Atmosphere-vegetation models

Nemry, B., Francois, L., Warnant, P., Robinet, R. and Gerard, J.-C. (1996). The seasonality of the CO2 exchange between the atmosphere and the land biosphere A study with a global mechanistic vegetation model, /. Geophys. Res. 101, 7111-7125. 

Figure 3.7. The scheme for carbon fluxes in the model of the atmosphere-vegetation-soil system.

Are multiple ec[uilibria just a matter of the atmosphere-vegetation system, or do they occur also in the atmosphere-ocean—vegetation system So far, we have not yet found multiple solutions in the model of GanopoLski et al. (1998). (The model attains multiple solutions associated with multiple states of the thermohaline convection.) I blame this deficit on the coarse resolution of this model, because north Africa is represented by just three grid boxes, Sahara, Sudan, and tropical north Africa. Subsequently,... 

Levis, S., Foley, J. A., Brovkin, V., and Pollard, D. (1999). On the stability of the high-latitude climate-vegetation system in a coupled atmosphere-biosphere model. Global Ecol Biogeography, 8(6), 489-500... 

In the following discussion, factors used for the transfer of from soil to plants and from animal feeds to animal products are those assembled by Soldat for the study of the potential doses to people from a nuclear power complex in the year 2000 (Fletcher and Dotson, 1971). Although a number of models for the environmental transport of radioiodine exist in the scientific and technical literature (many of them for the atmosphere — vegetation -> cow — milk — person pathway for 1), the concepts and values from the many other available models are similar to those presented in the Fletcher and Dotson report. 

Selection of pollution control methods is generally based on the need to control ambient air quaUty in order to achieve compliance with standards for critetia pollutants, or, in the case of nonregulated contaminants, to protect human health and vegetation. There are three elements to a pollution problem a source, a receptor affected by the pollutants, and the transport of pollutants from source to receptor. Modification or elimination of any one of these elements can change the nature of a pollution problem. For instance, tall stacks which disperse effluent modify the transport of pollutants and can thus reduce nearby SO2 deposition from sulfur-containing fossil fuel combustion. Although better dispersion aloft can solve a local problem, if done from numerous sources it can unfortunately cause a regional one, such as the acid rain now evident in the northeastern United States and Canada (see Atmospheric models). References 3—15 discuss atmospheric dilution as a control measure. The better approach, however, is to control emissions at the source. 

Taha, H. (1996). Modeling the Impacts of Increased Urban Vegetation on the Ozone Air Quality in the South Coast Air Basin. Atmospheric Environment 3(1 20) 3423—3430. 

Once the model was complete, it was adjusted to a steady state condition and tested using historic carbon isotope data from the atmosphere, oceans and polar ice. Several important parameters were calculated and chosen at this stage. Sensitivity analysis indicated that results dispersal of the missing carbon - were significantly influenced by the size of the vegetation carbon pool, its assimilation rate, the concentration of preindustrial atmospheric carbon used, and the CO2 fertilization factor. The model was also sensitive to several factors related to fluxes between ocean reservoirs. 

Several studies, based on models, examined the effects of land-use change on the global carbon cycle and conclude that there is a net release of carbon due to land clearing. However, the results and conclusions of these studies are based on assumed sizes of vegetation carbon pools which are inputs to the models. For example, Melillo et al. 24) concluded that boreal and temperate deciduous forests of the northern hemisphere are net sources of atmospheric carbon. Their analysis used values for carbon density derived by Whittaker and Likens 19) from work by Rodin and Bazilevich (27). Rodin and Bazilevich extrapolated results of small, unrelated studies in Europe and the USSR to estimate total biomass of Eurasian boreal and temperate deciduous forests. Their estimates have since been extrapolated to forests worldwide and are used often today. 

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