Dead Leaves Insulate Against Fire

photograph of reddish-orange flowers of aloe plant during the day

Biological Strategy

Cape aloe

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Image: Colin Watts / Unsplash / Free non-commercial use

Protect From Fire

Depending on location, fire can be either predictable or unpredictable. In some areas, fires occur in cycles ranging from annual to hundreds of years. Where fire is cyclic, living systems must be able to not only survive fire, but to quickly recover following it. For example, pine trees that live in areas with periodic fires have thick bark that provides insulation, thereby protecting the tree’s living tissue.

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Flowering Plants

Clade Angiosperms (“receptacle seed”): Dandelions, oaks, grasses, cacti, apples

With 416 families containing some 300,000 known species, angiosperms are the most diverse group of plants, and they can be found around the globe in a wide variety of habitats. They are characterized by seeds that grow enclosed in ovaries, which are enclosed in flowers. The floral organs then develop into fruits of myriad kinds and dimensions, from simple seed casings on maples to elaborate fleshy growths like papayas. The oldest flower known from fossils, Montsechia vidalii, appeared during the Jurassic Period 130 million years ago. They are the primary food source for herbivorous animals, which in turn makes them the indirect food source for carnivores as well.

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The stems of cape aloe resist fire via dead leaf insulation.

“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 supports 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.” (Bond 1983:110)

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