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The sustainable management of dry forests and woodlands of Sub-Saharan Africa (SSA) is crucial for the SSA economy and people’s livelihoods but it remains a key challenge to address. Maps of tree species distributions of economic value are lacking for the region; yet, this information is essential for supporting sustainable use. We capitalized on new nation-wide field survey data for the Republic of Zambia (Southern Africa) to generate the first suite of baseline species distribution models (SDMs) for 20 tree species of economic significance to support for sustainable management and conservation. We employed one regression- and two machine learning-based techniques to model and predict tree distribution. For each species, we compared the three model results for the relative importance of different predictive variables, revealing the most important predictors of each species niche and providing insight into how human activities influence current tree species distribution. Overall, environmental predictors that best explained tree species distribution were related to water availability, including mean potential evapotranspiration (PET), annual rainfall, and the variation in PET, as well as elevation and soil fertility. Human impact on distribution was notable for tree species used for charcoal and timber, including the proximity to roads for charcoal-favored species and the proximity to settlement for timber species. For all tree species, fire did not stand out as a variable of importance, contrary to expectations. The SDMs generated from this study will provide essential baseline information to support national conservation and management efforts, especially for preferred timber and charcoal species for which selective harvesting has had an impact on their distribution. Our results highlight the importance of rainfalls for the distribution of tree species in this seasonally dry region and calls for future research to forecast the impacts of climate change on habitat suitability.

Aim: In tropical Africa, savannas cover huge areas, have high plant species richness and are considered as a major natural resource for most countries. There is, however, little information available on their floristics and biogeography at the continental scale, despite the importance of such information for our understanding of the drivers of species diversity at various scales and for effective conservation and management. Here, we collated and analysed floristic data from across the continent in order to propose a biogeographical regionalization for African savannas. Location: We collated floristic information (specifically woody species lists) for 298 samples of savanna vegetation across Africa, extending from 18° N to 33° S and from 17° W to 48° E. Taxa: We focused on native woody species. Methods: We used ordination and clustering to identify the floristic discontinuities and gradual transitions across African savannas. Floristic relationships, specificity and turnover, within and between floristic clusters, were analysed using a (dis-)similarity-based approach. Results: We identified eight floristic clusters across African savannas which in turn were grouped into two larger macro-units. Ordinations at species and genus levels showed a clear differentiation in woody species composition between the North/West macro-unit and the South/East macro-unit. This floristic discontinuity matches to the High (i.e. N&W) and Low (S&E) division of Africa previously proposed by White () and which tracks climatic and topographical variation. In the N&W savannas, the floristic gradient determined by rainfall was partitioned into the Sudanian (drier) and Guinean (wetter) clusters. Within the highly heterogeneous S&E savannas and woodlands, six clusters were identified: Ugandan, Ethiopian, Mozambican, Zambezian, Namibian and South African. Main conclusions: The proposed pan-African classification of savannas and woodlands might assist the development of coordinated management and conservation policies., SCOPUS: ar.j, info:eu-repo/semantics/published

Occurrence data for Julbernardia globiflora and J. paniculata at 617 sites in the miombo woodland region of central, eastern and southern Africa and forest inventory data for 512 woodland plots in Zambia were used to determine species distribution and dominance. Distribution of the two Julbernardia species overlaps in the central region of the miombo woodland range while the eastern and western range regions are exclusively for only one of the two species. In the region of co-occurrence, there is a clear spatial separation in the dominance of the two species. In old-growth woodland a significant proportion of the variation in the dominance of J. globiflora was explained by the dominance of J. paniculata while mean annual maximum temperature and tree species richness negatively affect the dominance of J. paniculata. Old-growth woodland clearing changes the local climatic conditions and alters the way Julbernardia species in re-growth stands respond to potential evapo-transpiration (PET). Climate change, especially global warming, may further reinforce the impacts of PET to differentially favour J. globiflora. Because of this altered response of Julbernardia species in re-growth miombo, preserving old-growth miombo and preventing present human disturbances in designated areas, such as forest reserves and national parks, may be a useful climate adaptation strategy for these species.

Seed predation and seedling mortality can act as strong demographic “bottlenecks” to sapling recruitment in African savanna woodlands. Fire also limits tree recruitment from saplings by suppressing their growth. I conducted field experiments with 13 woody plant species to assess the effects of seed burial on seedling emergence rates and effects of fire on seedling and sapling survival and growth rates over a period of 8 years at a savanna plot in central Zambia, southern Africa. Seed removal rates by small rodents varied among years and buried seeds had significantly higher emergence rates than seeds exposed to predators in most but not all the species. Annual burning reduced sapling growth in some species but in other species saplings experienced successive shoot die back even in the absence of fire. The findings show that for some woody species, seed predation is an important constraint to seedling recruitment but not for others and annual fires are important hindrances to demography and growth for some species but not others. Thus, demographic “bottlenecks” occur at different life history stages in different savanna woody species and these have the potential to alter woody tree competitive relationships and ultimately savanna structure.

Aims In spite of the importance of African acacias in vegetation succession and provision of goods and services, little is known about life-history variations within and among species. Much of the work done on African acacias has focused on seed predation and germination and seedling establishment, especially of Acacia tortilis, Acacia nilotica and Acacia karroo. The primary aim of the present work is to investigate differences in the demography of Acacia polyacantha and Acacia sieberiana and the relationship between life-history characteristics and population size. A secondary objective is to assess how fire, an important ecological factor in savanna vegetation, might modify the growth and demographic dynamics of the two acacias. Methods The study was conducted at the Makeni savanna plot in central Zambia, southern Africa. Seedling emergence from both non-scarified and scarified seeds sown at different times in the wet season and the fate and growth of seedlings and saplings were monitored over a period of 4 years. Annual growth of permanently marked sample trees in annually burnt and fire-protected blocks was recorded over a 6-year period (2002–08) in order to assess inter-specific differences and how fire modifies tree growth patterns. Censuses of natural saplings and trees were conducted periodically in sample blocks to determine recruitment into these life-history stages. Important findings Seedling emergence and sapling survival rates were much higher in A. sieberiana than in A. polyacantha. However, both seedling and sapling growth rates were higher inA.polyacantha than in A. sieberiana but tree growth rates were similar in the two species. Under fire protection tree growth was significantly influenced by tree size and year while under annual burning only tree size significantly affected tree growth. The dominance of A. sieberiana over A. polyacantha at the study site was attributed to higher seedling emergence rate, higher sapling survival rate and a large sapling bank that forms a reliable source of tree recruitment. The life-history stage characteristics of A. polyacantha suggest that this is an early successional species.

The present study investigated how climate and plant size affect the growth of Bauhinia thonningii and how fire and source of regeneration (grown from coppice versus seedlings) might modify the results. The study was conducted over a period of 10 y, from 1997 to 2007, at a savanna site in central Zambia. Trees were marked and monitored throughout the entire period; they showed a phase of declining growth (1998–2003) and a phase of low growth (2004–2007). During the phase of declining growth autocorrelation was high but either weakened or disappeared during the phase of low growth. After adjusting data for autocorrelation, climate factors and tree size accounted for between 14% and 35% of the variation in annual tree radial growth. However, the growth responses of trees to climate factors and tree size varied with the source of regeneration (i.e. coppice or seedling) and fire treatment. Trees of seedling origin were only affected by climate factors and tree size when exposed to annual burning whereas all trees of coppice origin were significantly affected by climate factors and tree size, regardless of the fire treatment. However, basal radial growth of saplings that were monitored for 4 y (2003–2007) was significantly influenced by maximum temperature and rainfall that accounted for 33–47% of the variance in annual radial growth under fire protection. Saplings recovered from shoot die-back during the cool dry season by resprouting in the hot dry season and this annual die-back slowed the height growth of B. thonningii saplings.

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associate canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000 mm.yr−1 (water-limited forests) and to radiation otherwise (light-limited forests); on the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. Precipitation first-order control indicates an overall decrease in tropical forest productivity in a drier climate.

Made available in DSpace on 2018-12-11T17:02:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-04-28 The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000ĝ€-mmĝ€-yrĝ'1 (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000ĝ€-mmĝ€-yrĝ'1. Author(s) 2016. Remote Sensing Division National Institute for Space Research - INPE São José Dos Campos CIRAD UMR Ecologie des Forêts de Guyane INRA UMR EEF 1137 INRA UMR Ecologie des Forêts de Guyane Department of Biology University of Antwerp National Center for Monitoring and Early Warning of Natural Disasters - CEMADEN São José Dos Campos School of Geography University of Leeds Institute of Botany University of Hohenheim Laboratory for Wood Biology and Xylarium Royal Museum for Central Africa Programa de Pós-graduação em Ciências de Florestas Tropicais Instituto Nacional de Pesquisas da Amazônia Embrapa Florestas Brazilian Agricultural Research Corporation School of Biological Sciences University of Tasmania Institute of Geography University of Erlangen-Nuremberg Laboratory of Geo-information Science and Remote Sensing Wageningen University Centro de Ciências Biológicas e da Natureza Laboratóio de Botânica e Ecologia Vegetal Universidade Federal Do Acre Instituto Pirenaico de Ecologia Consejo Superior de Investigaciones Cientificas (IPE-CSIC) Instituto Boliviano de Investigacion Forestal (IBIF) Santa Cruz de la Sierra Centro de Energia Nuclear Na Agricultura Laboratóio de Ecologia Isotópica Universidade de SÃo Paulo Departamento de Botânica Universidade Federal Do Paraná Departamento de Botânica Universidade Federal de Juiz de Fora (UFJF) Programa de Pós-Graduação Ecologia e Manejo de Recursos Naturais Universidade Federal Do Acre Departamento de Ecologia Do Instituto de Biociências Universidade de São Paulo (USP) UMR 5174 Laboratoire Evolution et DiversitéBiologique CNRS and UniversitéPaul Sabatier Biological Sciences Department University of Zambia Department of Biology University of Missouri-St. Louis Coordenação de Pesquisas em Biodiversidade Instituto Nacional de Pesquisas da Amazônia Departamento de Engenharia Florestal Universidade Federal de Viçosa (UFV) Departamento de Engenharia Florestal Universidade Federal Do Paraná Centro de Ciêcias Biológicas e da Natureza Laboratório de Botânica e Ecologia Vegetal Universidade Federal Do Acre Prefeitura Municipal de Rio Branco Département Hommes Natures Sociétés Centre National de la Recherche Scientifique (CNRS) et UMR 208 Patrimoines Locaux et Gouvernance, Cedex 05 Dept. Forest and Wood Science University of Stellenbosch Meisterschule Ebern für das Schreinerhandwerk Floresta Estadual de Assis Tanzania Forestry Research Institute (TAFORI), P.O. Box Departamento de Ciências Florestais Universidade de São Paulo Escola Superior de Agricultura Luiz de Queiroz Departamento de Engenharia Florestal - DEF Universidade Estadual Do Centro-Oeste Departamento de Ciências Florestais Centro de Ciências Rurais Universidade Federal de Santa Maria Departamento de Botânica Laboratório de Fisiologia Vegeta Universidade de Brasília Instituto de Ciências Biológicas World Agroforestry Centre (ICRAF), P.O. Box Coordenação de Pesquisa em Ecologia Instituto Nacional de Pesquisas da Amazônia, C.P. 478 Departement of Land Resource Management Northern Territory Government Research Institute for Environment and Livelihoods Charles Darwin University Department of Biological Sciences Mount Holyoke College Department of Earth System Science Stanford University Department of Natural Resources and Environmental Sciences University of Illinois at Urbana Champaign Department of Plant Ecology Albrecht von Haller Institute of Plant Sciences University of Göttingen Departamento de Engenharia Florestal Universidade Do Estado de Santa Catarina - UDESC Tropical Peat Research Institute Biological Research Division Malaysian Palm Oil Board Departamento de Botânica Instituto de Ciências Biologicas Universidade Federal de Minas Gerais Division of Science and Environmental Policy California State University Monterey Bay Departamento de Biologia Universidade Federal de Sergipe Programa Forestal Colegio de Postgraduados Department of Geosciences and Geography University of Helsinki School of Geography and the Environment University of Oxford Departamento de Solos e Engenharia Agrícola Universidade Federal Do Paraná Laboratoria de Dendrochronologia y Anatomia de Maderas Espinoza Universidad Nacional de Loja Research Institute for the Environment and Livelihoods Charles Darwin University Center for Forest Disturbance Science USDA Forest Service Department of Biological Sciences Florida International University Graduate School of Agriculture Kyoto University Institut Français de Pondicherry UMR AMAP (BotAnique et BioinforMatique de l'Architecture des Plantes) IRD Tree Ring and Environmental History Laboratory Instituto Argentino de Nivología Glaciología y Ciencias Ambientales - CONICET Department of Earth and Environment Southeast Environmental Research Center Florida International University Departamento de Biologia Aplicada FCAV Universidade Estadual Paulista UNESP UR BandSEF (Biens et Services des Écosystèmes Forestiers Tropicaux) CIRAD School of Geosciences University of Edinburgh CarboForExpert HJ Andrews Experimental Forest Oregon State University Ibama PRONAT - Programa de Pós-Graduação em Recurso Naturais Universidade Federal de Roraima - UFRR School of Biological Sciences University of Aberdeen Departamento de Ciências Ambientais Universidade Federal Do Amapá Embrapa Cocais Brazilian Agricultural Research Corporation Instituto Boliviano de Investigacion Forestal (IBIF) Universidad Autonoma Gabriel René Moreno Department of Forest Vegetation Forestry and Forest Products Research Institute (FFPRI) Núcleo de Estudos e Pesquisas Ambientais (NEPAM) Universidade Estadual de Campinas (UNICAMP) Embrapa Roraima Brazilian Agricultural Research Corporation Crop Production Systems in the Tropics Georg-August-Universit Departamento de Engenharia Florestal Centro de Educação Superior Norte Universidade Federal de Santa Maria College of Life and Environmental Sciences University of Exeter Departamento de Biologia Aplicada FCAV Universidade Estadual Paulista UNESP

Seedling emergence from scarified seeds and mortality of different seedling cohorts of five African savanna woody species (Acacia polyacantha, A. sieberana, Bauhinia thonningii, Dichrostachys cinerea and Ziziphus abyssinica) were studied under field conditions at a site in central Zambia. The study was conducted over a 4-year period, from 2003 to 2007. The objectives of the study were to determine climate factors that significantly influence seedling emergence rate and mortality in order to assess likely responses of the studied species to a warmer climate. Mean seedling emergence rate was 12% in D. cinerea and Z. abyssinica, 17% in B. thonningii, 47% in A. poyacantha and 62% in A. sieberana. Climate factors did not significantly affect seedling emergence in A. sieberana while temperature significantly influenced seedling emergence rate in the other species. Under a 1° warmer climate, seedling emergence rate was predicted to decline in A. polyacantha, B. thonningii and Z. abysssinica but is likely to increase slightly in D. cinerea. Time of seedling emergence during the wet season did not appear to affect seedling survival. Temperature also significantly influenced seedling mortality in all the studied species such that under a warmer climate, mortality was predicted to increase in A. sieberana and D. cinerea but decrease in A. polyacantha, B. thonningii and Z. abyssinica. As the studied species exhibited differential optimum temperature conditions for seedling emergence and seedling survival, they are likely to respond to climate warming in different but predictable ways. The results of the study are useful to forest management and development of climate change adaptation strategies in southern Africa.

This study investigated the growth responses to defoliation, fire-exposure and climate factors of a widespread Africana savanna tree, Bauhinia thonningii Schumacher, at a site in central Zambia. Experimental trees (n = 47) were either exposed to fire (n = 12) in the first half of the dry season or protected from fire (n = 35). Some of the fire-protected trees (n = 12) were subjected to artificial defoliation in two consecutive years. Phenological responses (bud break, leaf flush and leaf production) to fire-exposure and defoliation were monitored on permanently marked sample shoots over a 2-year period. Radial tree growth (diameter at 1.3 m above ground) was measured annually over a 7-year period from 1998 to 2005. During the first two years, defoliation and fire-exposure advanced the onset of bud break and leaf flush but fire-exposed trees produced significantly less leaves than did trees protected from fire, probably because scorching caused more severe shoot die-back than is normal. Leaf production was also significantly affected by experimental treatments and their interaction with year. Although treatments had significant short-term effects on radial growth, previous-year growth significantly influenced current-year growth, thereby confirming the existence of autocorrelation in the time-series growth data of B. thonningii. The interaction between previous-year growth and climate factors explained a significant proportion (25–40%, P

—The traditional values of caterpillars to the Bisa people of northern Zambia were assessed through a questionnaire survey involving 104 households from 24 villages. Information validation was by Participatory Rural Appraisal, Focus Group Discussions, caterpillar collection and identification. Caterpillars of eight Saturniidae moth species are valued very highly by the Bisa. Six of these were collected and identified from the miombo woodlands of the study area. The harvesting of Gynanisa maja (Klug), Gonimbrasia belina (Westwood), China forda (Westwood), Imbrasia epimethea (Drury), I. rubra (Bouvier) and Imbrasia sp.3 caterpillars by local people, provides an alternative source of dietary animal protein and is associated with several cultural and spiritual processes and beliefs which bind the people together as one tribe. Edible caterpillars are bartered and sold at markets, enabling the local people to gain access to goods and services that normally are out of their reach. An individual collector processed 11.5 kg of sun-dried edible caterpillars worth Zambian Kwacha (ZK) 172,600 (US$ 52) during the caterpillar-harvesting period in 1999, while a household averaging six members processed 69.1 kg caterpillars worth ZK 1,036,098 (US$ 309). The income generated from sales of edible caterpillars far outstripped that generated from the sale of agricultural produce. Estimates of household incomes for 1999, an edible-caterpillar bumper harvest year, and the Bisa traditional edible-caterpillar management system are discussed.

The effect of tillage, clipping, precipitation and temperature on above-ground grass production was investigated in permanent plots at a Zambian savanna site for 5 y (1996^2001) by the harvest method. Mean species richness was 4.6 species m-2 with a total of 15 species at the study site. Mean end-of-season grass phytomass was 464 g m-2 with no statistically significant differences among years in control quadrats. Grass phytomass recovered within two wet seasons after tillage and a similar trend was observed after cessation of a 2-y monthly harvesting regime. However, in experimental quadrats, plot, treatment and year had significant effects on grass production. Previous- and current-season precipitation had no significant effect on end-of-wet-season grass phytomass but phytomass of the previous season explained 27-53% of the variation in end-of-wet-season phytomass. Grass production peaked in the wet season and declined sharply as the dry season progressed. The interaction between precipitation, temperature, harvesting and duration of the dry season explained 81-91% of the variation in daily grass production but the significance of the interactions varied with season and duration of harvesting. Precipitation-use efficiency (PUE) of grasses declined from 2.25 g m-2 mm-1 at the start of the wet season in December to 0.25 g m-2 mm-1 at the end of the season in March. Monthly harvesting for 1 y reduced PUE to less than 25%. The results indicate very complex relationships between above-ground grass production (dependent variable) and climate and land-use (independent) factors that makes the prediction of grass production in central southern African savannas difficult.

Aim Population pressure and communal land ownership are often perceived as serious threats to forest conservation in savanna woodlands of central and southern Africa. I aimed at testing the hypothesis that the rate of miombo woodland recovery after clearing and re-growth structure are determined by land tenure and use. Location Miombo woodland under customary, leasehold, forest reserve and national park on ten permanent and temporary sites was studied in central Zambia. Two sites were in mature woodland and eight sites were in re-growth miombo ranging in age from 1 to 30 years. Methods I enumerated and measured girth at breast height (1.3 m above ground) of trees/stems in sixty-four 20 × 10 m plots in 1982, 1986 and 2000 at six sites and annually from 1990 to 2001 at four sites to determine stem density and status (live, dead or cut) and wood biomass. A total of 239 trees were cut, wood biomass measured and the data used to develop equations for estimating wood biomass on study plots. Distance between each study site and the nearest human settlement was estimated during each sampling period using aerial photographs, topographical maps and the global positioning system. Results Land tenure was responsible for significant differences in stem density, wood biomass and rate of biomass accumulation in re-growth following clearing of mature miombo woodland. Although stem density was highest on customary land, wood biomass and accumulation rate were lowest. The highest biomass was on plots in forest reserves, with intermediate values for leasehold and national park. Fire was responsible for tree mortality at all the study sites and its impact was highest at a site in a national park. Sites close to human settlements had the highest density of cut stems but this activity did not significantly reduce wood biomass. Rate of woodland recovery was higher on sites cleared in the 1970s than on sites cleared in the 1990s, irrespective of age of re-growth. The development of the first, second and third re-growths following successive woodland clearing in 1972, 1981 and 1990, respectively, was not significantly different, except for stem density which was highest in the second re-growth. Analysis of interactions between five land tenure and use factors (independent variables) and re-growth structure revealed that 52% (P=0.0000) of the variation in stem density was because of re-growth age and decade in which the woodland was cleared while distance to human settlements and age of re-growth explained 42% (P=0.0000) of the variation in wood biomass. Individually, distance to human settlements explained 25% (P=0.0000) of the variation in wood biomass accumulation rate. Conclusion The results supported the hypothesis that rate of miombo woodland recovery and structure were influenced by land tenure and use. However, analysis of interactions between factors revealed that use related factors (i.e. decade in which woodland was cleared and distance to human settlements) and re-growth related factors (age and type of re-growth) were more important than land tenure per se in explaining variation in miombo recovery. The conclusion from these results is that regulation of land use is more important than change in land tenure to the proper management of miombo woodland.

A survey on customary land and an adjacent forest reserve was conducted in the Kopa area of northern Zambia in November 2000. The objectives of the survey were to describe habitats of edible caterpillars and assess temporal and spatial variations in caterpillar abundance, the impact of tree cutting during caterpillar harvesting and the potential of edible caterpillars as sources of income for rural households. The results showed that edible caterpillars have the potential, even in years of moderate abundance, to generate incomes of over US$60 per household that are comparable to, or even higher than, incomes from the sale of agricultural crops. The most favourable habitats for the production of the two most popular edible caterpillars, Gynanisa maja Strand and Gonimbrasia zambesina Walker, were in young re-growth Brachystegia-Julbernardia (miombo) woodland regenerating after abandonment of chitemene shifting cultivation, probably because of the increase in abundance of their main host tree, Julbe...

International audience; Terrestrial carbon stock mapping is important for the successful implementation of climate change mitigation policies. Its accuracy depends on the availability of reliable allometric models to infer oven-dry aboveground biomass of trees from census data. The degree of uncertainty associated with previously published pantropical aboveground biomass allometries is large. We analyzed a global database of directly harvested trees at 58 sites, spanning a wide range of climatic conditions and vegetation types (4004 trees ≥ 5 cm trunk diameter). When trunk diameter, total tree height, and wood specific gravity were included in the aboveground biomass model as co-variates, a single model was found to hold across tropical vegetation types, with no detectable effect of region or environmental factors. The mean percent bias and variance of this model was only slightly higher than that of locally fitted models. Wood specific gravity was an important predictor of aboveground biomass, especially when including a much broader range of vegetation types than previous studies. The generic tree diameter-height relationship depended linearly on a bioclimatic stress variable E, which compounds indices of temperature variability, precipitation variability and drought intensity. For cases in which total tree height is unavailable for aboveground biomass estimation, a pantropical model incorporating wood density, trunk diameter and the variable E outperformed previously published models without height. However, to minimize bias, the development of locally derived diameter-height relationships is advised whenever possible. Both new allometric models should contribute to improve the accuracy of biomass assessment protocols in tropical vegetation types, and to advancing our understanding of architectural and evolutionary constraints on woody plant development.

An assessment of the effects of wood carbonization by the traditional earth kiln method in Brachystegia-Julber-nardia (miombo) woodland on soil nutrients in the field and seedling growth under laboratory conditions was made from August 1992 to March 1993. Wood carbonization increased soil pH and exchangeable P and K. Generally seed germination was better in charcoal soil than in undisturbed soil among the seven indigenous woody plants studied. Seedling growth in charcoal soil was good, except for Isoberlinia angolensis which had lower growth rate than in undisturbed soil.

The recovery of miombo woodlands following clearance for woodfuel is being monitored at four sites in central Zambia. Charcoal production removes 50% of the total woody biomass and the woodland regenerates from a pool of stunted old seedlings and stumps of cut trees. Productivity is correlated to tree density before felling. Clearing of successive regrowth miombo does not appear to affect productivity. Annual wood biomass increment in unmanaged regrowth miombo is estimated at 2–3 t/ha pa of which about 1.1 t is cord wood suitable for charcoal production. However, the charcoal spots within the deforested area are severely impacted by the carbonization process which destroys soil structure, seedlings and root stocks. Woodland regeneration on such spots is protracted. Fortunately, charcoal spots only cover 2–3% of the deforested area. The concern about land degradation due to deforestation caused by woodfuel harvesting for urban charcoal in the miombo woodland region of central and southern Africa is not supported by the results of this study.

The development of seedlings of two miombo trees, Brachystegia spiciformis Benth. and Julbernardia paniculata (Benth.) Troupin, was studied during two growing seasons (December 1989–April 1991) at a Zambian grassland site. Seed germination rates under laboratory and field conditions were not significantly different although germination in the field was delayed by 1–2 weeks due to insufficient rainfall. After one year of storage J. paniculata seed germination had declined from 67% to 17% while germination of B. spiciformis seeds remained at about 83%.

The development of seedlings of the miombo tree (Julbernardia globiflora) was studied for 28 months (December 1987 - April 1990) at a Zambian grassland site from which fire has been excluded for many years. Germination occurred 10–25 days after seed planting and germination rates under laboratory and field conditions did not differ significantly. Seed germinability after one year of storage declined to 38 %. Leaf production occurred between December and April with peaks in January each year. Leaf fall occurred steadily throughout the dry season but leafless seedlings were first observed in August of each year. All seedlings had shed all their leaves by the end of November during the first year while 10% of the seedlings remained leafy throughout the second year. Annual seedling mortality was about 60 % during the first year and declined to 3 6 % during the second year. Survivorship appeared to stabilise at 3 8 % when seedlings were 5 5 - 5 9 weeks old. Every seedling experienced shoot die-back during the first hot dry season (September - November) when open-pan evaporation rates averaged 5–10 mm / day. However, shoot mortality did not necessarily result in plant mortality. Because of recurrent shoot die-back there was little increase in shoot biomass and height at the end of the second and third growing seasons. Seedlings that survived shoot die-back sprouted from roots which showed a steady annual accumulation of biomass. Early shoot die-back in seedlings of Julbernardia globiflora as documented in this study was not causedby fire but most probably by drought and / or nutritional stress.

A survey of woody biomass and its utilisation for charcoal production was carried out in Brachystegia-Julbernadia (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 (

A survey of standing woody (leaf and wood) biomass was made in a Zambezian Brachystegia/Julbernardia (miombo) woodland in the Copperbelt area of Zambia during 1988. Woody biomass data obtained from destructive stem samples from Central and Copperbelt areas of Zambia were used to develop regression models for estimating dry weights of woody biomass components from stem-diameter data. These models were then applied to stem census data collected during 1982–1988 from 45 coppiced and old-growth plots to determine the structure of woody biomass in miombo woodland in the Copperbelt area. Mean wood biomass of 234.7 t ha−1 ( sd = 35.9 ) on small (0.02 ha) sample plots was significantly higher than that of 89.2 t ha−1 ( sd = 13.6 ) on large (> 0.10 ha) sample plots (t = 7.68, P sd = 14.1 ) on large old-growth woodland plots was made up of 3.6% leaf and 96.4% wood. Mean annual increment ( mai ) in wood biomass in coppiced plots aged 3–29 years was estimated at 1.97 t ha−1 ( sd = 1.68 ), but this ranged from 0.41 t ha−1 ( sd = 0.34 ) on plots aged 3–6 years to 2.91 t ha−1 ( sd = 1.41 ) on plots aged 7–29 years. The mai in experimental plots aged 48–49 years was 1.68 t ha−1 ( sd = 0.39 ). Among coppiced plots aged 3–6 years the mai of 0.60 t ha−1 ( sd = 0.35 ) on early-burnt plots as 2.7 times that of 0.22 t ha−1 on the late-burnt plots. Leaf biomass was not significantly different between coppiced plots aged 7–29 years and old-growth miombo woodland plots. The overall mean leaf biomass was 3.62 t ha−1 ( sd = 1.90 ). Mean leaf biomass as a percentage of mai in wood biomass represented 128% in coppiced plots aged 7–29 years and 177% in experimental plots aged 48–49 years. However, in coppiced plots aged 3–6 years there was no significant difference between mai and leaf biomass.

Seasonality in nitrogen (N) and phosphorus (P) concentration in soil and shoots of five Brachystegia-Julbernardia (miombo) woodland trees was studied from September 1991 to March 1993 at two regrowth miombo sites in central Zambia. Shoot growth started in the dry season (September–November) and lasted until April during the 1991/92 season but had virtually ceased by January 1993 during the 1992/93 season. The shoot growing season was associated with low foliar N/P ratios. These ratios were much lower (

In 1933/34 eight coppice plots were established in Brachystegia-Julbemardia (miombo) woodland at Ndola in the Copperbelt area of Zambia by the Forestry Department. These plots have been maintained under fire protection, annual early or late dry season burning since 1934/35. Before establishment stems over 20.3 cm girth at breast height were enumerated. Three of the eight plots (one fire protected and two annually early burnt) were enumerated in 1982, 48–49 years after establishment. In addition, a coppice plot at Chitwi, 16 km southwest of the Ndola plots, cleared in 1972 and left to regenerate naturally was enumerated in May 1982 and August 1986 to assess woody plant growth.The density of stems over 20.0 cm girth in the 13-year-old coppice at Chitwi was 2.5 times that in an adjacent shelterbelt woodland. The stem density in the fire protected plot at Ndola in 1982 was 86% of the pre-felling density while in one of the early burnt plots it was 95% of the pre-felling density. The protected plot had the lowest species diversity after 49 years, largely because of the loss of 11 understorey species that were present before felling.There were no significant differences in stem mean girth at breast height (gbh) of canopy species in the Ndola plots under fire protection and early burning regimes. Mean annual gbh increments of abundant species were estimated at 1.17–2.21 cm yr−1 and 0.59–1.42 cm yr−1 during 0–9 and 0–49 year age-periods, respectively. Estimated mean annual basal area increments for stems over 30 cm gbh were 0.35 m2 ha−1 for the 13-year-old coppice and 0.24–0.27 m2 ha−1 for the 49-year-old coppice. These results indicate a decrease in both gbh and basal area increment with increasing age of miombo coppice

Between 1937 and 1983 a total of 391 400 ha of woodland, representing 51% of the 768 900 ha in the Zambia Copperbelt, had been deforested for industrial and household woodfuel. This has occurred in spite of a forest reservation programme that increased the area in forest reserves from 31 707 ha in 1942 to 252 715 ha in 1965. Between 1965 and 1980 the reserved forests were reduced to 246 930 ha and since then the area has remained static. The rapidly growing demand for charcoal by the increasing urban population, and the growing problem of acid dust and rain pollution from copper smelters, pose serious threats to forest conservation in this industrial region of Zambia. Current forest conservation is restricted to the establishment of exotic forest plantations and recently deforested areas are left to regenerate naturally. Forest destruction and conservation in the Copperbelt area were studied and the structure of old-growth and coppice woodland stands at 9 and 14 sites, respectively, investigated during 1982–1984. The Copperbelt vegetation is dominated by Brachystegia-Julbernardia woodland. Mean species diversity of 24·40·1 ha −1 in coppice stands was higher than that of 18·9 found in old-growth stands. Stem density in coppice was 3·3 times that observed in old-growth woodlands. The majority of species (over 50%) in both old-growth and coppice were represented by less than 11 stems per sampling plot. Mean basal area at breast height in coppice aged 19–23 years was 14·33 m 2 , which was 95% of the mean basal area of 15·15 m 2 found in old-growth woodlands.

The purpose of natural fallow in bush-fallow cultivaton systems is to improve soil fertility following a phase of cultivation and to provide useful forest products, including livestock feed. When natural fallow fails to serve these purposes, it can be supplemented or replaced by planted trees. This paper describes the development and function ofAcacia fallow in the Soli tribal land of central Zambia and examines the supplementary role of planted trees.

Temporal and spatial changes in land use, vegetation cover, deforestation and reforestation in the Zambian Copperbelt were studied using a combination of aerial photograph analysis, literature review and inquiries among relevant government institutions. The study showed that between 1937 and 1984 loss of natural woodlands in the Copperbelt of Zambia (total area of Copperbelt: 9,615 km2) amounted to 41 per cent woodland area (8,419 km2). The major causes of this deforestation are woodfuel collection (for firewood and charcoal), cultivation and replacement of natural woodland with forest plantations. These accounted for 38 per cent, 37 per cent and 15 per cent of the total deforestation, respectively. Before 1962 the copper mining industry used large quantities of firewood to generate electricity and this resulted in the loss of 150,413 ha of woodland between 1937 and 1961. When the mining industry switched to hydroelectricity, urban households became the major users of woodfuel. The urban population in the Copperbelt increased from 0.412 million in 1960 to 1.400 million in 1984 and its consumption of woodfuel led to the deforestation of at least 89,436 ha between 1962 and 1984. Deforested areas are left to regenerate naturally. However, due to poor management about 34 per cent of the area deforested before 1962 has failed to regenerate. Although 50,200 ha have been reforested with exotic trees, only 5,020 ha of this is on land previously deforested. Thus only about 10 per cent of reforestation efforts have contributed to the rehabilitation of damaged land. Ninety per cent of the reforestation has actually replaced standing indigenous woodland. Uncontrolled bushfires have destroyed forest plantations and have also caused the failure of woodland regeneration in deforested areas. These observations indicate that if forest resources in the Copperbelt of Zambia are to be properly managed it will be necessary: 1to effectively regulate land use changes and; 2to control bushfires.

The status of chitemene shifting cultivation, in northern Zambia was investigated and reviewed. This paper presents results concerning (a) changes in soil nutrients under chitemene shifting cultivation, (b) the relationship between population density and deforestation and (c) how the chitemene shifting cultivation system has survived under conditions of overpopulation relative to the critical population density.

A survey of 94 miombo woodland stands was conducted in different parts of Zambia, and stackwood yield for charcoal production was assessed at 90 sites. The basal area of miombo woodland stands was significantly correlated to the aridity ratio in the study areas. Mean basal area at breast height per ha differed significantly among the three aridity zones in which study areas were located. In the aridity ratio 0.7–1.0 zone, mean basal area at breast height was 11.66 m 2 per ha, and this increased to 13.02 m 2 in the aridity ratio 1.0–1.3 zone and to 16.52 m 2 in the aridity ratio 1.3–1.6 zone. But mean basal area of woodland stands in different topographic zones was not significantly different. The volume of stackwood yield per m 2 basal area at stump height did not differ significantly among study areas: mean stackwood yield was 14.8 m 3 per m 2 basal area. Correlationship and regression analysis of the data led to the development of regression models for estimating standing wood stocks and yield for charcoal production in miombo woodlands in different parts of Zambia. The results presented in the paper are useful for managing natural woodlands for fuelwood production.

Miombo woodland in Zambia is divided into wetter and drier types by the 1100 mm mean rainfall isohyet. In the present study two wetter (Northern, Northwestern) and three drier (Central, Eastern, Western) miombo subtypes were recognized.A survey of the woody flora of 94 old-growth and 58 coppice stands in the five miombo subtypes revealed some significant differences in species diversity among them. The floristic differentiantion of miombo subtypes was best achieved by the use of the Shannon species diversity index (H′) and species density (number of species 0.1 ha−1 or 0.4 ha−1). H′ in miombo decreased from 2.247 in Northwestern to 2.136 in Northern, 2.052 in Eastern, 1.918 in Central and 1.824 in Western subtypes. Although species density was not significantly different between wetter miombo subtypes, this decreased in a similar fashion from 18.78 0.1 ha−1 in Northwestern to 18.30 in Northern, 16.65 in Eastern, 14.79 in Central and 12.29 in Western subtypes. The low species diversity in Western drier miombo was attributed to the combined effects of low soil fertility and rainfall.Although the mean number of species per 0.1 ha plot was higher in coppice samples, species richness (d) and index of diversity (H′) were lower than in old-growth samples. These results indicate lower species diversity in regenerating miombo. The dynamic aspects of species structure should therefore be considered in the future conservation of biological diversity in miombo woodland.

SUMMARY (1) Two series of adjacent plots, one under early-burning and the other late-burning regimes, were set up in Marquesia woodland. Each series consisted of four plots representing standing and clear-felled woodland at 1-3 m (breast) height, 0 3 m (stump) height and below-ground. The experiment was designed to determine the effect on regeneration of woodland felled at different heights (for charcoal production) and under different burning regimes. (2) Regeneration in the plots was largely of seedling origin but because stumps and roots of cut trees bore multiple stems, regeneration from trunk- and root-suckers dominated stem populations in the coppiced plots. The difference in stump mortality in plots felled at breast- and stump-height was not significant. (3) Although stem mortality differed significantly under different cutting treatments it was generally much higher in late-burnt than in early-burnt plots. Although the population of dead stems was dominated by Albizia adianthifolia, Baphia bequaertii and Marquesia macroura, only A. adiathifolia and M. macroura appeared to be less firetolerant.