Subsistence use of wood products and shifting cultivation within a miombowoodland of eastern Tanzania, with some notes on commercial uses

摘要

This study categorizes different subsistence and commercial uses of resources and quantifies the amount of wood used for firewood and building poles within an eastern Tanzanian miombo woodland site. Data from questionnaire surveys were collected from 80 households sampled from two villages. Firewood was used solely at the subsistence level by 96% of the population, with a per capita consumption of 1.5 +/- 0.17 (SE) m(3) year(-1), whereas building poles were not only used at subsistence level but were partly commercialised in the informal market. Per capita consumption of wood for building poles was 0.138 +/- 0.01 m(3) year(-1), based on an average house life-span of eight years. Timber and charcoal production were the most commercialised resources. Shifting cultivation, which is undertaken in the majority of the areas cleared for charcoal, is practiced by 68% of the population while permanent cropping is practiced by 32% of the population. Both farming systems predominantly comprise mono-cropping and mixed-cropping of cereals with bean crops. Shifting cultivation changes vegetation structure from woodlands to bushlands because of a short fallow period of only four years after continuous farming for about six years. Current levels of subsistence use of firewood and poles appear to be sustainable, but levels of shifting cultivation are not. However, selection of favoured species for building poles often leads to over-exploitation, especially when these species are inherently scarce.