Production Efficiency - Ecosystem
The maximum amount of solar energy harvested by plants is about 5 per cent but the average for green plants, on the whole is only a small fraction of sunlight, i.e., 0.02 per cent reaching the atmosphere. The production efficiency that is the ratio of net primary production to gross primary production (of green plants) is on the average rather high. It varies between 40 to 85 per cent. The most efficient are those plants which have low maintenance requirement due to minimum non-photosynthetic (non green) tissues, such as in grasses, algae and phytoplankton. Algae and crops like corn have an efficiency of about 80 to 85 per cent, submerged aquatic plants 60 to 75 per cent, deciduous forests about 42 per cent. Different ecosystems have different productivities.
Productivity of ecosystems depends on a variety of factors such as sunlight, temperature, rainfall and the availability of nutrients. Those situations that provide the best circumstances for plant growth are the most productive. Warm, moist, sunny areas with high levels of nutrients in the soil are ideal. Some areas have low productivity because one of the essential factors is missing. Deserts have low productivity because water is scarce, arctic areas too have low productivity because temperature is low, and open oceans also have low productivity because nutrients are in short supply. Coral reefs and tropical rain forests have high productivity. Marshes and estuaries are-highly productive since waters running into them are rich in the nutrients and they also get enough light.