Deriving Biomass Allocation and Carbon Stocks in Fruit Components of Strychnos Madagascariensis (Poir.) And Strychnos Spinosa (Lam.) In South Africa

Abstract

Fruits contribute to carbon (C) fixation in fruit tree species of savannah woodlands despite that the C fixed in fruits is rapidly turned back to carbon dioxide (CO2) when the fruits decompose or are eaten. The aim of this study was to determine biomass allocation between fruit components of Strychnos madagascariensis and Strychnos spinosa and to derive the C stocks sequestrated by fruits. A total of 400 ripe fruits were harvested from trees distributed in seven plots across the UMkhanyakude district. Fruit shell and pulp were separated from seeds. Puree and juice of S. spinosa were separated by centrifugation and steam extraction, respectively. Moisture contents of the fruit components were measured. For S. madagascariensis fruits, seeds contributed the most biomass (50.2%), followed by the shell (30.8%), and pulp had the least biomass (16.7%). The loss of material was 2.3%. For S. spinosa, the largest part of fruit biomass was in the shell (41.8%), followed by puree (25.6%), seeds (18.6%), juice (6.2%), and pulp (0.9%). The loss of material was 6.9%. Fruit dry biomass (FDB; in g) and fruit carbon stocks (CB; in g) were both related to fruit diameter (D; in cm) for S. madagascariensis (FDB = 1.022 ᵡ D2.492; CB = 0.463 ᵡ D2.539) and S. spinosa (FDB = 1.015 ᵡ D2.38; CB = 0.198 ᵡ D2.821). Proportion values and regression techniques were both valid methods to derive biomass and carbon stocks of the fruit and its components.