Cover (area occupied) - Quantitative Characters
Cover or specifically herbage cover refers primarily to the area of ground occupied by the leaves, stems and inflorescence i.e. the above-ground parts of the plants, as viewed from above. Each layer of vegetation is considered separately, since overlapping usually occurs, so that a tall plant is rated apart from one growing under it. Basal area refers to the ground actually penetrated by the stems. This can be readily seen when the leaves and stems are clipped at the ground surface.
Figure: Diagrammatic sketch showing herbage cover and basal area in different plant