Environmental Engineering Reference
In-Depth Information
TABLE 2.2
Global primary production estimated using remote
sensing and terrestrial and marine models. Units are petagrams
(10
15
grams) per year.
Ocean
Pg/y
Oligotrophic
11
Mesotrophic
27.4
Eutrophic
9.1
Macrophytes
1
Total Marine
48.5
Land
Tropical rainforests
17.8
Broadleaf deciduous forests
1.5
Broadleaf and needleleaf forests
3.1
Needleleaf evergreen forests
3.1
Needleleaf deciduous forests
1.4
Savannas
16.8
Perennial grasslands
2.4
Broadleaf shrubs
1
Tundra
0.8
Desert
0.5
Cultivation
8
Total terrestrial
56.4
Total global
104.9
Source: (Data from
Field et al. 1998
)
areal average of the ocean is due to “competition for light between phytoplankton and
their strongly absorbing medium.” NPP in much of the ocean is also severely limited
by very low nitrogen, phosphorus, and in some areas iron concentrations. Increasing
these nutrients, as demonstrated in the iron fertilization experiment (see
Figure 2.5
), leads
to substantial increases in phytoplankton biomass and primary production.
FATES OF PRIMARY PRODUCTION
Primary production is consumed by herbivores, converted to detritus, stored in bio-
mass, consumed by fire or photo-oxidation, or exported (
Figure 2.1
). Typically over a year,
ecosystems accumulate little or no primary producer biomass with some notable
