Epiphytism

Epiphytism is the ecological habit of growing on the surfaces of other plants, typically trees, for physical support. Epiphytes are not rooted in the host or the soil and, unlike parasites, generally do not derive water or nutrients from the host. Instead they absorb moisture and nutrients from rain, dew, dust, and organic debris that accumulates on the host or in the surrounding microhabitat.

This growth form is widespread in tropical and subtropical forests, as well as in cloud forests, where stable humidity supports epiphytic communities. Epiphytes contribute significantly to forest diversity and structure, creating microhabitats for invertebrates, fungi, and other organisms. Common examples include orchids, bromeliads, many ferns, mosses, and lichens, as well as some cacti and other vascular plants.

Adaptations that support epiphytism include specialized aerial roots with absorptive tissues (such as the velamen in orchids), strategies to harvest water from rain and fog, and leaf adaptations for water storage or capture of organic matter. Many epiphytes, such as tank bromeliads, create water-holding "tanks," while others rely on CAM photosynthesis or efficient transpiration control to survive periods without soil moisture. Mycorrhizal associations often aid nutrient uptake from the surrounding organic matter.

Epiphytism is typically non-parasitic; hosts are usually not harmed directly, though heavy colonization can affect light availability or structural integrity in some cases. Epiphytes are valued in horticulture, especially orchids and bromeliads, and conservation concerns arise from habitat loss and deforestation.