Land pavement induced soil warming accelerates the leaf budburst of ash trees
With increasing urban greening, more and more trees have been planted in paved lands that are dominated in urban environment. However, it is less-known how the trees respond to land pavement yet. Available investigations have showed that land pavement would increase surface and soil temperatures, it is not clear if the increased temperature could alter plant phenology. In this study, the popular deciduous ash (Fraxinus chinensis) trees were planted in lands paved with pervious and impervious bricks and in soil (as control) at three densities (2m, 1m, and 0.5m apart). In the second spring, we monitored the soil temperature and moisture as well as leaf budburst rate in order to investigate the influence of land pavement on plant phenology.
The results showed that both paved lands have significantly higher soil temperature than the control for all densities during spring period from January to early April. The significant increments of soil temperature were 2.23 oC and 2.17 oC for pervious and impervious paved lands (P<0.05), respectively as compared with the control. There were not significant differences in soil temperature among three density treatments. Soil moisture varied with pavement and density, repeated ANOVA showed insignificant differences between pavements or densities.
The leaf budburst rate of ash in both paved lands were significant higher than the control for three density treatments (P<0.01), indicating land pavement could accelerate leaf budburst. It is worth noting that the leaf budburst rates were not significantly different between pervious and impervious pavements.
Leaf budburst was linearly and positively correlated with accumulated soil temperature, implying that land pavement induced soil warming accelerates leaf budburst. It can be concluded that tree phenology might be advanced by soil temperature, besides air temperature, in urban environment.