Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on June 11, 2009). Includes bibliographical references.

No description available.

In the savanna woodlands of Southern Africa, locally know as miombo, carbon cycling is poorly quantified and many of the key processes remain obscure. For example, seasonal constraints on productivity and leaf display are not well understood. Also, fire is known to be a key process, with around 50% of the annual global area burned occurring in Africa, but detailed understanding of its ecological effects is lacking. Land use change and woodland degradation are changing the structure and functioning of these tropical woodlands, which cover 2.7 million km2 of Southern Africa and provide ecosystem services which support the livelihoods of over 100 million people. In this thesis I quantify the major carbon stocks of the woodlands in Nhambita Regulado, Gorongosa District in Sofala Province, Mozambique. I also examine processes that affect these stocks, including fire and clearance for agriculture. Furthermore, I quantify the seasonal cycle of leaf display, and its relationship to climate. I conducted a series of experimental burns and found that fire intensity was strongly related to rates of top-kill and root stock mortality. Top-kill rates decreased as tree diameter increased up to 10 cm DBH. After this point increased size did not affect top-kill rates, possibly because of accumulated wounds and rottenness. I then extrapolated these results to long term predictions of tree populations and carbon stocks by modelling the interactions of fire, mortality and tree growth. The model was able to successfully predict woody vegetation structure at two sites with known fire regimes, including a 50-year fire experiment in Marondera, Zimbabwe. The results show that annual fires in miombo suppress all woody vegetation. Low intensity fires every 2.5 years are required to maintain observed stem biomass in Nhambita. High intensity fires lead to high top-kill rates (12%), even among large stems. Manipulating fire intensity rather than frequency seems to be the most practical approach to limiting degradation by fire in these ecosystems. Using a three year time series of hemispherical photographs of the tree canopy, combined with satellite data, I find that tree leaf phenology is not directly related to seasonal rainfall patterns, both in Nhambita and across Southern Africa. Pre-rain green-up is the dominant phenology, from the semi arid savannas of the south of the continent to the wet miombo of the Congo basin. Wet miombo woodlands have longer periods of green-up before rain onset (mean 60 days) compared with dry miombo (37 days). Green up-dates show little interannual variability but large spatial variability. The importance of pre-rain green-up in determining how these ecosystems will respond to changing rainfall patterns is unknown, but is an important area for future study. I quantified carbon stocks in the Nhambita woodlands in the soil (69% of total carbon stocks of 111 tC ha-1), tree stems (19%) and roots (8%) as well as other smaller pools. An allometric relationship between root and stem biomass and stem diameter was developed, and used to evaluate the uncertainties in stem carbon estimation at plot and landscape scale. We find that the uncertainty (95% confidence intervals) at plot scale can be quite large (60% of the mean) but this is reduced to around 25% at landscape scale. Strategies for effective inventories of miombo woodland are presented. Using a chronosequence of abandoned farmland, we estimate that stem biomass recovers from clearance after around 30 years of abandonment. Changes in soil carbon stocks are less well understood and need further work. This thesis concludes by outlining further work needed to model the carbon cycle of these woodlands, as well as discussing the implication of pre-rain green-up for satellite observations of land cover changes and biomass mapping.

Africa’s carbon (C) cycle is one of the least well understood components of the global C cycle. Miombo woodlands are the most common woodland type in southern Africa, but despite their vast extent and importance in the biogeochemical cycles of Africa, their C dynamics are not well understood. This thesis addresses a set of science questions related to miombo woodland C dynamics that cover a range of scales, from the leaf to the landscape. The questions are related to seasonal controls on C uptake at the leaf level, to spatial distributions and scales of variation of C stocks in the landscape, and to the drivers and spatial patterns of deforestation and degradation at the regional scale. In miombo woodlands, the seasonality of productivity remains poorly understood, and it is unclear whether stomatal limitations or variations in leaf traits cause seasonal changes in productivity. I use data of leaf gas exchange and leaf traits collected in dry and wet seasons to assess the response of photosynthesis to seasonality. I found a large degree of inter-specific responses, where photosynthetic capacity was maintained between seasons in some tree species but not in others. This was linked to inter-specific stomatal regulation on leaf gas exchange, access to soil water and varied leaf traits, indicating differing timing of leaf development during the dry season. Differing timing of leaf flushing can create niche separation, facilitating the co-existence of miombo woodland tree species. I use data collected along a 5 km transect through miombo woodland to characterise the spatial distributions and scales of variation of C stocks in woody biomass and soils, and assess the links between them. I found that on the scale of a few meters, soil C stocks varied in relation to soil texture. At the kilometre scale, surface soil and woody C stocks were coupled, and varied in relation to topography. By understanding the scales of variation I was able to make recommendations for optimal sampling of C stocks in a miombo woodland landscape for improved C stock assessments. I developed and tested a simple spatial model of deforestation and degradation, using a rule-based approach, to produce risk maps of areas more likely to be affected by deforestation and degradation for a study site in central Mozambique. I found that my model was able to accurately predict the locality of high risk areas, and that roads were the major axis for forest biomass loss. Risk maps created from this method are useful for exploring the drivers of deforestation and degradation in a region dominated by miombo woodland, and for targeting policy and management efforts. Overall, this thesis has contributed significantly to our understanding of natural and human driven miombo woodland C dynamics over a range of scales, from the leaf to the landscape. In the final chapter, I discuss the implications of each chapter for our understanding of miombo woodland C dynamics, and suggest areas for further research.

Miombo is dry deciduous woodland dominated by leguminous tree species, covering a significant area of Africa south of the equator, including large parts of Angola, Malawi, Mozambique, Tanzania, Zaire, Zambia and Zimbabwe. This woodland type reaches its driest, most species-poor limit in Zimbabwe. Brachystegia spiciformis and Julbernardia globiflora are the two main dominants of the drier form of miombo. Miombo woodland 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 development of sustainable management strategies for this resource has therefore been hampered by a lack of knowledge. For this reason, the overall objective of this research was to define the basis for sustainable management of these woodlands, firstly by developing techniques for measuring biomass and monitoring woody growth; secondly, by examining the effect of site conditions on productivity; and thirdly, by investigating biological and social aspects of the management of these woodlands. This research has found that good estimations of standing wood biomass of these two species can be derived from diameter and stem length measurements, thus providing woodland managers with a means of assessing the standing stock. The finding that B. spiciformis forms annual rings can be used in ageing the trees, projecting future yields more accurately, as well as monitoring the effects of management on growth. In the investigation of the effects of climatic and edaphic conditions on tree growth, soil depth was found to have the greatest influence, followed by mean annual rainfall and clay content. Dominant height was found to be the best morphological variable to estimate site potential, in the absence of detailed studies of soil characteristics. The experimental findings from silvicultural trials have important implications for management. Regrowth from coppice stools was vigorous even in dry years, and greatest from medium to large stools. Productivity in general was extremely variable, both of coppiced and uncoppiced trees, due to site effects. The most productive sites are also potentially the best for agriculture and are therefore unlikely to be left exclusively for woodland management. The silvicultural techniques of coppice reduction and water harvesting were not found to enhance coppice regrowth. Browsing by livestock was found to severely reduce coppice regrowth, particularly of J. globiflora, at least in the initial stages, so that protection from browsing in the first year or two after felling is recommended if maximum regrowth is desired. An assessment of the use and management of the indigenous wood resources in a resettlement area in central Zimbabwe suggests that the present harvesting of wood products is unsustainable, due largely to the lack of any woodland management policy for these areas. Local villagers feel powerless to exclude outsiders from their resource, and thus the incentives to manage it sustainably are low. Major changes in government legislation are necessary to alter this situation. In the interim, resource-sharing schemes are suggested as a method of improving the sustainability of use. Some of the results reported here have a direct application in miombo management; these are summarised at the end of this work in the form of guidelines for management. Others identify 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.

No description available.

A dissertation submitted in fulfilment of the requirements for the degree of Master of Science to the Faculty of Science, University of the Witwatersrand, Johannesburg, South Africa, 2019 / The Miombo woodlands are “disturbance driven savannas”, where people, elephants and fire prevent canopy closure and maintain tree-grass coexistence. Since the end of the 18th century, the woodlands have undergone dramatic changes to their disturbance regimes, through increases in human and decreases in elephant populations. This has resulted in a high concentration of human-driven disturbances in some areas of the woodlands and low disturbances in other areas. Consequently, in the areas affected by humans, there are high levels of biomass loss, while other areas experience woody plant encroachment. The ecological impacts of humans and elephants are comparable, but there are important differences. Although both remove woody biomass, they might impact vegetation composition and structure differently. The aim of this study was to investigate whether people can perform a similar functional role to elephants, with regards to biomass removal and potential changes to savanna structure and composition. Aboveground woody biomass estimates were obtained from Synthetic Aperture Radar backscatter and used to (1) compare biomass change at different levels of human (2010 human population density) and elephant influence (2009 Niassa elephant density); and (2) identify how the intensity of biomass loss differs for humans and historical elephant densities (1.4 elephants/km2) under different rainfall and initial biomass conditions. Biomass change was calculated between 2007 and 2010 and compared across equal areas inside and outside of Niassa National Reserve. For human influence, a regional analysis was also done. Published estimates of past elephant densities without poaching for Niassa National Reserve were used as the historical elephant density. Biomass loss increases with population density, for both people and elephants. However, rainfall responses show opposite patterns: biomass loss decreases with rainfall within Niassa National Reserve (under elephant influence) but increases outside of protected areas (under human influence). Under more mesic conditions, humans tend to remove more biomass than elephants. This suggests that woodlands with low rainfall and low human influence have more trees and higher biomass than if elephants were still present at their historical densities, and that some harvesting by people may be beneficial. People and elephants both remove woody biomass; however, they do not necessarily select the same stems. Therefore, species and size class preference of humans and elephants were compared, to identify potential differences in their impacts on vegetation structure and composition. I found that humans prefer a wider range of species than elephants, so might filter the canopy layer more strongly. Elephants’ preference for slightly larger stems suggests that areas utilised by elephants might result in a more left-skewed size-class distribution than humans in areas without a charcoal industry. The high regeneration ability of many species, the large overlap in stems used by people and iii elephants and the relative flexibility in what stems can be used for a specific purpose, suggests that many of these differences in impacts on composition and structure could be mitigated. While elephants and people clearly have different impacts on woody vegetation, people are a totally novel ecological and evolutionary force due to some similarities in how both use woody biomass. The type of human utilisation will determine the stems used and I suggest that since almost all aboveground woody biomass can be utilised for charcoal, the human impact on the woodlands could be reduced by decentralising the charcoal industry. Encouraging small scale production in low rainfall, low human impact areas, could alleviate the pressure on the hotspots of biomass loss. This could provide rural populations with an additional source of income, and the woodlands with a disturbance necessary in maintaining, to some extent, the ecosystem structure and functioning. However, care needs to be taken as increasing accessibility in remote areas could result in rampant deforestation. Results from this thesis suggest that forest management principals developed in other ecosystems, which haven’t had mega-fauna for thousands of years, need to be tailored to African ecosystems. African forest managers therefore need to develop policies that consider the past and present disturbance regimes of these ecosystems. / TL (2020)

Thesis (PhD (Forest and Wood Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The study aimed at developing a new understanding of the Miombo woodland recovery dynamics when exposed to single tree selection, slash & burn agriculture and charcoal production. Five specific studies were conducted to examine different parts of this overall study: Miombo woodland utilization, management and conflict resolution among stakeholders; speciesstem curves as a tool in sampling the development of Miombo woodland species richness in charcoal and slash & burn regrowth stands over time; the impact of human disturbance on the floristic composition of Miombo woodland; regeneration and recruitment potentials of key Miombo woodland species after disturbance; and age and growth rate determination using selected Miombo woodland species. Different methods were developed for each specific study. The study of woodland utilization and management employed semi-structured and key informant interviews. STATISTICA statistical package version 6.0 was used for data collation and analysis. Chi-square tests were used to show levels of significance in differences that existed between different user groups. Species-stem curves were used to determine the sample size to assess Miombo woodland dynamics in regrowth stands after slash & burn and charcoal production, and a fixed-area method was used for the mature woodland stands. The study sites in each of three study areas were selected to represent ages ranging from 2 to 15+ years since each disturbance was terminated. The undisturbed woodland was chosen to act as a control. Various analyses using the STATISTICA statistical package and CANOCO version 4.0 were conducted to understand responses of Miombo woodland to these different disturbances. The research revealed that single tree selection, slash & burn agriculture and charcoal production are the main forms of Copperbelt Miombo woodland utilization which will always be there. Additionally, the the Miombo woodland stands were characterized based on the size class profile they exhibit on exposure to human disturbance factors through forest utilization. The characterization has revealed that the woodland is dominated by light demanding species. As such single tree selection harvesting does not support the regeneration and establishment of the timber species which are canopy species under shade conditions. This implies that selection harvesting of timber species, although it appears to be a non event in terms of disturbance at stand level may be a disaster at population level. The study also revealed that clearing of the woodland for either slash & burn agriculture or charcoal production results in enhanced regeneration and establishment of the dominant Miombo woodland species. The study concludes that charcoal production and slash & burn agriculture are important components to which the woodland ecosystem is adapted. As such these disturbance factors may be considered as incorporated disturbances. It is recommended from the study that woodland utilization and management should integrate charcoal production and slash & burn agriculture into forest management. Cutting cycles should be based on growth rate of the selected species. Timber species harvesting should go side by side with these disturbance factors so as to open up the canopy in order that maximum sunlight can reach the regeneration stock. The study also brings out the other management and utilization opportunities (such as managing for Uapaca kirkiana and Anisophyllea boehmii fruits) that arise from different development stages of the woodland. Lastly, it is recommended to ascertain the optimum gap sizes for both charcoal production or slash & burn agriculture which would still support the Miombo woodland recovery. / AFRIKAANSE OPSOMMING: Hierdie studie is gedoen om ‘n nuwe begrip te ontwikkel vir die hersteldinamika van Miombo boomveld na onderwerping aan enkelboomseleksie, kap & brand lanbou en houtskoolproduksie. Vyf spesifieke studies is gedoen om verskillende komponente van die total studie te ondersoek: benutting, bestuur en konflikresolusie tussen gebruikers van Miombo boomveld; species-stam kurwes as ‘n instrument in die bemonstering van die ontwikkeling van Miombo boomveld species-rykdom oor tyd na afloop van houtskoolproduksie en kap & brand landbou; die impak van menslike versteuring op die floristiese samestelling van Miombo boomveld; verjongingspotensiaal van sleutelsoorte in Miombo boomveld na versteuring; en bepaling van ouderdom en groeitempo in ge-selekteerde Miombo boomveldsoorte. Verskillende metodes is ontwikkel vir elke spesifieke studie. In die studie van boomveldgebruik en –bestuur is semigestruktureerde en sleutel-informant onderhoude gebruik. Die STATISTICA statistiese packet weergawe 6.0 is gebruik vir dataverwerking en -ontleding. Chi-kwadraat toetse is gebruik om vlakke van betekenisvolheid te toon wat bestaan tussen verskillende gebruikersgroepe. Speciesstamkruwes is gebruik om monstergrootte te bepaal vir die evaluering van Miombo boomvelddinamika in hergroeiopstande na kap & brand en houtskoolproduksie, terwyl vastegrootte persele gebruik is vir volwasse boomveldopstande. Die studieplekke in elk van drie studiegebiede is geselekteer om verskillende ouderdomme tussen 2 en 15+ jaar na be-eindiging van die versteuring te verteenwoordig. Onversteurde boomveld is gebruik as kontrole. Verskeie ontledings, met die STATISTICA statistiese pakket en CANOCO weergawe 4.0 is gedoen om die reaksie van Miombo boomveld op die verskillende versteurings te verstaan. Die navorsing het getoon dat enkelboomseleksie, kap & brand landbou en houtskoolproduksie is die hoof vorme van Copperbelt Miombo boomveld benutting wat altyd daar sal wees. Verder is die Miombo boomveldopstande gekarakteriseer gebaseer op die grootteklasprofiel wat hulle vertoon na menslike versteuringsfaktore in die vorm van boomveldbenutting. Die karakterisering het getoon dat die boomveld gedomineer word deur ligeisende soorte. Daarom ondersteun enkelboomseleksie nie die verjonging en vestiging van die dominante houtsoorte wat kroonsoorte is onder skadutoestande. Dit impliseer dat selektiewe inoesting van houtsoorte, alhoewel dit voorkom as ‘n onbelangrike gebeurtenis in terme van versteuring op opstandsvlak, ‘n ramp is op populasievlak. Die studie het ook getoon dat skoonmaak van die boomveld vir of kap & brand landbou of houtskoolproduksie, lei tot verbeterde verjonging en vestiging van die dominante Miombo boomveldsoorte. Die studie lei tot die gevolgtrekking dat houtskoolproduksie en kap & brand landbou belangrike komponente is waarby die boomveldsisteem aangepas is. Daarom kan hierdie versteuringsfaktore beskou word as ingeslote versteurings. Vanuit die studie word daarom aanbeveel dat boomveldbenutting en –bestuur houtskoolproduksie en kap & brand landbou binne die bosbestuur integreerd moet word. Kapsiklusse moet gebaseer word op die groeitempos van geselekteerde soorte. Inoesting van houtsoorte moet saamloop met hierdie versteuringsfaktore sodat die kroondak oopgemaak kan word sodat maksimum sonlig die verjonging bereik. Die studie bring ook na vore die bestuur en benuttingsgeleenthede (soos bestuur vir die vrugte van Uapaca kirkiana en Anisophyllea boehmii) wat voorkom in verskillende ontwikkelingstadiums van die boomveld. Laastens word aanbeveel dat die optimum openinggroottes vir beide kap & brand en houtskoolbereiding wat herstel van Miombo boomveld ondersteun, bepaal.

Submitted by Natalie Mendes (nataliermendes@gmail.com) on 2015-07-25T15:13:48Z No. of bitstreams: 1 Dissertacao_Lucrencio_ultima_versao.pdf: 7732151 bytes, checksum: 29051dce818f171e5f68bd2dfd17cfd0 (MD5) / Made available in DSpace on 2015-07-25T15:13:48Z (GMT). No. of bitstreams: 1 Dissertacao_Lucrencio_ultima_versao.pdf: 7732151 bytes, checksum: 29051dce818f171e5f68bd2dfd17cfd0 (MD5) Previous issue date: 2014-06-30 / Mozambique is in the process of agricultural expansion, particularly in the areas of predominance of Miombo Biome, mostly located in the northern part of the country, driven by the trilateral cooperation program (ProSAVANA) involving Mozambique, Brazil and Japan. Some studies were already conducted by this program, for instance, related to the adaptability of maize and soybean seeds in this area. This study aims to analyze, by the biophysical point of view, the favorability of the agricultural expansion in the northern part of Mozambique in the scope of ProSAVANA, based on the Japan- Brazil cooperation program (PRODECER) experiences in the western part of Bahia. As basic materials, digital elevation models from the Shuttle Radar Topography Mission (SRTM) were used to generate hypsometric and slope maps from both sites, Tropical Rainfall Measuring Mission (TRMM) to compare rainfall data from both sites, data from MODIS/Terra (MOD13Q1) sensor to compare the structure of the most representative biome from both regions. Spatial database containing watershed boundary, forest reserves and soils types were also considered. Techniques of digital image processing, spatial analysis and spatial modeling available in the ENVI 4.8TM and ArcMapTM 10 software packages were used. For the best performance of the EVI data, the Double Logistic filter available in the TIMESAT 3xTM software was applied. Data were analysed based on statistical methods of frequency, histogram and regression. As results, a map of suitability for agricultural expansion areas based on physiographic parameters were obtained over 4.8 million hectares (73 percent of the total area) as well as a database with information of the physical conditions of the both region. The method used here was relatively simple and can be reproduced for other similar researches. / Mo?ambique encontra-se em processo de expans?o agr?cola, em especial, nas ?reas de predom?nio do Bioma Miombo, localizadas, em sua maior extens?o, ao norte do pa?s, impulsionado pelo programa de coopera??o trilateral envolvendo Mo?ambique, Jap?o e Brasil, denominado ProSAVANA. Alguns estudos j? foram conduzidos por esse programa, por exemplo, relacionados com a adaptabilidade das sementes de milho e sorgo na regi?o norte de Mo?ambique. Esse estudo procura analisar, sob ponto de vista biof?sico, a favorabilidade ? expans?o agr?cola da regi?o de predom?nio do bioma Miombo ao norte de Mo?ambique (Corredor de Nacala) no ?mbito do ProSAVANA, ? luz da experi?ncia do programa PRODECER do oeste da Bahia. Como materiais b?sicos, foram utilizados os modelos digitais de eleva??o da Shuttle Radar Topography Mission (SRTM) na gera??o de mapas de hipsometria e declividade, Tropical Rainfall Measuring Mission (TRMM) na an?lise comparativa de dados de precipita??o, dados do sensor MODIS/Terra (MOD13Q1) na compara??o da estrutura da vegeta??o predominante nas duas regi?es (oeste da Bahia e Nacala), al?m do banco de dados espaciais contendo dados sobre as bacias hidrogr?ficas, reservas florestais e solos. Foram utilizadas t?cnicas de processamento digital de imagens e an?lise espacial dispon?veis nos aplicativos ENVI 4.8 e ArcMap 10 e ferramentas de modelagem de dados geogr?ficos. Para uma melhor an?lise dos dados EVI, usou-se o filtro Log?stica Dupla dispon?vel no programa TIMESAT 3.x, que possibilitou a suaviza??o dos ru?dos presentes nesse tipo de dados. Os dados foram analisados com base em m?todos estat?sticos utilizando a regress?o linear e an?lises de frequ?ncia e histogramas. Como resultados, obteve-se um mapa de ?reas favor?veis ? expans?o agr?cola sob ponto de vista fisiogr?fico, na regi?o norte de Mo?ambique, avaliadas em cerca de 4.8 milh?es de hectares (73% da ?rea total), al?m de um banco de dados contendo informa??es sobre as condi??es f?sicas de ambas regi?es. O m?todo utilizado nesse estudo foi relativamente simples e pode ser estendida para outras pesquisas similares.

This study attempted a holistic synthesis of the problems of Sustainable Development (SD) and Sustainable Forest Management (SFM) in the dry deciduous forests of south western Zambia. There are scale-based implications across the entire range of actions required for SFM and REDD+ implementation in tropical forests. Addressing scale mismatches in ecological, social and socio-ecological systems is essential and may help resolve epistemological differences in interdisciplinary research. The importance of local context to SD and SFM supported a case study approach to the social-ecological system. Leaf phenology shows regional variation in deciduousness and varies spatially on a local scale. This highlights the need for researching the eco-physiological source of this variation to assess the effects of climate change on forest phenology. Livelihood analysis in forest communities showed that high levels of social and natural capital confer community resilience to climate change. Land use change was mapped between 1975 and 2005. Zambezi Teak forests decreased in area by 54% between 1975 and 2005. However, changes in area weighted Above Ground Biomass (AGB) are negligible because Zambezi Teak forests are replaced by other woody vegetation. The differences in AGB between plot-based field measurements of AGB and published global biomass maps mean that these maps are not useful for REDD+ projects at the project scale (~10,000 ha). Governance arrangements for Zambezi Teak forests differ between Zambia and Zimbabwe. Although the forests in Zimbabwe have an age structure skewed towards smaller age classes than forests in Zambia, possibly indicating a recovery from logging, this study has not accounted for other covariates which determine forest condition. This research emphasises the importance of case studies for building a global database for inclusion in a meta-analysis, and for the contextual focus which a holistic approach brings to the action-based agenda at the heart of SD and SFM.