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A New Ecology - Systems Perspective - Chapter 6

6 Ecosystems have complex dynamics (growth and development) 6.1 VARIABILITY IN LIFE CONDITIONS All known life on earth resides in the thin layer enveloping the globe known as the ecosphere. This region extends from sea level to 10 km into the ocean depths and approximately | Else_SP-Jorgensen_ch006.qxd 4 12 2007 17 59 6 Ecosystems have complex dynamics growth and development Openness creates gradients Gradients create possibilities What you gain in precision you lose in plurality Thermodynamics and Ecological Modelling 2000 S.E. Jorgensen ed. 6.1 VARIABILITY IN LIFE CONDITIONS All known life on earth resides in the thin layer enveloping the globe known as the ecosphere. This region extends from sea level to 10km into the ocean depths and approximately the same distance up into the atmosphere. It is so thin that if an apple were enlarged to the size of the earth the ecosphere would be thinner than the peel. Yet a vast and complex biodiversity has arisen in this region. Furthermore the ecosphere acts as integrator of abiotic factors on the planet accumulating in disproportionate quantities particular elements favored by the biosphere Table 6.1 . In particular note that carbon is not readily abundant in the abiotic spheres yet is highly concentrated in the biosphere where nitrogen silicon and aluminum while largely available are mostly unincorporated. However even in this limited domain the conditions for living organisms may vary enormously in time and space. The climatic conditions 1 The temperature can vary from-----70 to 55 centigrade. 2 The wind speed can vary from 0km h to several hundred km h. 3 The humidity may vary from almost 0-100 percent. 4 The precipitation from a few millimeter in average per year to several meter per year which may or may not be seasonally aligned. 5 Annual variation in day length according to latitude. 6 Unpredictable extreme events such as tornadoes hurricanes earthquakes tsunamis and volcanic eruptions. 103 Else_SP-Jorgensen_ch006.qxd 4 12 2007 17 59 e 104 104 A New Ecology Systems Perspective Table 6.1 Percent composition spheres for five most important elements Lithosphere Atmosphere Hydrosphere Biosphere Oxygen 62.5 Nitrogen 78.3 Hydrogen 65.4 Hydrogen 49.8 Silicon 21.22 Oxygen 21.0 Oxygen 33.0 Oxygen