Growing trees in road foundation materials.

摘要

The use of traditional methods for establishing road foundations makes root growth from trees planted in holes within the foundations or close to them impossible. The performance of commonly used urban tree species in traditional and alternative foundation materials was documented through a growth test in Denmark established in April 1994, which used a total of eight materials and three species of tree: Acer platanoides 'Emerald Queen', Fraxinus excelsior 'Westhof's Glory' and Tilia X vulgaris [Tilia europaea] 'Pallida'. Three crushed materials - granite, lava and brick - when combined with topsoil, allowed root growth and consequent crown growth, and are suited for practical use. The root/crown ratio for plants cultivated in the three mixtures, in which soil constituted a maximum of 30 per cent of the total volume, was higher than for plants cultivated in unmixed topsoil, which indicates that less growth will be obtained per unit soil volume of the mixture in relation to the same volume of unmixed topsoil. The study also shows that roots cannot grow in 'correctly' compacted foundations, and that standing water in plant holes is a strong limiting factor for the growth and vitality of the three tree species used in the study.