Global populations in towns and cities are continuing to rise resulting in the urbanisation of greenfield sites. Urbanisation converts permeable rural land into land for urban and industrial areas and increases the area of impermeable surfaces such as roofs, roads, driveways and pavements. An increase in impervious surfaces can impose dramatic changes to a catchment by altering the natural drainage characteristics. Impervious surfaces effectively seals off much of the underlying soil and prevents the infiltration of water, oxygen and nutrients to the soil below. Street trees are an integral part of everyday life. The role of street trees has adapted from one of ornamentation to service provision. Street trees provide a vast range of benefits in residential and community areas and support healthy communities by providing environmental, social and economic benefits. However, street trees often suffer in urban environments as a result of increased impervious surface areas and lack of available growing space. The installation and survival of urban trees is often challenging and urban designers must consider critical issues in their landscape design including space availability, ground conditions and maintenance requirements. The water, oxygen and nutrients essential for tree growth are often in short supply in urban soils due to the impervious surfaces, such as conventional asphalt, impervious blocks or concrete paving sealing off the soil surface. These undesirable site conditions for tree growth often lead to shorter life spans of urban trees compared to those in natural environments.
Submitted in the fulfilment of the requirements of the degree of Doctor of Philosophy, University of the Sunshine Coast, 2015.