Examining the differences between invasive Sonneratia apetala and native Kandelia obovata for mangrove restoration: soil organic carbon, nitrogen, and phosphorus content and pools.
Mangroves play an important role in enhancing soil organic carbon (SOC) and nutrient pools. The exotic Sonneratia apetala is widely used for the restoration of mangroves in China because of its fast growth. However, it is not clear whether S. apetala increases SOC, nitrogen, and phosphorus pools compared with the native mangrove species. Thus, the aims of this study were to determine whether Kandelia obovata and the fast-growing mangrove species S. apetala have advantages with regard to the SOC, nitrogen, and phosphorus content and pools and whether restored mangroves have SOC, nitrogen, and phosphorus content and pools similar to those of original mangroves. Four sites in the Qi'ao-Dangan Provincial Nature Reserve were selected: a 15-year-old planted S. apetala forest, a 15-year-old planted K. obovata forest, a native K. obovata forest, and an unvegetated mudflat. The content and pools of organic carbon, nitrogen, and phosphorus in the soil were compared. Compared with mudflats, the content and pools of SOC, nitrogen, and phosphorus were significantly increased by planting S. apetala. However, compared with the 15-year-old planted K. obovata, the fast-growing S. apetala showed no advantage. The content and pools of SOC and nitrogen in the 15-year-old planted S. apetala site were lower than those of native K. obovata forests. It is recommended that more native mangrove species be used for future mangrove restoration to increase the content and pools of SOC, nitrogen, and phosphorus.