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-2, current-year leaf productivity (CLP) of 241.5 g·m-2, 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-2, CLP of 212.8 g·m-2, 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.
为了解常绿乔木对城市夜间灯光的生长响应,以华东地区典型常绿行道树种香樟为对象,研究南京市一条典型道路上近灯处(路灯正下方)和远灯处(两相邻路灯中间位置)生长区位的夜间光照强度差异性对香樟生长性状的影响.结果表明: 近灯处香樟的平均胸径为16.8 cm,当年生小枝总生产力为309.4 g·m-2,当年生叶片生产力为241.5 g·m-2,叶片相对叶绿素含量为34.6 SPAD.远灯处香樟的平均胸径为15.5 cm,当年生小枝总生产力为273.4 g·m-2,当年生叶片生产力为212.8 g·m-2,叶片相对叶绿素含量为33.1 SPAD.近灯处香樟的平均胸径、当年生小枝总生产力、当年生叶片生产力及叶片相对叶绿素含量均显著高于远灯处.两处树木间比叶面积没有显著差异.夜间灯光的补充照明促进了近灯处香樟的生长,并改变了树冠生长对阳光的响应特征.
Keywords: Cinnamomum camphora; artificial nighttime light; functional trait; growth rate; urban ecosystem.