[Effects of urban nighttime light on the growth of Cinnamomum camphora].

To understand the effects of urban artificial nighttime light on the growth of evergreen trees, we conducted a field investigation in a typical urban street planted with Cinnamomum camphora (a common evergreen street tree species in eastern China) in the Nanjing City, China. Along the street, trees from two types of growing locations with contrasting distances from the street lamp (just under the lamp vs. between two adjacent lamps) were selected. The growth-related plant functional traits were measured and compared. The results showed that trees grown under the lamp had a mean diameter at beast height (DBH) of 16.8 cm, current-year branch productivity (CBP) of 309.4 g·m, current-year leaf productivity (CLP) of 241.5 g·m, and leaf relative chlorophyll content (LCC) of 34.6 SPAD. Trees grown between lamps had a mean DBH of 15.5 cm, CBP of 273.4 g·m, CLP of 212.8 g·m, and LCC of 33.1 SPAD. DBH, CBP, CLP and LCC of the trees under the lamp were significantly higher than those between lamps. There was no significant difference in specific leaf area between trees from the two locations. Our results suggested that urban artificial nighttime light could promote the growth of C. camphora, and alter sunlight-determined characteristics of canopy growth vigor.