the Conguill & iacute;o National Park in the Andes Cordillera. We aimed at determining the key factors that promote the invasion of P. menziesii outside the original plantations. We established five 1,000 m 2 sampling transects (i.e., 100 x10 m), considering two invasion conditions: (i) within the native forest and (ii) far into open scrub areas, both adjacent to P. menziesii plantations. We measured forest structure, soil nutrients, the floristic composition and pine regeneration before and after controlling the invasion within each study conditions. We found that P. menziesii density and soil nutrient availability in the soil decreased with the distance from the plantation. In addition, an increase in native species cover was found after removing pines, but also noted the ability of P. menziesii to readily re-invade the native forest after removal. These results indicate the need for continuous control of P. menziesii , especially inside the native forest at the early stages of invasion. We discuss the need for better plantation management to prevent its spread into natural areas and protect native forests from non -native conifers invasion.
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    Growth Equations in Forest Research: Mathematical Basis and Model Similarities
    (2021) Salas-Eljatib, Christian; Mehtatalo, Lauri; Gregoire, Timothy G.; Soto, Daniel P.; Vargas-Gaete, Rodrigo
    Purpose of Review Growth equations have been widely used in forest research, commonly to assess ecosystem-level behavior and forest management. Nevertheless, the large number of growth equations has obscured the growth-rate behavior of each of these equations and several different terms for referring to common phenomena. This review presents a unified mathematical treatment of growth-rates besides several well-known growth equations by giving their mathematical basis and representing their behavior using tree growth data as an example. Recent Findings We highlight the mathematical differences among several growth equations that can be better understood by using their differential equations forms rather than their integrated forms. Moreover, the assumed-and-claimed biological basis of these growth-rate models has been taken too seriously in forest research. The focus should be on using a plausible equation for the organism being modelled. We point out that more attention should be drawn to parameter estimation strategies and behavior analysis of the proposed models. Thus, it is difficult for a single model to capture all possible shapes and rates that such a complex biological process as tree growth can depict in nature. We pointed out misleading concepts attributed to some growth equations; however, the differences come from their mathematical properties rather than pure biological reasoning. Using the tree growth data, we depict those differences. Thus, comparisons of some functional forms (at least simple ones) must be carried out before selecting a function for drawing scientific findings.