Abstract

A general recommendation is that a mineral cap on a closed deposit should be covered by a soil or soil forming layer of at least one meter thickness. The reason for this is primarily to protect the cap from root penetration or other disturbances. Referring to an article by Hutchings et al (2001), they found evidence that the soil sickness should be 1.5 meters in order to protect from tree root penetration unless the cap is thoroughly compacted. In relation to our study they also found that growth of tree species was strongly influenced by soil depth, but probably through its control on available water. Our investigation was performed on the regional waste deposit Spillepeng in Malmö in southern Sweden. The deposit is still in use, but the earlier parts are closed and landscaped for recreational use. The cap consists of a 15-20 cm compact clay barrier. It is covered by soil of varying thickness (15-60 cm) with tree species of different age (9-14 years in 2003). The purpose of the investigation was to study the importance of soil and cap factors for the vegetation growth on the deposit. Thus 15 plots with different soil factors, land forms and altitudes were defined. Six different tree species were studied: birch, poplar, oak, white beam, maple, and lime. Growth variables in the form of tree height, stem perimeter, and lateral growth of annual rings were investigated. The survival of established trees and their growth was good in spite of the thin soil layers. It was only in the one location where the cap was missing that the trees survived to a lesser extent. The relatively good growth indicates that there was no impact on roots from underlying gas production and consequently no root penetration through the cap. The outcome of the statistical analysis showed consistently a strong relation between growth and altitude/land form and some relation between growth and soil clay content. The tendency was the same regardless of sample: singular species over the plots or normalized growth variables from all species. Both relationships suggest that the water holding capacity of the soil determines the growth. The soil thickness as such has no influence on the vegetation growth. Our conclusion from this preliminary investigation is that as long as the cap is thoroughly established, a thin soil layer is enough for vegetation growth, provided a good water holding capacity

Published in

Publisher: ISWA

Conference

ISWA Annual Congress 2005 in Argentina, 7-10 November in

SLU Authors

• Skärbäck, Erik

  • Department of Landscape Planning Alnarp, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Landscape Architecture


Permanent link to this page (URI)

https://res.slu.se/id/publ/6602