Note that other factors may also be used to stratify the unit as in annual crop systems. If, for example, inter-hedge distance varies considerably over the unit this might affect hedge growth and hence crop growth. The unit would then be divided into a wide hedge-spacing stratum and a narrow
hedge-spacing stratum (Fig. 3). Each of these is further divided into strata to account for the tree/crop interface. Other examples of this type of stratification are level and sloping parts of the unit, or the part damaged by pests and the undamaged part.