Animal and Plant Life

Building sites provide environments for a variety of plant and animal life. Bacteria, mold, and fungi break down dead animal and vegetable matter into soil nutrients. Insects pollinate useful plants, but most insects must be kept out of the building. Termites may attack the building's structure. Building occupants may welcome cats, dogs, and other pets into a building, but want to exclude nuisance animals such as mice, raccoons, squirrels, lizards, and stray dogs. You may want to hear the birds' songs and watch them at the feeder while keeping the cardinals out of the kitchen.

Grasses, weeds, flowers, shrubs, and trees trap precipitation, prevent soil erosion, provide shade, and deflect wind. They play a major role in food and water cycles, and their growth and change through the seasons help us mark time. Plants near buildings foster privacy, provide wind protection, and reduce sun glare and heat. They frame or screen views, moderate noise, and visually connect the building to the site. Plants improve air quality by trapping particles on their leaves, to be washed to the ground by rain. Photosynthesis assimilates gases, fumes, and other pollutants.

Deciduous plants grow and drop their leaves on a schedule that responds more to the cycles of outdoor temperature than to the position of the sun (Figs. 2-4, 2-5). The sun reaches its maximum strength from March 21 through September 21, while plants provide the most shade from June to October, when the days are warmest. A deciduous vine on a trellis over a south-facing window grows during the cooler spring, shades the interior during the hottest weather, and loses its leaves in time to welcome the winter sun. The vine also cools its immediate area by evaporation. Evergreens provide shade all year and help reduce snow glare in winter.

The selection of trees for use in the landscape should consider their structure and shape, their mature

Figure 2-4 Deciduous shade tree in summer:

Figure 2-5 Deciduous shade tree in winter:

Figure 2-4 Deciduous shade tree in summer:

Figure 2-5 Deciduous shade tree in winter:

height and the spread of their foliage, and the speed with which they grow. The density, texture, and color of foliage may change with the seasons. For all types of plants, requirements for soil, water, sunlight, and temperature range, and the depth and extent of root structures are evaluated. Low-maintenance native or naturalized species have the best chances of success. To support plant life, soil must be able to absorb moisture, supply appropriate nutrients, be able to be aerated, and be free of concentrated salts.

Trees' ability to provide shade depends upon their orientation to the sun, their proximity to the building or outdoor space, their shape, height, and spread, and the density of their foliage and branch structure. The most effective shade is on the southeast in the morning and the southwest during late afternoon, when the sun has a low angle and casts long shadows.

Air temperatures in the shade of a tree are about 3°C to 6°C (5°F-11°F) cooler than in the sun. A wall shaded by a large tree in direct sun may be 11°C to 14°C (20°F-25°F) cooler than it would be with no shade. This temperature drop is due to the shade plus the cooling evaporation from the enormous surface area of the leaves. Shrubs right next to a wall produce similar results, trapping cooled air and preventing drafts from infiltrating the building. Neighborhoods with large trees have maximum air temperatures up to 6°C (10°F) lower than those without. Remarkably, a moist lawn will be 6°C to 8°C (10°F-14°F) cooler than bare soil, and 17°C (31 °F) cooler than unshaded asphalt. Low growing, low-maintenance ground covers or paving blocks with holes are also cooler than asphalt.

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