The concept of green roofs is basically about growing plants on roofs, thus
helping to replace the green footprint that had been destroyed due to the
construction of the building. Green roofs are the most prevalent (流行) in
Germany, which is widely regarded as the leader in green roof
research. The green roofs that are used these days can be
classified as "extensive" and "intensive" systems. Extensive green roofs use
mosses, grasses and herbs, which are tolerant to droughts. These plants do not
need much maintenance, can be grown in a layer of substrate (土层) that can be as
shallow as 1.5 inches, and generally are inaccessible to the public. In
contrast, a wide range of species of plants are grown on intensive green roofs,
such as shrubs (灌木) and even trees, which require deeper substrate layers, and
are usually grown on fiat roofs. They need intensive maintenance, and are
usually areas that resemble parks which are accessible to people.
There are several benefits of adopting green roof technologies. Apart
from the obvious psychological and aesthetic (美学的) benefits of garden-like
environments surrounding you, some of the common economic and ecological
benefits are: a reduction in the consumption of energy; air and water
purification; recovering green spaces; and the mitigation (缓解) of the heat
island effect in urban areas. The green roof research that is
currently ongoing is focused on evaluating the species of plants that are
suitable to be grown on roofs, the methods of propagation (繁殖) as well as
establishment, nutrient (养料) and water requirement, substrates, and the quantity
and quality of water runoff. The evaluation criteria of plant species are: at
what rate they can be established their capacity to withstand invasive weeds;
tolerance of cold and heat; tolerance of drought conditions; capacity of
persistence and survival. A number of experiments are being
conducted on roof platform simulations at various research centers. These sites
are generally outfitted with equipment, which are used to measure temperatures
at different depths of the growing substrates, and the rate and volume of the
runoff of stormwaters from each of the platforms. Green roof
technology is representative of a completely new market for landscape
contractors, and all roofs that currently exist and the future ones to be
constructed are the potential market-a market that is too huge to be
overlooked.
单选题
It is estimated that around 10 percent of the flat roofs in Germany are
green.