North American forest ecosystems

In the USA, two focal points for biogeochemical research have been the forest catchment ecosystems at Hubbard Brook Experimental forest in the White Mountains of 

Fluxes and pools Northern Taiga Spruce Forest Southern Taiga Spruce Forest Sub-Boreal Oak Forest Southern Taiga Sphagnum Swamp 

New Hampshire and Coweeta Hydrologic Laboratory, located in the southern Appalachians of North Carolina. 

one should mention that the quantitative estimates of various links of biogeochemical cycles of elements and their interactions are of crucial importance for environmental risk assessment for the given ecosystems under anthropogenic pressure. 

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Nitrogen is the most commonly limiting nutrient in North American forest ecosystems (20, 21). The form of N used by terrestrial ecosystems strongly affects the acidifying potential of N deposition (Figure 1). Ammonium uptake is an acidifying process (i.e., uptake of NH4+ releases 1 mole of H per mole of N assimilated). 

Glycine mineralization in situ closely correlates with soil carbon availability across six North American forest ecosystems. Biogeochemistry 99 175-191... 

North American Forest-Meadow Steppe ecosystems... 

This part of Tundra ecosystems covers the northern coasts of the continent and the southern part of the North American archipelago. In the north it is bounded by the Arctic desert and in the south by the Boreal Taiga Forest ecosystems. 

According to the type of biogeochemical turnover, the North American part of Boreal Taiga Forest ecosystems is subdivided into two large geographical regions the Laurentian and the Alaskan-Cordillera. 

Boreal forest ecosystems provide the raw materials for lumber/pulp industries in Canada, Scandinavia and Russia. Unlike tropical forests, they receive relatively little publicity but are subject to as many threats deforestation is rife in the Russian Far East and Siberia and there are concerns about the sustainability of North American and Scandinavian boreal forests because of lumbering industries, as discussed in Section 6.2.2 below. 

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