Many suburban lots, like the Duncan residence, are laid out on an existing site that either is devoid of trees before development or is cleared in the process of development. In either case, new suburban single-family sites oftentimes have few or no existing trees to consider when creating a master plan. Conversely, some residential properties are placed in wooded locations where they are partially or even completely covered by existing trees. The presence of trees on a residential site establishes a unique environment that must be understood and respected if the trees are to be preserved as an integral part of the site over a number of years.
Special Site Conditions
Microclimate A stand of deciduous trees creates a distinct microclimate that varies over the course of a year (Figure 13—10). In the summer season, the leaves in the tree canopies block a significant amount of sunlight along with some precipitation. This creates a relatively dark, cool, and dry environment below. Air temperatures may be as much as 10 to 15 degrees Fahrenheit cooler in the shaded area below trees than in an open area exposed to direct sunlight. This microclimate is generally more comfortable and can produce substantial savings in air-conditioning costs for houses in wooded
The presence of deciduous trees will create distinctly different seasonal microclimates on a residential site.
areas (also see “Minimize Sun Exposure During the Hot Season” in Chapter 3). During the winter season, deciduous trees lose their leaves, thus allowing considerably more sunlight to penetrate. This sun exposure creates a warming effect during the season when it is needed. Thus, the presence of trees can work favorably with the cooling and heating needs of both indoor and outdoor spaces.
Tree Roots Tree trunks are obvious physical elements that must be worked around in a wooded site. Numerous tree roots are woven in a complex network below the ground surface and are usually located within the top several feet of soil directly below the tree canopy, though some roots extend well beyond the tree canopy (Figure 13—11). Tree roots are the source of food, water, and air for trees in addition to providing structural support. Tree roots are healthiest in a naturalized condition where a layer of leaf debris and rich, porous humus soil exist. Tree roots also need adequate moisture and air in the soil. Tree roots, and the related trees they support, are susceptible to soil compaction or change in drainage across the ground’s surface.
Visual Separation A grove of trees can create visual separation from nearby residential sites and the adjoining street. A cluster of tree trunks functions like a group of columns that helps to define and separate one space from another. Although tree trunks may not be dense enough to completely screen views, they nevertheless do imply a partition of one area from another. Thus, a wooded site frequently has a greater sense of seclusion and privacy even though it may not be completely screened from its surroundings (Figure 13-12).