CAPTURA. Repositorio Academico de la Universidad de Chile
(5.176 recursos)
Captura almacena y conserva la producción de conocimiento generado por docentes e investigadores de la Universidad de Chile, y la hace visible desde los portales académicos internacionales.
Mostrando recursos 1 - 20 de 92
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Nurse effect in seedling establishment: facilitation and tolerance to damage in the Andes of central Chile - Acuña Rodríguez, Ian S.; Cavieres, Lohengrin A.; Gianoli, Ernesto
Nurse effects, which occur when one plant species enhances the survival or growth of another plant species, are predicted to be most relevant in stressful environments. These effects are particulary important during seedling establishment due to their vulnerability to both biotic and abiotic factors, such as herbivory and drought. Tolerance to herbivory reflects the degree to which plants are able to regrow and reproduce after damage, and should vary with resource availability. In the high Andes of central Chile, the cushion plant Laretia acaulis (Apiaceae) acts as a buffer against environmental stress, enhancing survival of several associated plant species. We...
2.
Patterns in body mass distributions: sifting among alternative hypotheses - Allen, C. R.; Garmestani, A. S.; Havlicek, T. D.; Marquet, Pablo A.; Peterson, G. D.; Restrepo, C.; Stow, C. A.; Weeks, B. E.
Understanding how animals interact with their environment is critical for evaluating, mitigating and coping with anthropogenic alteration of Earth's biosphere. Researchers have attempted to understand some aspects of these interactions by examining patterns in animal body mass distributions. Energetic, phylogenetic, biogeographical, textural discontinuity and community interaction hypotheses have been advanced to explain observed patterns. Energetic and textural discontinuity hypotheses focus upon the allometry of resource use. The community interaction hypothesis contends that biotic interactions within assemblages of species are of primary importance. Biogeographical and phylogenetic hypotheses focus on the role of constraints on the organization of communities. This paper examines...
3.
The effects of invasive North American beavers on riparian plant communities in Cape Horn, Chile - Do exotic beavers engineer differently in sub-Antarctic ecosystems? - Anderson, Christopher B.; Griffith, Clayton R.; Rosemond, Amy D.; Rozzi, Ricardo; Dollenz, Orlando
North American beavers (Castor canadensis) were introduced into southern South America in 1946. Since that time, their populations have greatly expanded. In their native range, beavers shape riparian ecosystems by selectively feeding on particular plant species, increasing herbaceous richness and creating a distinct plant community. To test their effects as exotic engineers on sub-Antarctic vegetation, we quantified beaver impacts on tree canopy cover and seedling abundance and composition, as well as their impacts on herbaceous species richness, abundance and composition on Navarino island, Cape Horn County, Chile (550S). Beavers significantly reduced forest canopy up to 30 m away from streams,...
4.
Exotic vertebrate fauna in the remote and pristine sub-antarctic Cape Horn Archipelago, Chile - Anderson, Christopher B.; Rozzi, Ricardo; Torres Mura, Juan C.; McGehee, Steven M.; Sherriffs, Margaret F.; Schuettler, Elke; Rosemond, Amy D.
Pristine wilderness is a scarce global resource, but exotic species are so common that they constitute a principal component of worldwide ecological change. The relationship between these two topics, invasion and remoteness, was the impetus behind five years of fieldwork aimed at identifying the assemblage and range of exotic vertebrates in Cape Horn, Chile, identified as one of the world's most pristine wilderness areas. While the archipelago has extremely low human population density and vast tracts of undisturbed land, we discovered that several terrestrial vertebrate groups were dominated by exotic species. Native birds were diverse (approx. 154 spp), and only...
5.
On the relationship between productivity and food chain length at different ecological levels - Arim, Matías; Marquet, Pablo A.; Jaksic, Fabián
The effects of energy on food web structure have been debated for at least 80 years. Nevertheless, the empirical evidence is meager, especially from terrestrial ecosystems. We analyzed long-term temporal variation in food chain length in a semiarid continental ecosystem, where productivity shows large interannual variations. Incidence of nonherbivorous prey in predator diet was used as a proxy of trophic position, allowing us to analyze the effect of productivity on food chain length within the assemblage of top predators ( which comprises the most abundant and persistent top predators in the system) and to compare observed patterns at the species...
6.
Spread dynamics of invasive species - Arim, Matías; Abades, Sebastián R.; Neill, Paula E.; Lima, Mauricio; Marquet, Pablo A.
Species invasions are a principal component of global change, causing large losses in biodiversity as well as economic damage. Invasion theory attempts to understand and predict invasion success and patterns of spread. However, there is no consensus regarding which species or community attributes enhance invader success or explain spread dynamics. Experimental and theoretical studies suggest that regulation of spread dynamics is possible; however, the conditions for its existence have not yet been empirically demonstrated. If invasion spread is a regulated process, the structure that accounts for this regulation will be a main determinant of invasion dynamics. Here we explore the...
7.
On the relationship between trophic position, body mass and temperature: reformulating the energy limitation hypothesis - Arim, Matías; Bozinovic, Francisco; Marquet, Pablo A.
Understanding the factors that constrain and drive changes in food chain length represents an open challenge in ecology. Although several explanatory hypotheses have been proposed, no synthesis has yet been achieved. The role of body size has been well-studied in recent years because the hierarchy of trophic connections - in which large animals consume small ones - suggests a positive relationship between trophic position and body size. Empirical evidence, however, supports the existence of both positive and negative associations, and some studies have even reported no significant relationship between trophic position and body size. These results suggest that the relationship...
8.
Erratic pollination, high selfing levels and their correlates and consequences in an altitudinally widespread above-tree-line species in the high Andes of Chile - Kalin Arroyo, Mary T.; Muñoz, María S.; Henríquez, Carolina; Till-Bottraud, Irène; Pérez, Fernanda
Unfavorable temperatures and weather conditions for biotic pollination in above-tree-line alpine habitats predict self-compatibility, high levels of autogamy and small flower size ("autogamy reproductive assurance hypothesis"), or alternatively, compensatory measures such as greater flower longevity and larger display size so as to capture scarce visits and maintain outcrossing ("increased pollination probability hypothesis"). We assess these possibilities in a fine-tuned study of Chaetanthera euphrasioides (Asteraceae) populations located above-tree-line in the Andes of central Chile, where prior, independently obtained information on community flower visitation rates is available. Visitation by flies and Andrenid bees was highly erratic in all populations and among years,...
9.
Assessing impacts of ecosystem engineers on community organization: a general approach illustrated by effects of a high-Andean cushion plant - Badano, Ernesto I.; Jones, Clive G.; Cavieres, Lohengrin A.; Wright, Justin P.
Comparative and integrative tools are of fundamental value in ecology for understanding outcomes of biological processes, and making generalizations and predictions. Although ecosystem engineering has been shown to play a fundamental role in community organization, there are no standardized methods to measure such effects. We present a framework and methodology for assessing the impact of physical ecosystem engineers on three general features of community organization: (1) species richness and composition, (2) stability of richness over time, and (3) dominance patterns of species assemblages. We then apply the framework and methodology to assess the effects of the cushion plant Azorella monantha...
10.
Ecosystem engineering facilitates invasions by exotic plants in high-Andean ecosystems - Badano, Ernesto I.; Villarroel, Elisa; Bustamante, Ramiro O.; Marquet, Pablo A.; Cavieres, Lohengrin A.
1. Ecosystem engineers are organisms that change abiotic conditions in ways that affect the performance and distribution of other species, including exotics. Several mechanisms have been proposed for the successful establishment of exotic plants in natural communities, but the positive effects that native engineer species may have on the distribution and performance of exotic plants remain unknown.
2. In this study, we propose that amelioration of extreme abiotic conditions by ecosystem engineers can make stressful habitats invadable by exotic plant species, with larger positive effects on the performance of exotic plants as environmental harshness increases. We tested this hypothesis by assessing...
11.
Impacts of ecosystem engineers on community attributes: effects of cushion plants at different elevations of the Chilean Andes - Badano, Ernesto I.; Cavieres, Lohengrin A.
Ecosystem engineers are organisms able to modulate environmental forces and, hence, may change the habitat conditions for other species. In so doing, ecosystem engineers may affect both species richness and evenness of communities and, in consequence, change species diversity. If these changes in community attributes are related to the magnitude of the habitat changes induced by the engineers, it seems likely that engineer species will have greater effects on diversity in sites where they cause larger habitat changes. We addressed this issue by evaluating the effects of three alpine cushion plants on species richness, evenness, and diversity of high-Andean plant...
12.
Slope aspect influences plant association patterns in the Mediterranean matorral of central Chile - Badano, Ernesto I.; Cavieres, Lohengrin A.; Molina Montenegro, Marco A.; Quiroz, C. L.
The most important processes shaping communities are likely to leave observable imprints on their spatial structure. The net outcome of positive and negative interactions among plants has been proposed to vary inversely with environmental harshness. In the Mediterranean-type matorral of central Chile, slope aspect strongly influences mesoclimatic conditions: equatorial-facing slope are xeric and are dominated by spiny shrubs and cacti, while evergreen sclerophyllous trees dominate polar-facing slopes due to their more mesic conditions. Here we use spatial pattern analyses to infer on the interactions that shape community structure in this matorral. We sampled the vegetation on two polar- and equatorial-facing...
13.
The structure and rate of late Miocene expansion of C-4 plants: Evidence from lateral variation in stable isotopes in paleosols of the Siwalik Group, northern Pakistan - Behrensmeyer, Anna K.; Quade, Jay; Cerling, Thure E.; Kappelman, John; Khan, Imran A.; Copeland, Peter; Roe, Lois; Hicks, Jason; Stubblefield, Phoebe; Willis, Brian J.; Latorre, Claudio
This study uses stable isotope variation within individual Mio-Pliocene paleosols to investigate subkilometer-scale phytogeography of late Miocene vegetation change in southeast Asia between ca. 8.1 and 5 Ma, a time interval that coincides with dramatic global vegetation change. We examine trends through time in the distribution of low-latitude grasses (C-4 plants) and forest (C-3 plants) on Indo-Gangetic floodplains using carbon (delta C-13) and oxygen isotopic (delta C-18) values in buried soil carbonates in Siwalik Series sediments exposed in the Rohtas Anticline, north-central Pakistan. Revised, high-resolution magnetostratigraphy and a new Ar-40/Ar-39 date provide improved age control for the 2020 m Rohtas...
14.
Biocomplexity and conservation of biodiversity hotspots: three case studies from the Americas - Callicott, J. Baird; Rozzi, Ricardo; Delgado, Luz; Monticino, Michael; Acevedo, Miguel; Harcombe, Paul
The perspective of 'biocomplexity' in the form of 'coupled natural and human systems' represents a resource for the future conservation of biodiversity hotspots in three direct ways: ( i) modelling the impact on biodiversity of private land-use decisions and public land- use policies, ( ii) indicating how the biocultural history of a biodiversity hotspot may be a resource for its future conservation, and ( iii) identifying and deploying the nodes of both the material and psycho-spiritual connectivity between human and natural systems in service to conservation goals. Three biocomplexity case studies of areas notable for their biodiversity, selected for their...
15.
Browsing by guanaco (Lama guanicoe) on Nothofagus pumilio forest gaps in Tierra del Fuego, Chile - Cavieres, Lohengrin A.; Fajardo, Alex
The presence of guanaco (Lama guanicoe. Muller 1776. Camelidae) in forests of Nothofagus pumilio (Poepp. et Endl.) Krasser. (lenga) in Tierra del Fuego has been associated with browsing damage in the regeneration of these fore;Ass. but little quantitative data are available. In developing and implementing forest management plans for N. pumilio forests, the effects of guanaco browsing are a major source of variation in attaining regeneration and growth goals, however guartaco is not generally accounted for in manaaemen, planning in the region. In this study we examined the browsing damage levels of guanaico and introduced livestock on N. pumilio regeneration...
16.
Leaf litter of Kageneckia angustifolia D. Don (Rosaceae) inhibits seed germination in sclerophyllous montane woodlands of central Chile - Cavieres, Lohengrin A.; Chacón, Paulina; Peñaloza, Alejandro; Molina Montenegro, Marco A.; Kalin Arroyo, Mary T.
Leaf litter accumulation can have either positive, negative or neutral effects on seed germination and seedling recruitment. In montane woodlands of the Mediterranean zone of central Chile, large amounts of leaf litter accumulate beneath the crowns of the summer semi-deciduous tree Kageneckia angustifolia and no regeneration of this or other plant species has been observed beneath this tree throughout the year. In a sample plot of 5000 m(2) we selected ten K. angustifolia trees and measured (1) leaf litter accumulation beneath and outside canopy; (2) the effects of time elapsed since burial on viability of K. angustifolia seeds with and...
17.
Microclimatic modifications of cushion plants and their consequences for seedling survival of native and non-native herbaceous species in the high andes of central Chile - Cavieres, Lohengrin A.; Badano, Ernesto I.; Sierra Almeida, Angela; Molina Montenegro, Marco A.
Cushion plants are one of the most common growth forms in alpine habitats. Their low stature, dense canopy, and compact form allow them to decouple their microclimate from the surrounding environment, mitigating the effect of low temperatures and drought, enhancing the survival of other species. In this study, we evaluated the modifications on soil temperature and moisture over an entire growing season by two cushion species (Laretia acaulis and Azorella monantha) in alpine communities located at two different elevations in the central Chilean Andes. Additionally, we performed seedling survival experiments with two native herbaceous species (Hordeum comosum and Erigeron andicola)...
18.
Positive interactions between alpine plant species and the nurse cushion plant Laretia acaulis do not increase with elevation in the Andes of central Chile - Cavieres, Lohengrin A.; Badano, Ernesto I.; Sierra Almeida, Angela; Gómez González, Susana; Molina Montenegro, Marco A.
In alpine habitats, positive interactions among plants tend to increase with elevation as a result of altitudinal increase in environmental harshness. However, in mountains located in arid zones, lower elevations are also stressful because of scarce availability of water, suggesting that positive interactions may not necessarily increase with elevation.
Here we analysed the spatial association of plant species with the nurse cushion plant Laretia acaulis at two contrasting elevations, and monitored the survival of seedlings of two species experimentally planted within and outside cushions in the semiarid Andes of central Chile.
Positive spatial associations with cushions were more frequent at lower elevations....
19.
Do carbon-based defences reduce foliar damage? Habitat-related effects on tree seedling performance in a temperate rainforest of Chiloe Island, Chile - Chacón, Paulina; Armesto, Juan J.
Carbon-based secondary compounds (CBSCs), such as phenols or tannins, have been considered as one of the most important and general chemical barriers of woody plants against a diverse array of herbivores. Herbivory has been described as a critical factor affecting the growth and survival of newly established tree seedlings or juveniles then, the presence of secondary metabolites as defences against herbivores should be a primary strategy to reduce foliar damage. We examined whether light-induced changes in leaf phenolic chemistry affected insect herbivory on seedlings of two rainforest tree species, Drimys winteri (Winteraceae) and Gevuina avellana (Proteaceae). Seedlings of both species...
20.
Rarity in Chilean forest birds: which ecological and life-history traits matter? - Cofré, Hernán L.; Böhning Gaese, Katrin; Marquet, Pablo A.
While it is a truism that species rarity is non-randomly distributed across regions, habitats, and taxa, there is little consensus on which factors are the best predictors of low abundances and restricted geographical ranges. In this study, we evaluate the effects of ecological and life-history traits, as well as phylogeny, on rarity in the abundance and distribution of land birds inhabiting forest habitats in the Mediterranean and temperate regions of Chile. We use data on abundance collected at 16 sites and data on latitudinal distribution obtained from a literature compilation. Statistical analyses were based on multiple regression and multivariate models....
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