Abstract

Tools to support sustainable management of dry Miombo woodlands and precise assessment of carbon storage and sequestration potential are in most cases lacking in Tanzania. Accordingly, using Gangalamtumba Village Land Forest Reserve as a case study area located in Iringa region, this thesis aims to develop management tools and generate information that will enhance our understanding of the actual and potential contribution of dry Miombo woodlands in carbon cycling. This is done through a detailed assessment of floristic composition, structure, species associations and through development of models for wood basic density, volume, biomass and growth.

The overall research objective was thus to enhance the basis for good woodland management planning including exploring the extent to which dry Miombo woodlands in Tanzania store and sequester C from the atmosphere. Correct identification of 88 plant woody species belonging to 29 families assisted the selection of a total of 44 important species of trees (28) and shrubs (16). These species were harvested for the determination of basic wood density values and to develop wood basic density models for specific species and for groups of species, namely trees, shrubs and combined. Aboveground volume and biomass models for specific species and species groups were also developed. Growth models of the important species, Brachystegia spiciformis Benth. as influenced by three external factors; rainfall, soil fertility, and competition were also developed to assist planning of sustainable harvesting levels.

Finally, an application of data on forest structure, wood basic densities for trees and shrubs, and the developed models describing aboveground biomass and growth were used in assessing C stocks and sequestration potential of the woodland based on selected scenarios. Generally, the models appear robust and can thus be used in planning sustainable management of the woodlands. The developed models estimate that the dry Miombo woodland of Gangalamtumba Village Land Forest Reserve stores substantial amounts of C; 68.64 Mg C ha-1 both in above- and below-ground soil carbon pools. Assuming that other species’ production are equal to B. spiciformis, which is the most dominant species in the study area, the estimated C sequestration potential of the dry Miombo woodlands was found to vary from 0.42 ± 0.03 Mg C ha-1year-1 to 1.39 ± 0.08 Mg C ha-1year-1, depending on scenario.

Considering the vast areas covered by dry Miombo woodlands, sustainable management of this vegetation type clearly holds potential in preventing emissions of large amounts of C currently locked up in this ecosystem.