ABSTRACT
As well as being distinctive assemblages of plants and animals, ecosystems also carry out work. Solar energy is captured by plants and passed on to other organisms. All life ultimately depends upon the sun’s energy through the process of photosynthesis. Together with the flow of energy, ecosystems also depend upon the circulation of sufficient nutrients to maintain the healthy vegetative growth. Nutrients enter ecosystems from the atmosphere and from rock weathering, and can exit the ecosystem into the atmosphere and into drainage water. Nutrient cycles thus link the air, the rocks and the soils of the abiotic environment with the organisms of the biotic component of the ecosystem. Although each nutrient element has its own unique cycle, it is possible to generalize about different types of nutrient cycle. The processes involved in energy flow and nutrient cycling are analysed in the present chapter.
