Microbes uptake rate

Oxygen uptake rate by microbes [Oxygen Accumulation rate... 

Several studies have measured DFAA concentrations and turnover (see Chapter 4 and Munster, 1993), but here we concentrate on those that compare DFAA uptake with bacterial production. The fraction of bacterial production supported by DFAA is one index for the relative importance of amino acids, not only in supporting bacterial growth but also in the overall flux of DOM. ( Flux is used here to indicate both production and uptake in a quasi-steady state.) If DOM concentrations are constant, DOM production will equal total uptake rates by microbes there is no evidence of photo-oxidation of amino acids and of the other compounds discussed here (see Chapter 10). Total uptake includes respiration and assimilation into biomass. Here assimilation is defined as the appearance of a radioactive compound in cells (both cellular LMW and HMW pools) respiration is excluded. 

The quantities of nutrients in microbes are large compared with the annual plant nutrient uptake, suggesting that even relatively limited dieback of the microbial populations can lead to release of an appreciable proportion of the plants annual nutrient requirement. Indeed, it is known that the annual uptake of P by wet tundra vegetation can be almost entirely accounted for by P released through nutrient flushes from the microbial biomass (Chapin et al, 1978). It is possible, therefore, that the supply rate of nutrients to the soil inorganic pool varies depending on the conditions for microbial population growth or decline and that plant nutrient availability fluctuates inversely to microbial nutrient demand. 

Mineralization The conversion of organic nitrogen to its mineral forms (NH4 or NOj ) during decomposition. Gross N mineralization is the gross rate of the process, which can be determined using dilution. Net N mineralization is gross N mineralization minus N immobilization or uptake by microbes. 

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