Lesson 32 Mineral Cycling - Alaska Geobotany Center

Global budget of N 2 O–N (Tg)
• Estimated annual increase in
nitrous oxide (N 2
O) is about 3.5 x
10 12 g (3.5 Tg).
• Note the discrepancy between total
sources and total sinks and
accumulation, which is due mostly
to the large uncertainty factors.
• Major causes of increased N 2
O are
tropical forest clear-cutting.
• Tropical forests circulate more
nitrogen at higher concentrations
than do most boreal or temperature
forests and exhibit high N 2
O fluxes.
• Deforestation in the Amazon basin
has cleared at least 230,000 km 2 of
tropical forest by 1990.
Matson and Vitousek 1990