Biosphere Contents

1. Organic Matter

There is considerable global variability in biomass and net primary productivity

By far the largest amount of plant biomass on the planet is contained within the tropical rain forests. There are also substantial amounts of biomass in the temperate and in northern boreal forests. The amount of biomass in cultivated land is a relatively small, though increasing fraction of the global carbon reservoir.

Biome Net Primary Productivity (g m-2 yr-1)
Tropical forest 2000 - 3000
Savanna 400 - 600
Desert 0 - 120
Mediterranean 300 - 600
Temperate grassland 400 - 1000
Temperate forest 600 - 1500
Taiga 200 - 600
Tundra 100 - 200

The net primary productivity of terrestrial biomes is shown here as estimated by Forseth (2012). The total net primary productivity of rain forests is very high, at an estimated 21.9 x 1015 tonnes of carbon per year (Saugier et al. 2001). The net primary productivity of the oceans is a comparable amount even though the total primary producer biomass in the oceans is approximately one thousandth of that of rain forests. This is because there is a very rapid turnover of carbon in the oceans while the rain forests are relatively stable. In recent decades, human activities such as deforestation have had major impacts on the global carbon budget.

Are biomass and net primary productivity more or less the same worldwide?