Ecological effects of vehicle-generated particulate matter, and the use of magnesium chloride as a dust suppressant in Arches National Park, UT

Background/Question/Methods

Climate change and land-use intensification are predicted to lead to increased dust production from arid and semi-arid ecosystems. While dryland plant species are likely adapted to tolerating certain levels of airborne particulate matter, the effects of increased dust deposition are not known. Yet while the ecological consequences are poorly understood, the social consequences are clear: people view airborne dust as a nuisance, and potentially a health hazard. Accordingly land managers are responding to increasing vehicular traffic by implementing dust-suppression strategies. This research explores various dynamics of vehicular dust production and transport, and compares ecological effects of dust with those of using magnesium chloride (MgCl2) as a dust-suppression agent.  Roadside plots were established in Arches National Park, Utah, USA, where the National Park Service implemented a dust-management plan in 2010.  Dust levels produced by vehicular traffic were measured using wind-aspirated dust samplers on control plots along untreated sections of road, and on plots adjacent to sections of road treated with MgCl2. Relationships between leaf morphology and amounts of dust collected on leaf surfaces were evaluated. An experiment evaluated effect of three concentrations of MgCl2 applied directly to plants, as might occur during application to road surfaces.

Results/Conclusions

Dust collection on leaf surfaces was found to be associated with leaf morphology. Species with trichomatous leaf surfaces tended to trap greater amounts of windblown particulate matter than those with glabrous surfaces.  When MgCl2 was applied in the greenhouse to four species of plants found at the study site, seedling emergence was reduced for all four. However, the native grass Pleuraphis jamesii and the non-native invasive annual grass Bromus tectorum were found to be more robust to MgCl2 application than the native grass Stipa comata or the native perennial forb Sphaeralcea coccinea. Results will be used to develop a long-term monitoring protocol for NPS researchers to examine the effects of various methods of dust suppression.