3.3. soil enzyme activity
The results showed that N, P and NP additions significantly increased
the activities of INV, CBH, POX, UG and AP compared to CK treatment
(P<0.05) (Fig.4). During the litter decomposition, the
activities of INV, UG and AP decreased in the middle stage and increased
in the late stage. The CBH activity was highest in 90 days of
decomposition and then continued to decline, and the POX activity showed
an increasing trend. In the late stage, with increasing N addition, both
CBH and AP activities increased significantly, INV and POX activities
decreased significantly, while UG showed a trend of first increase and
then decrease. With the increase of P addition, the activities of INV,
CBH and AP decreased significantly, and the activities of POX showed a
trend of first increase and then decrease, while P addition had no
significant effect on soil UG activity. With increasing NP addition, AP
activity decreased significantly, INV and CBH activities showed a trend
of first increase and then decrease, while NP addition had no
significant effect on polyphenol oxidase and urease. The RM-ANVON showed
that the interaction of N and P addition and its synergistic effect with
decomposition time had significant effects on INV, CBH, POX, UG, and AP
(P < 0.001) (Table S3).