Desert succulents and their life strategies

Abstract

A succulent is a plant with water storing tissue, but succulence clearly is a quality that can be possessed to a higher or lesser degree. This paper gives a definition of succulence and discusses problems concerning Delf's measure of succulence. A new measure, Succulence Quotient, is proposed. It measures the amount of water that a plant can store at the expenditure of one gram of organic matter. We demonstrate this measure on a number of plants from the Namib desert, southern Africa, and compare it with the measured caloric values of the plant tissues. We also discuss life cycles of desert succulents in terms of utilizable and structural biomass and water. We contrast the concepts of growth form, life form and life strategy, and propose, on the basis of life cycle characteristics, an outline classification of life strategies of desert succulents. One detail of this outline classification is further worked out and illustrated for succulents from the Namib desert.