1.018/7.30J Ecology of the Earth System Readings : Lecture 7 Notes –Biogeochemical cycles Readings: Smith&Smith Chapter 25 514-523 and Chapter 26 525-537 (C cycle) Galloway, et al.Transformation of the Nitrogen Cycle: …. Science 320, 889 (2008) Oki, et al. Global Hydrological Cycles and World Water Science 313, 1068 (2006) Filippelli, The Global Phosphorus Cycle: Past, Present, and Future. Elements, Vol. 4, pg. 89-95 How much of an element or compound is present in a certain component of the biosphere? What is the global amount, the reservoirs, the compounds and their transformations ? The movements between reservoirs are fluxes. How much of an element or compound moves from one reservoir per unit time? 1.Global geochemical cycles are assessed in terms of fluxes and reservoirs. Typical fluxes range > teragrams (1012g) per year. 2. The different cycles of the elements (P, S, N, C) vary in terms of their major reservoirs, rates of flux, and biological interaction. 3.Change in valence (redox state) caused by biological processes greatly influence elemental paths in several biogeochemical cycles. 4.Human activities are influencing the flux within some elemental cycles on the same scales as all natural processes combined (P, N, S).