Dead leaves and fire survival in Southern African tree aloes

Many aloe species in southern Africa have stems clothed with a layer of persistent dead leaves. The degree of stem coverage is species-specific. The suggestion that persistent dead leaves have an insulatory function and are adaptive in fire-prone habitat was tested on Aloe ferox. Field surveys demonstrated a significant negative relationship between mortality and degree of stem coverage and laboratory studies confirmed the insulating properties of dead leaves. The distribution of southern African tree aloes supprts the prediction that bare-stemmed species would be confined to fire-free habitat whilst fully clothed species would occur in both fire-prone and fire-free habitat. The study suggests that harvesting of Aloe ferox leaves for medicinal purposes could result in significant mortality in fires.