Competitive Control of an Exotic Mangrove Species:Restoration of Native Mangrove Forests by AlteringLight Availability
Recently, many studies have focused on the possibility of restoring mangrove ecosystems by introducing fast-growing mangroves. However, methods for managing anexotic fast-growing species to restore mangrove ecosystemsand at the same time preventing invasion by introducedspecies remains unclear. Sonneratia apetala Buch-Ham isone example of an exotic mangrove with both high ecologi-cal value and potential risk for invasion after introduction.To investigate the possibility of reducing the potential forinvasion by altering light availability, we simulated differ-ent irradiances of S. apetala understory in the greenhouse.For each irradiance treatment, three levels of competi-tion between S. apetala and native mangroves Aegicerascorniculatum (L.) were used: no competition, intraspecificcompetition and interspecific competition. Compared withA. corniculatum, S. apetala showed a significantly highergrowth rate for both height and biomass accumulation under full irradiation. Compared to the full irradiationtreatment, the shading treatment significantly reduced theheight, total biomass and biomass allocation to leaves ofS. apetala by 61.31, 71.0, and 76.2%, respectively, whereasthe growth of A. corniculatum was not affected. The resultssuggested that lowering light availability could inhibit thegrowth of S. apetala and increase the competitiveness ofA. corniculatum. Planting introduced fast-growing man-groves at a density of approximately 2,000 plants/hm2is an effective strategy for preventing potential invasionand restoring wetland habitats. By taking advantage ofthe differences in shade tolerance between fast-growingexotic mangroves and native mangroves, introduction offast-growing mangroves in coastal areas could have hugepotential for reforesting mangrove ecosystems.