SUMMARYWetland plant community dynamics are strongly driven by abiotic factors such as nutrient levels and fire. In wetlands where invasive species are present assessing the role of abiotic factors in plant-plant interactions is fundamental for both understanding community dynamics and management. In this study the interaction between pairs of species was quantified between one non-invasive (Schoenoplectus americanus), one that can become overdominant after human disturbances (Typha domingensis) and one that has an invasive lineage present in North America (Phragmites australis), growing under different nitrate concentrations and subjected to fire. All species responded by increasing growth to nitrate addition, but depending on the species, the response was significant for different variables. Phragmites for height and root biomass, Typha for aerial and root biomass and Schoenoplectus for all variables. Interactions between species were complex and differed between sampling years. For the first year, only the effect of Typha on itself was significant. For the second year, the effect of Typha was negative on Phrangmites, the effect of Schoenoplectus was negative on itself and, the effect of Typha and Phragmites was negative on Typha. The effect of fire was significant for Phragmites and Schoenoplectus, not burned plant were taller. Interactions between plants were altered by fire, the presence of Schoenoplectus benefited the performance of Typha, and the opposite was also true. For early stages of these species growth, the strongest competition occurs between the native species, allowing the invasive to mostly respond to nitrate levels, and fire have a strong effect also on the interactions between the natives and not with the invasive.Key words: wetland, negative interactions, management, nutrients, ecological restoration. RESUMENLa dinámica de comunidades vegetales de humedales está influenciada por factores abióticos, como los nutrimentos y el fuego. En humedales en donde hay especies invasoras, determinar el papel de factores abióticos en las interacciones planta-planta es fundamental para entender la dinámica de la comunidad y para su manejo. En este estudio, la interacción entre pares de especies fue cuantificada entre una no invasora (Schoenoplectus americanus), una que puede volverse sobredominante como consecuancia de disturbios humanos (Typha domingensis) y una que posee un linaje que es invasor en norteamérica (Phragmites australis), las cuales crecieron bajo diferentes concentraciones de nitrato y fueron sometidas al efecto del fuego. Todas las especies respondieron a la adición de nitratos incrementando su crecimiento. Phragmites respondió en altura y biomasa de raíces, Typha en biomasa aérea y de raíces y Schoenoplectus para todas las variables. Las interacciones entre especies fueron complejas y variaron entre años. Durante el primer año, sólo el efecto de Typha en si misma fue significativo. Para el segundo año, el efecto de Typha fue negativo en Phrangmites, el efecto de Schoenoplectus fue negat...

Wood is an organic material that is a source of carbon of organisms called Wood-decay fungi, and to preserve the wood, various toxic compounds to man and the environment have been used. To analyze the effect of N,N-Dimethylhexadecylamine (DMHDA) on wood attacked by the rotting fungus Trametes versicolor L. We used an in vitro system to expose the fungus T. versicolor to different concentrations of the DMHDA (50, 150 and 450 µM). We quantified the diameter of mycelial growth and laccase activity, also, under these experimental conditions we studied morphological details of the organisms using different scanning equipment including scanning electron microscopy. The growth of T. versicolor exposed to DMHDA for 60 days, showed a concentration-dependent dose behavior, also, the electron microscopy analysis revealed that the morphology and mycelial density was affected by the DMHDA, showing a formation of atypical morphological and thickener folds. Finally, the pieces of wood treated with DMHDA and exposed to the fungus had a lower mass loss, after a period of 60 days of exposure, the values obtained were 0.7, 1.0 and 0.5 g of mass lost for the control, LoC and LoDMHDA treatments respectively. Wood-rot fungi have represented economic losses worldwide, the strategies used have been supported by toxic compounds for the environment. The DMHDA both in the Petri dish system and as a wood preservative was shown to significantly inhibit the growth of T. versicolor.

Introduction: Wood is susceptible to be used as a carbon source by fungal species damaging the wood. Its durability has been categorized according to its weight loss, without taking into account the decrease in the inherent physicochemical and mechanical properties. Objective: To evaluate how how weight loss affects the physicochemical and mechanical properties of Pinus pseudostrobus Lindl. wood exposed to brown-rot fungi Gloeophyllum trabeum (Pers.) Murrill. Materials and methods: Sawn timber pieces of P. pseudostrobus were inoculated with 50 mL of G. trabeum (106 UFC∙mL-1). Periodically (zero, three, six and nine months) and with the help of a universal testing machine, parallel compression (PC), static bending (SB) and perpendicular compression to the grain (CPG) were evaluated, and holocellulose, cellulose and lignin were quantified. Results and discussion: After nine months of interaction with G. trabeum, the pieces of wood were resistant to degradation, taking into account only weight loss. However, the chemical-mechanical properties evaluated showed that the fungus produced thinning and rupture of the tissue cells causing significant decrease in SB (100 to 56 N∙mm-2) and CPG (42.2 to 20.2 N∙mm-2), which reduced its resistance to mechanical stress. Conclusions: Wood exposed to fungal degradation is significantly affected in its mechanical properties, disqualifying it for construction. The damage is not reflected in the aesthetics of the material, which is surprising, since the common user of pine wood would not be able to notice the problem.

Introducción: La madera es propensa a ser utilizada como fuente de carbono por especies de hongos que la dañan. La durabilidad de la madera ha sido categorizada de acuerdo con la pérdida de peso sin considerar la disminución de las propiedades fisicoquímicas y mecánicas inherentes. Objetivo: Evaluar cómo afecta la pérdida de peso a las propiedades fisicoquímicas y mecánicas de la madera de Pinus pseudostrobus Lindl. expuesta al hongo de pudrición café Gloeophyllum trabeum (Pers.) Murrill. Materiales y métodos: Piezas de madera aserrada de P. pseudostrobus se inocularon con 50 mL de G. trabeum (10 6 UFC∙mL -1 ). Periódicamente (cero, tres, seis y nueve meses), y con la ayuda de una máquina universal de ensayo, se analizó la compresión paralela, la flexión estática (FE) y la compresión perpendicular a la fibra (CPF); además, se cuantificó la holocelulosa, celulosa y lignina. Resultados y discusión: Después de nueve meses de interacción con G. trabeum, las piezas de madera fueron resistentes a la degradación, considerando únicamente la pérdida de peso. No obstante, las propiedades químico-mecánicas mostraron que el hongo produjo adelgazamiento y ruptura de las células del tejido ocasionando disminución significativa de FE (100 a 56 N∙mm -2 ) y CPF (42.2 a 20.2 N∙mm -2 ), lo cual redujo su resistencia a los esfuerzos mecánicos. Conclusiones: La madera expuesta a la degradación por hongos está afectada significativamente en sus propiedades mecánicas, inhabilitándola para la construcción. Los daños no se reflejan en la estética del material, lo cual es alarmante, ya que el usuario común de la madera de pino no podría notar el problema.

open ground and generate a growth promoting species of interest in both agricultural and forest, thereby reducing production periods depending on the crop.