Abstract. In the absence of hwnan activities, biotic fiXation is the primary source of reactive N, providing about 90-130 Tg N yr-l (Tg-1012 g) on the continents. Hwnan activities have resulted in the fiXation of an additional::: 140 Tg N yr-l by energy production (:::20 Tg N yr-l), fertilizer

Abstract. We re-examine what controls the deep ocean N:P ratio in the light of recent findings that the C:N:P stoichiometry of phytoplankton varies with growth rate, nutrient and light limitation, species and phylum, and that N2-fixation may be limited by Fe, temperature and/or light in large parts

Significant amounts of soil nitrogen (N) are lost from the soil during timber harvesting and related activities. Sym-biotic N-fixing plants have the potential to replace much of these N losses on many sites in the Inland Northwest, espe-cially during early stand development. However, many

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differentially expressed genes indicated that several biological functions were affected. Systemin promotes the expression of an array of defense genes that are dependent on different signaling pathways and it downregulates genes connected with carbon fixation and carbohydrate metabolism. These alterations

and freshwater systems examined, the formation and mainte-nance of microzones were shown to override both trace metal and phosphorus availability as factors regulating magnitudes of N, fixation. The degree to which development of microzone-scale sym-biotic cyanobacterial-bacterial interactions occur in aquatic

fixative microorganisms, aerobic and anaerobic flora Eukaryotic and prokaryotic organisms are found in the soil and a complex interdependency is established between them, the stability and dynamics of which con-ditions the physical-chemical parameters of the soil. The latter along with abiotic and biotic

oceanic sequestration of atmospheric carbon dioxide. As one component of an integrated ‘Nitrogen Transport and Transformations ’ project, we have begun to re-assess our understanding of (1) the biotic sources and rates of N2 fixation in the world’s oceans, (2) the major controls on rates of oceanic N2

that multiple a-biotic environmental variables including nutrients DIN, dissolved organic nitrogen (DON) and DIP, trace metals like dissolved aluminum (DAl), as a proxy of dust inputs, dissolved iron (DFe) and Fe-binding ligands as well as oxygen and temperature influenced N2 fixation rates and the distribution

Coastal salinas (solar salterns) are human-made environments that comprise an array of evaporation ponds of increasing sali-nities. Therefore, salinas are appropriate systems to study the biotic communities and the different biogeochemical processes in relation to the water column salinity