Effect of anthropogenic vibratory noise on plant development and herbivory

A growth in anthropogenic activities and infrastructure has led to increasing subterranean vibratory noise levels. Inland wind energy turbines, which are mostly located in agricultural fields, are a fast growing source of vibrational noise. Plants, which are rooted in the soil are constantly exposed to windmill-induced vibrations propagating through the ground. We have little understanding on how anthropogenic seismic vibrations affect plant development and how that in turn can affect plant-insect interactions. In this study we investigated the effect of windmill-like underground vibrational noise on plant development and on a plant-herbivore interaction. We experimentally exposed Pisum sativum plants from seed stage to seed production stage to high and low vibrational noise levels and monitored them daily. We recorded germination, flowering and fruiting time, as well as daily shoot-length growth. Moreover, we tested the direct and indirect effects of vibrational noise on herbivory intensity by the generalist caterpillar Spodoptera exigua. We found that plants exposed to high vibrational noise grew significantly faster and taller than plants exposed to low vibrational noise. Additionally, plants treated with high noise germinated, flowered and produced fruits quicker than those treated with low noise. However, the differences in germination time, flowering time and fruiting time between the treatments were not statistically significant. Furthermore, we did not find an effect of vibrational noise on herbivory intensity. Vibrational noise could have consequences for both natural plant communities and agricultural crops by altering interspecific competition and by shifting growth-defence activation trade-offs.