Ecological Impacts of Degassing From Masaya Volcano, Nicaragua

Parkes, Bethan Rose Burson (2016). Ecological Impacts of Degassing From Masaya Volcano, Nicaragua. PhD thesis The Open University.



Persistent degassing is an unusual type of volcanic activity with considerable environmental impacts, although its effects on downwind ecosystems are poorly researched. Up to 1000 tonnes of SO2 per day are degassed from Masaya Volcano in Nicaragua, and trade winds blow the plume in a WSW direction. A cross-wind transect through this plume provides a natural laboratory for this study on volcanic gases and their impacts on the tropical dry forest. Measurements of gas concentration and deposition rates of SO2, HC1 and HF along the transect were described by Gaussian profiles. These were linked to gas emission at the crater and the wind direction estimated from the HYSPLIT model. SO2 concentration profiles were used to investigate the ecological response to exposure to the volcanic plume along the same transect at two scales: the vegetation community and individual plant traits. The plant community level study found high levels of volcanic SO2 were associated with low species richness, comprising mostly grasses and herbs, an acidic soil, an open canopy and a thin leaf litter layer. Local feedbacks with these environmental variables have likely slowed succession in this area, indicating long-term impacts of volcanic degassing. At the species level, Dalechampia scandens response to SO2 was surprising; its largest leaves were found where volcanic pollution was highest. Elevated H2O, CO2 or nutrient levels from the plume may have benefited these tolerant plants. Compared with vegetation composition, this likely shows a more short-term response to volcanic gas levels. As well as informing ecological studies, fitting Gaussian profiles to volcanic gas data has validated our understanding of plume dispersal. The first evidence of vegetation community and plant trait response to volcanic gases presented here may give useful insights into the impacts of other degassing volcanoes or future industrial pollution in the tropics.

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