Phosphorus cycle terrestrial

Cuevas, E., and E. Medina. 1990. Phosphorus/nitrogen interactions in adjacent Amazon forests with contrasting soils and water availability." In Phosphorus Cycles in Terrestrial and Aquatic Ecosystems, eds. H. Tiessen, D. Lopez-Hernandez, and I.H. Salcedo (Proc. SCOPE-UNEP Regional Workshop 3 South and Central America. Saskatchewan Institute of Pedology. Saskatoon, Canada), pp. 83-94. 

Phosphorus Cycling in Terrestrial Aquatic Systems Lakes, Rivers, and Estuaries... 

Filippelli G. M. and Souch C. (1999) Effects of climate and landscape development on the terrestrial phosphorus cycle. Geology 27, 171-174. 

The role of the atmosphere in the phosphorus cycle seems to be poorly understood. Since it does not exist in the form of stable gaseous compounds, phosphorus in the atmosphere is either adsorbed on particulate matter, e.g. dust (including pollen) and exhaust fumes or dissolved in sea-spray. The fallout of phosphorus, as dry deposition and precipitation, has been estimated to be within the range 3.6—9.2 Tg P y for terrestrial ecosystems, 0.054— 0.140 Tg P y for freshwater ecosystems, and 2.6—3.5 Tg y" for the marine ecosystem. This gives a total fallout from the atmosphere of 6.3—12.8 Tg P y i (Pierrou, 1976). It should be noted, however, that Emery et al. (1955)... 

Box 5. Conceptual models of sub-global phosphorus cycles (after Jahnke, 1992) Conceptual ideas behind simulation of P cycling are related to the construction of models for freshwater terrestrial ecosystems and a generalized oceanic system and understanding the restrictions of its application. 

SiBBESEN E (1989) Phosphorus cycling in intensive agriculture with special reference to countries in the temperate zone of western Europe. In Thiessen H, Syers JK, Ryszkowski L and Golterman HL, eds. Phosphorus cycle in terrestrial and aquatic ecosystems, pp. 221-228. Saskatchewan Institute of Pedology, Saskatoon. 

Svobodnikowa OV (1989) Phosphorus in Agroecosystems. In Phosphorus cycle in terrestrial and aquatic ecosystems, pp. 163-167. Saskatchewan Institute of Pedology, Saskatoon. 

Fig. 6.1. Abiotic reactions involved in the biogeochemical cycle of organic phosphorus in terrestrial and aquatic environments.

Plants are a key component of the phosphorus cycle in terrestrial ecosystems, because they contain a significant pool of phosphorus. Plants are also an important route for the incorporation of phosphate... 

In addition to providing water and physical support for plants, soil properties and processes regulate the cycling, retention and bioavailability of the major elements (Daily et al., 1997). Most of the phosphorus in terrestrial ecosystems is present in the soil. On a global scale it has been estimated that soil contains 96-160 X 10 Mg of phosphorus compared with only 2.6X10 Mg in biota (Stevenson and Cole, 1999). The proportion of total ecosystem phosphorus present in soil varies widely. For example, in a grazed permanent pasture, herbage phosphorus represented only 1% of the total phosphorus in topsoil (0-20 cm) (Williams and Haynes,... 

Fig. 15.1. Conceptual flow diagram for phosphorus cycling in terrestrial systems. This diagram is a modified version of a figure presented by Gijsman et al. (1996). 

Although phosphorus is the eleventh most abundant element in the Earth s crust, where it forms approximately 1120 mg kg , it is geochemically classed as a trace element [1,2]. In the lithosphere, it occurs as phosphates, and these may be leached by weathering processes into the hydrosphere. Phosphorus may then be precipitated as insoluble metal phosphates, which are incorporated into sediments and cycled on a geological timescale (millions of years), or it can participate in the rapid terrestrial and aquatic biological phosphorus cycles. 

Feedbacks may be affected directly by atmospheric CO2, as in the case of possible CO2 fertilization of terrestrial production, or indirectly through the effects of atmospheric CO2 on climate. Furthermore, feedbacks between the carbon cycle and other anthropogenically altered biogeochemical cycles (e.g., nitrogen, phosphorus, and sulfur) may affect atmospheric CO2. If the creation or alteration of feedbacks have strong effects on the magnitudes of carbon cycle fluxes, then projections, made without consideration of these feedbacks and their potential for changing carbon cycle processes, will produce incorrect estimates of future concentrations of atmospheric CO2. 

The land biota reservoir (3) represents the phosphorus contained within all living terrestrial organisms. The dominant contributors are forest ecosystems with aquatic systems contributing only a minor amount. Phosphorus contained in dead and decaying organic materials is not included in this reservoir. It is important to note that although society most directly influences and interacts with the P in lakes and rivers, these reservoirs contain little P relative to soil and land biota and are not included in this representation of the global cycle. 

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