Western North American Naturalist
Brigham Young University
Roads associated with energy development have fragmented much of the Uinta Basin, the Colorado Plateau in general, and other areas of western North America. Beyond reducing available habitat, spreading exotic species, and creating barriers to dispersal, unpaved roads also increase dust loads on plants and pollinators, which may reduce plant growth and reproduction. We studied the effects of an unpaved road on reproduction of an endangered Utah endemic shrub. We measured the size and reproductive output of 156 plants and the dust deposition in plots at increasing distances from the road. We also hand outcrossed 240 flowers from 80 plants to help determine if any reduced reproduction was due to pre- or postpollination mechanisms. Additionally, we experimentally dusted 3 leaves on 30 plants (n = 90) and measured stomatal conductance pre-dust and post-dust. We also dusted 3 flowers on 10 plants (n = 30) prior to hand pollination and measured fruit set. Generalized linear mixed models were used to examine the relationship between reproduction and dust deposition. When controlling for plant size and distance from the road, fruit set was negatively correlated with increasing levels of dust deposition (F1, 15 = 5.26, P = 0.036). The number of seeds per plant, mean plant seed weight, and the proportion of hand-pollinated flowers that set fruit were also negatively correlated with dust, although not significantly. Dusting significantly reduced stomatal conductance (F1, 58 = 87.56, P < 0.001). Eighty percent of hand pollinated flowers (24 of 30) set fruit after dusting. These results demonstrate that road dust reduces H. suffrutescens reproduction, although the mechanisms are not clear. Although dust negatively affected physiological processes, hand-pollination results suggest that dust might be disrupting pollination. This study documents the effects of road dust on the reproduction of an endangered shrub in Utah's Uinta Basin and highlights the need for further research into the effects of roads and dust on nearby plants.
Lewis, Matthew B.; Schupp, Eugene W.; and Monaco, Thomas A., "Road Dust Correlated with Decreased Reproduction of the Endangered Utah Shrub Hesperidanthus suffrutescens" (2017). Wildland Resources Faculty Publications. Paper 2667.