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Regression Equations for Estimating Tree Plot Volume for Eucalyptus camaldulensis in the Sudan Savanna Ecosystems of Nigeria

Magaji K, Saka M G, Jatau D F, and Yakubu, M

Abstract

This study used regression equation in estimating tree plot volume for Eucalyptus camaldulensis in the Sudan savanna ecosystem of Nigeria. Non-destructive sampling method was adopted, in which five (5) sample plots of 50 x 50m in size were laid across each of the age series. In each plots, all trees were marked, numbered and growth attributes such as diameter at breast height (DBH), diameter at the bottom (DB), diameter at the middle (DM), diameter at the top (DT) and height (HT) were measured and recorded. Seventy (70%) percent of the data set were used for the calibration, while thirty (30%) percent was used for data validation. Equations were developed for this research based on measurable tree variables and other parameters as primary predictors of tree volume. Paired sample T-test was used to authenticate the developed models. The development of diameter class regression models for estimating tree volume in Eucalyptus camaldulensis plantations from 1989 to 1991 in the study area demonstrates a statistically robust and practical approach to forest volume assessment. Across all three plantation years, model performances generally improved with increasing DBH class, as reflected in higher coefficients of determination (R²) and lower standard errors of estimate (SEE). In the 1989 plantation, the R² values ranged from 0.67 (10–40 cm) to 0.97 (>70 cm), while SEE decreased from 0.398 to 0.107. Similar patterns were observed in 1990 and 1991, with the trees greater thamn70 cm DBH class consistently exhibiting the highest predictive strength (R² ? 0.97). Conclusively, the regression models do not only provide a robust basis for generating localized volume tables but also serve as essential tools for estimating aboveground biomass and carbon sequestration potential when coupled with species-specific wood density, such applications are vital for sustainable forest management, climate change mitigation efforts, and forest carbon a

Keywords

Diameter classEucalyptus camaldulensisRegression equationsTree volume

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