Abstract
Increasing evidence suggests that artificial light at night (ALAN) can negatively impact organisms. However, most studies examine the impacts of ALAN on a single species or under high levels of artificial light that are infrequent or unrealistic in urban environments. We currently have little information on how low levels of artificial light emanating from urban skyglow affect plants and their interactions with herbivores. We examined how short-term, low levels of ALAN affect grass and insects, including growth rate, photosynthesis, and stomatal conductance in grass, and foraging behavior and survival in crickets. We compared growth and leaf-level gas exchange of Kentucky Bluegrass (Poa pratensis) under low-levels of ALAN (0.3 lux) and starlight conditions (0.001 lux). Furthermore, each light treatment was divided into treatments with and without house crickets (Acheta domesticus). Without crickets present, bluegrass grown under ALAN for three weeks grew taller than plants grown under natural night light levels. In the fourth week when crickets were introduced, grass height decreased resulting in no measurable effects of light treatment. There were no measurable differences in grass physiology among treatments. Our results indicate that low levels of light resulting from skyglow affect plant growth initially. However, with herbivory, the effects of ALAN on grass may be inconsequential. Gaining an understanding of how ALAN affects plant-insect interactions is critical to predicting the ecological and evolutionary consequences of anthropogenic light pollution.
Highlights
Artificial light at night (ALAN) is an anthropogenic pollutant that is increasing spatially by a rate of 2.2% per year (Kyba et al, 2017)
There was no difference in net photosynthesis, stomatal conductance, dark respiration, or PSII between grass grown in the two light treatments (Table 1)
Our study explored how short-term low levels of artificial light at night may affect immediate responses in plant photobiology and herbivore interactions
Summary
Artificial light at night (ALAN) is an anthropogenic pollutant that is increasing spatially by a rate of 2.2% per year (Kyba et al, 2017). A full moon could create ambient light levels of 0.3 lux on its brightest nights (Biberman et al, 1966; Kyba et al, 2017). These high light levels are representative of organisms functioning under direct light pollution, such as directly beneath a streetlight, whereas most urban environments exist at lower light levels due to skyglow (e.g., 0.1–1.0 lux), which can impact environments several hundred kilometers away from a direct light source (Gaston et al, 2013; Dominoni et al, 2014; Seymoure et al, 2019a). It remains an open question as to whether low levels of skyglow illumination (0.001–0.3 lux) affects communities to the same extent as direct illumination
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