Source-sink dynamics

What evidence exists that the niche affects microbial distributions We surveyed the literature for studies examining either niche or distribution for organisms with propagules < 1-2 mm. While many studies report ecological differences between species, we focused our search on those studies of quantitative niche characteristics that cause spatial segregation between species or result in apparent distributional boundaries at some scale. All studies we found consistently reported niche differences or local adaptation at intra- or interspecific levels, consistent with the fundamental niche in all cases and potentially related to the realised niche in a few cases (Table 15.1). Given that niche constraints on local persistence/occurrence have been observed for microbes, it is reasonable to expect that niche affects distribution of multiple microbial species, consistent with the environment selects portion of the EiE claim (and with much of evolutionary ecology). Tests for source-sink dynamics or dispersal limitation as alternative explanations of microbial niche-distribution relationships will require that the fundamental niche for a species is already... 

Fig 15.2 Niche-distribution relationships, based on Pulliam (2002). Zeros represent absence, and ones represent presence in niche space (e.g. two ordination axes). (A) The fundamental (Grinnellian) niche (or potential niche, Jackson and Overpeck, 2000 Soberon and Nakamura, 2009) is related to abiotic interactions. (B) The realised niche sensu Hutchinson) is due to the combined influence of abiotic and biotic interactions, where the dashed line represents niche space of a second species. (C) Source-sink dynamics represent one alternative to (A) and (B), where sink populations outside the fundamental (or realised) niche exist due to immigration from source populations. 

CDOM dynamics in natural waters Sources, sinks, and... 

Especially important under dynamic conditions, the role of a system and of each component can be disclosed by appropriate measurements. Thus, it can be estabhshed when the system environment is ready for a dynamic use, eg, if the pump is likely to perform as a molecular sink, a source, or some combination of these. 

The humidity and contaminant transport calculation is based on the previously calculated airflows, applying again the principle of mass conservation for the species under consideration. For each time step, the concentrations are calculated on the basis of the airflows, the source and sink strengths in the zones, and the concentration values at the previous time step. In contrast to the airflow calculation, which is a steady-state calculation at each time step, the contaminant transport calculation is dynamic. Therefore, the accuracy of the concentration results depends on the selected time-step interval. 

Several techniques are available for thermal conductivity measurements, in the steady state technique a steady state thermal gradient is established with a known heat source and efficient heat sink. Since heat losses accompany this non-equilibrium measurement the thermal gradient is kept small and thus carefully calibrated thermometers and heat source must be used. A differential thermocouple technique and ac methods have been used. Wire connections to the sample can represent a perturbation to the measurement. Techniques with pulsed heat sources (including laser pulses) have been used in these cases the dynamic response interpretation is more complicated. 

In Section 23.1, this procedure will be applied to just one completely mixed water body. This control volume may represent the lake as a whole or some part of it (e.g., the mixed surface layer). Section 23.2 deals with the dynamics of particles in lakes and their influence on the behavior of organic chemicals. Particles to which chemicals are sorbed may be suspended in the water column and eventually settle to the lake bottom. In addition, particles already lying at the sediment-water interface may act as source or sink for the dissolved chemical. In Section 23.3, two-box models of lakes are discussed, particularly a model consisting of the water body as one box and the sediment bed as the other. Finally, in Section 23.4, one-dimensional vertical models of lakes and oceans are discussed. 

If we apply these equations to the condensation of a fission product in a cooling nuclear fireball, we must deal with sources from radioactive growth, sinks from radioactive decay, and dynamic conditions of temperature drop. In the simple case of radioactive decay... 

In principle, both vacancies and self-interstitials may occur simultaneously and somewhat independently. Indeed, any relationship between Cv° and C j° may be dominated by the Si surface, which can act as a source or sink for either species. If a local dynamical equilibrium exists between re-... 

Studies by Kondratyev et al. (2004a, b) showed that consideration of the spatial heterogeneity of sinks and sources of atmospheric carbon and specification of the parameters of its fluxes at the atmosphere-land and atmosphere-ocean boundaries raised the accuracy of estimates, but did little to remove either imbalances or differences between carbon fluxes and the dynamics of the change in C02 partial pressure in the terrestrial atmosphere. 

Can we identify the specific features involved in spatiotemporal variability of sources and sinks of carbon over North America on timescales from seasonal to secular, and what are the processes that affect carbon cycle dynamics the most ... 

Nicolis C. and Nicolis G. (1995). From short-scale atmospheric variability to global climate dynamics Toward a systematic theory of averaging. J. of Atm. Sci., 52(11), 1903-1913. Nielsen T.T. (1999). Characterization of lire regimes in the Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO) study area. J. Geophys. Res., 104(D23),... 

Reactions in a condensed phase are never isolated but under strong influence of the surrounding solvent molecules. The solvent will modify the interaction between the reactants, and it can act as an energy source or sink. Under such conditions the state-to-state dynamics described above cannot be studied, and the focus is then turned to the evaluation of the rate constant k(T) for elementary reactions. The elementary reactions in a solvent include both unimolecular and bimolecular reactions as in the gas phase and, in addition, bimolecular association/recombination reactions. That is, an elementary reaction of the type A + BC —> ABC, which can take place because the products may not fly apart as they do in the gas phase. This happens when the products are not able to escape from the solvent cage and the ABC molecule is stabilized due to energy transfer to the solvent.4 Note that one sometimes distinguishes between association as an outcome of a bimolecular reaction and recombination as the inverse of unimolecular fragmentation. 

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