Browsing by Autor "Edgar E. Gareca"

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Dendrochronological investigation of the high Andean tree species Polylepis besseri and implications for management and conservation
(Springer Science+Business Media, 2010) Edgar E. Gareca; Milton Fernández; Sharon Stanton
Designing biological corridors for the Pilcomayo River region (Gran Chaco) of Argentina, Bolivia and Paraguay
(2023) Fátima Mereles; GABRIELA NAZARO; Laura Villalba; Edgar E. Gareca; Clara Echeverria
La region del río Pilcomayo del Gran Chaco, es compartida por tres países: Argentina, Bolivia y Paraguay. Los cambios en el uso del suelo en la region, afectaron creando brechas dentro de las formaciones vegetales y los corredores biológicos constituyen una herramienta de conservación para brindar mayor resiliencia a las formaciones restantes. El objetivo del trabajo es analizar los datos existentes para el diseño de corredores biológicos que salvaguarden la conectividad entre sitios importantes para la biodiversidad dentro del área del río Pilcomayo, sin que esto signifique un alto costo para la fauna mayor. Para ello se trabajó en el área compartida entre los tres países afectados. Como base para la conectividad se identificaron 14 zonas núcleo o HVCA: cinco en Argentina, dos en Bolivia, seis en Paraguay y una compartida entre Bolivia y Paraguay. Se generó una red minima de conexiones entre estas áreas y una matriz de costos, a partir de la cual se identificaron costos mínimos entre los HVCA. Los resultados indican que el 77% de las zonas núcleo son bosques y el 6% son áreas antropizadas. Se diseñaron catorce corredores biológicos para generar una red que garantice una conectividad entre ellos. De esta red, 53% se encuentra en Argentina, 27% en Paraguay y 15% en Bolivia.
Efectos de los árboles exóticos y del ambiente materno sobre la producción de semillas, la germinación y el crecimiento inicial de Polylepis subtusalbida (Rosaceae) en el Parque Nacional Tunari, Bolivia
(2018) Edgar E. Gareca; Yvonne Y. Martinez; Claudia Solís; Luís F. Aguirre
Polylepis subtusalbida’s woodlands at the Southern slope of Parque Nacional Tunari (Cochabamba, Bolivia) are key native vegetation remnants between 3200-3900 m; they provide ecosystem services, specially to the city of Cochabamba. However, these woodlands are highly fragmented and coexist with exotic trees (Pinus radiata and Eucalyptus globulus). This work shows the effects of the exotic trees and the maternal environment on seed production, germination and initial growth of Polylepis. Three settings for the exotic trees were studied: Polylepis woodlands a) surrounded by semi-natural grassland, b) surrounded by exotic trees and c) mixed with exotic trees. Fruits from 67 mother trees belonging to seven fragments were used. The percentage of fruits with full seeds was measured as an estimation of seed production. Germination and early growth were evaluated in a common garden with a complete randomized design (germination) and a complete randomized block design (early growth). Variables from the maternal environment were reduced via PCA and backward multiple regression followed by general mixed linear models which were performed to evaluate the effect of the exotic trees, maternal traits and maternal microsite on the seed production, germination and early growth. The percentage of fruits with full seeds diminished as bare soil under the maternal tree increased. Germination was high and it was not affected by the studied factors. Early growth of the progeny was affected by the presence of the exotic trees, bare soil, leaf cover and health of the maternal tree. Seed production was identified as a limiting stage for Polylepis regeneration, and the exotic trees and maternal environment affected early growth of the progeny in a common garden (maternal effects).https://doi.org/10.25260/EA.18.28.1.1.698
ENSAMBLE DE MURCIÉLAGOS EN SITIOS CON DIFERENTE GRADO DE PERTURBACIÓN EN UN BOSQUE MONTANO DEL PARQUE NACIONAL CARRASCO, BOLIVIA
(2008) Aideé Vargas Espinoza; Luís F. Aguirre; M. Isabel Galarza; Edgar E. Gareca
Assemblage of bats in sites with varying degrees of disturbance in montane forests of Carrasco National Park, Bolivia. Montane forests in Bolivia are characterized by sites with high biodiversity and endemism but are also faced by threats due to human activities, mainly agriculture. For a period of 11 months, we evaluated the effect of human disturbance due to traditional agricultural activities on bat communities in a montane forest in the foothills of the Santuario de Vida Silvestre Cavernas de Repechon, Carrasco National Park. We found that the total community contained 36 species based on a sample of 2518 individuals belonging to Phyllostomidae and Vespertilionidae. The most abundant species in all sites was Carollia perspicillata; in abandoned fields, young forest and mature forest C. brevicauda was the second most abundant species, whereas in agricultural lands Artibeus lituratus was the most common. Fruit-eating bats were the best represented trophic guild in terms of species and abundance. The sites with most similar species composition were abandoned fields and mature forests. Young forests were less similar to abandoned fields, and agricultural lands differed most from all other sites. Be- cause the study sites were small compared with the larger matrix consisting mostly of
Genetic diversity of AndeanPolylepis(Rosaceae) woodlands and inferences regarding their fragmentation history
(Oxford University Press, 2013) Edgar E. Gareca; Peter Breyne; Katrien Vandepitte; Jennifer R. A. Cahill; Milton Fernández; Olivier Honnay
There is a long-standing debate on whether the occurrence of the iconic high-Andes Polylepis woodlands as small and isolated fragments is of natural or anthropogenic origin. We make inferences regarding the fragmentation history based on both a new population genetic study on P. besseri and a synthesis of available studies on the population genetics of Polylepis woodlands. We infer the timing of the main woodland fragmentation event by analysing: (1) the remaining levels of population genetic diversity and the relation to population size; (2) among-population genetic differentiation; and (3) the difference in genetic diversity between the offspring and adult generation. We retrieved seven publications on the population genetics of five Polylepis spp. We did not find a relationship between population size and genetic diversity, and genetic differentiation was low compared with that reported for similar plant species. These findings do not support a history of long-term fragmentation. The offspring showed a loss of genetic diversity and increasing differentiation compared with adults, suggesting that the main habitat fragmentation event is of relatively recent origin. For P. besseri, no significant differences were found between the adult and offspring genetic variation. We discuss the conservation and restoration consequences for this important high-Andean genus.
Good news for habitat restoration projects: Eucalyptus does not inhibit the germination of Polylepis
(Wiley, 2022) Lidia Meneses; Yvonne Y. Martinez; Alexandre Antonelli; Edgar E. Gareca
Eucalyptus plantations outside their native range—either as an income source or aimed at sequestering atmospheric carbon to combat climate change—are increasingly known to reduce local biodiversity and groundwater levels, and to increase soil degradation and erosion. One additional but less understood effect of Eucalyptus on native floras is allelopathy—the chemical inhibition of other plants' germination. Here we investigate the putative allelopathic effects of Eucalyptus globulus on the germination of Polylepis subtusalbida , a keystone species that characterizes a species‐rich and highly threatened woodland habitat in the Bolivian Andes. We carry out controlled greenhouse experiments reflecting local rainfall, field litter quantity, and Eucalyptus leachate concentrations at multiple levels. Our results, based on five replicates with 390 Polylepis seeds each, show that contrary to our expectation Eucalyptus leachates does not affect germination significantly. Our findings suggest that projects aiming to remove Eucalyptus to restore Polylepis woodlands are likely to succeed even without the resource‐consuming removal of leaf litter, and potentially also bark and roots, from the ground after tree felling.
Hypseocharis reveals early history of physical dormancy in Geraniaceae
(Cambridge University Press, 2016) Filip Vandelook; Ann Van de Vyver; Edgar E. Gareca
Abstract Hypseocharis is a genus endemic to the high Andes and sister to all other Geraniaceae genera. Regarding its basal position in Geraniaceae evolution, its germination ecology can provide important insights into the early evolution of physical dormancy. Imbibition tests performed on seeds of two Hypseocharis populations from Bolivia indicate that their seeds indeed have physical dormancy like all other Geraniaceae. These results indicate that physical dormancy in Geraniaceae evolved during the Eocene before the uplift of the Andes mountains and before the events that led to the cross-Atlantic disjunct distribution of Geraniacae.
Polylepis woodland remnants as biodiversity islands in the Bolivian high Andes
(Springer Science+Business Media, 2010) Edgar E. Gareca; Martin Hermy; Jon Fjeldså; Olivier Honnay
Regeneration patterns of Polylepis subtusalbida growing with the exotic trees Pinus radiata and Eucalyptus globulus at Parque Nacional Tunari, Bolivia
(Springer Science+Business Media, 2007) Edgar E. Gareca; Yvonne Y. Martinez; Ramiro O. Bustamante; Luís F. Aguirre; Melicio M. Siles
Seed germination, hydrothermal time models and the effects of global warming on a threatened high Andean tree species
(Cambridge University Press, 2012) Edgar E. Gareca; Filip Vandelook; Milton Fernández; Martin Hermy; Olivier Honnay
Abstract Seed germination is a crucial event in a plant's life cycle. Because temperature and water availability are important regulators of seed germination, this process will likely be influenced by global warming. Insight into the germination process under global warming is thus crucial, and requires the study of a wide range of water availability and temperature conditions. As hydrothermal time (HTT) models evaluate seed germination for any combination of water potential and temperature, they can be suitable to predict global warming effects on seed germination. We studied the germination characteristics of the high Andean endemic tree species Polylepis besseri (Rosaceae), using HTT models. We were especially interested in the potential effects of global warming on seed germination. Assembly of HTT models for P. besseri was fairly straightforward due to the lack of a seed dormancy mechanism. The models allowed prediction of Polylepis germination under constant and alternating temperatures. Initially, a global warming induced increase in the field minimum and mean temperature will increase P. besseri germination, but as maximum temperatures rise above the optimum temperature for the species, seed germination will become jeopardized. Effects of global warming on seed germination are currently considerably underexplored. HTT models prove to be useful tools to study a plant species' general germination characteristics, and how they may become affected under global warming. For the endemic mountain tree species P. besseri , we predict an increase, followed by a decrease of seed germination under global warming.