Modeling Heterotrophic Respiration in Missoula, MT

1. Modeling Heterotrophic Respiration in Missoula, MT Anne Trainor Exercise 2 September 20, 2007

2. Introduction • Plants produce detritus which becomes food for heterotrophic organisms • All biomass eventually enters detrital pool • Seasonal fluctuation • Difficult to directly measure because need to quantify root growth and maintenance

3. Methods • Biome-BGC • Study System: Missoula, MT • Meteorological Data: 1950-1993 • Evergreen Needleleaf system • Used all defaults except reset canopy intercept to 0.01 • Ran simulation for 88 years with spin up • Soil type: Loamy • 30% sandy, 50% silt, 20% clay • 1 m soil depth

4. Methods Cont. Selected a dry and wet year to compare extremes 1980: 49.9 1952: 22.6

5. Relevant Variables Modeled

6. No Relationship observed for HR in relation to Soil Pressure

8. LAI: Greater during summer of a wet year compared to dry year • HR: Fluctuates throughout the year with the only major differences between wet and dry year is ~ day 160

10. Discussion • There was a minimal variation in HR between an extremely wet and dry year • During wet years this is greater HR in relation to Soil Temperature and NPP

11. Conclusion • Heterotrophic respiration is a small portion of total respiration • Effected by disturbances and climate change because tight connection to upper soil horizons moisture and temperature • Important to continue field monitoring and modeling to examine HR in relation to disturbances