Respiration heterotrophic

The subsequent fate of the assimilated carbon depends on which biomass constituent the atom enters. Leaves, twigs, and the like enter litterfall, and decompose and recycle the carbon to the atmosphere within a few years, whereas carbon in stemwood has a turnover time counted in decades. In a steady-state ecosystem the net primary production is balanced by the total heterotrophic respiration plus other outputs. Non-respiratory outputs to be considered are fires and transport of organic material to the oceans. Fires mobilize about 5 Pg C/yr (Baes et ai, 1976 Crutzen and Andreae, 1990), most of which is converted to CO2. Since bacterial het-erotrophs are unable to oxidize elemental carbon, the production rate of pyroligneous graphite, a product of incomplete combustion (like forest fires), is an interesting quantity to assess. The inability of the biota to degrade elemental carbon puts carbon into a reservoir that is effectively isolated from the atmosphere and oceans. Seiler and Crutzen (1980) estimate the production rate of graphite to be 1 Pg C/yr. 

Thompson, M. V., Randerson, J. T., Malmstrom, C. M. and Field, C. B. (1996). Change in net primary production and heterotrophic respiration How much is necessary to sustain the terrestrial carbon sink . Global Biogeochem. Cycles 10, 711-726. 

Microorganisms at aqueous-solid phase interfaces have different respiration modes which include (a) aerobic heterotrophic, (b) aerobic autotrophic, (c) facultative anaerobic heterotrophic, (d) facultative anaerobic autotrophic, and (e) anaerobic heterotrophic respiration modes [36,41,43,47, 55]. Table 3 shows the main differences between these different respiration modes. 

Aerobic Many microorganisms on solid phases undergo aerobic heterotrophic heterotrophic respiration (e.g., Pseudomonas and Bacillus), as follows ... 

When nitrification occurs 4.57 gram oxygen are used per gram of ammonia nitrogen oxidised. Thus the total oxygen demand is then the sum of the autotrophic and heterotrophic respiration rates. 

The metabolic machinery responsible for the heterotrophic respiration reactions is contained in specialized organelles called mitochondria. These reactions occur in three stages (1) glycolysis, (2) the Krebs or tricarboxylic acid cycle, and (3) the process of oxidative phosphorylation also known as the electron transport chain. As illustrated in... 

In the anoxic zone, heterotrophic respiration of particulate Mn02 and Fc203 or FeOOH causes manganese and iron to be reduced to Mn (aq) and Fe (aq). As dissolved ions, these trace metals diffuse through the pore waters. The ions that diffuse upwards will reenter the oxic zone, where they react with O2 to reform the oxyhydroxides. This produces a metal-enriched layer that lies just above the redox... 

Despite its importance in ecosystem C fluxes, soil respiration has limitations as a constraint on SOM turnover, for two main reasons. First, it is difficult to partition soil respiration into its two sources (1) decomposition of SOM by microbes (heterotrophic respiration) and (2) respiration from live plant roots (autotrophic respiration) (Kuzyakov, 2006). As a result, an increase in soil respiration may indicate not only an increase in SOM decomposition but also an increase in root respiration. Second, it is likely that in most soils only a small fraction of total SOM contributes to heterotrophic respiration. As a result, respiration measurements provide information about the dynamic fraction of SOM (particularly when combined with 14C measurements of respiration) but do not provide information about the large, stable pools unless they are destabilized and contribute to respiration (detectable with 14C02 respiration measurements). Attributing the sources of respiration from different SOM reservoirs, which may respond differently to climatic variables, is not... 

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. 

Bhupinderpal-Singh, Nordgren, A., Ottoson-Lofvenius, M. et al. (2003). Tree root and soil heterotrophic respiration as revealed by girdling of boreal Scots pine forest extending observations beyond the first year. Plant, Cell and Environment, 26, 1287-96. 

If El Nino conditions persisted for several years, however, this effect of drought-causecf heterotrophic respiration of the land biota would disappear. The balance between the mid-latitude areas of net CO2 flux... 

Heterotrophic respiration fueled by the rain of organic matter from the surface ocean is ubiquitous in marine sediments. Its rate determines one of the important characteristics of the sedimentary environment the depth of redox horizons below the sediment-water interface. Heterotrophic respiration is the process by which carbon and nutrients are returned to the water column it is important in the marine fixed nitrogen and sulfur cycles and the accumulation of metabolic products sets the conditions for the removal of phosphorus from the oceans in authigenic minerals. A great deal of effort has been directed toward quantifying the rates, pathways, and effects of metabolism in sediments. 

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... 

Microorganisms. Microorganisms are the primary agent of carbon mineralization in the detritus-soil continuum. Greater than 90% of total heterotrophic respiration is attributable to the metabolic activity of the microflora (Foissner, 1987). While acknowledging that microorganisms... 

Figure 15.6. Photosynthesis and respiration, (a) A well-balanced ecosystem may be characterized by a stationary state between photosynthetic production, P (rate of production of organic material) and heterotrophic respiration, R (rate of destruction of organic matter). Photosynthetic functions and respiratory functions may become vertically segregated in a lake or in the sea. In the surface waters the nutrients become exhausted by photosynthesis, (b) The subsequent destruction (respiration) of organism-produced particles after settling leads to enrichment of the deeper water layers with these nutrient elements and a depletion of dissolved oxygen. The relative compositional constancy of the aquatic biomass and the uptake (P) and release (R) of nutritional elements in relatively constant proportions (see equation 3) are responsible for a co-variance of carbon, nitrate, and phosphate in lakes (during stagnation period) and in the ocean an increase in the concentration of these elements is accompanied by a decrease in dissolved oxygen, (c, d) The constant proportions AC/AN/AP/AO2 typically observed in these waters are caused by the stoichiometry of the P-R processes.

Marra, J. and R. T. Barber (2004) Phytoplankton and heterotrophic respiration in the surface layer of the ocean. Geophys. Res. Lett. 31, L09314, doi 10.1029/ 2005GLO19664. 

Balance Between Photosynthesis and Respiration. We may consider a stationary state which involves photosynthetic production, P = dp/dt (rate of production of organic material) and heterotrophic respiration, R (rate of destruction of organic material) (Figure 3). We can characterize this steady state chemically by a simple stoichiometry ... 

The soil/groundwater determining the isotopic composition of CO2 generated by heterotrophic respiration. 

Terrestrial and oceanic biospheric processes drive with similar relative weight the 0/" 0 ratio of atmospheric O2. The most important effect is the fractionation occurring during consumption of O2 by heterotrophic respiration. This fractionation leads to a global atmospheric 0/ 0 isotope ratio enriched by about 23.5%... 

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