Nontimber Forest Product Yield and Income from Thaumatococcus daniellii under a Mixed Tree Plantation System in Ghana

Abstract

Thaumatococcus daniellii is a wild sourced tropical understorey herb that is harvested for its foliage and fruits from which thaumatin—a proteinous sweetener—is extracted. With increased demand for natural sweeteners, uncontrolled harvesting of T. daniellii from the wild is suggested to be neither sustainable nor match industrial demands. This study determined the implication of controlled foliage harvesting of T. daniellii under a mixed indigenous tree plantation stand. T. daniellii plants within plots of dimension 3 m × 4 m were thinned to uniform foliage population of about 12 leaves/m2 and subsequently harvested at 16 weeks interval for 64 weeks at four different foliage harvesting intensities: (i) no harvesting (control), (ii) 25% harvest, (iii) 50% harvest, and (iv) 75% harvest. Data on agronomic characters and total income from the sale of fruit and harvested foliage were collected and analysed. We found that foliage harvest intensity affected (P 6 (25%) ≥ 1 (50%) and 0 (75%). Foliage harvest intensity also significantly (P=0.036) influenced fruit number and ranged from 11458/ha for the control to 4583/ha for the 75% harvest. Total income from fruit and foliage sales was greatest for the 50% harvest (US $ 17,191.32), followed by 75% harvest (US $ 12, 310.24) and lowest for the no harvest treatment (US $ 107.44). Thus, proper management of T. daniellii through controlled harvesting of the foliage under mixed tree plantation system could promote sustainable yield and income to farmers.