Mass of Prunus africana stem barks on Tchabal mbabo and Tchabal Gang Daba Mountain Forests, Cameroon

Abstract

Prunus africana is a species of the Rosaceae family, known under its common name as pygeum or African cherry. The bark is the major source of an extract used to treat benign prostatic hyperplasia, an increasingly common health problem in older men in the western world. A study which aimed to produce a formula for establishing the mass of the bark of Prunus africana specimens was carried out in May 2011 on Tchabal Mbabo and Tchabal Gang Daba mountain forests, in the Adamaoua region of Cameroon. The diameter at breast height (DBH), the height of the tree and the thickness of the stem bark of each pygeum tree were recorded in order to establish the cubic volume of each specimen. This data was used to calculate the relationship between the diameter and the volume of the bark. Samples of bark were collected in order to establish the relationship between the volume of the bark and its mass (measure mass per cubic metre). A total of 105 pygeum trees were sampled, including 50 trees in Gang Daba considered as an un-exploited production site and 55 trees in Mbabo referred to an exploited production site. The best equation which links the volume (Vb) of fresh barks to the diameter (D) of each pygeum tree is Vb=a/(1+b*exp(-cD)) with a = 1.79588278896E-001, b =  5.29124992540E+002, c = 1.45488065368E-001. The average thickness of the bark is 13.01 ± 4.8 mm. This value is comprised between that of unexploited (16.99 ± 3.7 mm) and exploited (9.40 ± 2.07 mm) pygeum trees. Considering that for all trees above 30 cm DBH, only two quarters of the bark are taken from the main stem up to the first branch, the average sustainable mass of pygeum tree in Adamaoua region will be about 69.3 kg of fresh bark per tree. This value is comprised between that of unexploited (80 kg) and exploited (60 kg) pygeum trees in Ganga Daba and Mbabo respectively.

Key words: Threatened species, Prunus africana, pygeum, Tchabal  mountain forests, Bitterlich’s Relascope, cubic tariff, CITES.