Statistical models for biomass and volume of Azadirachta indica A.Juss. grown under rainfed conditions in semi-arid region of central India

Abstract

Four non-linear functions, viz., Exponential, Logistic, Schumacher and Chapman-Richards were fitted for bole biomass, total wood biomass and bole volume (over bark) of Azadirachta indica. The functions were fitted using 13.5 years old trees data and explanatory variables ‘D’and ‘D2H’, where D- diameter at breast height and H- height of tree. The goodness of fitted models was judged by mean square error and adjusted R2 criteria. These models were also subjected to graphical analysis for selecting best model. In case of bole biomass and total wood biomass, the Logistic models B1 = 82.882[1 + exp (1.908-9.443 D2H)]-1 and B2 = 156.677[1 + exp (1.963-9.897 D2H)]-1; where B1- bole biomass in kg/tree, B2- total wood biomass in kg/tree; were found to be best fit. Whereas in case of bole volume, the Chapman-Richards model V= 0.99[1 – exp (-0.259 D2H)]0.969, where V- bole volume (over bark) in m3/tree, was found best fit on the basis of statistical and graphical criteria. Hence, the proposed models may be used for estimating the bole biomass, total wood biomass and bole volume (over bark) of Azadirachta indica tree in semi-arid region with reasonable accuracy.