Abstract:
Forest ecosystems are very important as they reduce the atmospheric CO2 amounts and thereby control global warming and climate change effect. Estimation of forest biomass values is vital to determine the carbon contents of trees. The objective of this study is to map and model Above-Ground Tree Biomass (AGTB) within Omo Biosphere Reserve, Ogun State, Nigeria. Ten (10) sample plots were randomly selected within the biosphere reserve for data collection. All trees ≥10 cm Diameter at Breast Height (DBH) within the sample plots were identified and their DBH taken. As well two mean trees per species group were selected for tree above-ground biomass estimation. Biomass models were developed for the study area as well as some species biomass models. Also spatial explicit of biomass/carbon distribution was mapped. Omo Biosphere Reserve contains some important indigenous hardwood species which spread across various families within the tropical rainforest, including; Ebanaceae, Ulmaceae and Meliaceae. Other important families dominating this reserve include the Euphorbiaceae, Moraceae, Olacaceae, Meliaceae, and Moraceae. In the quest to predict above-ground tree biomass using both DBH and/or tree total height, excluding the untransformed variables, four forms of transformations were used for the variables for model construction to obtain the best fit model. Six models were selected preliminarily based on higher adjusted coefficient of determination (AdjR2) values for further analysis. Amongst the preliminary models selected, the final selection was done using the Furnival index value and standard residual distribution. After the final evaluation, log-transformed model (Ln(1/B) = −3.342 − 0.104(D)) gave the best fit for the study having the smallest Furnival index value, and better randomly distributed residuals. The digitized imagery of the biosphere reserve showed the reserve covered about 10,200.57 hectares of land. The spatial distribution pattern of the biomass/carbon was mapped using the above-ground tree biomass data. Omo Biosphere Reserve has 160.17 t ha-1 of biomass and 80.09 t ha-1 of carbon. Also, a cumulative total of 1,633,860.72 tons of biomass and 816,930.36 tons of carbon were reported for the entire biosphere reserve.
