When one enters a rain forest in Central America, one enters a new world. The most biodiverse places on Earth open up a new human perspective, as countless species originating from different times and lineages face off. Competition drives a series of adaptations that aid plants, animals and fungi to fill every single ecological niche there is. Everywhere you look, something is making a living. In one of these places, you are filled with wonder, and understand that there are much greater processes going on that we simply could not experience in our own lifetime. Processes that have been going on since life gained a foothold on Earth.
In Central America and other biodiverse rainforest ecosystems, the carbon cycle moves more rapidly than what I'm used to. Since so many species are competing, the organic layer covering the forest floor is not deep at all, because it is quickly re-assimilated into living flora and fauna. For this reason, the root structures of plants don’t burrow deep into the ground, but stay near the soil surface to gain the freshly fallen nutrients from other plants and animals. The hardy organic material is broken down by fungi on the forest floor where proper temperature and moisture content persists.
The leaf I found that helped me realize biological limitations
Sometimes, away from the forest floor, conditions for decomposition are not present. This was true for this leaf I found perched atop a handrail on a trail, while hiking in Costa Rica. The easily decomposable plant material (labile carbon) has been weathered away, while the tougher, more indigestible material (recalcitrant carbon) has stayed intact. Without direct contact with the soil fungi, we get to see this leaf skeleton made up of the hardier plant products. This leaf was not only away from the ground, but in a really warm position in direct sunlight. Fungal spores that may have dispersed to this leaf may not have germinated in this position of heat and desiccation. Saprotrophic fungi are marvels of the ecological world, but it took this leaf for me to understand that even the finest decomposers have their limitations.
The indigestible leaf material (recalcitrant carbon) left behind after natural weathering.
In a Costa Rican rainforest, I understood that what I saw was the pinnacle of life on Earth for rainforest adapted species. Given enough time, species avoid competition by drifting into different ecological niches. This results in diverse, colorful communities that cover every square inch of the forest floor. Central America filled a void in me. I acquired a new appreciation for the biological world after my first trip to Costa Rica. With a head chockfull of wonder and excitement I can’t wait to go back. I need to go back.