References

Role of Microorganisms in Carbon Cycling in Soils 141
Table 1. Microbial C content (Cmic) of soils from different ecosystems. Microbial biomass
was measured by the fumigation extraction or substrate-induced respiration method
Ecosystem Horizon Cmic Reference
(cm) (µg/g) Corg
(%)
Arable soils 0–20 70– 720a 1.0–3.8 Beck et al. (1997)
0–15 420– 980 2.5–5.5 Franzlübbers et al. (2000)
0– 5 250– 1080 3.0–6.0 Hu et al. (1997)
Grassland Litter 9650 2.1 Ross et al. (1996)
0–10 2670 2.9
10–20 1120 1.9
20–30 470 2.0
F 25900a ND Johnson et al. (1998)
0– 7 6600–15700a ND
0–10 1120– 1510 ND Bardgett et al. (1999)
Temperate forest 0–10 420– 1770a 0.9–2.6 Beck et al. (1997)
0– 5 800– 1670 1.2–6.0 Hu et al. (1997)
5–10 160– 430 ND
5–10 370– 600 ND
Litter 10830 2.3 Ross et al. (1996)
FH 7670 2.0
0–10 1670 2.1
10–20 730 1.8
20–30 260 1.0
Subtropical forest 0–10 330– 1090 0.9–1.8 Maithani et al. (1996)
10–20 200– 790 0.7–1.3
Tropical forest 0–10 210– 490 2.1–3.4 Salamanca et al. (2002)
Tropical forest 0–12 170– 860 0.5–1.1 Waldrop et al. (2000)
Tropical forest 0–10 950– 1970 1.4–2.9 Cleveland et al. (2004)
Tundra 0– 5 2990–13900 2.1–3.6 Weixin and Ross (1993)
Alpine meadows 0–10 1000– 2750 1.7–2.8 Zeller et al. (2001)
Boreal forest Litter 2500– 6000 ND Schimel et al. (1999)
Semiarid 0–15 120– 330 3.2–4.8 Kanchikerimath
and Singh (2001)
Arid/Mediterranean 0–20 30– 700 0.8–8.0 García et al. (1994)
ND, Not determined
a Results based on the measurement of substrate-induced respiration
In principle, soil organic carbon is derived from autotrophic organisms
– higher plants and autotrophic microorganisms. Dead plant and microbial
material are the most important energy sources for soil microorganisms.
The organic debris is either mineralized, i.e., completely decomposed to
CO2, or humified. The latter process leads to soil organic matter fractions
of widely varying turnover half-lives, from several decades to thousands of
years. Note that mineralization and humification are parallel processes. De-