Types of rarity of plant communities

The concept of rarity has been used in an ambiguous and confused way in veg etation science. Some authors have defined rarity of plant communities in t erms of frequency of occurrence, while others have used the term with refer ence to the abundance of participating species. Association rarity can be d efined in three dimensions: geographical extent of occurrence, absolute fre quency of occurrence within the geographical range, and characteristic size of individual stands of the association. Here, each dimension is considere d as a binary variable, and seven types of rarity are defined and discussed with examples.