Fugitive road dust alters annual plant physiology but perennial grass growth appears resistant

摘要

Dust is a feature of the natural environment that can be exacerbated by anthropogenic activities. A range of physiological impacts have been attributed to dust deposition on plant leaves, including altered gas exchange and reduced photosynthetic activity-traits associated with yield and overall productivity. Substantially increased traffic along rural unpaved roads following the development of shale petroleum deposits in the Bakken region of North Dakota, USA, prompted us to investigate the effect of heavy dust exposure on economically important annual crops and perennial forage grasses. In a greenhouse study, we exposed six species of annual plants (barley Hordeum vulgare, durum wheat Triticum durum, maize Zea mays, sorghum Sorghum bicolor, lentil Lens culinaris, pinto bean Phaseolus vulgaris, sunflower Helianthus annuus) and eight species of perennial grasses (creeping bentgrass Agrostis stolonifera, crested wheatgrass Agropyron cristatum, intermediate wheatgrass Thinopyrum intermedium, tall fescue Schedonorus arundinaceus, Bermuda grass Cynodon dactylon, blue grama Bouteloua gracilis, buffalograss Bouteloua dactyloides, switchgrass Panicum virgatum) to 40 g of scoria road dust every other day for 10 and 14 days, respectively, resulting in cumulative dust exposure of 200 g/m(2) for annual plants and 280 g/m(2) for perennial grasses. Chlorophyll concentration tended to increase in all annual plants within 1-2 h of dust exposure, which remained high (along with photosynthetic yield) over the duration of the study. Stomatal conductance tended to decrease over the 2-week study period, which was expected, while leaf temperature also decreased for most species, which was contrary to previous research. Conversely, we found little evidence that high levels of dust reduce the ability of perennial grasses to recover from repeated defoliation, regardless of photosynthetic pathway or functional group. While perennial grass growth appears unaffected by the heavy dust emissions produced by traffic associated with energy extraction, the effect on annual plants is difficult to determine because dust might actually have a positive, light-scattering effect that improves plant performance.