About 10 per cent of Earth's plant species are epiphytes, and they play a critical role in forest ecosystems. But their importance is often neglected by superficial conservation efforts. Many of them are easily grown in the home, which is a great way to learn about their unusual ecology.
Epiphytes are plants that grow on other plants without parasitizing them. They draw moisture and food from the atmosphere itself, contributing significantly to the nutrients contained in forest ecosystems.
Feeding the forest
Their importance is explained in "Concepts in ecosystem management: forest canopy" on the Olympic National Forest home page:
- As the plants die, nutrients are retained in the canopy, building up into thick mats of decaying vegetation. Recent research has shown that maple, red alder, and various tropical hardwoods are able to grow canopy root systems in order to access these pockets of nutrients in the treetops.
Most epiphytes belong to five plant groups:
- Orchidaceae, the orchid family
- Bromeliaceae, the bromeliad family
- Araceae, the aroid, arum or calla family
- Division Pteridopsida, the ferns
- Lichens, symbiotic organisms derived from Protista (algae), fungi and Monera (blue-green algae or cyanobacteria)
Lichens with cyanobacteria can even fix atmospheric nitrogen into a form which is available to plants. This group's ecological role is further described in "Mysterious green crust on a blasted planet."
Mini habitats
As reservoirs of water and nutrients, epiphytes also attract insects and other organisms. Species of frogs and dragonflies are known to complete their entire life cycles in the leaf-bound pools enclosed within tropical bromeliads. These pools are called phytotelmata. The outer bracts do not contain water but terraria of moist, decomposing matter providing an entirely different microenvironment. For more information see "Bromeliad biota".
Epiphytes are a subtle presence within woodland habitats, so conservation activities like simple tree planting tend to neglect them. But scientists can measure the relative age and health of a forest by the abundance of plants growing in the canopy. As more and more forests are harvested for lumber and to create agricultural land, many epiphytic plants and the organisms that depend on them are threatened.
Crown of the angels
The largest fern in the Americas is an epiphyte called crown of the angels (Platycerium andinum), and it is on the verge of extinction. It was first described in 1891, then went unreported until 1962 when a cluster was discovered near Pucallpa, Peru. The only species of staghorn fern native to the Western Hemisphere, it is found in two small pockets of dry tropical forest, one in Peru and one in Bolivia.
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