Universidad de Magallanes
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Equivalent impacts of logging and beaver activities on aboveground carbon stock loss in the southernmost forest on Earth
No full textThe conservation of forest landscapes is crucial for global climate strategies, and the forest in Tierra del Fuego, located in Patagonia, represents the southernmost example on Earth. These ecosystems are critical for Chile's roadmap toward carbon neutrality. Unfortunately, these ecosystems have been impacted by logging and beaver activities. Currently, the precise contribution of each driver to forest cover and carbon stock loss remains insufficiently quantified, impeding effective policymaking and the implementation of strategies to safeguard and enhance carbon stocks in these ecosystems. In this study, we conducted an assessment of forest carbon stock loss resulting from both logging and beaver activities in Chilean Tierra del Fuego from 1986 to 2019. While beavers have received significant attention for their substantial contribution to forest cover loss (56.1% forest cover, approximate to 1.4 MtC), our findings suggest that logging has nearly equally contributed to carbon stock depletion (43.8% forest cover, approximate to 1.2 MtC). Consequently, the prevailing focus on beavers has obscured the ongoing logging-induced carbon stock loss. The implications of our study highlight the urgency for comprehensive consideration of both drivers in Chile's climate strategy to fulfill the country's mitigation commitments
Tree-cavity survival for biodiversity in temperate forests of South America: A multi-scale approach
No full textTree cavities are critical habitat attributes for a diversity of species that use them for reproduction and shelter. Worldwide, their availability has shown an intense decline in forests because of the loss of old-growth stands and the reduction in cavity recruitment. These disturbance processes are influenced by factors occurring across different scales: from cavities to landscapes. We analyzed the survival of 613 cavities in 455 trees in old-growth and second-growth forests over 10 years in Andean temperate forests in southern South America, Chile. Kaplan-Meier and Cox proportional hazards models were used to determine median cavity survival and its influencing factors at the cavity, tree, stand and landscape scales. The median survival was six years. Nonexcavated cavities (6 years) survived longer than excavated cavities (4 years), with a significantly longer lifespan in large decaying trees. Cavities' survival was strongly influenced by cavity- and tree-scale factors, including their origin, the vertical cavity depth, tree decay class, tree branch order and tree diameter class. In old-growth forests, most cavities were found in live decaying trees, while in second-growth forests they were mostly in longdead trees (snags). We suggest that management should maintain forest structural complexity, retaining dead wood and trees in different stages of decay to permit a continuous supply of substrates over time for the formation of cavities
Exploring Machine Learning Algorithms and Numerical Representations Strategies to Develop Sequence-Based Predictive Models for Protein Networks
No full textPredicting the affinity between two proteins is one of the most relevant challenges in bioinformatics and one of the most useful for biotechnological and pharmaceutical applications. Current prediction methods use the structural information of the interaction complexes. However, predicting the structure of proteins requires enormous computational costs. Machine learning methods emerge as an alternative to this bioinformatics challenge. There are predictive methods for protein affinity based on structural information. However, for linear information, there are no development guidelines for elaborating predictive models, being necessary to explore several alternatives for processing and developing predictive models. This work explores different options for building predictive protein interaction models via deep learning architectures and classical machine learning algorithms, evaluating numerical representation methods and transformation techniques to represent structural complexes using linear information. Six types of predictive tasks related to the affinity and mutational variant evaluations and their effect on the interaction complex were explored. We show that classical machine learning and convolutional network-based methods perform better than graph convolutional network methods for studying mutational variants. In contrast, graph-based methods perform better on affinity problems or association constants, using only the linear information of the protein sequences. Finally, we show an illustrative use case, expose how to use the developed models, discuss the limitations of the explored methods and comment on future development strategies for improving the studied processes
Biotopes of the intertidal zone in Clarence Island (south of the Strait of Magellan)
No full textBackground The characteristics of the Strait of Magellan promote the formation of unique environments, with diverse habitats and marine organisms. This fragmentation of the landscape generates diverse little-explored ecological associations, especially in the zone of sub Antarctic islands of the Tierra del Fuego archipelago. One way to address this lack of knowledge is through the biotope characterization methodology, with ecological units composed of the habitat and the communities associated with these environments, obtaining data and information on the dominant and incidental taxonomic groups. This is a good research model to conduct baseline studies in coastal benthic marine environments. New information A data set in Darwin Core standard is presented of the species that make up the intertidal biotopes of Clarence Island (Tierra del Fuego Archipelago, south of the Strait of Magellan). This includes 50 identified species and the specific coordinates for each sampled location, with a total of 1400 georeferenced records. Mollusks were the most diverse taxon with 21 species, followed by algae (14 species). Sessile organisms such as the barnacles Elminius kingii and Austromegabalanus psittacus predominate in these ecosystems, followed by bivalve mollusks such as Choromytilus chorus and Mytilus chilensis, which together with Nacella magellanica and the alga Hildenbrandia sp. make up more than 50% of the total records. The inclusion of biotope patterns in this study complements the information on benthic marine flora and fauna in the intertidal zone, including new records for the coast in the Clarence Island area, which is within the boundary of the Kawesqar National Park
A universal approach to alpha-cellulose extraction for radiocarbon analysis of 14C-free to post-bomb ages
No full textIn order to expand our in-house capabilities for tree-ring 14C measurements in support of atmospheric 14C reconstruction research, we designed a very versatile and inclusive procedure to produce high-quality alpha-cellulose homogenized extracts. The procedure can be easily scaled up or down (<= 10 to 40 samples) and/or modified on demand (chemical steps can be easily adjusted to sample requirements as well, e.g., increased or diminished, according to the amount of available material and/or contaminants to be removed). Procedure setups are straightforward, and all products and instruments required are off-the-shelf. One to three days may be used to extract chipped wood to alpha-cellulose homogenized fibers that can be further used by high-precision 14C accelerator mass spectrometry (AMS) analysis. The full procedure, which includes recommendations for wood reduction to chips, chemical treatment, and 14C-AMS sample processing, measurements and data handling was tested on over 110 wood samples from post-bomb 1950AD to 14C limit. Radiocarbon results were in the order of 0.29% or better, based on replication and regardless of the age group studied. Best background was in the order of 54 kyrs BP, without any type of background correction. Fourier transform infrared (FTIR) analysis was used as a characterizing tool to confirm the removal of unwanted carbon compounds during the production of alpha-cellulose extracts. For those analysis, we chose woods that are normally rich in resinous and parenchymatous structures. Results confirmed that our protocol produces pure alpha-cellulose extracts for 14C analysis, and therefore this procedure can be safely applied to atmospheric 14C reconstructions at pantropical regions
The revision of fossil big-eyed bugs suggests a peculiar evolutionary history of a peculiar true bug family (Heteroptera: Lygaeoidea: Geocoridae)
No full textThe fossil record of the lygaeoid true bug family, Geocoridae so far consisted of a compression fossil from the Florissant Formation, Geocoris infernorum, and a mould fossil from the Izarra Formation, G. monserrati. Here, we report the third taxon, Protogeocoris arcanus gen. et sp. nov. from Cenomanian Burmese amber along with revision of the two previously mentioned species. The study of the specimens resulted in erecting a new genus, Eocenogeocoris gen. nov. to accommodate G. infernorum [ = Eocenogeocoris infernorum (Sudder, 1890) comb. nov.], because of its unique combination of characters compared to extant geocorine true bugs. Furthermore, the interpretation of the novel morphological data acquired from the study of the fossil geocorids in the context of the knowledge on extant representatives of the family suggests that characteristic groups of the family may have been evolved until the mid-Cretaceous, whilst the species-level diversity of the nominotypical genus, Geocoris Fallen, 1814, and closely allied genera is possibly resulted by quick radiation event after a climatic changes at the Eocene-Oligocene boundary
Ground-based measurements of the weather-driven sky radiance distribution in the Southern Hemisphere
No full textThe angular distribution of the sky radiance determines the energy generation of solar power technologies as well as the ultraviolet (UV) doses delivered to the biosphere. The sky-diffuse radiance distribution depends on the wavelength, the solar elevation, and the atmospheric conditions. Here, we report on ground-based measurements of the all-sky radiance at three sites in the Southern Hemisphere across a transect of about 5,000 km: Santiago (33 degrees S, a mid-latitude city of 6 million inhabitants with endemic poor air quality), King George Island (62 degrees S, at the northern tip of the Antarctic Peninsula, one of the cloudiest regions on Earth), and Union Glacier (79 degrees S, a snow-covered glacier in the vast interior of Western Antarctica). The sites were strategically selected for studying the influence of urban aerosols, frequent and thick clouds, and extremely high albedo on the sky-diffuse radiance distribution. Our results show that, due to changing site-specific atmospheric conditions, the characterization of the weather-driven sky radiance distribution may require ground-based measurements
Dendroecological analysis of the remote endemic Nothomyrcia fernandeziana forests of Robinson Crusoe Island in the Southeast Pacific
No full textJuan Fernandez Archipelago National Park is located in the Southeast Pacific Ocean similar to 670 km off the coast of Chile. Composed by three islands, encompasses an ecosystem with 208 native plant species of which 64% are endemic. Robinson Crusoe Island (RCI) is the largest and the only with a permanent human population. Among the tree species of RCI, Nothomyrcia fernandeziana is the most abundant and dominant forming part of this fragile forest ecosystem. Despite this, there is very little information regarding its autoecology and conservation. Therefore, the objective of this work was to determine the radial growth patterns of N. fernandeziana and its longevity using dendrochronological methods. For this purpose, cross sections of trees blown down by wind were collected in conjunction with park rangers from five different sites and analyzed using tree-ring methods. Our results confirm that N. fernandeziana is a shade-tolerant species capable of maintaining extremely low initial growth rates under the canopy for several decades. Individual growth series were found to respond rapidly to changes in environmental conditions, revealed by abrupt positive and negative changes in their annual growth. Our data indicate a longevity of up to 450 years, with one N. fernandeziana individual established in the mid XVII century before the arrival of humans to the pristine island ecosystem. The results of this study are essential to strengthen RCI conservation plans considering restoration actions based on the autoecology of this rare endemic tree species, and the control of exotic invasive species that presently threatens the RCI forests ecosystems
Consensus for Oncology Genetic Counseling and Molecular Diagnosis: The Punta Arenas Statement
No full textCarbazole Degradation and Genetic Analyses of Sphingobium sp. Strain BS19 Isolated from Antarctic Soil
No full textThe Antarctic region is facing a higher risk of hydrocarbon pollution due to increased human activities. Compounds such as polycyclic aromatic hydrocarbons (PAHs) and heterocyclic compounds available in fuel are highly stable and can reside in the environment for prolonged periods if left untreated. The isolation of native strains is needed to develop bioremediation applications suitable for Antarctica. Strain BS19 was isolated as heterocyclic compound carbazole-degrading bacterium from Antarctic soil through culture enrichment. The 16S rRNA gene sequences identified strain BS19 as a member of the Sphingonium genus. Strain BS19 could remove 75% of carbazole after 15 days of culture at 15 degrees C. Whole genome sequencing resulted in incomplete genomes of 4.77 Mb in 96 contigs with the lowest GC content among Sphingobium sp. strains. The analyses revealed car gene cluster and ant genes and cat gene cluster required for the complete metabolism of carbazole as a source of carbon and energy. The comparison of the car gene cluster showed a similarity to the car gene cluster of Novosphingobium KA1. The expression of the car gene cluster was confirmed with an RT-PCR analysis indicating the involvement of the predicted genes in carbazole degradation. The findings from this study could provide more insight into developing bioremediation applications and approaches for Antarctica and other cold environments