Assessment of potential contributions of biomass load to fire hazards in Arakanga Forest Reserve, Ogun State, Nigeria

Abstract

Forest fire is an uncontrolled combustion that burns through the forest's organic materials, such as trees, brush and grasses.  Arakanga Forest Reserve is prone to fire outbreak and there is lack of data to understand fire risks, extent and potential biomass load that contribute to fire outbreak and biomass loss. fire risk indices (FRI) were determined from historical records in 2021 of six (6) burnt patches identified in the forest reserves. Eight (8) temporary sample plots (TSP) of 20m x 20m were systematically demarcated in each of the identified burnt patch where complete enumeration of tree species, including their height and diameter at breast height (DBH) were measured.  Above ground biomass (AGB) was computed from combination of tree height, DBH, form factor and biomass expansion factor (BEF).  Data were analysed using analysis of variance (ANOVA). Total of 520 tree stands, comprising of Azadirachta indica, Gmelina arborea, Pinus carribaea and Tectona grandis were enumerated.  Mean DBH and height of tree observed were 10.3 ± 0.41 cm and 12.60 ± 3.23 m respectively.  Burnt patches identified in Arakanga Forest Reserve from historical records ranged between 4.32 ha and 10.4 ha. The amount of AGB load was highest in Patch 1 at 828.77 ± 166.35 Mg/ha, followed by Patch 3 at 806.89 ± 246.05 Mg/ha, with the least AGB load occurring in Patch 4 as 514.55 ± 215.38 Mg/ha.  There was no significant difference (p > 0.79) in the AGB load among the burnt patches identified in the forest reserve.  However, FRI was significantly (p<0.05) highest in Patch 1 where AGB was highest and least in Patch 4 where AGB was lowest. This study provides documentary evidence of amount of potential AGB load that could contribute to significant fire risk and destruction of forest ecosystem.