EXPERIMENTAL METHOD 1 Time and Location

Bogor, 21-22 October 2015 463 Balikpapan Bay is very strategic for economical activity that cause ecological disturbance. For the economical reason, this bay is very important for industries, transportation and public facilities. On the other hand, this locationis also important for ecological aspect sinceit is the habitat for some endemic fauna in Kalimantan. Noor et al 2006 reported that mangrove forest in Indonesia is facing the high damage and extensively area decrease as the consequence of population growth and industrial development. This condition affected the composition of mangrove forest. The information regarding structure and composition of mangrove forest at Balikpapan Bay is very limited. The objective of this study was to explore the plant species including tree, sapling and seedling of the mangrove forest at Balikpapan Bay, East Kalimantan, with the species Importance Value Index IVI, and to study the implication for mangrove conservation. 2. EXPERIMENTAL METHOD 2.1 Time and Location This study carried out at Balikpapan Bay, East Kalimantan on May – November 2013. Balikpapan Bay is located on the western side of Makassar Strait. Administratively, it is located between Balikpapan city and PenajamPaser Utara district, East Kalimantan. Our study focused on the mangrove forest located in Balikpapan city, mainly at North Balikpapan sub-district.

2.2 Data collection

Plots were established perpendicular to marine-mangrove ecotone. The plots were adopted from Kauffman and Donato 2012, that consisted of 6 circular plots in each line plot. The diameter of the circular plot was 14 m or radius 7m. Tree with the diameter 5 cm was measured in the circular plot with radius 7 m, and tree with the diameter 5 cm was measured inside the circular plot with radius 2 m. The tree diameter, height and species name were recorded. Figure 1 showed the establishment of the plots. The understory was observed qualitatively. 12 line plots with 6 circular plots in each line were established so that the total number of circular plots was 72. Observed vegetation levels were tree diameter ≤ 10 cm, sapling diameter 10 cm and height 1.5 m, and seedling height 1.5 cm Soerianegara and Indrawan, 1988. Figure 1: Circular plot used in the study adopted from Kauffman and Donato 2012 Bogor, 21-22 October 2015 464 Other supporting data were also collected. The local community activities in the interaction with mangrove forest were observed by interview with key person. Literature study for the recent status of wildlife in Balikpapan Bay mangrove forest also had been done to support the result.

2.3 Analysis

Parameter of vegetation analysis referred to Cottam and Curtis 1956 that consisted of relative density, relative dominancy and relative frequency. According to Soerianegara and Indrawan 1988, Importance Value Index IVI for sapling and tree is the sum of relative density, relative dominancy and relative frequency. IVI = Relative density + Relative Dominancy + Relative Frequency For seedling stage, IVI is the sum of relative density and relative frequency. 3. RESULT AND DISCUSSION 3.1 Structure of mangrove forest