In this study, the relative contribution of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to nitrification were investigated in acidic forested soils derived from granite in Wanmulin nature reserve, Jianou, Fujian Province of southern China. The abundances of AOA and AOB communities were determined by real-time quantitative polymerase chain reaction (qPCR), while gross nitrification activity was measured using 15N-pool enrichment technique in soils under five different vegetations over 600 years plantation one orange cultivation system. The results showed that soil pH, the abundance of AOB and gross nitrification rate were significantly lower in natural vegetation soil than those soil cultivated with orange plant. Furthermore, a significant correlation between the population size of soil AOB and soil gross nitrification activity suggested that AOB might dominate autotrophic nitrification in forested soil typical of the low-pH ecosystems, particularly in orange soil. The copy number ratio of archaeal amoA to crenarchaeota-specific 16S rRNA genes varied from 0.01% - 0.64% in all five natural vegetation soils while up to 5.32% in orange soil. The results indicated that not all archaea possessed ammonia-oxidizing functional gene of amoA and fertilization may facilitate AOA growth in soils cultivated with orange as well.