Walking through a tropical forest is overwhelming and sometimes you leave thinking it was just an entire mass of greenery. However, if you look closely enough, observe long enough, you’ll soon find that the tropics are composed of common structural characteristics that plants share in order to outcompete one another and continue their lineage. Don’t let the tranquility of the forest fool you! It’s practically a war zone, where the search for sustenance in the form of sunlight, nitrogen or organic matter creates the unique and intricate ecosystem you’ll find in the forest today. Below are a list of terms, one may find useful in differentiating plants during any hike.
1) Canopy Trees: The largest trees you’ll find in the forest. Their survival strategy is based on building mass and weight so they invest most of its energy in the growth of its trunk than in their leaves (hence, most are small, compound leaves). They are slow-growing as well as shade tolerant and so will have banks of saplings that will work their way up for years. They are the best competitors in the forest, but because it takes them a while to colonize, it will take hundreds and hundreds of years to restore a mass of canopy trees that have been deforested. 100% Photon Flux Density (PFD; or the amount of light absorbed).
Examples of canopy trees are Bursera Simaruba, Manilkara zapota, Hymenaea courbail.
2) Pioneer species: It’s a fight for time for these trees and so their reproductive strategy is to spread as much of their seeds as possible (normally through wind-dispersal) and to grow as quickly as possible. They are sun-thirsty and not shade tolerant, like the canopy trees, and so they have seed banks instead, with seeds waiting for years to germinate until a treefall gap is available. Unlike canopy trees, which are long-term plants, pioneer trees are short-term, making them great colonizers but poor competitors. 20% PFD.
An example of a true pioneer (life history in canopies) is Cecropia.
An example of a persistent pioneer (grows in gaps, in wide open areas and in some cases actually benefits from deforestation) Pachota Quinata.
3) Understory plants: Living underneath the canopy trees, understory plants mainly struggle with access to light. Consequently, rather than invest in support structures, like canopy trees do, they invest most of their energy in leaf structures and adaptations, such as drip-tips and the ability to drop of older leaves during dry season. <0.05% PFD.
Examples of understory plants are Helioconaceae and Piperaceae.
4) Lianas & Vines: Their main survival strategy is finding support. Vines are thin herbaceous climbers and are more like understory plants in PFD (0.05-20%), and prefer open, sunny areas though they are shade-tolerant as well. Lianas are woody vines and tend to grow towards the canopies (about 100% PFD). They are the things Tarzan swings from tree to tree!
An example of a liana is a Bauhinia. An example of a vine is Passaflora.
5) Epiphytes: Their survival strategy is to grow on host trees, which causes them to leave contact from the ground. As a result, they are stressed for nutrients. Epiphytes characterizes tropical forests and make them unique from their temperate counterparts!
Examples of epiphytes are bromeliads and orchids.