Net biome productivity

The assimilation of C02 on land is determined by net biome productivity (NBP), which is the balance between net primary productivity (NPP 56.4 109 tC yr-1) and carbon losses due to heterotrophic respiration and burning processes. According to observational data for many ecosystems, with increasing C02 concentration the NPP should grow with a gradual transition toward saturation at reaching a C02 concentration in the atmosphere of 800 ppm-1,000 ppm. 

Net-Biome-Productivity-NBP (= change in charcoal resiliant humus)... 

The quantity of litter input provides the second critical link between NPP and decomposition because NPP governs the quantity of organic matter inputs to decomposers. When biomes are compared at steady state, heterotrophic respiration (i.e., the carbon released by processing of dead plant material by decomposer organisms and animals) is approximately equal to NPP. In other words, net ecosystem production (NEP), the rate of net carbon sequestration, is approximately zero at steady state, regardless of climate or ecosystem type. This indicates that the quantity and quality of organic matter inputs to soils, as determined by... 

Table 2 Area, carbon in living biomass, and net primary productivity of major terrestrial biomes.

FIGURE 10 The relationships between evapotranspiration and net primary production as they emerge from the Century model, applied globally. The near-linear realtionship between evaporation and NPP, very similar to those observed In semi-arid lands, is an emergent property. The differences in slope between biomes are largely due to differences in the C N ratio of different plant functional types. Indicating that ecosystem composition has direct effects on biogeochemistry (Scholes et al., 1999). 

Table 6.1. Data on carbon storage and net primary productivity in the world s major biomes...

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