Biomass estimation equation of Nyirih tree (Xylocarpus granatum Koenig. 1784) in Batu Alam natural forest, Kalimantan Barat

Abstract

In relation to global warming issues, forests function as CO2 absorber from the atmosphere and as biomass reservoir. Mangrove has twice productivity compared to primary forest and is estimated to have a good biomass sink and biomass reservoir ability. To estimate biomass amount in a forest, a non direct approach can be applied using allometric model and BEF method. The objective of this research is to build an allometric equation to estimate Nyirih biomass. This research was conducted in Nipah Panjang village, Batu Ampar for two weeks. The equation is made based a hypothesis that there is a strong correlation between tree parameters and biomass value of each tree sections. To meet the objective of this research, 30 tree samples were randomly chosen based on diameter representative. Afterwards, biomass was measured using destructive sampling method. Trunk section was measured using volume approach while other sections were measured using direct weighing method. Tree data collected in standing position included breast height diameter, total height and average height. Afterwards each tree section was separated and weigh. Water content data were obtained by taking samples from each section and tested for 11 repetitions. Biomass estimation model were built by analyzing the correlation of each biomass value with tree dimensions. A strong correlation among variables implies that these variables can consistently represent the tree biomass. Positive correlation between tree sections with its diameter was higher than with its total height. Correlations are then explained in regression equation. The best equation was obtained by testing four linier and non-linier regression equations. The best equation is that which has the lowest deviation (s) value, the highest determination coefficient (R2) value and the highest corrected determination coefficient (R2) value. Moreover, the equation had to have an estimation value that resembles actual biomass the most; fulfill remnant normality assumption and model additives. The result of the research showed that the highest value of biomass was found in trunk section which reached 52,5% of total tree biomass above land surface. Then it was followed by branch (26%), twig (15,5%) and leaf (6%). Research on Mahoni species by Adinugroho (2002) showed that trunk section reached 73% of total biomass. Thus, it can be concluded that Nyirih has a great amount of branching Based on the tested regression equations, the best alometric equation to estimate biomass value of each tree section were as follows: 􀂃 Trunk Biomass : Btrunk = 0,0813D2,28 􀂃 Branch Biomass: Bbranch = 0,0063D2,78 􀂃 Twig Biomass : Btwig = 0,1D1,79 􀂃 Leaf Biomass : Bleaf = 0,1076D1,51 􀂃 Total Biomass : Btotal = 0,1832D2,21 The BEF value of Nyirih was 1,806 for total biomass estimation based on direct measuring and 1,737 based on tree volume data. The increase of diameter size caused BEF value to decrease. Based on its high BEF value, it can be concluded that Nyirih has a great amount of branching.