add new pft physiology from NGEE-Arctic IM4

[peterdschwartz]

Description: Plant functional type definition and physiological changes for improved arctic vegetation representation. (1) flexible Arctic PFT definitions, currently 12 PFTs, with lifeforms of non-vascular, woody, graminoid, or cropped, plus properties such as climate-zone, N-fixer, and needle-leaf type; (2) allow dormancy of root respiration during winter period; (3) add 'Rhizome' as coarse root for non-woody PFT; (4) Allow evergreen PFT to have storage pool as well; and (4) Allow N fixation parameterized for individual PFT.

[peterdschwartz]

• [x] Some forcing files still need to be added to data server
• [x] Refactor duplicated code into functions
• [ ] clean-up comments

[peterdschwartz]

@fmyuan I think it'd be best if you or someone from the NGEE-Arctic team wrote the PR description.

[fmyuan]

@fmyuan I think it'd be best if you or someone from the NGEE-Arctic team wrote the PR description.

I will. And I believe Ben already put something into E3SM repo/archive, but let me check.

[fmyuan]

IM4 new feature overview.pdf I attached Ben Sulman's overview on the features included in this PR.