Resource availability
Based on measurements in 2013, community successional stage was
positively correlated with resident diversity (r = 0.679) and negatively
correlated with soil nitrate (-0.861; Table S7a). Effects of disturbance
on soil N varied with successional stage (Table S7b-d, Fig. S6);
disturbed plots had lower soil N than undisturbed plots in early
succession (r = -0.42), but higher soil N in mid and late succession (r
= 0.64 and 0.44 respectively). Light levels at ground level declined
with successional stage and time, and were higher in disturbed than
undisturbed plots (r = 0.711), especially in mid and late successional
communities (r = 0.90 and r = 0.95 respectively; Table S7, Fig. S8).
Soil moisture was highest in late successional communities and lowest in
mid successional communities (Fig. S7). Disturbed plots had lower soil
moisture than undisturbed plots, especially in mid successional
communities (r = -0.71) where soil moisture was already very low (Fig.
S7). Apart from soil moisture, these correlations provide evidence that
competition generally increased and availability of key resources,
namely soil nitrate, decreased with succession.