Global carbon cycle fluxes, influencing

Rainwater and snowmelt water are primary factors determining the very nature of the terrestrial carbon cycle, with photosynthesis acting as the primary exchange mechanism from the atmosphere. Bicarbonate is the most prevalent ion in natural surface waters (rivers and lakes), which are extremely important in the carbon cycle, accoxmting for 90% of the carbon flux between the land surface and oceans (Holmen, Chapter 11). In addition, bicarbonate is a major component of soil water and a contributor to its natural acid-base balance. The carbonate equilibrium controls the pH of most natural waters, and high concentrations of bicarbonate provide a pH buffer in many systems. Other acid-base reactions (discussed in Chapter 16), particularly in the atmosphere, also influence pH (in both natural and polluted systems) but are generally less important than the carbonate system on a global basis. 

Shikazono, N. and Kashiwagi. H. (1999) Carbon dioxide flux due to hydrothermal venting from back-arc basin and island arc and its influence on global carbon dioxide cycle. 9th Annual V.M. Gohl.schmidt Conference, August 22-27. Harvard, Abstr., p. 272. 

In Chapter 3, hydrothermal and volcanic gas fluxes from submarine back-arc basins and island arc are estimated. These fluxes are compared with midoceanic ridge hydrothermal fluxes. Particularly, hydrothermal flux of CO2 is considered and the influences of this flux on global long-term carbon cycle and climate change in Tertiary-Quaternary ages are discussed in Chapter 4. 

This chapter is an attempt to give an account of the fundamental aspects of the carbon cycle from a global perspective. An outline of the details we shall encounter is shown in Fig. 11-1. After a presentation of the main characteristics of carbon on Earth, four sections follow a section about the carbon reservoirs within the atmosphere, the hydrosphere, the biosphere, and the lithosphere a section covering the most important fluxes between the reservoirs a section giving brief accounts of selected models of the carbon cycle and a final section describing cultural influences on the carbon cycle today. 

Other chapters in this volume have explored carbon cycles within and among ecosystems, especially their response to the global changes that are occurring on earth today. In this chapter, the focus shifts from factors that inlluence carbon flux dynamics to the ways in which the composition of the atmosphere and thermal environment influence the type of photosynthetic system that predominates within a terrestrial ecosystem. In turn, the kind of photo.synthetic. system present has signihcant impacts on the distribution of the grazing animals that are dependent on primary productivity generated acro.ss the land.scape, both in the. shortterm and over evolutionary time periods. 

Figure 1.5 extends this notion to the geochemical level which shows an estimate of the influence of the global biosphere carbon and oxygen cycles on the fluxes of major elements through the terrestrial reservoirs, and includes the effects of both primary and secondary biogeochemical processes. 

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