Trees are increasingly planted within paved environments in cities. However, little is known regarding growth responses of trees to different pavements. In this study, three popular urban forest tree species, pine (Pinus tabuliformis Carr.), ash (Fraxinus chinensis), and maple (Acer truncatum Bunge), were planted on different paved and unpaved plots (pervious brick pavement, impervious brick pavement, and no pavement as the control) at three different densities (0.5 m × 0.5 m, 1.0 m × 1.0 m, and 2.0 m × 2.0 m apart). Soil temperature and soil moisture were measured continually using an infrared thermometer and TDR300. Survival rates for each plot were recorded in the spring of 2013. Tree height and basal diameter of all trees were monitored monthly over two growing seasons from 2012 to 2013.
Results/Conclusions
Land pavement significantly increased surface temperature, changed soil moisture, and decreased survival rate of maple, and height and basal diameter increments of all three species, except for ash at the 0.5 m × 0.5 m density. There were significant interactions between pavement and densities on tree height and basal diameter increments. Interestingly, the effects of pavement on the microenvironment and tree growth varied with pavement type, tree species, and planting density. Surface temperature was higher on pervious pavement than on impervious pavement, and decreased with increasing density. The pavement-induced reductions in tree growth were not always alleviated by pervious pavement because of the presence of strong heat stress. Linear regression analysis showed that increased surface temperature was the primary contributor to decreased tree survival and growth. Therefore, alleviating the increased surface temperature induced by the pavement is important for guaranteeing tree survival and growth. The confounding effects of pavement, tree species, and density require more measurements of the microenvironment as well as plant physiological and growth characteristics.