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Odee D.W.,UK Center for Ecology and Hydrology | Odee D.W.,Kenya Forestry Research Institute | Telford A.,UK Center for Ecology and Hydrology | Wilson J.,UK Center for Ecology and Hydrology | And 2 more authors.
Heredity | Year: 2012

Drylands are extensive across sub-Saharan Africa, socio-economically and ecologically important yet highly sensitive to environmental changes. Evolutionary history, as revealed by contemporary intraspecific genetic variation, can provide valuable insight into how species have responded to past environmental and population changes and guide strategies to promote resilience to future changes. The gum arabic tree (Acacia senegal) is an arid-adapted, morphologically diverse species native to the sub-Saharan drylands. We used variation in nuclear sequences (internal transcribed spacer (ITS)) and two types of chloroplast DNA (cpDNA) markers (PCR-RFLP, cpSSR) to study the phylogeography of the species with 293 individuals from 66 populations sampled across its natural range. cpDNA data showed high regional and rangewide haplotypic diversity (hT(cpSSR) = 0.903-0.948) and population differentiation (GST(RFLP) = 0.700-0.782) with a phylogeographic pattern that indicated extensive historical gene flow via seed dispersal. Haplotypes were not restricted to any of the four varieties, but showed significant geographic structure (GST(cpSSR) = 0.392; RST = 0.673; RST >RST (permuted)), with the major division separating East and Southern Africa populations from those in West and Central Africa. Phylogenetic analysis of ITS data indicated a more recent origin for the clade including West and Central African haplotypes, suggesting range expansion in this region, possibly during the Holocene humid period. In conjunction with paleobotanical evidence, our data suggest dispersal to West Africa, and across to the Arabian Peninsula and Indian subcontinent, from source populations located in the East African region during climate oscillations of the Plio-Pleistocene. © 2012 Macmillan Publishers Limited All rights reserved. Source

Sprent J.I.,University of Dundee | Odee D.W.,UK Center for Ecology and Hydrology | Odee D.W.,Kenya Forestry Research Institute | Dakora F.D.,University of South Africa
Journal of Experimental Botany | Year: 2010

Although nodulated legumes have been used by indigenous peoples in Africa for centuries, their full potential has never been realized. With modern technology there is scope for rapid improvement of both plant and microbial germplasm. This review gives examples of some recent developments in the form of case studies; these range from multipurpose human food crops, such as cowpea (Vigna unguiculata (L.) Walp.), through to beverages (teas) that are also income-generating such as rooibos (Aspalathus linearis (Burm. f.) R. Dahlgren, honeybush (Cyclopia Vent. spp.), and the widely used food additive gum arabic (Acacia senegal (L.) Willd.). These and other potential crops are well-adapted to the many different soil and climatic conditions of Africa, in particular, drought and low nutrients. All can nodulate and fix nitrogen, with varying degrees of effectiveness and using a range of bacterial symbionts. The further development of these and other species is essential, not only for African use, but also to retain the agricultural diversity that is essential for a changing world that is being increasingly dominated by a few crops such as soybean. Source

Isaac M.E.,Montpellier SupAgro | Isaac M.E.,University of Toronto | Harmand J.-M.,Montpellier SupAgro | Lesueur D.,Montpellier SupAgro | And 2 more authors.
Forest Ecology and Management | Year: 2011

Acacia senegal, an important leguminous tree in arid and semi-arid environments, has shown promise as a multipurpose species, including gum production and soil fertility improvement, linked with N2-fixation capabilities. Of particular interest are ontogenetic and edaphic effects on A. senegal performance in natural populations. Our research objectives were to investigate the effect of tree age and site phosphorus conditions on (1) tree N2-fixation and (2) soil N and C dynamics in natural stands of A. senegal var. senegal, Baringo District, in the Rift Valley, Kenya. Sites consisted of A. senegal saplings (9 months) and mature A. senegal trees (7 years) along an edaphic gradient of soil P availability. A single-tree neighborhood approach was employed using a two by two factorial design: site conditions [high and low soil P contents] and tree age class [juvenile and mature]. Soil (N and C pools and fluxes) and plant metrics were quantified. A soil transfer experiment was also employed to confirm age and site effects on soil N mineralization. On the high soil P site, A. senegal had significantly lower foliar (15N levels than neighboring non-leguminous species (Balanites aegyptiaca), while foliar δ15N values in A. senegal on the low P site exhibited no significant difference with our reference plant, B. aegyptiaca. Across P sites, B. aegyptiaca had similar foliar δ15N values. These results indicate that the rate of N2-fixation of A. senegal trees, as determined with foliar 15N natural abundance methodology, increased with increasing soil P availability in these natural populations. However, N2-fixation rates declined with age. Although soil texture and soil CO2 efflux did not differ between sites or across ages, soils under mature A. senegal at the high P site exhibited significantly greater total N content and total C content in comparison to soils at the low P site and under juvenile plants. Furthermore, under mature A. senegal trees, soil N mineralization rates were significantly greater as compared to under saplings. Soil transplants confirmed that soil microbial activity may be stimulated under mature trees as N mineralization rates were 2-3 fold greater compared to under A. senegal saplings. Our findings suggest that tree age and soil P availability are important factors in the nitrogen budget of natural populations of A. senegal, determining N2-fixation rates, and potentially influencing soil total N and C pools and soil mineral N. This study provides information regarding the adaptation of A. senegal under differing edaphic conditions thus increasing accuracy of management support for A. senegal populations as productive agroforests. © 2010 Elsevier B.V. Source

Gachathi F.N.,Kenya Forestry Research Institute | Eriksen S.,Norwegian University of Life Sciences
Climate and Development | Year: 2011

Frequent droughts and conflicts are key challenges faced by nomadic pastoralists in Kenya's drylands. Few options exist for alternative livelihoods. This article investigates the potential of collecting plant gums and resins for livelihood diversification and for contributing to sustainable adaptation to climate change in Kenya's drylands. Observations were made in various studies over a period of two years on dryland vegetation resources, and interviews undertaken with gum collectors. This research found that many households currently collect and sell plant gums and resins as alternative to livestock production. These include gum arabic from Acacia senegal and Acacia seyal; myrrh from Commiphora myrrha; hagar from Commiphora holtziana; and frankincense from Boswellia neglecta. Collectors include poor people, women and children and some opportunists. Incomes are relatively low, however, and several factors constrain the activity. The case of gums and resins illustrates that key principles of sustainable adaptation are related: supporting local knowledge and adaptation strategies (one key principle of sustainable adaptation) does not contribute to sustainability unless at the same time contextual factors that marginalize livelihoods are addressed (another key principle). © 2011 Earthscan. Source

Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 1.10M | Year: 2015

East Africa (EA) has one of the worlds fastest growing populations, with maxima around water-bodies and rapid urbanisation. Climate change is adding to existing problems increasing vulnerability of the poorest. HyCRISTAL is driven by EA priorities. EA communities rely on rainfall for food via agriculture. EAs inland lakes are rain-fed and provide water, power and fisheries. For EAs growing cities, climate impacts on water resources will affect water supply & treatment. HyCRISTAL will therefore operate in both urban & rural contexts. Change in water availability will be critical for climate-change impacts in EA, but projections are highly uncertain for rain, lakes, rivers and groundwater, and for extremes. EA Long-Rains are observed to be decreasing; while models tend to predict an increase (the EA Climate paradox) although predictions are not consistent. This uncertainty provides a fundamental limit on the utility of climate information to inform policy. HyCRISTAL will therefore make best use of current projections to quantify uncertainty in user-relevant quantities and provide ground-breaking research to understand and reduce the uncertainty that currently limits decision making. HyCRISTAL will work with users to deliver world-leading climate research quantifying uncertainty from natural variability, uncertainty from climate forcings including those previously unassessed, and uncertainty in response to these forcings; including uncertainties from key processes such as convection and land-atmopshere coupling that are misrepresented in global models. Research will deliver new understanding of the mechanisms that drive the uncertainty in projections. HyCRISTAL will use this information to understand trends, when climate-change signals will emerge and provide a process-based expert judgement on projections. Working with policy makers, inter-disciplinary research (hydrology, economics, engineering, social science, ecology and decision-making) will quantify risks for rural & urban livelihoods, quantify climate impacts and provide the necessary tools to use climate information for decision making. HyCRISTAL will work with partners to co-produce research for decision-making on a 5-40 year timescale, demonstrated in 2 main pilots for urban water and policies to enable adaptive climate-smart rural livelihoods. These cover two of three areas of need from the African Ministerial Council on Environments Comprehensive Framework of African Climate Change Programmes. HyCRISTAL has already engaged 12 partners from across EA. HyCRISTALs Advisory Board will provide a mechanism for further growing stakeholder engagement. HyCRISTAL will work with the FCFA global & regional projects and CCKE, sharing methods, tools, user needs, expertise & communication. Uniquely, HyCRISTAL will capitalise on the new LVB-HyNEWS, an African-led consortium, governed by the East African Community, the Lake Victoria Basin Commission and National Meteorological and Hydrological agencies, with the African Ministerial Conference on Meteorology as an observer. HyCRISTAL will build EA capacity directly via collaboration (11 of 25 HyCRISTAL Co-Is are African, with 9 full-time in Africa), including data collection and via targeted workshops and teaching. HyCRISTAL will deliver evidence of impact, with new and deep climate science insights that will far outlast its duration. It will support decisions for climate-resilient infrastructure and livelihoods through application of new understanding in its pilots, with common methodological and infrastructure lessons to promote policy and enable transformational change for impact-at-scale. Using a combination of user-led and science-based management tools, HyCRISTAL will ensure the latest physical science, engineering and social-science yield maximum impacts. HyCRISTAL will deliver outstanding outputs across FCFAs aims; synergies with LVB-HyNEWS will add to these and ensure longevity beyond HyCRISTAL.

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