Cascaded performance and compartments of constructed wetlands may harbor the internal eco-environmental gradients and further differentiate the niche and community structure of ammonia-oxidizing archaea (AOA). Here, we used quantitative PCR and 454 pyrosequencing of AOA amoA gene to investigate the abundance, diversity, composition, and driving factors of sedimentary AOA community in a created riparian wetland---Shijiuyang constructed wetland (SJY-CW) in China. Results showed that the heterogeneous wetland with serial-connected combinations of pretreatment pond, plant-bed/ditch system, and post-treatment pond as well as the third through fifth year succession (2011--2013, corresponding to the third through fifth year of actual operation after the initial two-year trial operation) had exerted significant spatiotemporal niche selection effects on AOA abundance and composition. AOA abundance in the pre- and post-treatment ponds was almost invariant in 2011--2012 and decreased in 2013, while the abundance in the plant-bed/ditch system decreased gradually with the succession of SJY-CW. The AOA abundance ended up with one order of magnitude lower and tended to be consistent in the whole wetland. In contrast to abundance, the temporal niche differentiation of AOA diversity was insignificant. Nonetheless, a rough decrease trend was detected for the average community richness index Chao1 and diversity index Shannon H' in 2011--2013. Community structure analysis showed that Nitrososphaera was dominant genus, while Nitrosopumilus cluster and Nitrososphaera sister cluster increased with the succession of SJY-CW. Hierarchical clustering analysis and redundancy analysis both verified the horizontal shifts of AOA communities and these shifts inclined to occur in the most heterogeneous plant-bed/ditch system. Operational duration of the wetland which comprehensively reflected the wetland hydrology, water quality, and associated functions became the key factor driving the AOA abundance and community shift in SJY-CW sediments. In a nutshell, with the third through fifth year succession of wetland, the sedimentary ammonia-oxidizing archaea tended to be characterized by temporally decreased and spatially consistent abundance, while spatially variable and temporally decreased richness and diversity; regarding the AOA community structure, temporally from local species and relatively uniform distribution to mixing with allochthonous species and highly diversified distribution, while spatially occurring significant horizontal shifts of AOA amoA genes. These results showed the considerable if not significant niche selection effect of AOA abundance, diversity, and community structure with the operation of SJY-CW, and this will have some implications on the microbial ecology of archaeal ammonia-oxidization in a man-made wetland ecosystem.