| Changes in soundscapes from human-caused noise disturbance alter avian and mammalian community assemblages, their foraging behavior, and reproductive success. Little is known, however, about how changes in insectivorous predators can directly, or indirectly, affect plant physiology and productivity. We continuously broadcasted (24-hrs /day) recordings of natural-gas compressor station extraction from April through October 2015 in sagebrush-steppe habitat in Idaho, USA. We hypothesized that effects of an altered soundscape would change existing insect abundances (via changes in avian predators; assessed in a separate study) and therefore insect herbivory on plant physiology and productivity in sagebrush shrubs (Artemisia tridentata ssp. wyomingensis). We predicted that we would observe increases in shrub herbivory at Noise-On sites, because of reductions in avian predation on herbivorous insects. We further predicted that we would observe decreased physiology and productivity in shrubs at Noise-On sites because of physiological costs associated with increased herbivory damage. Total arthropod abundance was not statistically significantly different between noise treatments; however, greater numbers (13.5%, n.s.) of insects from sap-sucking families occurred on shrubs in Noise-On sites. Stem elongation per cm during the growing season was 19.5% greater at Noise-On sites, contrary to our initial hypotheses. Noise significantly increased both shrub respiration (Rd) and photosynthesis (Anet), and a significant day×noise interaction occurred for light-reaction photochemistry (ΦPSII) and Anet. We hypothesize that the increases in Anet and Rd that we observed—which were opposite our hypotheses—were compensatory responses from increased sap-feeding damage in sagebrush at Noise-On sites. Boosts in photosynthesis and growth because of modest increases in herbivory have been reported in previous studies, whereas more intense herbivory can lead to declines in photosynthesis. Collectively, our research indicates that chronic human noise has the capacity to affect ecosystem functioning at multiple trophic levels because of altered soundscapes. |