Closed System Thermodynamics
•1st Law of Thermodynamics – Irreversible processes result in spontaneous conversion of internal energy to heat and work – At equilibrium a state of minimum internal energy is attained –Enthalpy Closed System Thermodynamics
•2nd Law of Thermodynamics – All isolated systems will spontaneously approach a state of equilibrium – Entropy Open System Thermodynamics
• Natural setting – only closed system is the entire universe • Most natural bodies/systems are open – allowing energy/material to flow into and out of them • Natural systems – highly ordered and energy rich – goes against idea of increasing entropy and decreasing enthalpy
Equilibrium versus Steady State
• Closed systems – move towards equilibrium – time invariant state with entropy maximization
• Open systems – move towards steady- state and entropy minimization Energy Source Energy Flow Energy Sink
Dissipative Processes E ppt Soil System • Respiration • Humus Decomposition
Enpp • Mineral Weathering • Leaching • Erosion
Ordering Processes • Humus Accumulation • Structure Formation • Horizonation •Illuviation–Eluviation • 2º Mineral Formation
Pedogenic Trajectory
• Rasmussen et al. (2005)
Testing hypothesis that if soils are open systems, one should be able to quantify soil forming environment and soil development based on energy flux into the soil system Energy Source Energy Flow Energy Sink
Dissipative Processes E ppt Soil System • Respiration • Humus Decomposition
Enpp • Mineral Weathering • Leaching • Erosion
Ordering Processes • Humus Accumulation • Structure Formation • Horizonation •Illuviation–Eluviation • 2º Mineral Formation • How to quantify energy flux?
– Effective precipitation
– Biologic production
• Water balance • Timing of precipitation 300000
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Calculated energy flux versus quantitative Si flux data from White and Blum
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-1 -2 Pedogenic Trajectory Table 3. Average slope for soil orders† High slope and landscape Soil Order Slope %‡ stability Andisol 26 (2.1) a Inceptisol 26 (1.2) a Impacts on pedogenic Spodosol 26 (3.4) ab trajectory and degree of Entisol 15 (1.1) bc soil development Mollisol 12 (0.5) cd Alfisol 10 (0.7) de Ultisol 10 (0.5) e Aridisol 9 (1.9) cde †Average of map unit slope from STATSGO ‡Values in parentheses are standard errors of the mean. Pairwise comparison done with Tamhane post-hoc test (95% confidence interval). Slopes followed by the same lowercase letter are not significantly different. Ein (kJ m-2 yr-1) High : 162,260
Low : 0
Figure 1. EIN for the continental U.S. Calculated using the PRISM dataset (30 yr average MAP and MAT, 1971-2000)