Browsing by Author "Novoa Galaz, Fernando Javier"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Efectos de los incendios forestales sobre los gremios de aves del bosque templado andino del sur de Chile
    (2019) Novoa Galaz, Fernando Javier; Ibarra Eliessetch, José Tomás; Pontificia Universidad Católica de Chile. Facultad de Agronomía e Ingeniería Forestal
    Los eventos de perturbación, tales como los incendios, modifican la composición y estructura de los ecosistemas de bosque. Estudiamos la diversidad de los gremios de aves que habitan bosques de Nothofagus y Araucaria araucana en los bosques templados andinos del sur de Chile, en tres sitios afectados por incendios forestales con distintas historias de fuego (intervalo de tiempo y frecuencia de un evento) durante 2016-2018. Establecimos 40 puntos de conteo y 40 parcelas de vegetación para determinar la riqueza y densidad de aves, junto con los atributos vegetacionales en cada sitio. En total 35 especies de aves fueron registradas al muestrear sitios control, quemados dieciséis y dos años después de la perturbación de un incendio, observamos que al pasar el tiempo la comunidad de aves se volvió más similar al sitio control sin quemar. Los gremios de uso de hábitat, alimenticio y nidificación difirieron mayormente en sus respuestas al aumento de la frecuencia y el tiempo transcurrido desde el incendio; la mayoría de los gremios de aves disminuyeron ante el efecto del fuego, aunque los granívoros, generalistas de arbustos, aves no nidificadoras de cavidades y aves migrantes mostraron respuestas positivas. Estas respuestas se relacionaron fuertemente con los cambios asociados en la estructura del hábitat post-fuego, apoyando las hipótesis testeadas de perturbación intermedia y estructura vertical vegetacional. La posibilidad de que los incendios forestales beneficien a algunas especies y gremios de aves específicos debe considerarse entre los objetivos al diseñar el manejo post-incendio de la biodiversidad de los bosques templados.
  • Thumbnail Image
    Item
    Fire regimes shape biodiversity: responses of avian guilds to burned forests in Andean temperate ecosystems of southern Chile
    (RESILIENCE ALLIANCE, 2021) Novoa Galaz, Fernando Javier; Altamirano Oyarzún, Tomás Alberto; Bonacic Salas, Cristian; Martin, Kathy; Ibarra Eliessetch, José Tomás
    Fire regimes of forests, i.e., time interval, frequency, extent, and severity of fire events, influence structural changes in the vegetation, and thus shape the composition of avian communities. We studied the diversity of avian guilds in sites with different fire regimes (unburned, burned 2002, burned 2015, and burned 2002 and 2015), testing both the "intermediate disturbance" and "vertical vegetation structure" hypotheses, in globally threatened temperate forests in Chile. From 2016 to 2018, we quantified habitat attributes (160 plots) and estimated avian richness and density (160 point counts). The site that was burned once in 2015 showed the highest density of standing dead trees at 96.5% higher than the unburned/control site, whereas the site that burned twice showed the lowest density of live trees, lowest average diameter at breast height of trees (DBH), and smallest volume of coarse woody debris. Overall, we recorded 35 avian species with the highest richness (n = 24 species) in the site that was burned once in 2002. We found that, 16 years after a site was burned, the avian community composition became relatively similar to the unburned site. The density of most avian guilds decreased in burned sites but granivores, shrub users, and migrants showed positive responses. Understory users, foliage users, and resident species showed negative responses to burned sites. These responses were strongly related to fire-driven changes in habitat attributes, supporting both of our tested hypotheses. Given that increasing levels of disturbance from fire are anticipated, future management of temperate forest biodiversity should consider that specific species and guilds will depend on remnant habitat attributes in burned sites.
  • Thumbnail Image
    Item
    Structural complexity is a better predictor than single habitat attributes of understory bird densities in Andean temperate forests
    (Oxford Univ. Press Inc., 2023) Concha, Victoria C.; Caviedes Paul , Julián José; Novoa Galaz, Fernando Javier; Altamirano Oyarzun, Tomás Alberto; Ibarra Eliessetch, José Tomás
    The simplification of forest structural complexity, caused by anthropogenic land-use practices, is one of the main threats to understory specialist birds. We examined the association of both single structural attributes and structural complexity, with the density of 4 understory bird species in the Global Biodiversity Hotspot "Chilean Winter Rainfall-Valdivian Forests" of South America. Between 2011 and 2013, we surveyed habitat attributes and conducted bird point counts in 505 plots in Andean temperate ecosystems in Chile. In each habitat plot, we measured understory density, volume of coarse woody debris (CWD), number of snags, diameter at breast height (DBH) of trees, and leaf litter depth. With these attributes, we developed an index of stand structural complexity (ISC). On average, old-growth forests had higher values for understory density, CWD volume, DBH, and litter depth than secondary forests and open fields, and thus greater values of ISC. The density of understory birds was positively correlated with the ISC for the Rhinocryptidae Pteroptochos tarnii, Scelorchilus rubecula, and Scytalopus magellanicus. We also found a positive association between understory density and litter depth, with the density of the Furnariidae Sylviorthorhynchus desmursii. However, this latter species showed a negative association with the density of snags. Our results suggest the utility of using an index of structural complexity, rather than single or even additive habitat attributes, for determining the density of understory specialist birds. We recommend that management plans should promote the retention of habitat attributes that contribute to the structural complexity of temperate forests of South America and beyond.
  • No Thumbnail Available
    Item
    Tree cavity density is a limiting factor for a secondary cavity nester in second-growth Andean temperate rainforests
    (2024) Altamirano Oyarzún, Tomás Alberto; Novoa Galaz, Fernando Javier; Ibarra Eliessetch, José Tomás; Navarrete Campos, Sergio Andrés; Bonacic, Salas Cristián; Martin, Kathy
    Cavity-nesting bird populations are most frequently limited by the number of tree cavities available in second-growth forests. However, this possible limitation of a key resource is less clear in old-growth forests. We compared forest attributes (i.e., basal area, density of larger trees, density of dead trees, and tree cavity density) in second-growth and old-growth stands in Andean temperate rainforests in southern Chile. To examine the role of nest-site availability in limiting the populations of Aphrastura spinicauda (Thorn-Tailed Rayadito), a secondary cavity-nesting bird species, we conducted an experiment in which nest boxes were added and removed in old-growth and second-growth forests during a 5-yr period (20082013). In old-growth forests, as compared to second-growth forests, we found a more than double basal area (99.6 vs. 43.7 m2 ha–1), a three times higher density of larger trees (88.2 vs. 36.4 trees ha–1), and a 1.5 times higher number of small cavities (25.9 vs. 10.3 cavities ha–1). The density of cavities also strongly increased with tree diameter and basal area. In secondgrowth forests, A. spinicauda showed a strong response to the addition and removal of nest boxes, with population abundance increasing by 13% and then decreasing by 50%, respectively. In contrast, we found no impact in old-growth stands. Our experiment emphasizes the importance of maintaining large and dead trees in second-growth, disturbed, and managed forests. These trees provide suitable cavities for A. spinicauda, and likely many other secondary cavity nesters, increasing their abundances in a Globally significant Biodiversity Hotspot in southern South America.