Glossary for agroforestry

Compiled and edited by Peter Huxley and Helen van Houten, International Centre for Research in Agroforestry - 1997

under bark

Measurement of the diameter or circumference of a trunk or branch made with the bark removed. See also over bark

undercut seedling

A nursery-grown seedling that has had its tap root cut by passing a blade or wire through the seedbed a few centimetres below ground level. This process encourages the growth of lateral roots and is an alternative to transplanting as a means of obtaining sturdy planting stock with a well-branched root system. Often moved as balled roots.

understorey

The portion of a tree in a forest stand below the overstorey. See also stratified

underwood

A tree crop growing beneath the main canopy and forming a distinct lower storey. It is usually of coppice but can be of planted or naturally seeded trees.

uneven-aged

The presence of at least three distinct age classes, usually a range of size classes ('seedling', 'sapling', 'pole' and 'sawtimber'). See also all-aged, even-aged

uniformity trial

Planting a test crop at a carefully controlled planting density and under a consistent level of good management over an area on which a field experiment is to be carried out, so as to use the data when it is harvested from small, equal-sized plots over the whole area, to assess how 'uniform' this area is. It can be used to define blocks where non-uniformity occurs and locational control is part of the experimental design (for example, in a 'randomized block layout', or for covariance analysis).