Tropical Rainforest Primary Productivity.
Productivity is one of the primary features of any ecosystem, and what determines how an ecosystem thrives and prospers. Most of the matter and energy within rainforests are contained in the biomass. Green plants, which photosynthesize and convert solar energy into chemical energy, are known as primary producers (autotrophs). The photosynthetic capacity of these primary producers is known as the primary production. The gross primary productivity of a biome (GPP) is the rate at which the primary producers in an ecosystem convert the sun’s energy into chemical energy in the form of biomass found in their tissues. However, not all of the chemical energy produced is available to others in an ecosystem; the producers need some of the energy for themselves to live. Net primary productivity (NPP) is the rate at which producers photosynthesize minus the rate at which they use some of this for their own respiration.
On land, net primary productivity per metre decreases between the Equator and the poles in response to the amount of solar radiation available to producers. This is due to the fact that plants need sunlight to photosynthesize – the more sun radiation, the more they are able to produce. In tropical rainforests, the average NPP in grams per metres squared every year (g/m2/year) is 2200 (2.2kg). This figure is well above the average net primary productivity of many other biomes, with biomes such as temperate grasslands having only about 600g/m2/year. This high primary productivity is due to the positioning of the biome. As the tropical rainforests are found near the equator, they have much more sunlight than other biomes and so the plants are able to photosynthesize to a greater extent. This means that the tropical rainforests have lots of food energy for the consumers, and are able to support a much more extensive biome with a large diversity of life forms.