Correa Araneda, Francisco

The Andean lakes of northern Chile and southern Bolivia are characterized by their high salinity due to arid climate and high evaporation. These lakes are poorly studied due to access difficulties. The aim of this study is to characterize two shallow saline lakes in northern Chile (Salar de Atacama, 23°S, Chile) and South Lipez of Bolivia (Khalina lake, 22.61°S) using satellite images (Landsat 8). The data involved surface temperature, chlorophyll-a concentration, and meteorological parameters (wind speed, relative humidity, atmospheric pressure). The available data revealed marked monthly variations in limnological and meteorological parameters that would be associated. The exposed antecedents revealed that the use of remote sensing techniques can be an important tool for limnological studies in zones with geographical access difficulties.

Background: Forest ecosystems provide services that are important for human use; one of the most critical ecosystem services is the provision and regulation of water. Basins with high forest improves hydrological functionality by promoting reduction in surface runoff, increase infiltration and aquifer recharge, and ensures base flow regulation amongst others. On the other hand, the conversion towards highly anthropized productive systems is usually accompanied by precarious environmental management that alters the hydrological cycle and reduction in water quality in basins. Aim: The goal of this study was to analyze land use changes and their effect on water efficiency index (WEI) in three sub-basins. Methodology: The methodology included a multi-temporal analysis of satellite images to identify land uses, also the use of SWAT (Soil and Water Assessment Tool) model for hydrological analysis in each sub-basin, information needed for calculating the WEI. Results: The results revealed the existence of no significant difference in terms of WEI between the sub-basins with predominant tree cover of native or artificial, being higher (0.89) than the WEI values reported by the sub-basin with agricultural land use (0.65). It is concluded that hydrological functions are more efficient in basins with forest cover, made up of native or exotic species, than agricultural land use with annual crop rotations. The results contribute to decision making on public policies associated to the rural productive activities. Concluded: Finally, we conclude the necessity of the promotion of forest plantation management techniques that avoid clear-cutting and multiple rotations in basin headwaters and riparian areas.

Stream ecosystems are highly vulnerable to changes in land use and vegetation in their catchments for two reasons: firstly, they receive inputs of nutrients, contaminants and sediments through runoff; and secondly, terrestrial leaf litter is the major basal resource supporting their food webs. Leaf litter decomposition by microorganisms and detritivores is thus a key stream ecosystem process, and a valuable functional indicator of impacts associated to agriculture and other alterations of human origin. Here, we investigated the joint effects of land use changes associated to agriculture (low, medium and high intervention areas: LI, MI and HI, respectively) in a tropical lowland catchment in Panama, through a decomposition experiment using three leaf litter types differing in nativeness (Ficus insipida, native to the study area; Alnus acuminata, native to Panama but not present in the study area; and Musa balbisiana, exotic to Panama). Lowland tropical areas are often poor in litter-consuming detritivores, and we accordingly observed a high contribution of microorganisms to total decomposition (>60% on average). However, only in the presence of detritivores, decomposition of Alnus discriminated among different degrees of agricultural intervention, being higher at the LI area. Leaf litter of the native Ficus showed higher microbial decomposition than the other types, possibly in relation to a home-field advantage effect. Despite the scarcity of detritivores in tropical lowland streams compared to tropical highland or temperate streams, our study indicates that their activity reflects impacts of land use change on these streams and they should therefore be included in assessments of anthropogenic impacts. © 2023 The Author(s)

During the past three decades, various methods have been developed to improve the classification accuracy in very high resolution (< 2 m) satellite data. This study's main goal was to evaluate and select the most suitable classification approach for detecting deadwood potentially useful for energy projects that would satisfy part of the demand for heating in the area. We compare five classification approaches using a WorldView-2 (Digital Global, Ins) standard, an orthorectified image of the Aysén region of the Chilean Patagonia. The five classifiers were evaluated and selecting the best one was carried out through a confusion matrix and Kappa coefficient. The results showed that the two non-parametric classifiers used (neural net and support vector machine) offered the best performance (98%) and the best Kappa coefficient (0.97). We conclude that it is essential to promote the development of innovative projects in native forests by local owners can contribute, to the formulation of public policies that directly benefit the Aysén region's inhabitants.

Forest wetlands are biodiversity hotspots that perform functions of vital ecological importance, but they are among the world's most threatened ecosystems. Due to their high diversity of habitats and species, the study of their benthic macroinvertebrate communities is challenging, and there is no consensus on which sampling methods allow a better representation of these communities. Here we compared the performance of 3 sampling methods (hand net, corer and litterbags) in 2 temporary and 3 permanent forested wetlands in southern Chile, which were bimonthly sampled throughout a year, with 108 samples per wetland. Our results indicated that the greatest abundance and diversity were collected with the hand net, followed by the litterbags and the corer. The composition of communities collected by the hand net and litterbags were more similar between them than that of communities collected by the corer (where Chironomidae and Oligochaeta were common). We suggest that the combined use of the hand net and corer could provide a good representation of macroinvertebrate communities in forest wetlands, as they would allow recording most of the diversity, including taxa that are both sensitive and tolerant to stressors.

Background: Wildfires have strong impacts on terrestrial and aquatic ecosystems, whose frequency, severity, and intensity are increasing with climate change. Moreover, the expansion of exotic monoculture plantations, such as those of eucalypts, increases this risk. When wildfires do not cause the disappearance of riparian vegetation, they still imply the fall of leaf litter exposed to the fire (i.e., crown scorch), which consequences for ecosystems are unknown. Experimental design: To explore how these leaf litter inputs may affect stream ecosystem functioning, we conducted a microcosm experiment where we quantified the decomposition of leaf litter from three tree species (alder, oak, and eucalypt) under two conditions (control litter simulating natural entries and litter subjected to 150 °C for 3 h mimicking exposure to fire). We also examined the interaction between this factor and a temperature rise (which is often associated to the loss of riparian vegetation caused by the wildfire) by manipulating water temperature (10, 12.5, and 15 °C). Finally, we explored the effects of these variables on the growth of a common detritivore, the caddisfly Sericostoma pyrenaicum. Results: Control alder presented the highest decomposition rates, which were notably reduced due to fire exposure. On the contrary, eucalypt litter decomposition was even slower than that of oak and hardly showed any effect derived from fire exposure. The different leaf litter types determined detritivore growth, to a greater extent than variation related to warming, which generally had negligible effects. Conclusions: Our study shows the negative effects of wildfires on stream ecosystem functioning even when they only involve brief exposure of leaf litter to the fire. Effects are greater on the most palatable native species, which represents the highest quality input in streams of the study area. Our results highlight the importance of protecting riparian forests, especially those composed of native species, against wildfires. © The Author(s) 2024.

Several human activities often result in increased nitrogen (N) and phosphorus (P) inputs to running waters through runoff. Although headwater streams are less frequently affected by these inputs than downstream reaches, the joint effects of moderate eutrophication and global warming can affect the functioning of these ecosystems, which represent two thirds of total river length and thus are of major global relevance. In a microcosm study representing streams from a temperate area (northern Spain), we assessed the combined effects of increased water temperature (10.0, 12.5, and 15.0 °C) and nutrient enrichment (control, high N, high P, and high N + P concentrations) on the key process of leaf litter decomposition (mediated by microorganisms and detritivores) and associated changes in different biological compartments (leaf litter, aquatic hyphomycetes and detritivores). While warming consistently enhanced decomposition rates and associated variables (leaf litter microbial conditioning, aquatic hyphomycete sporulation rate and taxon richness, and detritivore growth and nutrient contents), effects of eutrophication were weaker and more variable: P addition inhibited decomposition, addition of N + P promoted leaf litter conditioning, and detritivore stoichiometry was affected by the addition of both nutrients separately or together. In only a few cases (variables related to detritivore performance, but not microbial performance or leaf litter decomposition) we found interactions between warming and eutrophication, which contrasts with other experiments reporting synergistic effects. Our results suggest that both stressors can importantly alter the functioning of stream ecosystems even when occurring in isolation, although non-additive effects should not be neglected and might require exploring an array of ecosystem processes (not just leaf litter decomposition) in order to be detected. © 2023 The Authors

High Andean freshwater ecosystems are highly threatened by scarce water availability, species invasion, and global climate change, so generating knowledge about their ecological characteristics is extremely important for conservation decision-making. In this work, the seasonal variations and relationships between physico-chemical variables and the structure and composition of the macroinvertebrate community were analyzed considering “season”, “type of ecosystem” and “site” factors. Five sites of representative ecosystems at Lauca River Basin of the Chilean Altiplano were sampled, two of them lentic and three lotic. Two field-sampling periods within a year according to the pre-and post-rain seasons characteristic of the Altiplano climate were considered. Thirty-five taxa were identified, and it was observed that the taxa Orthocladiinae, Austrelmis sp., Hyallela cf kochi, Podonominae and Helicopsychidae were indicator taxa that contributed the most to differences among sites or ecosystems (≥ 10 %.). No significant differences were found in the alpha diversity indicators used, except for some abundance values and Pielou’s Evenness index (J´), which varied significantly between lotic and lentic systems. The results of the ordination analysis showed a significant differentiation considering physical and chemical variables and macroinvertebrates assemblages that responded to “sites” (ANOSIM R Global = 0.64, p = 0.001) and “type of ecosystem” factors (ANOSIM R Global = 0.31, p = 0.02). The “season” factor was not statistically significant to explain the variability of biological data (ANOSIM R Global =-0.003, p = 0.47) and was slight and marginally significant with the physical and chemical data (ANOSIM R Global = 0.1, p = 0.04). In addition, the linear redundancy analysis (RDA) showed that physico-chemical variables related to hardness, temperature, phosphorous, and nitrogen explained most of the variance in the biological data (the first two canonical axes RDA1 and RDA2 explained 45.23 % of the total variation, p = 0.004). These results support the relevance of local conditions for high altitude wetlands and how those environmental characteristics can be reflected in the macroinvertebrate assemblages that inhabit them. © Asociación Ibérica de Limnología, Madrid. Spain.

Temuco (Chile) is one of the most polluted cities in Chile and Latin America. Although the fine fraction of particulate matter (PM2.5) has been extensively studied and monitored due to its negative impact on public health, its microbiological components remain unknown. We explored, the airborne bacterial community in PM2.5 under good, moderate, alert, pre-emergency and emergency indices of air quality (AQIs) established by the Chilean government. Bacterial community relationship with environmental factors (PM2.5, PM10, carbon monoxide, among others), was also evaluated. Significant differences in PM2.5 bacterial community composition associated with AQIs were revealed, using 16S rRNA target sequences of denaturing gradient gel electrophoresis (DGGE) bands. Bacterial communities in PM2.5 were mainly clustered (80%) into emergency and pre-emergency samples. The dominant phylum was Proteobacteria and most abundant genus was Novosphingobium, traditionally related to opportunistic respiratory diseases. The main factors associated with community structure were PM2.5, PM10 and carbon monoxide concentrations. This study exposed that bacterial community composition in Temuco varies according to AQIs, with the occurrence of potential opportunistic bacteria on heavily polluted days.