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Abstract. Hilmi E, Sari LK, Cahyo TN, Muslih, Mahdiana A, Samudra SR. 2021. The affinity of mangrove species using Association and Cluster Index in North Coast of Jakarta and Segara Anakan of Cilacap, Indonesia. Biodiversitas 22: 2907-2920. The affinity of mangrove species using association and cluster index describe relationship among mangrove species. The species association and clustering explain the degree of utilization of resources and space by mangrove species. The association and cluster also describe specific species adaptation in mangrove ecosystems. This paper was aimed to analyze species affinity using association and clustering index of mangrove species. The association index used Chi-square equation and the clustered index used Euclidian distance analysis. The results showed that (i) mangrove density in Segara Anakan (166-4000 trees ha-1) > North Jakarta (220-1100 trees ha-1). (ii) Nypa fruticans, Avicennia marina, Rhizophora stylosa and Rhizophora apiculata dominated in Segara Anakan of Cilacap, and Rhizophora stylosa and Avicennia marina dominated in North Jakarta (iii) The association index had 12 pairs of negative species association and 17 pairs of positive species association, but most of mangrove vegetations had no association. (iv) mangrove ecosystem in Segara Anakan and North Jakarta had four clusters with Euclidean distance (ED score) 484 to describe cluster between Bruguiera parviflora-Bruguiera sexangula until 76430847 to describe cluster among Bruguiera gymnorrhiza, Bruguiera parviflora, Ceriops decandra, Exoecaria agallocha, Nypa fruticans, Ceriops tagal, Rhizophora stylosa, and Sonneratia caseolaris

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The mangrove zoning and landscape express the correlation between mangrove vegetation (density, biodiversity and species distribution) with environment factors like as water inundation, seatide, and soil properties. The research was conducted in Segara Anakan Lagoon to analysis community structure and mangrove landscape based on species distribution, biodiversity, environment factors, and mangrove zoning. The results showed that (a) Segara Anakan Lagoon had 4 mangrove zone's were dominated by Sonneratia alba, Rhizophora mucronata, Avicennia marina, Rhizophora apiculata, Rhizophora styllosa, and Nypa frutican; (b) the structure of ecosystem was showed by trend of mangrove ecosystem with equation y = 35.34x2 923.85x + 12817 with x = time (year) and y = mangrove area (ha), mangrove density between 1333367 ind ha-1 (West Segara Anakan) and 899–567 ind ha-1 (East Segara Anakan), dominated species were Nypa frutican, Rhizophora stylosa, Rhizophora apiculata, and Aegiceras corniculatum and mangrove biodiversity between 2,572,65 (moderate); (c) structure of environment factor showed single and semi double-type tides, water debit between 0.360.73 m s-1; water depth between 0.20–23.7 m and water inundation between 480cm; soil texture was clay and loam, soil nitrate of 1.5 mg 100 g-1, soil phosphate of 1.5 mg 100 g-1, C organic of 1.31%, soil pH of 6–7, and soil salinity of 6.5–10 ppt.

Segara Anakan Lagoon (SAL) as the specific ecosystem is arranged by the mangrove ecosystem and lagoon ecosystem. The mangrove ecosystem in SAL needs high adaptation to reduce the impact of water tide, water inundation, water salinity, and other factors. This research aimed to analyze mangrove clustering in Segara Anakan Lagoon. The method of this research used Hierarchical Clustering Methods based on mangrove density to analyze cluster adaptation of the mangrove ecosystem. The result showed that (1) The mangrove density (diameter > 4 cm) to analysis mangrove clustering showed that East Segara Anakan had density between 900 – 5425 trees ha-1 (low-very high density ) and West Segara Anakan had density between 133 – 3.367 (low – high density). (2) the mangrove clustering showed that West Segara Anakan had three clusters. The first cluster was arranged by clustering of stations {((15.18),(9.17),(3.6)),8)); ((1.2),5)}. The second cluster was arranged by clustering of stations {(((4.10),14,12))}. And the third cluster was arranged by clustering of stations{(((11.20)16));(7.19))}. (b) East Segara Anakan also was formed by three clusters were the first cluster was formed by clustering of stations (2-(((4, 13), 6) ((1.12), ((4.13) ((5.10) (7.11)))) The second cluster was arranged by clustering of stations (9; ((8.15), (19, (20.21)))) The third cluster was formed by clustering of stations (18 (17, (14,16))).