Browsing by Author "Fierro, Andres"

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    Climate-induced tree senescence leads to a transient increase in reproductive success of a large woodpecker species
    (2022) Carvajal, Mario A.; Alaniz, Alberto J.; Vergara, Pablo M.; Hernandez-Valderrama, Carlos; Fierro, Andres; Toledo, Gisela; Gamin, Juan
    Climate change-induced mortality of trees is a concerning phenomenon for global forest ecosystems. The rapid decay and death of long-lived trees can significantly impact forest dynamics, with effects that transmit through ecological networks, becoming more evident in organisms occupying high trophic levels, such as large and spe-cialized woodpecker species. However, understanding how populations of high trophic level species respond to climate change is still a challenge. In this study it was analyzed 32-year data of social groups of the Magellanic Woodpecker (Campephilus magellanicus) in North Patagonia, a region facing increasingly frequent droughts and increased temperatures. A positive trend in the size of woodpecker social groups as a response to climate-induced tree senescence was tested. A causal structural equation model examining climate-tree senescence-woodpecker relationships was used. Increasing nonlinear trends and positive interannual growth rates (>10%) for tree senescence and group size were found. Lowland forest sites had higher levels of tree senescence and more numerous social groups. The causal model supported the positive effect of mean temperature on tree senes-cence and the positive association of woodpeckers with tree senescence. These results provide evidence of a climate-induced increase in tree senescence that causes an increase in the size of woodpecker social groups. It is suggested that accelerated decay and mortality of trees in the northern Patagonian forests will decrease the stocks of deadwood in the long term, threatening the persistence of this large woodpecker species. (c) 2021 Elsevier B.V. All rights reserved.
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    Environmental and biotic filters interact to shape the coexistence of native and introduced bees in northern Patagonian forests
    (2023) Vergara, Pablo M.; Fierro, Andres; Carvajal, Mario A.; Alaniz, Alberto J.; Zorondo-Rodriguez, Francisco; Cifuentes, Maria C.; Castro, Sergio A.
    Native and introduced species can coexist in rich ecosystems where competition for resources is less intense; however, native species can be excluded from suitable habitats hosting a high abundance of introduced species. To test these hypotheses, we estimated the probability of introduced bees (buff-tailed bumblebees and honeybees) to co-occur and dominate giant bumblebees in forested landscapes of northern Patagonia. We evaluated the effects of 29 remote-sensing variables of forest ecosystems on bee abundance using data from 56 landscapes. Then, we used a probabilistic Bayesian model to estimate the effects of the most important predictors of bee abundance on their co-occurrence and dominance probabilities. Introduced and native bees exhibited heterogeneous and scale-dependent responses to environmental conditions, with only six variables affecting their cooccurrence and dominance probabilities. A high maximum temperature was associated with both a decreased co-occurrence and an increased dominance of introduced bumblebees, and the opposed pattern was found for vegetation continuous fields, an index of canopy continuity. Similar responses were found for the co-occurrence probability of honeybees and giant bumblebees. Thus, species dominance and co-occurrence changed differently along environmental gradients, with co-occurrence increasing as native and introduced species become more abundant. A high dominance of introduced bees in unsuitable habitats suggests interspecific competition is strengthened as resources become scarcer, thus reinforcing the idea that abiotic and biotic filters interact with each other.
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    Fire Severity Causes Temporal Changes in Ground-Dwelling Arthropod Assemblages of Patagonian Araucaria-Nothofagus Forests
    (2022) Zuniga, Alfredo H.; Rau, Jaime R.; Fierro, Andres; Vergara, Pablo M.; Encina-Montoya, Francisco; Fuentes-Ramirez, Andres; Jaksic, Fabian M.
    Fire is one of the main drivers of anthropogenic disturbances in temperate forest ecosystems worldwide, with multiple effects spread across ecological networks. Nevertheless, the biodiversity effects of fire are poorly known for species-diverse groups such as arthropods. In this research, we used a burn gradient generated two and three years after a large fire event to assess how different levels of fire severity affect arthropod diversity in the forest with the main forest forming long-living tree species Araucaria araucana, in southern Chile. The species richness and abundance of arthropods among trophic guilds was estimated annually in four fire-severity levels. We found that arthropods responded differently to fire severity levels, depending on their trophic guilds and years after fire (two and three years after fire). During the second year after fire, zoophages, phytophages, and parasitoids were more diverse in areas with high fire severity within the second year after fire, as compared to those in areas with low severity or unburned stands. In the third year after fire, a change in this trend was observed, where the abundance of all groups dropped significantly, with positive changes in the diversity in zoophages, phytophages, polyphages and saprophages, which is more noticeable in sites with high severity. These results indicate that annual variation in environmental conditions triggers bottom-up cascading effects for arthropods. Forests stands severely impacted by fires support highly fluctuating and possibly unstable arthropod assemblages. Hence, restoration efforts should be focused on recovering microhabitat conditions in these stands to allow the persistence of arthropods.
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    Multiple environmental drivers for the Patagonian forest-dwelling beetles: Contrasting functional and taxonomic responses across strata and trophic guilds
    (2022) Vergara, Pablo M.; Fierro, Andres; Carvajal, Mario A.; Alaniz, Alberto J.; Quiroz, Madelaine
    changes in forest-dwelling beetle communities. However, the effects of multiple environmental factors can be complex to detect in ecosystems that offer a broad variety of microhabitats for a great variety of beetle species. This is the case in Patagonian temperate forests, where the use of remote sensing provides an opportunity to evaluate the sensitivity of beetle species to environmental changes. Here, we identified the environmental drivers of forest-dwelling beetle communities in the ground and canopy of 34 north Patagonian-forest landscapes. We analyzed the associations of the taxonomic and functional diversity of five trophic guilds with 30 remote-sensing variables of landscape structure, composition, and disturbances; vegetation and soil properties; and climate and physical variables. Hierarchical clustering analysis was used to identify trophic guilds responding similarly to predictors. Segmented regression analysis was used to evaluate functional redundancy from taxonomic-functional richness relationships. A total of 583 species (23,848 individuals) of beetles were recorded for both strata. The effects of environmental variables were heterogeneous across strata and guilds. Canopy beetles were especially sensitive to early successional conditions, and canopy attributes, but also benefited from the canopy openness. Forest specialists of the ground and canopy responded differently to environmental variables. Ground-dwelling beetles were mostly affected by fires, human modifications, edge closeness, high temperatures, and soil properties, responding weakly to canopy properties. Functional redundancy
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    Remote-sensing estimates of forest structure and dynamics as indicators of habitat quality for Magellanic woodpeckers
    (2021) Alaniz, Alberto J.; Carvajal, Mario A.; Fierro, Andres; Vergara-Rodriguez, Valentina; Toledo, Gisela; Ansaldo, Diego; Moreira-Arce, Dario; Rojas-Osorio, Alejandro; Vergara, Pablo M.
    Bridging remote-sensing ecosystem indices with biodiversity conservation implies converting these indices into habitat quality indicators for species playing an important role in communities and ecosystems, such as woodpeckers. However, an ecologically reliable estimation of habitat quality necessarily involves an assessment of fitness components ultimately responsible for population persistence. Here, we assessed the relationship between remote-sensing indices of forest structure, dynamics and composition with the breeding performance of Magellanic woodpeckers in conservation areas of southern Chile. We used a Bayesian-spatial model based on age and sex information from woodpecker?s social group data collected seasonally in seven years. The probability of a young remaining in the group decreased with the mean group size during the previous year, with group size fluctuating temporally in all conservation areas. Tree senescence had a positive effect on the pairing probability of woodpeckers, but this effect became more marked in sites of higher altitude. Paired woodpeckers were more likely to be observed in sites supporting more than 69% of forest cover. The probability of the young remaining in the territory was positively affected by the interaction between forest canopy continuity and altitude, with retention of the young being more likely in sites located higher than 1000 masl. Social groups were larger in sites where the continuity of canopy increased over time. Those findings suggest that remote sensing indices representing the structure and dynamics of forest ecosystems are important indicators of the habitat quality for woodpeckers. Thus, forest biodiversity that depends on the woodpecker?s engineering function may be conserved through the retention of senescent trees and the maintaining of critical levels of forest cover ensuring high habitat-quality for breeding woodpeckers.
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    Unravelling the cavity-nesting network at large spatial scales: The biogeographic role of woodpeckers as ecosystem engineers
    (2024) Alaniz, Alberto J.; Carvajal, Mario A.; Quiroz, Madelaine; Vergara, Pablo M.; Marquet, Pablo A.; Fierro, Andres; Sieving, Kathryn E.; Moreira-Arce, Dario; Hidalgo-Corrotea, Claudia; Rodriguez-San Pedro, Annia; Allendes, Luis; Machuca, Katerine
    AimPrimary cavity nesters (e.g. woodpeckers) act as ecosystem engineers by providing tree cavities to several vertebrates that use them as nests or refuges. Although diverse assemblages of primary excavators are assumed to increase the number of tree cavities, environmental factors can limit populations of primary excavators, thus weakening their ecological function. We aim to test the biogeographical-scale relationships between primary excavators and cavity users by distinguishing the contribution of environmental variables.LocationSouthern South America.Materials and MethodsWe used species distribution models, which combine bioclimatic and remote sensing derived variables, to map the richness of vertebrates composing the cavity-network of temperate and Mediterranean forests of South America. Based on a resampling procedure for ensuring spatial independence, we fitted structural equation models to estimate relationships between forest characteristics and cavity user vertebrates.ResultsRichness of secondary cavity users (mammals, obligated, habitat generalists and forest specialists) were positively and strongly influenced by the richness of primary excavators. Environmental variables affected differently the richness of primary and secondary cavity users. The richness of primary cavity users responded to tree richness and height while that of habitat specialist secondary users was positively affected by primary productivity and negatively by sclerophyll forests.Main ConclusionsOur results confirm the role of primary excavators as ecosystem engineers but highlight the importance of considering large spatial scales when analysing cavity-nesting networks. Biogeographical patterns of tree diversity and forest structure can be important drivers of cavity nesting networks that remain hidden when studies are conducted over fine spatial scales.
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    Using sonic tomography to assess the relationship between internal wood decay and saproxylic beetle communities
    (2022) Vergara, Pablo M.; Fierro, Andres; Carvajal, Mario A.; Alaniz, Alberto J.
    Although wood-inhabiting beetle species are known to contribute to the progressive degradation of wood by building larval galleries and dispersing fungal propagules, the relationship between decaying wood and beetle communities is difficult to be assessed. The ecological properties of trees, such as their mortality status and species, could modify the relationships between beetle communities and decaying wood. We used recently developed techniques of sonic tomography for the first time to address how the trophic structure of beetle communities varies with the internal wood decay. We developed a paired design where sonic tomograms taken in the trunk sections of live and dead trees of the Patagonian forest were related with beetles sampled with emergence traps. Beetles captured in the trunks of live trees responded weakly to the internal wood decay. Indeed, the diversity of predators in live trees was likely influenced by bark microhabitats. Conversely, most of the guild assemblages in the trunks of dead trees were impoverished as wood decay was more advanced, possibly due to decreasing microhabitat quality. Our preliminary study suggests sonic tomography offers the opportunity to distinguish how beetles modulate decaying wood, but also provides insights about the assessment of live trees with tomograms. (C) 2022 The Author(s). Published by Elsevier B.V.