Topic 4.2: Shrubs

A “shrub” is technically defined as a multiple-stemmed woody plant.  Some foresters use the term more loosely to include small-statured trees (=treelets) but the presence of multiple stems may be ecologically important.  The distinction between shrubs and trees in tropical forests is obscured by large trees that also can spread vegetatively and therefore should technically be called giant shrubs.  Multiple-stemmed palms are even more difficult to classify since they lack “wood,” which is technically defined as the product of secondary thickening which of course does not occur in palms (see below).

Small statured woody plants, whether they are single or multiple stemmed, can be a silvicultural blessing or a nuisance.  Because they do not grow to be very tall, typical shrubs can serve as very effective “nurse plants” or severe competitors with tree seedlings.  Seedling survival, growth, and stem quality may all benefit from the shade cast by shrubs in otherwise high light and high temperature environments.  Alternatively, the shade and root competition of shrubs, coupled with their capacity to spread vegetatively, may suppress tree seedling growth for many years or even decades.  “Arrested succession” due to shrub-domination of abandoned agricultural clearings is a familiar phenomenon in many parts of the tropics.