Browsing by Author "Vargas-Gaete, Rodrigo"

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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.
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    Tree Cover Species Modify the Diversity of Rhizosphere-Associated Microorganisms in Nothofagus obliqua (Mirb.) Oerst Temperate Forests in South-Central Chile
    (2022) Almonacid-Munoz, Leonardo; Herrera, Hector; Fuentes-Ramirez, Andres; Vargas-Gaete, Rodrigo; Larama, Giovanni; Jara, Ronald; Fernandez-Urrutia, Camila; da Silva Valadares, Rafael Borges
    Chilean native forests have been subjected to several types of disturbances, with one of them being the replacement by exotic species. Pinus radiata D. Don is a widespread exotic tree that forms extensive plantations in southern Chile. It covers extended areas, affecting the landscape, biodiversity, and ecosystem services associated with native forest ecosystems. Although advances in assessing the impact of exotic plant species have been conducted, few studies have focused on the alteration of soil microorganisms. This study aimed to characterize the rhizosphere bacterial and fungal communities associated with the tree species Nothofagus obliqua inside a native forest stand and within a P. radiata plantation growing nearby. We used a 16S rRNA gene and ITS region metabarcoding approach. Using bioinformatics, diversity indices, relative abundance, preferential taxa, and predicted functions and guilds were estimated. The beta-diversity analysis showed that both factors, the type of soil (rhizosphere or bulk soil) and the type of site (native forest or P. radiata plantation), were significant, with the site explaining most of the variation among bacterial and fungal communities. Proteobacteria and Basidiomycota were the most abundant bacterial and fungal phyla in both types of soil and sites. Similarly, bacteria showed similar abundant taxa at the family level, independent of the soil type or the site. The main fungal taxa associated with native forests were Tricholomataceae and Cantharellales, whereas in P. radiata plantations, Russulaceae and Hyaloscyphaceae were the most abundant families. The main bacteria functional groups were chemoheterotrophy and aerobic chemoheterotrophy, without significant differences between the type of soil or sites. Overall, these results demonstrate that the composition and diversity of bacterial and fungal communities associated with native N. obliqua forest are influenced by the surrounding forest, and mainly depend on the site's characteristics, such as the lignin-rich wood source. These results improve our understanding of the impact of native forest replacement on soil microbial communities, which can alter microbial-related soil ecosystem services.
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    What fire didn't take away: plant growth-promoting microorganisms in burned soils of old-growth Nothofagus forests in Los Andes Cordillera
    (2024) Almonacid-Munoz, Leonardo; Herrera, Hector; Fuentes-Ramirez, Andres; Vargas-Gaete, Rodrigo; Toy-Opazo, Octavio; Costa, Paulo Henrique de Oliveira; Valadares, Rafael Borges da Silva
    Background and aims Wildfires can dramatically alter forests, their biodiversity and goods they provide to society. In the Andes Cordillera, Nothofagus pumilio is a native, fire-sensitive tree species that is completely excluded from severely burned areas. Therefore, it is of interest to evaluate whether there are differences in the microbial soil communities that could contribute to improve the recruitment of N. pumilio after a fire. We aimed at determining the diversity of soil bacteria and fungi associated with Nothofagus pumilio in old-growth forests affected by a moderate severity wildfire in the Andes Cordillera of south-central Chile in 2015. Methods Eight years after fire, soil samples were collected from selected N. pumilio rhizosphere and bulk soil in fire-affected areas, and were compared with those from unburned areas using a metabarcoding approach. Results We found that symbiotic microorganisms such as saprophytic, ectomycorrhizal fungi, ericoid mycorrhizal taxa and N-fixing bacteria were present with high abundances in the burned area. The most abundant bacterial genera were Mycobacterium, Rhodoplanes and Bryobacter. Meanwhile, Cortinarius and Penicillium were the most common fungal genera identified in burned and unburned sites. Conclusions Moderate severity wildfires in Nothofagus pumilio forests do not result in significantly different soil microbiomes eight years post-burn in either the rhizosphere or bulk soil, which could be key for N. pumilio establishment and survival after fire. Identifying the microbial diversity associated with native trees after fire is essential to know symbiotic microorganisms supporting the recovery of plant species.