Impact of balata tapping on growth and reproduction of Manilkara bidentata in Iwokrama, Guyana

• Main Author: Hall, Lorna
• Published: University of the West of England, Bristol 2003
• Subjects: 634.98609881
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407315

Despite their wide use, the effects of harvesting most wild, tropical non-timber forest products are poorly known. This study concerns the tree Manilkara bidentata (A.DC.) Chev. (Sapotaceae). The tree is a source of balata latex, a potentially exploitable resource in the Iwokrama rainforest in central Guyana. The latex is tapped by ascending the bole of the tree making a herringbone pattern of slashes allowing the latex to drain down the trunk for collection at the base. The population was investigated to quantify latex yield and how tapping affected the tree's growth rates and reproduction. In the population, the mean .density of individuals over 3 cm diameter at breast height (dbh) was 17.2 trees per hectare, with a mean dbh of 0.48 m. Both seedling and tree growth was highly variable and probably related to availability of light resources, in line with other studies. Dry latex yields per area of bark harvested (g m-2 ) were not correlated with tree diameter, but did vary significantly between seasons, probably due to differences in water availability. Tapping did significantly decrease growth rates, particularly where ascent of the bole was involved to a great height or repeated on several occasions. Tapping also significantly increased leaf drop. Although fruit abortions were apparently unaffected, latex harvesting did reduce the maximum potential fruit weight attained. This was probably because the elevated leaf drop reduced the plants' ability to synthesise carbohydrate, causing resource limitations. The co-ordination of maximum fruit weight with maximum fruitdrop was also affected