Table 2

Number of prokaryotes in soil

Ecosystem type*Area, × 1012 m2No. of cells, × 1027
Tropical rain forest17.01.0
Tropical seasonal forest7.50.5
Temperate evergreen forest5.00.3
Temperate deciduous forest7.00.4
Boreal forest12.00.6
Woodland and shrubland8.028.1
Savanna15.052.7
Temperate grassland9.031.6
Desert scrub18.063.2
Cultivated land14.049.1
Tundra and alpine8.020.8
Swamps and marsh2.07.3
Total123.0255.6
  • * From ref. 73

  • For forest soils, the number of prokaryotes in the top 1 m was 4 × 107 cells per gram of soil, and in 1–8 m, it was 106 cells per gram of soil (16). For other soils, the number of prokaryotes in the top 1 m was 2 × 109 cells per gram of soil, and in 1–8 m, it was 108 cells per gram of soil (18). The boreal forest and tundra and alpine soils were only 1 m deep. A cubic meter of soil was taken as 1.3 × 106 g.