Aboveground and belowground biomass
Nitrogen addition treatments, regardless of adding N levels and
frequencies, significantly increased aboveground biomass (AGB) and
belowground biomass (BGB) (P < 0.01). However, mowing
showed no significant effect on AGB (P > 0.05) but
significantly decreased BGB (P < 0.001). Besides, the
levels and frequency of N addition and mowing interactively affected AGB
and BGB, respectively (P < 0.01, Table 1).
Across all N addition levels, AGB increased by 30.92% on average in
control (no mowing, P < 0.05) and by 40.80% in mowed
plots (P < 0.05) at the lower frequency N addition
(twice a year) (Fig. 1a). AGB also increased by 10.67% in control plots
(P > 0.05) and by 74.81%
in mowed plots (P <
0.05) at the higher frequency of N addition (monthly) (Fig 1a). At the
highest N addition level (N-50), AGB tended to be higher in mowed versus
control plots, and AGB at higher N addition levels (N-20, N-50) was
significantly higher in mowed than un-mowed plots at the higher
frequency of N addition (P < 0.05, Fig. 1a). However,
no significant effect of lower-frequency N addition was found on AGB
(Fig. 1a). BGB at the lower frequency of N addition was significantly
lower than that at high frequency of N addition under relatively lower N
addition levels (N-2, N-10) (P < 0.05, Fig. 1b) while
opposite trends were observed under relatively higher N addition levels
(N-20, N-50) (Fig. 1b). BGB was significantly increased by 41.46%
(P < 0.05) under N
addition, and it increased with increasing N addition levels at lower N
addition frequency (P < 0.05).