Spatially varying biogeochemistry

[kmdeck]

Is your feature request related to a problem? Please describe.
The soil biogeochemistry model does not support spatially varying parameters. That means that we currently have a mismatch in soil porosity between biogeochemistry and the full soil model in global runs.
#591

Describe the solution you'd like
Spatially varyin biogeochemistry parameters consistent with the soil. To do this, store porosity, theta_100, and b inside the PrognosticMet struct. either pass directly, or compute from van genuchten