Figure captions
Figure 1 Changes in the amoA gene abundance of AOA, AOB, comammox Nitrospira clade A and clade B during N addition and N cessation. Different letters denote significant differences among treatments (P < 0.05).
Figure 2 Principal component analysis (PCA) patterns of community compositions of AOA (a), AOB(b), comammox Nitrospira clade A(c) and clade B(d) during N cessation. points are marked according to fertilization treatments.
Figure 3 Whole co-occurrence network of AOA operational taxonomic units (OTUs), AOB OTUs, and Nitrospira clade A OTUs and clade B OTUs during N cessation. A summary of node statistics is provided to bottom of the network.
Figure 4 Changes in net N mineralization rates and nitrification rates during N cessation. Different letters mean significant differences at P = 0.05 level under different treatments.
Figure 5 Structural equation model (SEM) analysis of the effects of N addition (a) and N cessation (b) on AOB and nitrification. Numbers at arrows are standardized path coefficients. R2 values associated with response variables indicate the proportion of variation explained by relationships with other variables.
Figure 6 A conceptual framework of ecosystem nitrogen (N) cycling processes to N addition (a) and N cessation (b) based on this study.