Regeneration and management of Brachystegia spiciformis Benth. and Julbernardia globiflora (Benth).
1996
Grundy, I. | Mushove, P. T. | Shumba, E. M. | Matose, F.
This paper describes aspects of a research programme designed to investigate the regeneration and use of Brachystegia spiciformis/Julbernardia globiflora woodland in Zimbabwe, in an attempt to generate guidelines for its sustainable management. Miombo woodland, often dominated by B. spiciformis and J. globiflora, represents a rich and diverse resource base for small scale farmers throughout the region, the importance of which has been ignored in the past by managers and policy-makers. The developmennt of sustainable strategies for this resource has therefore been hampered by a lack of knowledge. For this reason, the overall research from which this paper is drawn had a number of interdependent objectives, directed at defining a basis for sustainable management of dry miombo woodland dominated by these two species. This paper concentrates on two of the objectives: to investigate whether growth rings can be used to determine the age of trees; and to determine whether wood production of coppice regrowth after harvesting can be enhanced by the use of silvicultural techniques. The first section of the paper is concerned with determining the age of B. spiciformis using annual rings. It was found that the tree makes annual xylem rings bounded by marginal parenchyma bands which are clearly visible when the wood is polished. Bands may be discontinous, and false rings may occur. Initial investigations show that there is some correlation between ring width and annual rainfall. In the second section of the paper, the use of silvicultural techniques such as water harvesting, protection from browsing, and coppice reduction to improve the rate of regrowth after felling is investigated. Findings show that regrowth from coppice stools was vigorous, even in dry years, and greatest from medium to large stools (between approximately 10 and 30 cm stump diameter). Productivity in general was extremely variable due to site effects. The most productive sites were also potentially the best for agriculture and are therefore unlikely to be left exlusively for woodland management. Neither coppice reduction nor water harvesting in the experiment imporoved growth. Browsing by livestock was found to severely reduce coppice regrowth, particularly of J. Globiflora, at least in the initial stage, so that protection from a browsing in the first year or two after felling is recommended if maximum regrowth is desired. The results reported here have a direct application in miombo management, but also highlight the need for further work to expand these initial findings. One of the outcomes of this research has been the reminder of how little is known of the appropriate management of this important vegetation type.
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