WOODY BIOMASS STRUCTURE AND UTILIZATION FOR CHARCOAL PRODUCTION IN A ZAMBIAN MIOMBO WOODLAND

A survey of woody biomass and its utilisation for charcoal production was carried out in Brachystegia-Julbernardia (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 (greater-than-or-equal-to 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.