Interactions between dominant hydrophytic species of the wetlands of western Mexico mediated by fire and nitrate concentration

Abstract

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...

Invasiveness of Phragmites australis in communities dominated by native species after fire disturbance under controlled conditions

“…A pesar de lo citado, los resultados de esta investigación indican que incluso después de incendios que eliminan el dosel de especies nativas, la supervivencia y crecimiento de los fragmentos de P. australis fue muy baja. Resultados similares fueron reportados por Montejo-Mayo et al (2015).…”

Ten-year study of vegetation dynamics in wetlands subject to human disturbance in Western Mexico

“…In a previous short term study of the same area before the major fires of 2009 (Escutia-Lara et al, 2009), we concluded that fires might play a positive role in maintaining plant diversity in Western Mexico wetlands. This can still be the case for low-intensity infrequent fires, that open the canopy of the obligate dominant hypdrophytes (Typha domingensis and S. americanus), and allow other natives to be present as shown by harvesting experiments in the same wetlands (Hall et al, 2008) and reducing its competitiveness (Montejo-Mayo et al, 2015). But intense and frequent fires, especially during the growing season, alter significantly the wetland plant community composition.…”