One factor that contributes to our limited understanding of the
sensory functions is the difficulty to quantify the visual effects
of urban forests, which we discussed in more details in the next
section. However, various studies have shown that the amount of
vegetation that can be viewed fromthe ground may have an impact
on people’s perception of an urban forest. Thayer and Atwood
(1978) found that the existence of vegetation usually increased people’s
rating of urban scenes. Smardon and Goukas (1984) pointed
out that an increase in the amount of green in presented planting
designs led to an increase in people’s positive responses to the
designs. Schroeder and Cannon (1983) and Buhyoff et al. (1984)