More and more trees have been planted in paved lands that are dominated in urban environment because trees are able to provide large ecosystem services. Unfortunately, these trees are generally stressed by elevated surface temperature and subsequently fail to grow well. It is supposed that tree transpiration would be enhanced by elevated surface temperature due to land pavement. However there are few evidences to confirm that. Two experiments were designed herein. One is to measure transpiration from three tree species (Pinus tabulaeformis, Fraxinus chinensis and Acer truncatum) growing in fields of pervious and impervious pavement and control by sap flower meter. Another is to measure water loss from two tree species (Fraxinus chinensis and Ginkgo biloba) growing in pot on paved and non-paved lands by weight method.
Under pavement, tree transpirations in field were reduced. The significances of reduction were specific to species. Sap flow rates were significantly lower under impervious pavement than the control for Pinus tabulaeformis, significantly lower under both pavements than the control for Acer truncatum (P<0.05), and insignificantly lower under both pavement than the control for Fraxinus chinensis. The reason might be that pavement retard tree growth and consume less water.
Weight method showed that transpirations of both tree species (Fraxinus chinensis and Ginkgo biloba) growing in pots were significantly enhanced on pavement compared with on non-pavement, especially in early stage of growing. This might be related to elevated surface temperature cased by land pavement. With growing, trees might be adaptive to altered environment.
So it is complex how tree transpiration responds to land pavement. Long-term monitoring is necessary in field to assess the influence of land pavement on tree physiological and growth.