Browsing by Author "Smith-Ramirez, Cecilia"

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    Bad company expands in highland areas: Overlapping distribution, floral resources and habitat suggest competition between invasive and native bumblebees
    (2023) Barahona-Segovia, Rodrigo M.; Smith-Ramirez, Cecilia; Duran-Sanzana, Vanesa; Huaranca, Juan Carlos; Pliscoff, Patricio
    Bumblebees are key pollinators, but their global decline is being driven by factors such as invasive species. Bombus terrestris has invaded many countries, displacing and competing with native bumblebees for resources throughout many different habitats, which causes native populations to decline. In the Chilean highlands, Bombus funebris-a Chilean species under threat-shares its habitat with B. terrestris, suggesting that the two species could be competing for resources (e.g., flowers or habitats) within this ecosystem. However, an information gap in this regard prevents us from proposing conservation measures. Our goals were (1) to assess overlapping distribution between native and invasive Bombus species, (2) to determine any niche overlap in the use of flowers between the two bumblebee species, and (3) to document the predictors that influence their abundance. We conducted a survey in northern Chile between 2017 and 2019 with different latitudinal and altitudinal sampling points to count bumblebees and record their interaction with flowers, both in natural and perturbed habitats. We analyzed their overlapping distribution using the chi-square test and evaluated the use of floral resources and their overlap niche through an interaction network analysis. Predictors and bumblebee abundance were associated with a general linear mixed model. We found the distribution of both bumblebees overlapped by 94.3 %, whereas the overlap niche index (NO) for the common use of flowers was high between B. terrestris and B. funebris (NO = 0.78). The abundance of both bumblebee species was associated with the use of natural scrubland in the highlands. Our results suggest that both species are likely to have a competitive dynamic for floral resources in the high Andean scrubland. As such, we propose implementing an export ban on invasive bumblebee species, coordinating measures between bordering countries, removing any remaining B. terrestris populations, and restoring native flora to attract native pollinators and to provide and manage pollination services in the Chilean highlands.
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    Combining remote sensing and field data to assess recovery of the Chilean Mediterranean vegetation after fire: Effect of time elapsed and burn severity
    (2022) Smith-Ramirez, Cecilia; Castillo-Mandujano, Jessica; Becerra, Pablo; Sandoval, Nicole; Fuentes, Rodrigo; Allende, Rosario; Acuna, Maria Paz
    It has been debated if Chilean sclerophyllous vegetation can recover after fire of different severity and short and long term. We evaluated the resiliency of this vegetation type after single-occurrence fires of different severities that occurred 30, 20 and 10 years in Central Chile before the study. Two approaches were followed: satellite image analysis and vegetation sampling. Wildfires that occurred between 1985 and 2015 were identified based on Landsat images. We selected 30 sites burned by a single fire in either 1985, 1995 or 2005, and that was not converted to another land use by 2015, then determined the percentage cover by vegetation type. We recorded or estimated the independent variables of burn severity, slope, altitude, pre-fire vegetation type and latitude of the sites. Composition, richness, and abundance of adult and regeneration of woody vegetation and herbaceous cover were sampled. Generalized linear models were used to evaluate the effect of the independent variables and the time elapsed since the fire on vegetation recovery. The proportion of dense vegetation forest cover was significantly higher with more time elapsed since the fire, while semi-dense forest/shrubland and open shrubland vegetation cover returned to pre-fire levels more quickly. The richness and abundance of regenerated woody species was significantly greater with more time elapsed since the fire. However, no relationship was found between species richness and abundance of adult woody species and time elapsed post-fire. We found that vegetative recovery over time was not related to burn severity. Forested and mixed forest/shrubland cover is reached 10-20 years after the fire, if no further intervention occurs. Richness and species abundance was similar to that of unburned sites after 20 or more years post-fire. This study provided evidence that forest vegetation in the Chilean Mediterranean ecosystem is resilient to fires of at least low and medium intensities.
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    Decadal trends in the pollinator assemblage of Eucryphia cordifolia in Chilean rainforests
    (2014) Smith-Ramirez, Cecilia; Ramos-Jiliberto, Rodrigo; Valdovinos, Fernanda S.; Martinez, Paula; Castillo, Jessica A.; Armesto, Juan J.
    Long-term studies of plant-pollinator interactions are almost nonexistent in the scientific literature. The objective of the present study was to determine changes and trends in the pollinator assemblage of ulmo (Eucryphia cordifolia; Cunoniaceae), a canopy-emergent tree found in Chilean temperate rainforests. We assessed the temporal variability of the pollinator assemblage and identified possible modulators of the observed temporal shifts. We sampled insect visitors to the flowers of 16 individual trees of E. cordifolia during 10 consecutive flowering seasons (2000-2009), recording a total of 137 pollinator species with a mean number of species per year of 44. Only three pollinator species (2.2 %) were recorded every year. Two bee species accounted for 50 % of all insect visits to flowers. One bee species, Bombus dahlbomii (native), was dominant in one season, whereas Apis mellifera (exotic) dominated during the next season. These interannual shifts in population abundances presented first-order dynamics that were characterized by oscillations with a period of 2 years. Changes in the abundances of the dominant pollinators, as well as differences in temperature and precipitation during insect emergence and flowering, led to a nested temporal structure of pollinator composition. Furthermore, the abundances of less common pollinators were sensitive to the abundance of the dominant bee species and to monthly maximum temperatures and the average precipitation during spring and summer. Based on our results and those from other studies, we predict a decline in the numbers of Bombus dahlbomii and nondominant native pollinators in response to new exotic arrivals.
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    Drought and Wildfire Trends in Native Forests of South-Central Chile in the 21st Century
    (2024) Duarte, Efrain; Rubilar, Rafael; Matus, Francisco; Garrido-Ruiz, Claudia; Merino, Carolina; Smith-Ramirez, Cecilia; Aburto, Felipe; Rojas, Claudia; Stehr, Alejandra; Dorner, Jose; Najera, Francisco; Barrientos, Guillermo; Jofre, Ignacio
    Over the last decades, Chile has experienced a long-term drought with significant consequences for water availability, forest productivity, and soil degradation, ultimately dramatically increasing the surface of burned area. Here, we quantify the Palmer Drought Severity Index (PDSI) to ascertain the extent of "moisture deficiency" across the central-southern region of Chile from 2000 to 2023 to assess the drought's relationship with the frequency of wildfires focusing on the impact of native forests. Our methodology quantifies the PDSI from the burned area data using MODIS MCD64A1 satellite imagery, validated by in situ wildfire occurrence records. The findings indicate that 85.2% of fires occurred under moderate to severe drought conditions. We identified 407,561 ha showing varying degrees of degradation due to wildfires, highlighting the critical areas for targeted conservation efforts. A significant increase in both the frequency of wildfires and the extent of the affected area in native forests was observed with the intensification of drought conditions in the 21st century within mesic to humid Mediterranean climatic zones where drought explains up to 41% of the variability in the burned area (r(2) = 0.41; p < 0.05). This study highlights the relationship between drought conditions and wildfire frequency, showing the paramount need to adopt comprehensive wildfire mitigation management in native forests.
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    Facilitation by pioneer trees and herbivore exclusion allow regeneration of woody species in the semiarid ecosystem of central Chile
    (2023) Gomez-Fernandez, Nicolas A.; Smith-Ramirez, Cecilia; Delpiano, Cristian A.; Miranda, Alejandro; Vasquez, Inao A.; Becerra, Pablo I.
    Questions: Facilitation by pioneer plants and herbivore exclusion may contribute to plant regeneration and restoration of degraded semiarid ecosystems. In this study we evaluated the main and interactive effects of the exclusion of large and medium-sized mammal herbivores and the presence of the pioneer tree Vachellia caven on natural regeneration of woody species in degraded savannas.
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    Habitat use of remnant forest habitats by the threatened arboreal marsupial Dromiciops gliroides (Microbiotheria) in a rural landscape of southern Chile
    (2010) Smith-Ramirez, Cecilia; Celis-Diez, Juan L.; von Jenstchyk, Erik; Jimenez, Jaime E.; Armesto, Juan J.
    Context. Remnant forest patches in rural landscapes may be important sites for maintaining viable populations of restricted forest species, especially when these remnant habitats maintain some connectivity, for instance through riparian vegetation strips and other forest patches.
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    Linking sedimentological and spatial analysis to assess the impact of the forestry industry on soil loss: The case of Lanalhue Basin, Chile
    (2021) Alaniz, Alberto J.; Abarzua, Ana M.; Martel-Cea, Alejandra; Jarpa, Leonora; Hernandez, Marjorie; Aquino-Lopez, Marco A.; Smith-Ramirez, Cecilia
    Soil loss has become one of the main problems associated with global change over the last decades. New assessments are needed in order to improve our understanding of the real impacts of human productive activities on the natural dynamics linked to erosion in lake basins. We analyzed the recent and historical dynamics of soil loss in a coastal lake basin of central Chile (Lanalhue lake), evaluating land use impacts and proposing management changes to control erosion and restore the soil. We implemented two approaches: A) Using a high-resolution sedimentological proxy and a high-accuracy chronology of cores to determine the sediment accumulation rate, organic/inorganic matter and granulometry for the last 120 years; and B) applying the Universal Soil Loss Equation to estimate erosion of soil from hills during the last 32 years, considering a combination of satellite, climate, soil, and land-cover topographic data. We found that the sedimentation rates, as well as the concentration of organic matter in lake sediments, were relatively constant from 1900 to 1950; after that, they experienced a significant increase. The same pattern of rapid increase was found for sand content. We found that erosion during the last 30 years has been high and constant, especially in bare soil (mainly clear-cutting areas) and exotic forest plantations. Erosion has been significantly higher within exotic forest plantations, reaching 31 ton/ha/yr in clear-cutting areas. Three industrial forestry companies accounted for 61.5% of the basin surface where urgent erosion control is needed. Our findings support the indication that industrial forestry is the main activity affecting erosion dynamics in the basin; secondarily, earthquakes have been important modulators of the sediment dynamics in Lanalhue during these last 120 years.
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    Multiscale spatial analysis of headwater vulnerability in South-Central Chile reveals a high threat due to deforestation and climate change
    (2022) Alaniz, Alberto J.; Smith-Ramirez, Cecilia; Rendon-Funes, Adriana; Hidalgo-Corrotea, Claudia; Carvajal, Mario A.; Vergara, Pablo M.; Fuentes, Norka
    Headwaters represent an essential component of hydrological, ecological, and socioeconomical systems, by providing constant water streams to the complete basin. However, despite the high importance of headwaters, there is a lack of vulnerability assessments worldwide. Identifying headwaters and their vulnerability in a spatially explicit manner can enable restauration and conservation programs. In this study, we assess the vulnerability of headwaters in South -Central Chile (38.4 to 43.2 degrees S) considering multiple degradation factors related to climate change and land cover change. We analyzed 2292 headwaters, characterizing multiple factors at five spatial scales by using remote sensing data related to Land Use and Cover Change (LUCC), human disturbances, vegetation cover, climate change, potential water demand, and physiography. We then generated an index of vulnerability by integrating all the analyzed vari-ables, which allowed us to map the spatial distribution of headwater vulnerability. Finally, to estimate the main drivers of degradation, we performed a Principal Components Analysis with an Agglomerative Hierarchical Clustering, that allowed us to group headwaters according to the analyzed factors. The largest proportion of most vulnerable headwa-ters are located in the north of our study area with 48.1 %, 62.1 %, and 28.1 % of headwaters classified as highly vul-nerable at 0, 10, and 30 m scale, respectively. The largest proportion of headwaters are affected by Climate Change (63.66 %) and LUCC (23.02 %) on average across all scales. However, we identified three clusters, in which the north-ern cluster is mainly affected by LUCC, while the Andean and Coastal clusters are mainly affected by climate change. Our results and methods present an informative picture of the current state of headwater vulnerability, identifying spa-tial patterns and drivers at multiple scales. We believe that the approach developed in this study could be useful for new studies in other zones of the world and can also promote Chilean headwater conservation.
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    Recovery of Chilean Mediterranean vegetation after different frequencies of fires
    (2021) Smith-Ramirez, Cecilia; Castillo-Mandujano, Jessica; Becerra, Pablo; Sandoval, Nicole; Allende, Rosario; Fuentes, Rodrigo
    Post-fire recovery of sites in the Chilean Mediterranean vegetation were evaluated 20-30 years after the last fire. We mapped all fires that occurred between 1985 and 2015 in Central Chile using Landsat images. In order to conduct a spatial analysis of vegetation recovery and field sample, we chose sites burned between 1985 and 1995 that retained native vegetation and cover until 2015. In a sampled of these sites, richness and abundance of woody vegetation, and herbaceous richness were recorded. We contrasted our results from field sampling with control (unburned) sites at the species level. Generalized linear models (GLM) were used to evaluate the relationship between the percentage of vegetation recovered with fire frequency, pre-fire cover, topographic and geographic factors. In addition, GLM were used to evaluate the effects of fire frequency on species richness, abundance, and cover. We found that the proportion of dense and semi-dense vegetation cover were similar in sites burned once and twice, and higher than sites burned three times. Besides, the proportion of dense and semidense vegetation cover were higher in lower elevation sites, in those with higher slopes, and far from population centers. The richness and abundance of adult woody species, richness of regeneration and richness of native herbs, were greater in sites that had lesser fire frequency. Mean species richness of native herbaceous species decreased as fire frequency increased, exotic herbaceous cover had no relation with fire frequency, and both native and exotic herbaceous cover were greater at driest latitudes but were not related to fire frequency. Mean species richness after one fire was higher than in unburned sites, but some plant species were found only at unburned sites. We conclude that the Mediterranean vegetation of Chile is able to regenerate to pre-fire conditions after one and two fires, but three consecutive fires reduced its cover, richness and abundance, even 20 years after the fire.
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    Regeneration of Fitzroya cupressoides after indigenous and non-indigenous timber harvesting in southern Chilean forests
    (2007) Smith-Ramirez, Cecilia
    Fitzroya cupressoides (Cupressaceae) is an endemic and long-lived conifer of southern Chile and Argentina (40-43 degrees S). This species has been subject to continuous exploitation since the 16th century, causing extensive population decline. Historically, the main labour force for the exploitation of F cupressoides (alerce) was the indigenous Mapuche-Huilliche population, first under the command of the Spanish settlers and later, of non-indigenous Chileans. In coastal forests, timber of alerce has been harvested by Huilliche communities as well as by Chilean and international forestry companies. Records of the regeneration of this pioneer tree after exploitation in the Andean mountains have generally shown limited regeneration depending on the intensity of harvest. Because indigenous exploitation does not use machinery for timber harvesting, and is supposedly less utilitarian than commercial harvest, I propose that areas in the Coastal Range harvested by Huilliche communities should present higher regeneration of alerce than areas harvested by forestry companies. To test this hypothesis, I sampled 10 stands harvested and abandoned by forestry companies and 10 stands harvested by Huilliche communities in the coastal range of the Osorno Province (41 degrees S, 400-800 m). In each stand, I estimated the density of regeneration (sapling stage), number of stumps, number of live adults, and the number of standing and fallen dead alerce. Each stand was characterized by elevation, forest-type, incidence of fire, and vegetation cover. Results showed that forests harvested by Huilliches had higher numbers of live, remnant adult trees with a dbh >= 60 cm than forests harvested by timber companies. The number of stumps with a dbh >= 60 cm was significantly higher in stands harvested by timber companies than in Huilliche stands. Despite large differences in sapling densities among stands, regeneration density of alerce was unrelated to the type of harvest used by indigenous people or forestry companies. (c) 2007 Elsevier B.V. All rights reserved.
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    Toward Integrated Analysis of Human Impacts on Forest Biodiversity: Lessons from Latin America
    (2009) Newton, Adrian C.; Cayuela, Luis; Echeverria, Cristian; Armesto, Juan J.; Del Castillo, Rafael F.; Golicher, Duncan; Geneletti, Davide; Gonzalez-Espinosa, Mario; Huth, Andreas; Lopez-Barrera, Fabiola; Malizia, Lucio; Manson, Robert; Premoli, Andrea; Ramirez-Marcial, Neptali; Benayas, Jose-Maria Rey; Rueger, Nadja; Smith-Ramirez, Cecilia; Williams-Linera, Guadalupe
    Although sustainable forest management (SFM) has been widely adopted as a policy and management goal, high rates of forest loss and degradation are still occurring in many areas. Human activities such as logging, livestock husbandry, crop cultivation, infrastructural development, and use of fire are causing widespread loss of biodiversity, restricting progress toward SFM. In such situations, there is an urgent need for tools that can provide an integrated assessment of human impacts on forest biodiversity and that can support decision making related to forest use. This paper summarizes the experience gained by an international collaborative research effort spanning more than a decade, focusing on the tropical montane forests of Mexico and the temperate rain forests of southern South America, both of which are global conservation priorities. The lessons learned from this research are identified, specifically in relation to developing an integrated modeling framework for achieving SFM. Experience has highlighted a number of challenges that need to be overcome in such areas, including the lack of information regarding ecological processes and species characteristics and a lack of forest inventory data, which hinders model parameterization. Quantitative models are poorly developed for some ecological phenomena, such as edge effects and genetic diversity, limiting model integration. Establishment of participatory approaches to forest management is difficult, as a supportive institutional and policy environment is often lacking. However, experience to date suggests that the modeling toolkit approach suggested by Sturvetant et al. (2008) could be of value in such areas. Suggestions are made regarding desirable elements of such a toolkit to support participatory-research approaches in domains characterized by high uncertainty, including Bayesian Belief Networks, spatial multi-criteria analysis, and scenario planning.