Woody biomass structure and utilisation for charcoal production in a Zambian Miombo woodland

Abstract

A survey of woody biomass and its utilisation for charcoal production was carried out in Brachystegia-Julbernadia (miombo) woodland in Central Zambia during 1988–89 and regression equations were developed for estimating oven-dry weight yields. These equations were applied to stem census data collected during 1982–88 from 17 woodland plots to determine woody biomass structure, production and spatial variability. The mean wood biomass of 141·8 t ha −1 on small (< 0·1 ha) sample plots was significantly higher than that of 78·4 t ha −1 on large (≥ 0·1 ha) sample plots (t = 5·8, P = 0·001). The overall mean standing woody biomass of 81·0 t ha −1 (SD = 7·3) on large plots was made up of 3% leaf and 97% wood. Charcoal was made by the traditional earth kiln method using 93% of the standing log wood biomass while 7% remained in incut stems. A conversion rate of 23·3% was estimated, or about 13–14% on an air-dry weight basis. Yields of coppiced plots aged 6–29 years were estimated at 2·49 t ha −1 year −1. However, wood of suitable size for charcoal production by the earth kiln method was absent in coppiced plots of less than 7 years and constituted less than half of total wood biomass up to 12 years or more after felling.