Cycling studies terrestrial

Despite their critical role in biogeochemical cycles in terrestrial ecosystems, the relationships between root activity, mineral weathering and the bioavailability of metals are largely unknown. Hence, a study was designed to establish the impact of root activity on mineral weathering, and to determine its consequences for the spatial distribution of trace metal forms in the vicinity of roots. 

Various aspects of mineral and nutrient cycling in terrestrial systems are, generally speaking, more easily studied in plant and invertebrate populations than in the more mobile, lower-density populations of vertebrates, particularly the higher forms of vertebrates. Consequently, the literature stresses the former, and this will be reflected in our discussions. 

The Table of Contents for this collection will facilitate this discussion. Notice that the papers are grouped into the categories of Atmospheric, Aquatic and Terrestrial Components, Global Carbon Cycle and Climate Change, and Global Environmental Science Education. The reader may want to consider the various chemical species studied in each paper. Next, the reader may wish to group the papers by whether they address the source or the receptor, the transport or transformation processes for the chemical species. Finally, the reader needs to establish the time scales and the spatial resolution used. 

The exchange of CO2 between the atmosphere and terrestrial biota is one of the prime links in the global carbon cycle. This is seen by studying the variations of C in the atmosphere. Figure 11-14 presents atmospheric A C for the years... 

ABSTRACT The locations, magnitudes, variations and mechanisms responsible for the atmospheric C02 sink are uncertain and under debate. Previous studies concentrated mainly on oceans, and soil and terrestrial vegetation as sinks. Here, we show that there is an important C02 sink in carbonate dissolution, the global water cycle and photosynthetic uptake of DIC by aquatic ecosystems. The sink constitutes up to 0.82 Pg C/a 0.24 Pg C/a is delivered to oceans via rivers and 0.22 Pg C/a by meteoric precipitation, 0.12 Pg C/a is returned to the atmosphere, and 0.23 Pg C/a is stored in the continental aquatic ecosystem. The net sink could be as much as 0.70 Pg C/a, may increase with intensification of the global water cycle, increase in C02 and carbonate dust in atmosphere, reforestation/afforestation, and with fertilization of aquatic ecosystems. Under the projection of global warming for the year 2100, it is estimated that this C02 sink may increase by 22%, or about 0.18 Pg c/a. 

Previous studies addressed oceans and terrestrial vegetation as C02 sinks. Here, we describe an important C02 sink in carbonate dissolution, the global water cycle (GWC), and uptake of dissolved inorganic carbon (DIC) by aquatic. The sink is larger than previous estimates (Meybeck 1993 Gombert 2002). 

Ehleringer JR (1991) 13C/12C fractionation and its utility in terrestrial plant studies. In Coleman DC, Fry B (eds) Carbon isotopic techniques. Academic, New York, pp 187-200 Ehleringer JR, Buchmann RN, Flanagan LB (2000) Carbon isotope ratios in belowground carbon cycle processes. Ecol Appl 10 412-422... 

Naturally occurring stable isotopes of C, N, and S have been used extensively for over a decade as direct tracers of element cycling in marine and terrestrial food webs (34-39). Carbon and sulfur isotopes fractionate very little between food and consumer thus their measurement indicates which primary producers or detrital pools are sources of C and S for consumers. For example, a study of plants and animals in Texas sand dunes showed that insect species had 813C values either like those of C3 plants or like those of C4 plants (-27 and -13%o, respectively). Rodent species had intermediate values near -20%o that indicated mixed diets of both C3 and C4 plants (40). The 13C measurements, used in simple linear mixing models, proved to be quick and reliable indicators of which plant sources provided the carbon assimilated by higher trophic levels. 

Variations in the biochemistry and physiology of fish from one year to another must be accepted as real. Such a cycle would be linked to long-term changes in the climate resulting from solar activity (Chizhevsky, 1976). The trouble is that observations are insufficiently representative to yield clear patterns. As with diurnal variation, much of the published work relates to terrestrial organisms rather than fish, and much of the study has centred on fluctuations in the abundance of species which tend to develop outbreaks - sudden marked increases in numbers. However, fish such as salmon, cod, herring, sardines and other species have also been shown to exhibit long-term fluctuations in their numbers. Klyashtorin (1996) has found a close correlation between the velocity of rotation of the earth, which affects the intensity of circulation of the water in the oceans, and the abundance of stocks of many species of fish. 

Some plants are also known to emit dimethyl sulfide, DMS, (13.371. carbonyl sulfide, COS, (291. and carbon disulfide, CS (13.37-411. and possibly ethyl mercaptan (40.411. A study conducted in a tropical rain forest which focused on Stryphnodendron excelsum is trteated in more detail in a following chapter (411. It is quite possible that additional studies as described in Chapter 5 (411 will lead to die discovery of other terrestrial "hot spots which may be important in biogenic sulfur cycling. 

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