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TURFGRASSEN IN URBAN ENVIRONMENT
A turf is like a miniature wood. The plants are cut differently but the amount of light absorbed, O2 generated, CO2 captured and biomass produced is the same.
A grass surface is more practical because it is just a few centimetres thick (whereas a wood is several metres tall) and it also grows wherever you choose to place it. It just needs light, water and nutrients.
A number of studies have shown the physical and psychological benefits deriving from the presence of turfgrasses, which is why, ever since ancient times, people have tried to grow lawns near their homes.
Nowadays, thanks to the development of new technology, we can even have turfs on roofs, on the outside surfaces of buildings and even inside living spaces.
Grass surfaces have very ancient origins, but it is only really over the last few decades that the industry has really taken off, particularly in the wealthiest countries. Imported into North America in the 19th century to copy a European fashion, turfs really grew in importance as cities expanded, until they became firmly entrenched in North American culture. At the present moment the USA is the "leading" country in this sector with the highest number of employees, researchers, associations in the industry and an overall surface area of turf covering close to 19,000,000 hectares. Until very recently the small amount of turfs in Italy was mainly due to the lack of know-how of people working in the industry. From the mid-1990s onwards, a knowledge on turf spread throughout our country, backed up by specific University research, which had been non-existent until then.
The importance now given to grass surfaces is not only due to the need to recreate pleasant environments, but also the positive effects in terms of environmental protection they are acknowledged as having, particularly in highly urbanised areas. Different types of grass surfaces have been developed over the years, serving increasingly specific roles, which have resulted in the perfecting of cultivation methods, the choice of vegetation used and maintenance techniques.
THE ADVANTAGES OF A GRASS SURFACE:
- High C02 absorption capacity: a lawn covering 300 square metres absorbs the same amount of CO2 as an average-size car produces while driving a distance 20.000 km, and the same surface area generates the amount of oxygen required for two adults to breathe.
- Dust trapping: turfs help improve the air quality in the city, because they are capable of trapping dust and various kinds of particulate deposited in urban areas.
- Filtering and purifying: in urban areas rainwater and sediment running off impermeable surfaces may be contaminated by polluting substances such as heavy metals (Pb, Cd, Cu, Zn) and hydrocarbons sush as lubricants, fuels and solvents. Depending on the species, season and cultivation method, the biomass of leaves and stems in a turf performs an efficient filtering action in relation to these pollutants. Moreover, the organic substance in the thatch and radical residuals host a high population of microorganisms: so a turf is a biologically active system combining a filtering action with a purifying action, whose synergic effects can help degrade polluting substances.
- Preventing fire from spreading: a turf helps to prevent fire from spreading; plus, provided it is looked after properly, it is also inflammable due to its water content of approximately 80%.
- Heat dissipation and temperature control: turfs unlike non-evaporating surfaces, absorb heat through evapotranspiration (2.43 kJ g-1 of transpired water), thereby cooling down the surface and, as a consequence, the surrounding air. The climatising effect of grass and vegetation in general can also enable notable energy savings on air-conditioning buildings.
- Reducing noise and reverberation: studies have shown that a turf absorbs significantly more sound than rigid surfaces, so it is highly effective at reducing noise. The multidirectional reflection of light is significantly reduced by the presence of turf.
- Reducing allergens: quality turf surfaces are only minimally affected by weeds, so the risk of generating allergen pollens is almost non-existent. In addition, if cut regularly, turfs do not generate inflorescence.
- Enhancing buildings: another significant aspect is connected with the notable appreciation in value of properties enveloped in a quality turf surface, which translates into a rise in real-estate value of approximately 15%.
- Psychological aspects: various studies show that the presence of vegetation, particularly in urban areas, has psychological, aesthetic and therapeutic benefits on people, such as: pleasant feelings, relaxation, better mood, reduced stress.
TYES OF GRASS SURFACES
The species which can be used for making turfs are grouped into cool season grasses and warm season grasses and only about fifteen of which are widely used.
COOL SEASON TURFGRASSES (CST)
Cool season turfgrasses grow most during the spring and autumn periods. Generally speaking, the optimum temperature range for growing is between 15°-25°C. Compared to warm season species, they have more shallow roots, greater resistance to cold weather, but less tolerance to heat, drought and salinity. They can be grown in pure o mixed stands. The most commonly used species in Italy are Festuca arundinacea, Lolium perenne, Poa pratensis and Festuca rubra.
WARM SEASON TURFGRASSES (WST)
Warm season turfgrasses are adapted to hot or temperate climates. Optimum growth temperature is between 25°-35°C. These species grow more slowly at temperatures below 20°C and actually stop growing at approximately 10°C. When the temperature drops below 0°C they lose their green colour and enter into a state of dormancy. The most common Warm season turfgrasses are: Cynodon dactlylon, Paspalum vaginatum, Stenotaphrum secundatum and various Zoysia grasses. They are characterised by considerable lateral growth through their stolons and rhizomes, they have deep roots, a high recovery capacity following stress, and exceptional resistance to high temperatures, drought and salinity.