Pavement induced soil warming accelerates leaf budburst of ash trees

Urban greening is becoming increasingly popular in cities around the world, which is leading to the planting of more and more trees in paved areas in urban environments. However scientifically it is not well understood how pavement may impact tree greening efforts. In this paper, we investigated plant responses to pavement in the suburb of Changping District, Beijing, China. We planted the popular deciduous ash tree (Fraxinus chinensis) in three different pavements: pervious bricks; impervious bricks; and no pavement (i.e., control) at three densities (0.5 m × 0.5 m, 1.0 m × 1.0 m, and 2.0 m × 2.0 m apart). We investigated the influence of pavement type on plant phenology by monitoring soil temperature and moisture as well as leaf budburst rate from January to April in 2014. Our results show that pavement can significantly increase soil temperature, and decreased soil moisture except pervious pavement at the 1.0 m × 1.0 m density. The significant relationship between the leaf budburst rate and accumulated soil temperature implies that pavement induced soil warming can accelerate leaf budburst, suggesting that pavement contributes to tree leaf budburst acceleration by probably both increasing soil and air temperatures in urban environments.