1. Examining the Accuracy of Nutrient Cycles in Climate Models
Lena Dubitsky, Medvigy Research Group

2. Why is understanding soil important?
Decomposition is a vital part of the carbon cycle
Releases nitrogen
Current decomposition models are mostly untested
Goal: examine different models and try to improve accuracy with in-field results

3. Current soil cycles DAYCENT model
- above and below ground are separate
processes
- 2 litter pools
- varying number of soil organic matter pools
Current soil cycles
Cascade Model
- no distinction between
above and below ground
- 3 litter pools
- 3 soil organic matter pools

4. Cascade Carbon Model

5. Methods Simple, 2 pool carbon-only system
Calculate total carbon in each time step
Vary decomposition fractions using LIDET data
Used LTER Intersite Fine Litter Decomposition Experiment (LIDET), 10 year study in North and Central America
Methods

6. Old values for Litter and Soil Organic Matter pools: 0. 7 (LIT1), 0
Old values for Litter and Soil Organic Matter pools: 0.7 (LIT1), (SOM1)
New optimized values: (LIT1), (SOM1)
Results supported by Bonan (2013)
Optimization

7. Final Thoughts Good introduction to Fortran, MATLAB and optimization
Program structure of climate models
Challenges of creating realistic results
Understanding of how plants utilize carbon and nutrients, how that might change in the future with climate change
Think critically about the soil model
Final Thoughts

8. Acknowledgements
Thanks to Professor Medvigy and his entire research group, Xiangtao, and Kelly