Raptor functional diversity in scrubland-agricultural landscapes of northern-central-Mexican dryland environments

"Raptor birds have widespread distributions in different environments throughout the planet. Yet, they are highly sensitive to landscape disturbances. We studied raptors in northern-central Mexico at the Highland plateau of San Luis Potosí and Zacatecas, in three landscape types that differed in proportion of agriculture. Our main goal was to determine whether small proportion of agriculture at the landscape level influences species richness, ecological diversity, and functional diversity. We conducted raptor road surveys during 1 year, from April 2015 to February 2016. We registered a total of 332 birds belonging to 14 diurnal raptor species. The most abundant species were Cathartes aura (turkey vulture), Falco sparverius (American kestrel), Caracara cheriway (crested caracara), and Buteo jamaicensis (red-tailed hawk). Three species: Aquila chrysaetos (golden eagle), Pandion haliaetus (osprey), and Falco columbarius (merlin) were exclusively recorded in the less-degraded, scrubland landscapes. However, no significant differences on average diversity were found between landscape types. Contrastingly, scrubland landscapes had the highest average functional diversity, followed by mixed landscapes, and then by agricultural landscapes, with significant differences in functional diversity between scrubland and agricultural landscapes. Overall, observed species richness in the study area formed four functional groups. These groups change and loose species as proportion of agriculture in the landscape progressively increases. The results suggested that the contribution of species richness to functional diversity, both for scrubland landscapes, which have the greatest functional diversity, and agricultural landscapes, which hold the smallest functional diversity, is important because there is substantial functional redundancy among landscape types.

Richness and abundance of granivorous vertebrates determine acorn removal patterns in a human modified oak forest

"Most forests of the Earth have been affected by human activities and this can alter the plant-animal interactions on which depend the functional integrity of these ecosystems. In this study, we assessed the relationships between acorn removal rates and the richness and abundance of granivorous vertebrates along a forest-edge-clearing gradient. We also evaluated whether removal rates differed among oak species with different acorn size. To this purpose, a field experiment was performed including acorns of five oak species, which were exposed to seed consumers in the three different habitats (forest interior, man-made clearings and the edge between these habitats). The experimental units consisted in five paper trays containing 50 acorns of each oak species located at different distances from the edge towards the forest and the man-made clearing (0, 20 and 50 m). Experimental sites were equipped with phototraps to record the identity of the visiting granivorous vertebrates. Richness and abundance of granivores increased from the edge towards the forest interior, while the converse patterns were observed in the man-made clearing. For most oak species, acorn removal patterns was positively correlated with richness and abundances of granivores, though in all habitats small-sized acorns were removed much faster and in larger proportions than big-sized acorns. Although these results are specific for the study site, they suggest that man-made clearings reduce the richness and abundance of granivores, thus negatively affecting the secondary dispersion of zoochoric tree species towards open habitats. Further, it also seems that large-seeded oak species face greater dispersal limitations than small-seeded oaks, because of the lack of animals able to scatter them from the forest to the clearings.

Bancos de semillas en dos estadios sucesionales de bosque andino en el noreste de Colombia

"Background: Soil seed banks play an important role in post-disturbance regeneration and succession of species from different successional stages. Questions: 1) What is the most effective method for determining the composition and structure of the soil seed bank of Andean forests? 2) What is the composition and structure of soil seed banks in old-growth forest and shrubland sites in the Andean montane tropical forest of the North Santander region of Colombia? Study site: Andean forest, Pamplona, Colombia Methods: We surveyed the soil seed bank in two successional stages of Andean forest and examined its structure using two sampling methods: direct separation and germination. Results: Soil seed bank density was higher (18-fold in old-growth forest and 666-fold in shrubland) with the direct separation method than with germination; however, under the germination method, we found four species that we did not detect through the direct separation method. Soil seed banks from shrublands were mainly dominated by species from disturbed areas (91 %), while those from the old-growth forest presented early, intermediate and late species; e.g., Miconia summa, Myrsine dependens and Solanum sp., respectively. In the old-growth forest (especially for late species), density increased with depth. This pattern was not observed in shrubland. Seeds obtained by using the direct separation method presented low (< 7 %) viability. Conclusion: We consider the two methods to be complementary and recommend the use of both for a thorough characterization of soil seed banks from Andean forests. At different successional stages in the Colombian Andean forest, the soil seed bank may contain early, intermediate and late species, and it therefore plays an important role in the regeneration of this threatened ecosystem.""Antecedentes: Los bancos de semillas del suelo juegan un papel importante en la regeneración de especies de diferentes etapas de sucesión. Preguntas: 1) ¿Cuál es el método más eficaz para la descripción de la composición y la estructura del banco de semillas del suelo de los bosques andinos? y 2) ¿Cómo es la composición y estructura de los bancos de semillas del suelo en un bosque primario y un matorral en el bosque andino en Colombia? Sitio de estudio: Bosque andino en Pamplona, Norte de Santander, Colombia Métodos: Se estudiaron el banco de semillas del suelo en dos etapas de sucesión de bosque andino y se examinó la estructura mediante dos métodos de muestreo: separación directa y la germinación. Resultados: La densidad del banco de semillas en el suelo fue mayor (18 veces en bosques primarios y 666 veces en matorral) con el método de separación directa que con el método de germinación; Sin embargo, bajo el método de germinación, se encontraron cuatro especies que no detectamos a través del método de separación directa. Los bancos de semillas de matorrales fueron dominados principalmente por especies de las áreas perturbadas (91 %), mientras que en el bosque primario se encontraron especies de estados sucesionales tempranos, intermedios y tardíos, por ejemplo, Miconia summa, Myrsine dependens y Solanum sp., respectivamente. En el bosque maduro (especialmente para las especies de estapas sucesionales tardías), la densidad aumenta con la profundidad. Este patrón no se observó en el matorral. Aunado a esto, las semillas obtenidas mediante el método de separación directa presentaron baja (7 % <) viabilidad. Conclusión: Consideramos que los dos métodos son complementarios y recomendamos el uso de las dos metodologías para una adecuada caracterización de los bancos de semillas del suelo de los bosques andinos. El banco de semillas del suelo puede contener especies de diferentes estadios sucesionales, por lo que tiene un papel importante en la regeneración del bosque andino de Colombia.

La ganadería ante escenarios complejos.

La calidad de las contribuciones, producto de la pluma de especialistas en los temas tratados, el presente es un libro que esperamos, basándonos en la importancia de los temas tratados, sea de utilidad y abone a la reflexión de los estudiosos de la ganadería mexicana y, por supuesto, en beneficio de las familias ganaderas y de los consumidores de sus productos.este libro refleja en muchos sentidos la situación de la ganadería mexicana, a la que se le están demandando mayor producción y productividad, que los procesos productivos tengan la menor huella ecológicposible, que los alimentos sean inocuos, que se abatan costos de producción y, cada vez aumentan las presiones de diversos grupos para, que se incluyan los protocolos de bienestar animal, solamente por citar algunos de los retos que tiene. Algunas de estas demandas son complementarias, otras se contraponen, lo que hace valiosos a los estudios que desde las ciencias sociales se realizan y, desde diversas ópticas, se hagan propuestas de política pública balanceadas que consideren lo mejor de cada enfoque, pero sin desechar por completo los antagónicos.Universidad Autónoma Chaping

Habitat suitability models to make conservation decisions based on areas of high species richness and endemism

"Biodiversity positively relates with the provisioning of ecosystem services and preserving areas with elevated diversity of highly-functional species could help to ensure human well-being. Most studies addressed to make these decisions use maps relying on species occurrences, where sites containing several species are proposed as priority conservation areas. These maps, however, may underestimate species richness because of the incompleteness of occurrence data. To improve this methodology, we propose using habitat suitability models to estimate the potential distribution of species from occurrence data, and later shaping richness maps by overlapping these predicted distribution ranges. We tested this proposal with Mexican oaks because they provide several ecosystem services and habitat suitability models of species were calibrated with MaxEnt. We used linear regressions to compare the outputs of these predictive maps with those of maps based on species occurrences only and, for both mapping methods, we assessed how much surface of sites with elevated richness and endemism of oaks is currently included within nature reserves. Both mapping methods indicated that oak species are concentrated in mountain regions of Mexico, but predictive maps based on habitat suitability models indicated higher oak richness and endemism that maps based on species occurrences only. Our results also indicated that nature reserves cover a small fraction of areas harboring elevated richness and endemism of oaks. These results suggest that estimating richness across extensive geographic regions using habitat suitability models quickly provides accurate information to make conservation decisions for highly-functional species groups.

Acorn weight as determinant of germination in red and white oaks: evidences from a common-garden greenhouse experiment

"Key message In Mexican oaks, germination increases with acorn fresh weight across oak species. Within species, these relationships are stronger in red oaks than in white oaks. In both oak groups, fresh weight of acorns increases with their dry biomass. Context Mexican oaks are phylogenetically grouped in red and white oaks. White oaks produce heavier acorns than red ones, but no studies have assessed whether this leads to different germination patterns. Aims This study was aimed to determine the influence of the fresh weight of acorns on their germination. Methods Acorns of red and white oaks were hydrated, weighed, and sowed under greenhouse conditions to assess whether their fresh weight was related with germination. We also assessed whether fresh weight of acorns was related with their dry biomass and/or water accumulation capability. Results Hydrated acorns of white oaks were heavier and germinated faster than those of red oaks. Germination percentages increased with acorn fresh weight across oak species. Within species, germination probability increased with acorn fresh weight, but these relationships were more marked in red oaks. Germination speed decreased with acorn fresh weight in red oaks, but these relationships were not found in white oaks. Fresh weight was positively related with acorn dry biomass in all oak species, but it was not related with water content. Conclusion Increasing acorn fresh weight enhances germination across oak species. Within species, however, this trait seems to have more influence in red than in white oaks.

Revista Divulgación Científica Universidad del Rosario No. 6

Esta publicación tiene la decidida intención de acercar la investigación que realiza la Universidad del Rosario de Bogotá, Colombia, a un gran número de lectores para mostrarles, desde el periodismo científico, el quehacer investigativo de la institución.This publication has the determined intention of bringing the research carried out by the Universidad del Rosario in Bogotá, Colombia, to a large number of readers to show them, from scientific journalism, the investigative work of the institution

La geografía y la economía en sus vínculos actuales : una antología comentada del debate contemporáneo

Desde hace décadas, La Geografía y la Economía han forjado un espacio de discusión que debate sobre las intersecciones dadas entre ambas disciplinas. A raíz del surgimiento de la llamada Nueva Geografía Económica, asociada al laureado Premio Nobel de Economía, Paul Krugman, ha surgido un intenso debate acerca de los vínculos entre estas dos ramas del conocimiento y de su relevancia para las Ciencias Sociales de hoy en día. A su vez, dicho debate se ha visto enriquecido con el avance metodológico que tanto la Geografía como la Economía han experimentado en años recientes, para estudiar analítica y empíricamente diversos procesos regionales