Anurans trophic dynamic and guild structure in tropical dry forests of the Caribbean region of Colombia.

Studies on the exploitation of trophic resources allow to establish interactions between predators and predator-prey, and this dynamic can present fluctuations over time and space. We analysed stomach contents of 19 anuran species from tropical dry forests of Colombia, quantified the overlap between species and identified anuran trophic guilds. Most of the species were generalists in diet (89.5%), some with strong prey dominance and only two species were classified as specialists. Two anurans guilds were identified according to diet structure and habitat use: "ground foraging anurans, consuming Formicidae and Isoptera" and "arboreal 'sit-and-wait' predators, primarily consuming arachnids". A considerable number of species did not clearly group in community trophic structure analysis. The level of taxonomic resolution with that preys are worked affects analysis of trophic niches segregation when analyzing regional and local patterns. Anuran species of tropical dry forest in the Colombian Caribbean display trophic resources partitioning at the level of species and/or morphospecies, as a mechanism of coexistence.

Habitat Heterogeneity Affects Plant and Arthropod Species Diversity and Turnover in Traditional Cornfields.

The expansion of the agricultural frontier by the clearing of remnant forests has led to human-dominated landscape mosaics. Previous studies have evaluated the effect of these landscape mosaics on arthropod diversity at local spatial scales in temperate and tropical regions, but little is known about fragmentation effects in crop systems, such as the complex tropical traditional crop systems that maintain a high diversity of weeds and arthropods in low-Andean regions. To understand the factors that influence patterns of diversity in human-dominated landscapes, we investigate the effect of land use types on plant and arthropod diversity in traditionally managed cornfields, via surveys of plants and arthropods in twelve traditional cornfields in the Colombian Andes. We estimated alpha and beta diversity to analyze changes in diversity related to land uses within a radius of 100 m to 1 km around each cornfield. We observed that forests influenced alpha diversity of plants, but not of arthropods. Agricultural lands had a positive relationship with plants and herbivores, but a negative relationship with predators. Pastures positively influenced the diversity of plants and arthropods. In addition, forest cover seemed to influence changes in plant species composition and species turnover of herbivore communities among cornfields. The dominant plant species varied among fields, resulting in high differentiation of plant communities. Predator communities also exhibited high turnover among cornfields, but differences in composition arose mainly among rare species. The crop system evaluated in this study represents a widespread situation in the tropics, therefore, our results can be of broad significance. Our findings suggest that traditional agriculture may not homogenize biological communities, but instead could maintain the regional pool of species through high beta diversity.

Grupos funcionaees de plantas con potencial usopara la restauración en bordes de avance de un bosque altoandino / Plant Functional Groups of Potential Restoration Use in Advancing Edges of High Andean Forests

El estudio de grupos funcionales de plantas es una herramienta útil en la identificación de características ecológicas de importancia en la regeneración de una comunidad. El objetivo de este estudio fue la identificación de grupos funcionales de plantas en bordes de avance de un bosque alto andino y la evaluación de su importancia en el curso de la sucesión secundaria en pastizales abandonados. Con base en levantamientos de vegetación de 10 x 10 m para el estrato arbóreo-arbustivo y de 1 x 1 m para el estrato herbáceo, y la revisión de atributos vitales de las especies registradas, se realizó una clasificación multivariante de las especies en grupos emergentes de plantas. Los atributos más importantes para la clasificación de los grupos emergentes fueron el método de dispersión y la ramificación basal de tallo; adicionalmente se presentaron diferencias entre los grupos del estrato arbustivo-arbóreo en la presencia de propagación vegetativa, el área foliar específica y el cociente altura/diámetro a la altura del pecho. Se definieron cuatros grupos para las especies de estrato herbáceo y cinco para las del estrato arbustivo-arbóreo, los cuales reúnen especies con estrategias de colonización similares. Dentro de los grupos definidos, las especies herbáceas dispersadas por diversos medios abióticos, las especies arbustivas con ramificación basal dispersadas por viento y las especies dispersadas por aves representan estrategias claves en la colonización del área de potrero adyacente dominada por Holcus lanatus y en la facilitación del establecimiento de especies del bosque secundario.

The study of plant functional groups constitutes a useful tool in the identification of ecological characteristics relevant in community regeneration. The aim of this study was to identify plant’s functional groups in high Andean forest advance edges and to evaluate their role during secondary succession in abandoned pasturelands. Based on 10 x 10m vegetation relevees for the shrubby-arboreal stratum and 1 x 1 m plots for the herbaceous stratum and the revision of vital attributes for each of the species found, this study uses a multivariate approach to construct a trait-based emergent group’s classification. The most important attributes in the definition of the groups were the dispersion mechanism and the presence of basal trunk ramification in woody species; in addition differences in the presence of vegetative propagation, specific leaf area index and the ratio height/diameter at breast height were found between groups of the shrubby-arboreal stratum. Four distinct groups were defined in the herbaceous layer and five in the shrubby-arboreal layer, each group contains species with similar colonization strategies. Among the defined groups, the herbaceous species dispersed by various abiotic factors, the shrubby species with basal ramification and dispersed by wind and the species dispersed by birds constitute key strategies in forest recovery in adjacent abandoned pasturelands dominated by Holcus lanatus, and facilitate the establishment of secondary forest species.

Dinámica espaci--temporal del humedaljuan amarillo entre 1950 - 2005 / Dynamics Space Temporary Juan Amarillo WetlandBetween 1950-2005

Se analizó la dinámica del Humedal Juan Amarillo durante el periodo comprendido entre los años 1950-2005. Los resultados muestran que la configuración paisajística del ecosistema ha cambiado notoriamente con una tendencia al incremento en el número, tamaño y tipo de parches. Igualmente se presentan diferencias estructurales importantes entre los diversos periodos de tiempo analizados, ocasionados principalmente por la disminución y desaparición de espejos de agua y el aumento de pasto kikuyo (Pennisetum clandestinum). En cuanto al arreglo espacial de los elementos paisajísticos, no sucedieron cambios importantes en los patrones de distribución espacial de los elementos paisajísticos del humedal. De acuerdo con la dimensión fractal, los elementos del paisaje presentan dos tendencias en cuanto a su complejidad: los elementos introducidos poseen las formas más complejas y los elementos propios del ecosistema tienen formas más regulares. Finalmente, la dinámica del humedal fue modelada con el fin de interpretar cómo las múltiples interacciones entre los elementos paisajísticos han influido en la configuración del humedal a lo largo del tiempo.

The dynamics of Juan Amarillos’ wetland were analyzed during 55 year between 1950 and 2005. The results showed that the landscape configuration of the ecosystems has dramatically changed within a trend to increase in number, size, and patch type. Likewise, important structural differences came up between the various periods in question; such differences appear to be related to the reduction and disappearance of the pond and the significant increase of the non native kikuyo grass (Pennisetum clandestinum). Regarding the spatial arrangement of the landscape elements, there were no significant changes in spatial distribution patterns. According to the fractal dimension and complexity, the landscape elements showed two trends: non native and man-made elements are more complex in shape, whereas native elements showed more regular shapes. Finally, the wetland dynamics were modelled with the aim of construing how the multiple interactions of the landscape elements have influenced the wetland configuration over time.