Urban Micro Environment and Photosynthesis of Street Trees

Abstract

Micro meteorological factors and leaf photosynthesis of Ilex rotunda were investigated on a median strip in a commercial district to clarify characteristics of the urban micro environment for street trees and the acclimation of leaf photosynthesis to the environment. Diminished sunlight, high air temperature and soil drought in summer were characterized as urban micro environment.
Photosynthetic rate of street trees was lower than for suburban trees from July to September and higher from October to March. High photosynthetic rate in autumn and winter depended on high carboxylation efficiency, and low photosynthetic rate in summer might depend on air pollution. Intrinsic water use efficiency was higher in street trees because of the high carboxylation efficiency and, especially in summer 1994, the low stomatal conductance. The results suggest that these photosynthetic characteristics of street trees represent the acclimation to the urban micro environment.