fix-ups to appendix plots

[teixeirak]

@beckybanbury ,

• [x] Figs. S8-S9 (growing season climate) currently have climate variables labeled as MAT, MAP... please fix labels to growing season climate variables (see my new abbreviations in Table S1)
• [x] include units on x-axes
• [x] dashed lines at y=0 (figs. S5-S7) are confusing. See issue #83. Helene interpreted them as y=0, not regressions (but there seems to be at least one that fits #83).
  • Show best model, even when non-signficant (intercept-only = mean) on all plots
  • If you intend to show y=0, (1) either show on all plots for which these are in range, or none; (2) make these black.
• [x] issue #55
• [x] Helene comments that there's too much white space. I agree, but wouldn't spend much time on it (unless its a super quick fix), given that these are just SI figures.
• [x] Helene suggests annotate plots with just R2=[2 digits], as opposed to R-sq=[4 digits]. Again,I agree, but wouldn't spend much time on it (unless its a super quick fix), given that these are just SI figures.
• [ ] Helene comments that we should use the same x-axis range/ scale for the whole column. Again,I agree, but wouldn't spend much time on it (unless its a super quick fix), given that these are just SI figures.

Ratio grid plots:

• [x] I'm currently confused on the ratio grid plots--which will be used? (#91 )

• [x] Helene suggests grouping ANPP:NPP, BNPP:NPP, and ANPP:BNPP together for easier interpretation.

• [x] Helene suggests give n sites for each row (maybe in row label)

• [ ] for true ratios, it could help to have a reference line at y=1

• [x] Helene has lots of suggestions for mainly cosmetic changes to FIg. S2. See this file

[beckybanbury]

@teixeirak I think this is largely okay now - I haven't changed the scale in the columns because I think it might be a bit fiddly to go through + I'm trying to prioritise, but I can do it later on if necessary