Patterns in primary productivity

The net primary production of the planet is estimated to be about 105 petagrams of carbon per year (1 Pg = 1015 g) (Geider et al., 2001). Of this, 56.4 Pg C year-1 is produced in terrestrial ecosystems and

48.3 Pg C year-1 in aquatic ecosystems (Table 17.1). Thus, although oceans

... primary and secondary productivity, autotrophic respiration,...

... net ecosystem productivity, and heterotrophic and ecosystem respiration primary productivity depends on, but is not solely determined by, solar radiation

Marine

NPP

Terrestrial

NPP

Tropical and subtropical oceans

13.0

Tropical rainforests

17.8

Temperate oceans

16.3

Broadleaf deciduous forests

1.5

Polar oceans

6.4

Mixed broad/needleleaf forests

3.1

Coastal

10.7

Needleleaf evergreen forests

3.1

Salt marsh/estuaries/seaweed

1.2

Needleleaf deciduous forests

1.4

Coral reefs

0.7

Savannas

16.8

Perennial grasslands

2.4

Broadleaf shrubs with bare soil

1.0

Tundra

0.8

Desert

0.5

Cultivation

8.0

Total

48.3

Total

56.4

Table 17.1 Net primary production (NPP) per year for major biomes and for the planet in total (in units of petragrams of C). (From Geider et al., 2001.)

Table 17.1 Net primary production (NPP) per year for major biomes and for the planet in total (in units of petragrams of C). (From Geider et al., 2001.)

cover about two-thirds of the world's surface, they account for less than half of its production. On the land, tropical rainforests and savannas account between them for about 60% of terrestrial NPP, reflecting the large areas covered by these biomes and their high levels of productivity. All biological activity is ultimately dependent on received solar radiation but solar radiation alone does not determine primary productivity. In very broad terms, the fit between solar radiation and productivity is far from perfect because incident radiation can be captured efficiently only when water and nutrients are available and when temperatures are in the range suitable for plant growth. Many areas of land receive abundant radiation but lack adequate water, and most areas of the oceans are deficient in mineral nutrients.

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