carbon cycle is unique because it is a very important element and t helps make all organic matter including parts of the human body,like DNA RNA, proteins and fat. carbon is usually found in carbon dioxide.It can also be dissolve in water, or stored in sediments. sulfur is unique because it is found in small quantities usually in amino acids. it can be found in the air as sulfur dioxide and in water. nitrogen cycle is unique because it can be absorbed by plants and animals and humans breath it.Phosphorus cycle is unique cause it is a element that is found in DNA. A example of primary succession in the rain forest is rock->lichen->moss->grass->shrub->trees->oak hickory forest. A example of secondary succession in the tropical rain forest is grass->shrub->trees->oak hickory forest. soil, water, temperature, humidity and air are the abiotic components or tropical forest.