Gross primary productivity

Predicting the effect of the terrestrial vegetation response to C02-induced climate change for a particular site involves explicit treatment of feedbacks. These are diagramed in Figure 3. The balance between decomposition + autotrophic respiration and gross primary production (GPP) determines the net storage and release of carbon to atmosphere. Climate meets each of these... 

Gross primary production (GPP) is the total rate of photosynthesis including organic matter... 

Many estimates of total terrestrial net primary production are available, ranging between 45.5 Pg C/yr (Lieth, 1972) and 78 Pg/yr (Bazilevich et al., 1970). Ajtay ef oZ. (1979) have revised the various estimates and methods involved, they also reassess the classifications of ecosystem types and the extent of the ecosystem surface area using new data and arriving at a total NPP of 60 Pg C/yr. Gross primary production is estimated to be twice net primary production, i.e., 120 Pg C/yr. This implies that about 60 Pg C/yr are returned to the atmosphere during the respiratory phase of photosynthesis. It is well known that carbon dioxide uptake by plants follows daily cycles most plants take up CO2... 

B. (1995). Monitoring seasonal and interannual variations of gross primary productivity, net primary productivity and net ecosystem productivity using a diagnostic model and remotely-sensed data, Tellus, Ser. B, 47,178-190. 

Myneni, R. B., Los, S. O. and Asrar, G. (1995). Potential gross primary productivity of terrestrial vegetation from 1982-1990, Geophys. Res. Lett. 22, 2617-2620. 

Nutrient Higher concentration eutrophication Primary producers Potential bottom up-effects Higher gross primary production Lower efficiency on materials processing... 

River functioning (globally expressed as metabolism) does not often show unidirectional responses to stress, and therefore makes difficult the prediction of changes. Gross Primary Production (GPP) may be first enhanced because the decrease of water flow may result in shallower water depths and lead to more underwater light... 

Table 13.6 Annual average rates of gross primary production, total respiration, and net ecosystem metabolism (NEM) (g O2 m-2d-1) at National Estuarine Research Reserve (NERR) sites.

Gross primary production the amount of carbon fixed (CO2 converted into organic matter) by photosynthetic organisms (per unit time per unit volume). 

Unknown allocation in Ryan et al. (1996) invoked to close mass balance was interpreted by Waring and Running (1998) as allocation to mycorrhizal fungi and exudates. NPP is net primary production, GPP is gross primary production. 

Figur 33 1 Physical and biological upwelling response simulated by the Wroblewski (1977) 2-dimensional coastal upwelling model (A) The circulation in the transverse plane normal to the coast, the bottom topography, and the wind stress. The maximum u and w velocities in the field are —2.9 cm s and 1.4 x 10 cm s , respectively. (B) The daily gross primary production of the water column. (C) The distribution of phytoplankton. Contour intervals are 1 jimol N 1. Redrawn with permission from Wroblewski (1977).

Each year the atmosphere exchanges —120 Pg C with terrestrial ecosystems through photosynthesis and respiration (Eigure 1 and Table 1). The uptake of carbon through photosynthesis is gross primary production (GPP). At least half of this production... 

Fig. 3.5 Relationships between phytoplanktonic production, respiration and depth (after Lalii Parsons 1997).The compensation depth is where the rate of respiration equals that of production.The critical depth is where the total respiration in the water column above equals the gross primary production (i.e. the areas under the two shaded curves are equal).

In the atmosphere carbon exists mainly as carbon dioxide (Fig. 6.1), which is taken up by plants during photosynthesis.The amount of solar energy captured by plants during photosynthesis is referred to as gross primary production and can be measured by the amount of carbon dioxide that has been fixed. As noted in Section... 

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