Effects of coal dust on vascular plant growth and species composition of vascular plants, mosses, and lichens in an arid environment

Prevailing south-west winds have deposited a plume of coal dust on the soil and vegetation next to a coal storage area at the Portland General Electric coal-fired power generation plant in Boardman, Oregon. A study was conducted to characterize the growth of vascular plants and species composition of vascular plants, lichens and mosses growing on and off the coal dust plume.; While few differences in the frequency and percent cover of vascular plants, or in biomass of perennials, were found on the coal dust plume, the biomass of annuals was significantly higher. Growth characteristics of three vascular plant species were not significantly different on and off the plume. Plant growth seems to occur earlier on the plume, possibly due to the significantly higher soil temperature. In addition to increased soil temperature, decreased pH, and increased moisture-holding properties on the plume, some heavy metal concentrations were also higher. These edaphic features may be responsible for the lower frequencies and diversity of lichen species on the plume. Moss diversity, frequency and percent cover are similar on and off the plume with the exception of Ceratodon purpureus. The increased percent cover of C. purpureus on the plume may be attributed to an adaptive tolerance for certain heavy metals found in the coal dust that provides a competitive advantage. Lichens play a vital role in natural desert ecosystems by increasing soil surface stability against wind erosion, adding nitrogen to the soil, and improving water retention, thus potentially enhancing the growth of vascular plants. Although there were small differences found among vascular plant communities on and off the plume, over the long term a decrease in abundance of lichens may have a negative effect on vascular plant species.