Riqueza y diversidad de hormigas (Hymenoptera: Formicidae) según uso de suelo en dos paisajes agroforestales de Colombia / Richness and diversity of ants (Hymenoptera: Formicidae) according to land use in two agroforestry landscapes of Colombia

Introducción: Las hormigas cumplen funciones ecológicas importantes en muchos ecosistemas, y son altamente sensibles a los cambios en el uso del suelo. Sin embargo, la respuesta ante estos cambios está poco documentada, a grandes escalas espaciales y en distintos usos de suelo, en ecosistemas poco estudiados como la Serranía del Perijá. Objetivo: Analizar la riqueza, diversidad y composición de las comunidades de hormigas en cuatro usos de suelo de dos paisajes agroforestales de la Serranía del Perijá, Cesar, Colombia. Métodos: En dos paisajes agroforestales (compensación y no compensación) se delimitaron dos ventanas de muestreo de 4 × 4 km. Dentro de cada ventana y paisaje se escogieron cuatro usos de suelo: bosques, sistemas agroforestales de café, regeneración natural y pastizales, en los cuales se aplicaron dos métodos de captura: trampas Pitfall y sacos Winkler. Se midieron seis variables ambientales: cobertura de dosel, altura de la hojarasca, densidad aparente, temperatura, humedad y dureza del suelo. El esfuerzo de muestreo fueron 384 trampas Pitfall y 192 m2 de extracción de hojarasca. El trabajo de campo se realizó entre febrero y marzo de 2021. Resultados: Las hormigas mostraron alta sensibilidad a los cambios en el uso del suelo. La diversidad y riqueza de especies disminuyó en los usos de suelo con menor cobertura vegetal natural, como los pastizales; mientras que los bosques, en ambos paisajes, conservaron la mayor riqueza de especies. La cobertura de dosel y la disponibilidad de hojarasca fueron los parámetros ambientales que favorecieron la diversidad y riqueza de las comunidades de hormigas en todos los usos de suelo. No se encontraron diferencias entre la composición de hormigas de los dos paisajes estudiados. Conclusiones: Las hormigas responden a los cambios de uso de suelo y en particular a la cobertura vegetal. Se confirmó nuestra hipótesis puesto que los usos de suelo con alta cobertura vegetal fueron los hábitats con mayor riqueza y diversidad de hormigas. La heterogeneidad ambiental, producto de la dinámica de transformación de los paisajes es un elemento que debe considerarse en futuras investigaciones.

Introduction: Ants fulfill important ecological functions in many ecosystems and are highly sensitive to changes in land use. However, the response to these changes is poorly documented, at large spatial scales and in different land uses, in poorly studied ecosystems such as the Serranía del Perijá. Objective: To analyze the richness, diversity, and composition of ant communities in four land uses of two agroforestry landscapes of the Serranía del Perijá, Cesar, Colombia. Methods: Two sampling windows of 4 × 4 km were delimited in two agroforestry landscapes (compensation and non-compensation). In each window and landscape four land uses were chosen: forests, coffee agroforestry systems, natural regeneration and pastures, in which two trapping methods were applied: Pitfall traps and Winkler bags. Six environmental variables were measured: canopy cover, leaf litter height, bulk density, temperature, humidity and soil hardness. The sampling effort was 384 Pitfall traps and 192 m2 of leaf litter extraction. The fieldwork was conducted between February and March 2021. Results: Ants showed high sensitivity to changes in land use. Species diversity and richness decreased in land uses with less natural vegetation cover, such as pastures; while forests, in both landscapes, retained the highest species richness. Canopy cover and leaf litter availability were the environmental parameters that favored the diversity and richness of ant communities in all land uses. No differences were found between the ant composition of the two landscapes studied. Conclusions: Ants respond to changes in land use, particularly to vegetation cover. Our hypothesis was confirmed since land uses with high vegetation cover were the habitats with the greatest richness and diversity of ants. Environmental heterogeneity, a product of the dynamics of landscape transformation, is an element that should be considered in future research.

Limited evidence of coupling between above and belowground functional traits in tropical dry forest seedlings / Evidencia limitada de acoplamiento entre rasgos funcionales por encima y por debajo del suelo en plántulas de bosque seco tropical

Abstract Introduction: Water availability is one of the main factors determining the distribution of woody species in the tropics. Although the functional mechanisms that determine the species tolerance to water deficit have been extensively studied in adult individuals, the responses of early ontogenetic stages have been less explored. Objective: To identify functional strategies and trait correlations between different seedlings' dimensions (leaf, stem, and root). We expect limited coordination between above and below-ground functional traits due to a single conservation-acquisition trade-off cannot capture the variability of functions and environmental pressures to which the root system is subjected. Methods: We measured 12 functional traits belonging to 38 seedling species in a tropical dry forest in Colombia. We explored the relationships between pairs of traits using Pearson correlations, and to obtain an integrated view of the functional traits, a principal component analysis (PCA) was performed. Results: The results showed limited evidence of linkage between above- and below-ground traits, but we did find significant correlations between traits for the continuum of conservative and acquisitive strategies. Root traits related to water and nutrient take capacity formed an orthogonal axis to the acquisitive-conservative continuum. Conclusions: Our results showed that dry forest seedlings have different functional strategies to cope with water deficit. The incorporation of root traits helps to explain new functional strategies not reported for leaf and stem traits. This study contributes to understanding the mechanisms that explain species coexistence and is particularly relevant for predicting future forest trajectories.

Resumen Introducción: La disponibilidad de agua es uno de los principales factores que determina la distribución de las especies leñosas en los trópicos. A pesar que los mecanismos funcionales que determinan la tolerancia de las especies al déficit hídrico han sido ampliamente estudiados en los individuos adultos, las respuestas de estados ontogenéticos tempranos han sido menos exploradas. Objetivo: Identificar las estrategias funcionales y las correlaciones de rasgos entre diferentes dimensiones de las plántulas (hoja, tallo y raíz). Nosotros esperamos baja coordinación entre los rasgos funcionales sobre y bajo el suelo debido a que un único trade-off conservación-adquisición de recursos, no puede capturar la variabilidad de funciones y presiones ambientales a las que están expuestas las raíces. Métodos: Medimos 12 rasgos funcionales pertenecientes a 38 plántulas en un bosque seco en Colombia. Exploramos las relaciones entre pares de rasgos usando correlaciones de Pearson, y para tener una visión integrada de los rasgos funcionales, usamos un análisis de componentes principales (ACP). Resultados: Reportamos limitada evidencia de acoplamiento entre los rasgos sobre y bajo el suelo, pero encontramos correlaciones significativas entre el continuo de estrategias conservativas y adquisitivas. Los rasgos de raíz relacionados con la capacidad de absorción de agua y nutrientes formaron un eje ortogonal al continuo adquisitivo-conservativo. Conclusiones: Nuestros resultados mostraron que las plántulas del bosque seco tienen diferentes estrategias funcionales para lidiar con el déficit hídrico. La incorporación de los rasgos de la raíz ayuda a explicar nuevas estrategias funcionales no reportadas por los rasgos de hoja y tallo. Este estudio contribuye al entendimiento de los mecanismos que explican la coexistencia de especies y es particularmente relevante para predecir las trayectorias de los bosques futuros.

Unveiling the age and origin of biogenic aggregates produced by earthworm species with their NIRS fingerprint in a subalpine meadow of Central Pyrenees.

In this study the near-infrared reflectance (NIR) spectra signals (750-2,500 nm) of soil samples was compared with the NIR signals of the biogenic aggregates produced in the lab by three earthworm species, i.e., Aporrectodea rosea (Savigny 1826), Lumbricus friendi Cognetti, 1904 and Prosellodrilus pyrenaicus (Cognetti, 1904) from subalpine meadows in the Central Pyrenees. NIR spectral signatures of biogenic aggregates, root-aggregates, and non-aggregated soil were obtained together with soil carbon (C), nitrogen (N), [Formula: see text] and [Formula: see text] determinations. The concentrations of C, N and C:N ratio in the three types of soil aggregates identified were not statistically significant (ANOVA, p>0.05) although non-macroaggregated soil had slightly higher C concentrations (66.3 g kg-1 dry soil) than biogenic aggregates (earthworm- and root-aggregates, 64.9 and 63.5 g kg-1 dry soil, respectively), while concentrations of [Formula: see text] and [Formula: see text] were highest in the root-attached aggregates (3.3 and 0.31 mg kg dry soil-1). Total earthworm density and biomass in the sampled area was 137.6 ind. m-2, and 55.2 g fresh weight m-2, respectively. The biomass of aggregates attached to roots and non-macroaggregated soil was 122.3 and 134.8 g m-2, respectively, while biomass of free (particulate) organic matter and invertebrate biogenic aggregates was 62.9 and 41.7 g m-2, respectively. Multivariate analysis of NIR spectra signals of field aggregates separated root aggregates with high concentrations of [Formula: see text] and [Formula: see text] (41.5% of explained variance, axis I) from those biogenic aggregates, including root aggregates, with large concentrations of C and high C:N ratio (21.6% of total variability, axis II). Partial Least Square (PLS) regressions were used to compare NIR spectral signals of samples (casts and soil) and develop calibration equations relating these spectral data to those data obtained for chemical variables in the lab. After a derivatization process, the NIR spectra of field aggregates were projected onto the PLS factorial plane of the NIR spectra from the lab incubation. The projection of the NIR spectral signals onto the PLSR models for C, N, [Formula: see text] and [Formula: see text] from casts produced and incubated in the lab allowed us to identify the species and the age of the field biogenic aggregates. Our hypothesis was to test whether field aggregates would match or be in the vicinity of the NIR signals that corresponded to a certain species and the age of the depositions produced in the lab. A NIRS biogenic background noise (BBN) is present in the soil as a result of earthworm activity. This study provides insights on how to analyse the role of these organisms in important ecological processes of soil macro-aggregation and associated organic matter dynamics by means of analyzing the BBN in the soil matrix.

Contribución de Pheidole fallax y Ectatomma ruidum (Hymenoptera: Formicidae) en la dispersión y germinación de semillas en áreas rehabilitadas de la mina de carbón del Cerrejón, Colombia / Contribution of Pheidole fallax and Ectatomma ruidum (Hymenoptera: Formicidae) to the dispersion and germination of seeds in rehabilitated areas of the Cerrejón coal mine, Colombia

ResumenLa dispersión de semillas es un proceso clave en el restablecimiento de la vegetación en áreas rehabilitadas. El objetivo de este trabajo fue determinar la contribución de las hormigas Ectatomma ruidum y Pheidole fallax en la dispersión y germinación de semillas en áreas rehabilitadas en la mina de carbón del Cerrejón, Colombia. En cada área se instalaron cuatro parcelas de 6 x 40 m, donde se contó el número de nidos por especie y se midió la distancia entre los nidos más próximo de cada especie. De los nidos contabilizados cinco nidos fueron seleccionados para la extracción de semillas, por cada nido extraído se tomó un control. Un total de 295 nidos fueron contabilizados, 59 para la época seca y 236 para la época de lluvia, 84 pertenecían a P. fallax y 211 a E. ruidum. Un total de 21 304 semillas fueron encontradas en los nidos y suelos control, 19 349 fueron obtenidas de los nidos y basureros de P. fallax y 318 en nidos de E. ruidum, en el suelo control se hallaron 597 semillas. El número de semillas extraídas en los nidos fue significativamente mayor a la de los controles. El número de semillas removidas por P. fallax presentó diferencias significativas respecto a las removidas por E. ruidum. El porcentaje de germinación en los nidos fue mayor que en los controles, en el caso de P. fallax, el porcentaje de germinación fue bajo en los controles y alto tanto en los basureros como los nidos. Nuestros resultados sugieren que E. ruidum y P. fallax podrían contribuir a la dispersión de las semillas y al restablecimiento de la vegetación en las áreas donde se encuentran, lo cual es un aporte significativo para la rehabilitación de las áreas degradas por la minería.

AbstractSeed dispersal is a key process in the re-establishment of vegetation on reclaimed lands. The aim of this study was to determine the contributions of the ant species Ectatomma ruidum and Pheidole fallax to seed dispersal and germination on reclaimed lands in the Cerrejón coal mine, Colombia. Four 6 x 40 m plots were installed in each area, in which the number of nests by species was counted and distances between closest nests of each species were measured. Five of the nests counted were chosen for seed extraction, and a nearby control sample was taken from each nest. In total, 295 nests were counted: 59 nests during the dry season and 236 nests during the rainy season, of which 84 belonged to P. fallax and 211 belonged to E. ruidum. A total of 21 304 seeds were found in nests and control samples, of which 19 349 were obtained from P. fallax nest refuse, and 318 were obtained from E. ruidum nests; 597 seeds were found in control samples. The number of seeds extracted from nests was significantly higher than the number of seeds removed from control samples. There was a significant difference between the number of seeds removed by P. fallax and the number of seeds removed by E. ruidum. The seed germination percentage from nests was higher than the percentage from seeds in control samples. In the case of P. fallax, the germination percentage was lower in control samples and higher in nests and refuse. The results suggest that the ant species E. ruidum and P. fallax may contribute to seed dispersal and re-establishment of vegetation in areas where they were found. These ants may thus significantly contribute to restoration processes in areas degraded by mining.