Gross nitrogen ammonification and nitrification rates
Nitrogen addition level and frequency had significant effects on both
gross ammonification (GA, P < 0.05) and gross
nitrification rates (GN, P < 0.05) while mowing showed
no significant effects on GA and GN. Besides, the interaction of N
addition level and N addition frequency was significant for GA (P< 0.001), but not for GN. In contrast, there were significant
interactions between mowing and N addition level or N addition frequency
on GN (P < 0.01), but not on GA (Table 2).
Across the N addition levels, the highest N addition (N-50)
significantly increased GA by 278.45% (P < 0.05). For
the lowest addition level (N-2), GA was significantly decreased by
44.61% (P < 0.05), but was not significantly changed
at higher N addition levels (N-10, N-20) with mowing (Fig. 2a, Table 2).
Higher N addition levels (N-10, N-20) significantly increased GN by
398.61% and 548.75% (P < 0.05, Fig. 2b). N addition
with mowing significantly increased GN (P < 0.05, Fig.
2b). However, the frequency of N addition and mowing had no interactive
effects on GN (Fig. 2b).