Developing prediction models for biomass components of Gmelina arborea (Roxb.)
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
The present investigation entitled DEVELOPING PREDICTION MODELS FOR BIOMASS COMPONENTS OF Gmelina arborea (Roxb.) was carried out at the University Seed Farm, Ladhowal, Punjab Agricultural University (PAU), Ludhiana, during the year 2015-16. Gmelina arborea (Roxb.) belongs to family Verbenaceae is a moderately fast growing, most widely distributed and economically important species for timber, fuel and pulp production. It has been introduced recently in Punjab and showing encouraging results but no biomass prediction models/equations are available to ascertain its growing stock, which usually is a handy tool to know the biomass. The proposed study was a step taken in this direction. The best fit equations were found with polynomial regression functions using DBH and DBH2*H parameters as independent factor with dependent factors as total green and dry biomass (TGB & TDB), total above and below ground green (AGB & BGB) and dry biomass (ADB & BDB). The polynomial models TGB (9558.813 DBH2 - 864.442 DBH – 57.263) and TDB (4108.320 DBH2 + 127.773 DBH + 6.375) with maximum Adj. R2 value of 0.986 and 0.973, respectively were found best fit lines to predict total green and dry biomass. Similarly for above-ground green and dry biomass the polynomial functions AGB = 7400.147 DBH2 494.264 DBH + 24.284 and ADB = -23.509 (DBH2×H)2 + 241.634 DBH2×H+ 0.571 with maximum Adj. R2 of 0.984 and 0.972 respectively were found best fit and for below-ground green and dry biomass prediction, polynomial function BFB = 2298.654 DBH2 - 427.945 DBH + 36.369 and BDB = 1187.836 DBH2 – 230.039 DBH + 20.127 with maximum Adj. R2 value of 0.952 and 0.951, respectively were found best fit. Although the regression coefficient of the linear and polynomial function was very high but in validation these models show less reliability in prediction for higher and lower DBH class components so preference was given to power functions due to there more compatibility with all components in all DBH classes. Biomass expansion factor (BEF) showed decreasing trend as the range of the girth classes increased. For different GBH classes, the values of BEF ranged from 1.36 to 1.17 and with increase in girth class, the low BEF indicated that the proportion of the stem in comparison to other parameters increased in total tree biomass.
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