PATTERNS OF SOIL DRYING AND MOISTURE DEFICIT IN THE VICINITY OF TREES ON CLAY SOILS

Existing guidelines on the proximity of trees and buildings are based on the concept of permitting minimum foundation depths and then trying to ensure sufficient separation between the tree and building to prevent damage. Such guidelines are impractical and are not universally accepted or implemented. The alternative approach is to increase foundation depth to permit most tree planting designs and natural regeneration, but in the past very little information has been available on the necessary depths. The Paper describes research into the patterns of deficit near 36 different trees, covering a range of tree species and clay types. It demonstrates that poplars have much greater effects than the other species which are investigated. Clay type makes little difference to the patterns of deficit, although it is important because of differences in permeability and the amount of shrinkage which occurs. Differences between individuals of the same tree species are comparatively small, unless there are anomalies in...