Worked on Fig. 6 -- 90% complete, some issues to resolve

NOTES TO DISCUSS:

1. ALL CORRELATIONS ARE THE SAME (!)

2. PEAK MAGNITUDE DATES ARE IDENTIFIED BASED ON AGE_TOP, WHEREAS
BIOGEOCHEM DATES ARE IDENTIFIED BASED ON MID-DEPTH AGE.

3. C:N PLOT HAS A HIGH VALUE ON Y-AXIS CUT OFF IN PUBLICATION PLOT.
DELTA 15N PLOT, FOR 20-50 YR POST FIRE IS ALSO DIFFERENT.

4. WILL BE EASY TO MAKE THIS THE SCRIPT FOR FIGURE S4 TOO.