Does Laguncularia racemosa have more advantages on leaf energetic cost than Sonneratia apetala in Southern China?

Laguncularia racemosa (Lr) is the most widely used exotic mangrove species in afforestation during the last 20 years in addition to Sonneratia apetala (Sa), another exotic species, in Southern China. Sa has been considered as an invasive species although its invasiveness is still debatable. The distribution and aggressiveness of Lr were even more serious than that of Sa in the North of Fujian province of China, therefore, it is essential to understand the biological characteristics and the invasive potential of Lr. Construction cost (CC) is a quantifiable measure of energy demand for biomass production, and low CC is hypothesized to give an exotic plant growth advantages and increase its potential to be an invader. In this study, we compared CC and other growth traits between Lr and Sa, as well as with two native mangrove species, namely Kandelia obovate and Aegiceras corniculatum. Results showed that CC (1.30 g glucose/g), caloric values (16.96 KJ/g) and carbon concentration (43.19 g/g) of Lr not only lower than those of Sa (1.37 g glucose/g, 17.84 KJ/g and 43.49 g/g) but also were significantly lower than those of native mangrove species (1.47 g glucose/g, 19.13 KJ/g and 45.87 g/g), while specific leaf area (SLA) was just the opposite (SLA of Lr VS Sa VS native: 8.28 VS 8.21 VS 5.72 m2/kg). Lower CC and higher SLA make Lr grow fast and result in higher height (4.83 m) and wider chest circumference (40.03 cm) than those of Sa (4.43 m and 35.63 cm) and the two native mangrove species (2.42 m and 26.78 cm).  These findings indicated that the invasive potential of Lr could be higher than that of Sa, explaining why Lr has wider distribution and is more aggressive than Sa in North Fujian, China.