Development of allometric equations for grafted sapota (Manilkara zapota) through destructive tree sampling for non-destructive estimation of tree biomass

Sapota fruit tree biomass cannot be estimated using general forest tree allometric equations involving measurement of diameter at breast height (DBH) as grafted sapota tree branches below this height. Therefore grafted sapota trees of commercial orchards require an independent allometric equation for nondestructive estimation of tree biomass. Sapota allometric equations were hence developed with a destructive sampling of grafted sapota trees using parameters other than DBH and compared with other equations developed for grafted mangoes. The selected allometric parameters were significantly related to the age of the trees. The root-to-shoot ratio also differed from those reported for forest trees. The biomass expansion factor by and large attained stability beyond 16 years of tree age. The equations so developed generally fitted the data well, and in most cases, more than 50% of the observed variation in biomass was explained by primary branch girth ´ number of primary branches. There was a good agreement between the observed and the predicted bio­mass using both multiple linear regression and power model equations. Further, our purpose was to see if the grafted mango tree equation can predict sapota tree biomass. The results of this study confirmed that the mango equation equally predicts sapota tree biomass and hence the mango tree allometric equation can also be used for estimating sapota tree biomass efficiently.