What constrains life in the rainforest? Here we see plants growing upon plants growing upon plants – nearly every part of this tree trunk is covered with another organism. Ecosystems appear in miniature the closer one looks. So what prevents a baroque elaboration of this arrangement to infinite numbers of infinitely small plants? Resource limitation. Here, plants are competing primarily for space and light. These epiphylls gain some advantage by relying on the host plant for structural support, but are also constrained in their growth, typically to low-light environments. Some large lianas (woody vines) can climb up dozens of meters to the brighter forest canopy – often strangling their host tree in the process. These lianas can then grow onto other trees or re-root far from their point of origin, making them less reliant on the structural support of their original host. This life is very different from the life of most desert plants, which have abundant light and abundant space – but very little water. The most limiting resource for an organism depends on its environment.
This photograph was taken at the Luquillo Long Term Ecological Research site in the forests of northeastern Puerto Rico. I will be conducting research here for the next month, and plan to post a new photo every day while on the trip!