Mangrove seedling abundance in mangrove ecosystem outgrowth in Ajkwa Island, Mimika Regency, Papua

Mangrove is one of the essential ecosystems for coastal areas. Mangrove is an individual or community which survives in tidal areas. Ajkwa Island is an island created by sedimentation activities from Ajkwa river. Ajkwa Island has a tidal supply well and it makes this island be an essential area for mangrove growth. This research was conducted in Ajkwa Island, Mimika Regency, Papua Province. The research is in permanent monitoring plots in 2011, 2014, and 2018. Based on the research, 2 categories were found in the monitoring plot, there are seedling and herbs. Species for seedling category are Avicennia marina, Bruguiera gymnorrhiza, Bruguiera cylindrica, Diospyros sp., Nypa fruticans, Sonneratia alba , and Xylocarpus sp. Species for herbs category are Allamanda cathartica and Hoya sp. Mangrove ecosystem type in Ajkwa Island is over-wash mangrove. The result, Sonneratia alba and Bruguiera gymnorrhiza had density and important value index higher than the other species in every monitoring year. Mangrove spreading in Ajkwa Island increases in each monitoring year. Mangrove seedling spread significantly from 2014 to 2018. On the monitoring plots, mangrove density in 2014 is 41.700 ind/ha and for 2018 is 74.000 ind/ha. Beside vegetation analysis, this research does spatial analysis to support the result from field monitoring data. Spatial analysis also proved the spreading of the seedling increased significantly from 2014 to 2018.