Stem-Succulent Trees from the Old and New World Tropics

Abstract

Stem-succulent trees are common in tropical drylands. Besides their ability to store water, these trees also possess photosynthetic bark, which can re-assimilate internally respired CO2 at virtually no water cost. Both of these traits are advantageous in seasonally dry ecosystems, where plants are exposed to periods of limited water availability and, consequently, carbon gain. In most species, plants do not use the stored water in stems to buffer daily water deficits; they use this water to flush new leaves before the onset of rains. This gives an extra advantage to stem-succulent trees over other functional groups because leaves are already present when the first rain falls. Having succulent stems does not pose a mechanical constraint in these plants, rather the succulence of the tree stem can act as hydrostatic pressure against the bark, contributing to the biomechanical support of tall trees. Stem-succulent trees are also able to maintain physiological processes and growth during drought, making them good candidates to be used in reforestation of degraded arid lands.