Ectomycorrhizal fungal communities in natural and urban ecosystems: Quercus humboldtii as a study case in the tropical Andes.

Worldwide urban landscapes are expanding because of the growing human population. Urban ecosystems serve as habitats to highly diverse communities. However, studies focusing on the diversity and structure of ectomycorrhizal communities are uncommon in this habitat. In Colombia, Quercus humboldtii Bonpl. is an ectomycorrhizal tree thriving in tropical montane forests hosting a high diversity of ectomycorrhizal fungi. Q. humboldtii is planted as an urban tree in Bogotá (Colombia). We studied how root-associated fungal communities of this tree change between natural and urban areas. Using Illumina sequencing, we amplified the ITS1 region and analyzed the resulting data using both OTUs and Amplicon Sequence Variants (ASVs) bioinformatics pipelines. The results obtained using both pipelines showed no substantial differences between OTUs and ASVs for the community patterns of root-associated fungi, and only differences in species richness were observed. We found no significant differences in the species richness between urban and rural sites based on Fisher's alpha or species-accumulation curves. However, we found significant differences in the community composition of fungi present in the roots of rural and urban trees with rural communities being dominated by Russula and Lactarius and urban communities by Scleroderma, Hydnangium, and Trechispora, suggesting a high impact of urban disturbances on ectomycorrhizal fungal communities. Our results highlight the importance of urban trees as reservoirs of fungal diversity and the potential impact of urban conditions on favoring fungal species adapted to more disturbed ecosystems.

Diversidad florística y captura de carbono en robledales y pasturas con árboles en Santa Isabel, Tolima, Colombia / Floristic diversity and carbon capture in oak groves and pastures with trees in Santa Isabel, Tolima, Colombia

Introducción: La acelerada transformación de los usos del suelo en los Andes colombianos han afectado la diversidad y la provisión de servicios ecosistémicos. Objetivo: Se caracterizó la estructura y composición florística, junto a la estimación del carbono almacenado en biomasa de bosques primarios intervenidos y pasturas con árboles en Santa Isabel, Tolima. Métodos: En cada sistema, se establecieron cinco parcelas de muestreo: rectangulares de 1 000 m2 cada una en bosques y circulares de 707 m2 en pasturas, para medir todos los individuos con diámetro a 1.30 m de altura, ≥10 cm. La biomasa se estimó a partir de modelos alométricos multi-especies y un modelo genérico en el caso de biomasa abajo del suelo. Resultados: En el bosque se registró una abundancia promedio de 642 ± 125 individuos/ha, se encontraron 25 familias, 39 géneros, 43 especies y morfoespecies en 0.5 ha de muestreo. Quercus humboldtii y Ladenbergia macrocarpa fueron las especies con el mayor Índice de Valor de Importancia (IVI = 32.5 y 11.2, respectivamente) en los bosques. En pasturas se encontraron 175.0 ± 21.3 individuos/ha, pertenecientes a 8 familias, 9 géneros, 10 especies y morfoespecies en 0.35 ha de muestreo. Eugenia spp. y Weinmannia pubescens tuvieron la mayor importancia ecológica (19.5 y 17.6 %, respectivamente) en pasturas. El bosque almacenó en promedio 125.0 ± 30.0 t C/ha, comparado con 18.4 ± 1.8 t C/haen pasturas. Conclusiones: Estos hallazgos muestran alta capacidad de almacenamiento de carbono en estos usos del suelo, lo cual contribuye a mantener o disminuir la concentración de gases de efecto invernadero en la atmósfera, y por ende, son un referente que permite desarrollar estrategias de conservación, con miras a mitigar el cambio climático.

Introduction: The accelerated transformation of land uses in the Colombian Andes has affected diversity and the provision of ecosystem services. Objective: The structure and floristic composition and the estimation of the carbon stored in biomass of intervened primary forests and pastures with trees in Santa Isabel, Tolima, was described. Methods: In each system, five sampling plots were established: rectangular of 1 000 m2 each in forests and circular of 707 m2 in pastures to measure all individuals with a diameter of 1.30 m in height, ≥10 cm. The biomass was estimated from multi-species allometric models and a generic model in the case of below-ground biomass. Results: In the forest, an average abundance of 642 ± 125 individuals / ha was recorded, finding 25 families, 39 genera, 43 species and morphospecies in 0.5 ha of sampling. Quercus humboldtii and Ladenbergia macrocarpa were the species with the highest Importance Value Index (IVI = 32.5 and 11.2, respectively) in the forests. In pastures, 175.0 ± 21.3 individuals / ha were found, belonging to 8 families, 9 genera, 10 species and morphospecies in 0.35 ha of sampling. Weinmannia pubescens and Eugenia spp. had the greatest ecological importance (19.5 and 17.6 %, respectively) in pastures. The forest stored an average of 125.0 ± 30.0 t C/ ha, compared to 18.4 ± 1.8 t C/ha in pastures. Conclusions: These findings show high carbon storage capacity in these land uses, which contributes to maintain or decrease the concentration of greenhouse gases in the atmosphere, and therefore, are a benchmark that allows to develop conservation strategies, with a view to mitigate climate change.

Volatile composition and sensory characteristics of Carménère wines macerating with Colombian (Quercus humboldtii) oak chips compared to wines macerated with American (Q. alba) and European (Q. petraea) oak chips.

Different oak species or origins have been studied to find an alternative to traditional ones and Quercus humboldtii from Colombia is a candidate. Some studies analyse the composition of this oak, but no work has been found to study its use for wine treatment. The aim was to evaluate volatile composition of toasted Q. humboldtii oak chips and the wines treated with these chips. To evaluate its oenological potential Q. alba and Q. petraea have been included in this trial. The wines were subjected to a sensory analysis. Results indicated that oak chips and wines macerated for 90 days with toasted Colombian chips exhibited higher 5-methylfurfural, guaiacol, trans-isoeugenol and syringol concentrations than others, while the furfural and cis-ß-methyl-γ-octalactone content was lower. Sensory analysis showed that the wines treated with Colombian oak presented more notes of smoked and less of coconut. Therefore, this oak could probably be considered suitable for ageing.

Efectos de la iuuminación relativa y la fertiliación sobre el crecimiento de pplántulas de roble andino en vivero / Effects of Light Intensity and Fertilization on the Growth of Andean Oak Seedlings at Nursery

Quercus humboldtii es una especie vegetal nativa de mucha importancia en Colombia por su uso en repoblamiento forestal y restauración de tierras altoandinas degradadas. La especie se encuentra fuertemente amenazada y es necesario establecer programas de propagación de la misma. Sin embargo, poco se conoce sobre sus exigencias nutricionales y lumínicas. El objetivo de este estudio fue determinar los efectos simples y combinados de la iluminación relativa (IR) y la fertilización sobre el crecimiento de plántulas de Q. humboldtii en vivero. Para esto se establecieron en combinación tres condiciones contrastantes de iluminación relativa (alta, media y baja IR) y nueve tratamientos de fertilización: completa (TC), con un elemento faltante (-N, -P, -K, -Ca, -Mg, -S, -B) y un testigo sin fertilización (T0). La condición de IR media presentó el mejor desarrollo de las plántulas. Todos los tratamientos con deficiencias nutricionales produjeron disminuciones en el desarrollo de las plántulas con respecto a TC, excepto en el tratamiento -B. El N fue el elemento más limitante, con rendimientos similares a los del tratamiento testigo. El orden de limitación que produjeron los tratamientos aplicados siguió la secuencia: T0,-N > -Ca, -K, - P > -Mg, -S > TC,-B. No se detectó interacción significativa IR x Fertilización sobre el desarrollo de las plántulas.

Quercus humboldtii is a native plant species of great importance in Colombia for use in reforestation and restoration of degraded Andean highlands. The species is highly threatened and it is necessary to establish programs of propagation and planting. However, little is known about their nutritional and light requirements. The aim of this study was to determine the effects of single and combined relative illumination (IR) and fertilization on the growth of seedlings of Q. humboldtii at nursery. For this purpose three contrasting IR regimes (high, medium, and low IR) and nine fertilization treatments were established: complete (TC), a missing nutrient (-N,-P,-K,-Ca,-Mg, -S,-B) and a control without fertilization (T0). The best development of seedlings was showed in the medium IR condition. All treatments with a lacking nutrient showed decreases in seedling development regarding TC, except in the -B treatment. Nitrogen was the most limiting nutrient yielding biomass similar to that of T0. The impact of nutrient limitation on seedling performance was in the following order:-N>-Ca,-K,-P>-Mg,-S>-B. No significant interaction IR x Fertilization was detected on seedling development.

Ciclos biogeoquímicos en bosques naturales y plantaciones de coníferas en ecosistemas de alta montaña de Colombia

Biogeochemical cycles in natural forest and conifer plantations in the high mountains of Colombia. Plant litter production and decomposition are two important processes in forest ecosystems, since they provide the main organic matter input to soil and regulate nutrient cycling. With the aim to study these processes, litterfall, standing litter and nutrient return were studied for three years in an oak forest (Quercus humboldtii), pine (Pinus patula) and cypress (Cupressus lusitanica) plantations, located in highlands of the Central Cordillera of Colombia. Evaluation methods included: fine litter collection at fortnightly intervals using litter traps; the litter layer samples at the end of each sampling year and chemical analyses of both litterfall and standing litter. Fine litter fall observed was similar in oak forest (7.5Mg ha/y) and in pine (7.8Mg ha/y), but very low in cypress (3.5Mg ha/y). Litter standing was 1.76, 1.73 and 1.3Mg ha/y in oak, pine and cypress, respectively. The mean residence time of the standing litter was of 3.3 years for cypress, 2.1 years for pine and 1.8 years for oak forests. In contrast, the total amount of retained elements (N, P, S, Ca, Mg, K, Cu, Fe, Mn and Zn) in the standing litter was higher in pine (115kg/ha), followed by oak (78kg/ha) and cypress (24kg/ha). Oak forests showed the lowest mean residence time of nutrients and the highest nutrients return to the soil as a consequence of a faster decomposition. Thus, a higher nutrient supply to soils from oaks than from tree plantations, seems to be an ecological advantage for recovering and maintaining the main ecosystem functioning features, which needs to be taken into account in restoration programs in this highly degraded Andean mountains. Rev. Biol. Trop. 59 (4): 1883-1894. Epub 2011 December 01.

La caída y descomposición de hojarasca representan los principales ingresos de materia orgánica y nutrientes a los ecosistemas forestales. Se estudiaron la caída y acumulación de hojarasca fina y el retorno de nutrientes, en un robledal (Quercus humboldtii) y en plantaciones de pino (Pinus patula) y ciprés (Cupressus lusitanica) en tierras altas de Colombia. La caída de hojarasca fina fue similar entre el robledal (7.5Mg/ha.a) y el pinar (7.8Mg/ha.a), y muy inferior en el cipresal (3.5Mg/ha.a). El mantillo representó 1.76, 1.73 y 1.3Mg/ha.a en el robledal, pinar y cipresal, respectivamente. El tiempo medio de residencia (TMR) del mantillo siguió la secuencia: cipresal (3.3 años)>pinar (2.1 años)>robledal (1.8 años). La cantidad de nutrientes retenidos en el mantillo siguió la secuencia: pinar (115kg/ ha)>robledal (78kg/ha)>cipresal (24kg/ha). Los menores TMR de nutrientes se presentaron para la hojarasca foliar del robledal, en su mayoría inferiores a 1.0 años. En términos de la función ecosistémica en el robledal los procesos estudiados son muy superiores vía provisión de nutrientes al suelo y regulación de los ciclos biogeoquímicos, aspectos que deben ser considerados previa implementación de programas de repoblamiento forestal.

Estructura y composición florística de tres robledales en la región norte de la cordillera central de Colombia

Structure and floristic composition of three oak forests in the northern region of the Central Cordillera in Colombia. Andean ecosystems harbor a high floristic diversity, which is being threatened by human disturbances such us deforestation and by the expansion of the agricultural frontier. One of these ecosystems are the Andean oak forests dominated by Quercus humboldtii, a threatened species in Colombia. We assessed the floristic composition and structure of three Andean oak forests located in three localities (San Andrés de Cuerquia, Belmira and Guarne) of Antioquia. The main goal was to determine whether these forests showed similarities in their structure and floristic composition. In each site, a permanent plot of 5000 m2 (0.5 ha) was established. All trees with D ≥ 10 cm were sampled and identified to species. The Importance Value Index (IVI) was calculated as the sum of relative density (DeR), dominance (DoR) and frequency (FR) of a species. Trees with 5 ≤ D < 10 cm and 2 ≤ D < 5 cm were registered in sub-plots of 0.05 and 0.0144 ha, respectively. Finally, we used Jaccard’s Index to quantify the floristic similarity among oak forest. When we considered all trees with D ≥ 10 cm in the three forests, the number of species ranged from 18 to 54, whilst the number of individuals ranged from 326 to 680. The Guarne oak forest showed the highest species richness. In all sites, Q. humboldtii (Fagaceae) was the most important species in relation to the IVI, while Clusia sp. (Clusiaceae) and Myrsine coriaceae (Myrsinaceae) were the most important species in San Andrés de Cuerquia, Clethra fagifolia (Clethraceae) was important only in Belmira and Myrcia popayanensis (Myrtaceae) was important in Guarne. The families with the highest number of species were Fabaceae, Melastomataceae and Rubiaceae. Floristic similarity among places was low. The size distribution of trees had an inverse J- shape curve for all sites with changes in the abundance for size class. The three oak forests differed in their structure and floristic composition probably because of different disturbance degrees. Rev. Biol. Trop. 57 (4): 1165-1182. Epub 2009 December 01.

La alta diversidad florística que albergan los ecosistemas andinos está siendo amenazada por fuertes presiones de origen antrópico. Uno de estos ecosistemas son los robledales, bosques dominados por la especie Quercus humboldtii, que se encuentra seriamente amenazada en Colombia porque su madera es valiosa comercial y dendroenergéticamente. En este estudio, se caracterizó la composición florística y la estructura de tres robledales de los Andes colombianos, con el fin de determinar su similaridad. En cada sitio, se estableció una parcela permanente (5 000 m²) donde se muestrearon todos los árboles con D ≥ 10 cm. En los tres sitios, la especie dominante fue Q. humboldtii, pero la similitud florística entre ellos no fue alta. La estructura por clases de tamaño para los tres sitios fue en forma de J invertida, aunque varió la abundancia de individuos por clase diamétrica. Los resultados indican que los robledales estudiados difieren en su composición florística y estructura a pesar de presentar características biofísicas similares. Las diferencias encontradas se deben posiblemente, a los diferentes factores que interactúan en cada sitio como la historia de uso, intensidad y duración de las perturbaciones antrópicas pasadas, topografía, fauna y clima local, que se ven reflejados en los parámetros estructurales de la vegetación.