3.4 Watershed characteristics effects
To better understand which watershed and fire characteristics may
control differences in effect sizes of nitrate and DOC, we plotted
feature importance determined by Random Forests for each solute (Fig.
5). R2 values indicate that less than half of
the variability in nitrate effect sizes was explained
(R2 = 0.47), while most of the variability in DOC
effect sizes were explained by the six watershed and fire
characteristics (R2 = 0.80). For DOC, maximum
elevation was the most important predictor (40%) followed by catchment
area (27%), while the remaining variables were considerably less
important (<15%), with climate and time-since-fire as the
least important. For nitrate, maximum elevation was also the most
important variable (29%). However, unlike DOC, all other predictors
were at least half the feature importance of maximum elevation
(15-17%). Slope was the least important predictor for nitrate (9%). We
observed the DOC effects are better explained by watershed and fire
characteristics compared to nitrate (Fig. 5).