Browsing by Author "Cavieres, Lohengrin A."

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    Assessing impacts of ecosystem engineers on community organization: a general approach illustrated by effects of a high-Andean cushion plant
    (2006) 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 on high-Andean plant communities on two mountaintops. Substrate temperatures, soil moisture and the availability of mineral nutrient resources were compared between A. monantha and surrounding open areas to ascertain whether cushions altered abiotic environmental conditions, while community analysis assessed changes in species richness, composition and abundances at patch and landscape levels. Cushions thermally buffered temperature extremes and increased soil moisture, but had no detectable effect on soil mineral nutrients. Cushion habitat was not more species rich than surrounding areas, but cushions added new species into the community, altering species composition and markedly enhancing landscape-level richness. Cushions also showed potential for stabilizing species richness over time, and changed patterns of species dominance. Findings were consistent across mountaintops. We evaluate the general utility of the framework and call for its application in other systems as a means to generate comparative data sets for assessing the general effects of ecosystem engineers on community organization.
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    Ecological and metabolic implications of the nurse effect of Maihueniopsis camachoi in the Atacama Desert
    (2024) Diaz, Francisca P.; Dussarrat, Thomas; Carrasco-Puga, Gabriela; Colombie, Sophie; Prigent, Sylvain; Decros, Guillaume; Bernillon, Stephane; Cassan, Cedric; Flandin, Amelie; Guerrero, Pablo C.; Gibon, Yves; Rolin, Dominique; Cavieres, Lohengrin A.; Petriacq, Pierre; Latorre, Claudio; Gutierrez, Rodrigo A.
    Plant-plant positive interactions are key drivers of community structure. Yet, the underlying molecular mechanisms of facilitation processes remain unexplored. We investigated the 'nursing' effect of Maihueniopsis camachoi, a cactus that thrives in the Atacama Desert between c. 2800 and 3800 m above sea level. We hypothesised that an important protective factor is thermal amelioration of less cold-tolerant species with a corresponding impact on molecular phenotypes.To test this hypothesis, we compared plant cover and temperatures within the cactus foliage with open areas and modelled the effect of temperatures on plant distribution. We combined eco-metabolomics and machine learning to test the molecular consequences of this association.Multiple species benefited from the interaction with M. camachoi. A conspicuous example was the extended distribution of Atriplex imbricata to colder elevations in association with M. camachoi (400 m higher as compared to plants in open areas). Metabolomics identified 93 biochemical markers predicting the interaction status of A. imbricata with 79% accuracy, independently of year.These findings place M. camachoi as a key species in Atacama plant communities, driving local biodiversity with an impact on molecular phenotypes of nursed species. Our results support the stress-gradient hypothesis and provide pioneer insights into the metabolic consequences of facilitation.
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    Geographic mosaics of plant-soil microbe interactions in a global plant invasion
    (2012) Andonian, Krikor; Hierro, José L.; Khetsuriani, Liana; Becerra Osses, Pablo Ignacio; Janoyan, Grigor; Villarreal, Diego; Cavieres, Lohengrin A.; Fox, Laurel R.; Callaway, Ragan M.
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    Azorella Cushion Plants and Aridity are Important Drivers of Soil Microbial Communities in Andean Ecosystems
    (2021) Rodriguez-Echeverria, Susana; Delgado-Baquerizo, Manuel; Morillo, Jose A.; Gaxiola, Aurora; Manzano, Marlene; Marquet, Pablo A.; Gonzalez, Leticia; Cavieres, Lohengrin A.; Pugnaire, Francisco I.; Armas, Cristina
    Cushion plants are specialized keystone species of alpine environments that can have a positive effect on ecosystem structure and function. However, we know relatively little about how cushion plants regulate the diversity and composition of soil microbial communities, major drivers of soil processes and ecosystem functioning. Identifying what factors drive the diversity and composition of soil microbial communities in high-elevation ecosystems is also fundamental to predict how global changes will affect their conservation and the services and functions they provide. Thus, we sampled four sites along the southern Andes following the vegetation belt of Azorella cushion species. The field sites spread along a latitudinal gradient and had contrasting levels of aridity, UV-B radiation, mean temperature and soil properties. Overall, Azorella, as well as aridity and UV-B radiation, were the major drivers of the distribution, composition and diversity of soil microbial communities in the studied ecosystems of the Chilean Andes. UV-B radiation affected particularly soil fungi, while soil properties such as pH, total C and N content, essential predictors of microbial diversity globally, had a much lower effect on the composition of soil microbial communities. Understanding the factors driving the structure and composition of microbial communities, particularly the role of cushion plants and the feedbacks between plant, climate and soil is of uttermost importance for the preservation of the functionality of high-elevation ecosystems threatened by climate change.
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    Testing the stress gradient hypothesis in soil bacterial communities associated with vegetation belts in the Andean Atacama Desert
    (2023) Mandakovic, Dinka; Aguado-Norese, Constanza; García-Jiménez, Beatriz; Hodar, Christian; Maldonado, Jonathan E.; Gaete, Alexis; Latorre, Mauricio; Wilkinson, Mark D.; Gutiérrez Ilabaca, Rodrigo Antonio; Cavieres, Lohengrin A.; Medina, Joaquín; Cambiazo, Verónica; Gonzalez, Mauricio
    Background Soil microorganisms are in constant interaction with plants, and these interactions shape the composition of soil bacterial communities by modifying their environment. However, little is known about the relationship between microorganisms and native plants present in extreme environments that are not affected by human intervention. Using high-throughput sequencing in combination with random forest and co-occurrence network analyses, we compared soil bacterial communities inhabiting the rhizosphere surrounding soil (RSS) and the corresponding bulk soil (BS) of 21 native plant species organized into three vegetation belts along the altitudinal gradient (2400–4500 m a.s.l.) of the Talabre–Lejía transect (TLT) in the slopes of the Andes in the Atacama Desert. We assessed how each plant community influenced the taxa, potential functions, and ecological interactions of the soil bacterial communities in this extreme natural ecosystem. We tested the ability of the stress gradient hypothesis, which predicts that positive species interactions become increasingly important as stressful conditions increase, to explain the interactions among members of TLT soil microbial communities. Results Our comparison of RSS and BS compartments along the TLT provided evidence of plant-specific microbial community composition in the RSS and showed that bacterial communities modify their ecological interactions, in particular, their positive:negative connection ratios in the presence of plant roots at each vegetation belt. We also identified the taxa driving the transition of the BS to the RSS, which appear to be indicators of key host-microbial relationships in the rhizosphere of plants in response to different abiotic conditions. Finally, the potential functions of the bacterial communities also diverge between the BS and the RSS compartments, particularly in the extreme and harshest belts of the TLT. Conclusions In this study, we identified taxa of bacterial communities that establish species-specific relationships with native plants and showed that over a gradient of changing abiotic conditions, these relationships may also be plant community specific. These findings also reveal that the interactions among members of the soil microbial communities do not support the stress gradient hypothesis. However, through the RSS compartment, each plant community appears to moderate the abiotic stress gradient and increase the efficiency of the soil microbial community, suggesting that positive interactions may be context dependent.
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    Vegetation drives the response of the active fraction of the rhizosphere microbial communities to soil warming in Antarctic vascular plants
    (2022) Parada-Pozo, Genesis; Bravo, Leon A.; Saez, Patricia L.; Cavieres, Lohengrin A.; Reyes-Diaz, Marjorie; Abades, Sebastian; Alfaro, Fernando D.; De la Iglesia, Rodrigo; Trefault, Nicole
    In the Antarctic Peninsula, increases in mean annual temperature are associated with the coverage and population density of the two Antarctic vascular plant species-Deschampsia antarctica and Colobanthus quitensis-potentially modifying critical soil processes. In this study, we characterized the diversity and community composition of active microorganisms inhabiting the vascular plant rhizosphere in two sites with contrasting vegetation cover in King George Island, Western Antarctic Peninsula. We assessed the interplay between soil physicochemical properties and microbial diversity and composition, evaluating the effect of an in situ experimental warming on the microbial communities of the rhizosphere from D. antarctica and C. quitensis. Bacteria and Eukarya showed different responses to warming in both sites, and the effect was more noticeable in microbial eukaryotes from the low vegetation site. Furthermore, important changes were found in the relative abundance of Tepidisphaerales (Bacteria) and Ciliophora (Eukarya) between warming and control treatments. Our results showed that rhizosphere eukaryal communities are more sensitive to in situ warming than bacterial communities. Overall, our results indicate that vegetation drives the response of the active fraction of the microbial communities from the rhizosphere of Antarctic vascular plants to soil warming.