The following has been modified from my field notes from when I took tropical ecology and did a field session in Belize.
In the rainforest ecosystem, the number of symbiotic relationships between organisms is astounding. For example, the relationship between leafcutter ants and the fungus is highly observable in Belize. There is such a great number of these ants that paths are created by them. Leafcutter ant is a generic term for one of 47 species, in the orders Atta and Acromyrmex. They take leaves from plants and chew them up, this plant material is then fed to a fungus, which they eat. In a sense they are farmers. Since the fungus receives a habitat and the ant receive food, this symbiotic relationship is mutualism. There is a dark side to this relationship though. If a plant is highly desirable by ants they will highly predate on said plant. Because of this, they are seen as pests by farmers, whose crops they can destroy.
We saw a wide variety of epiphytes growing on a wide range of trees. Epiphytes are plants that live on the bark and the branches of other trees. This feature allows the plant to gain access to light with a limited energy investment. Most plant growth is limited by sunlight, water availability, and temperature. They are not parasitic but their weight can damage trees. This is an example of commensal as the trees are not harmed but the epiphyte benefits from the relationship. At the Mayan ruins, we saw one plant that has adapted to solve this issue by shedding its bark, so the epiphytes fall off with the bark. This worked fairly well for the tree but in one area a plant had managed to survive on the tree. The most commonly recognized epiphytes are pitcher plants, “air plants”, and mistletoe (Santalales).
We witnessed the low variation in the temperature change from day to day. It cooled off at night and in times of rain but other than that the temperature stayed fairly consistent. Often in the tropics, the daily temperature change is more than the temperature change over the course of the year, as witnessed by being able to wear shorts in the middle of “winter”. The rainfall pattern was also highly indicative of evapotranspiration. This occurs when water that has evaporated from plants falls in the form of rain. The sun would come up in the morning and heat the plants, clouds would build, and then in the afternoon, the rain would fall. In the Amazon, as much as 75 percent of the water falling on the forests comes from this.
The forest was stratified in many areas. There were a few emergent trees or trees that were taller than others. There was a large number of canopy trees, but there were poorly defined sub-canopy and understory in many of the places that we visited. This was for two main reasons. Most of the forests we visited where secondary forests, so they were not as structurally complex as primary forests. The other reason was the large cut paths that we traveled on provided lots of light on the sides of the path thus plants not evolved to the understory could grow there. This is a type of forest gap. Other gaps were created naturally from fallen trees. In areas of deeper shade, this was not the case and the layers were much more defined.
Biodiversity is all the species, ecosystems, and genetic material on the earth. In the forest, we were also able to witness all six of the values of biodiversity. The economic value we saw as chocolate made from cacao and the local businesses supported by eco-tourism like the caving tubing company. We witnessed the ecological life support in the forms of fresh air, and the water used by the local Maya to wash their clothes. The cultural value was seen in the traditional uses of plants, and the national pride of the people stemming from the beauty of their country. By bird watching, hiking, and swimming we took full advantage of the recreational value. The scientific value was found in the research being done at the community baboon sanctuary, and the cockscomb reserve. Lastly, we did witness some of the negative values through insects, and potential diseases.
We witnessed many plant adaptations in the forest. The plants were very adapted to the large downpours that often occurred on our trip. The leaves often had drip tip while allowing water to drip off the leaf. The leaves also had smooth edges instead of rough ones which would limit water dripping off them. They also have a concave shape which allows water to easily fall off of them. The roots were also buttressed in some areas of support, water absorption, and nutrient absorption. Surface roots also allow for increased absorption of nutrients. The flowers were also adapted to specific animals, identifiable by the smell and coloration of the flowers. We also saw a number if lianas and strangler pants. These either start as vines and become shrubs or start as shrubs and become vines. In time they will kill their host plant.
The forest had a low number of individuals in each species. Only a few species were seen more than once. Once we learned what a species was it was rare to see it again. The exception to this were toco toucans (Ramphastos toco), red-lored parrots (Amazona autumnalis), and a few species of palms. Because of this, there is a high evenness in the tropics. There can be up to 100 species of tree in one hectare. Many think that this high number of species is due to a low extinction rate, a high speciation rate, or a combination of both. Other factors that may influence biodiversity include a stable climate over time, high productivity, interspecific competition, and predation intensity.
Monkeys that we saw had tails that they used for climbing. Their tails can hold their whole body weight, and all the new world monkeys have tails. This allows them to be more agile and above predators on the ground. In addition, our guide at the baboon reserve said that howler monkeys have adapted to eat fruit so that they can get their daily water intake within being exposed on the ground near the water. On the spider monkeys (Ateles), I also observed a lack of thumbs. This means that they can travel at higher speeds as they can use their hands as hooks.