Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Frankincense in peril
Bongers, Frans ; Groenendijk, Peter ; Bekele, Tesfaye ; Birhane, Emiru ; Damtew, Abebe ; Decuyper, Mathieu ; Eshete, Abeje ; Gezahgne, Alemu ; Girma, Atkilt ; Khamis, Mohamed A. ; Lemenih, Mulugeta ; Mengistu, Tefera ; Ogbazghi, Woldeselassie ; Sass-Klaassen, Ute ; Tadesse, Wubalem ; Teshome, Mindaye ; Tolera, Motuma ; Sterck, Frank J. ; Zuidema, Pieter A. - \ 2019
Nature Sustainability 2 (2019). - ISSN 2398-9629 - p. 602 - 610.
The harvest of plant parts and exudates from wild populations contributes to the income, food security and livelihoods of many millions of people worldwide. Frankincense, an aromatic resin sourced from natural populations of Boswellia trees and shrubs, has been cherished by world societies for centuries. Boswellia populations are threatened by over-exploitation and ecosystem degradation, jeopardizing future resin production. Here, we reveal evidence of population collapse of B. papyrifera—now the main source of frankincense—throughout its geographic range. Using inventories of 23 populations consisting of 21,786 trees, growth-ring data from 202 trees and demographic models on the basis of 7,246 trees, we find that over 75% of studied populations lack small trees, natural regeneration has been absent for decades, and projected frankincense production will be halved in 20 yr. These changes are caused by increased human population pressure on Boswellia woodlands through cattle grazing, frequent burns and reckless tapping. A literature review showed that other Boswellia species experience similar threats. Populations can be restored by establishing cattle exclosures and fire-breaks, and by planting trees and tapping trees more carefully. Concerted conservation and restoration efforts are urgently needed to secure the long-term availability of this iconic product.
Incense Woodlands in Ethiopia and Eritrea: Regeneration Problems and Restoration Possibilities
Abiyu, A. ; Bongers, F. ; Eshete, A. ; Gebrehiwot, K. ; Kindu, M. ; Lemenih, M. ; Moges, Y. ; Ogbazghi, W. ; Sterck, F.J. - \ 2010
In: Degraded Forests in Eastern Africa: management and resoration / Bongers, F, Tennigkeit, T, London : The Earthscan Forest Library - ISBN 9781844077670 - p. 133 - 152.
The effect of tapping for frankincense on sexual reproduction in Boswellia papyrifera
Rijkers, A.J.M. ; Ogbazghi, W. ; Wessel, M. ; Bongers, F.J.J.M. - \ 2006
Journal of Applied Ecology 43 (2006)6. - ISSN 0021-8901 - p. 1188 - 1195.
resin flow - scots pine - trees - defenses - balance - plants - myrrh
1. In the Horn of Africa, frankincense (an aromatic hardened wood resin) is obtained by tapping Boswellia papyrifera. World-wide, frankincense is of great economic and social importance as an important element of incense and perfumes. The production is declining as a result of poor natural regeneration of the Boswellia woodlands, possibly as a result of the low production of viable seeds. We hypothesize that this is because of the current intensive tapping regime, which might favour allocation of carbohydrates for synthesis of resin at the expense of allocation for generative growth. 2. Investigations were carried out at sites in different agro-ecological zones with annually tapped trees and with trees that had not been tapped for several years. Seed viability and germination success were determined for 200 randomly collected seeds in each site. For three stands, the sexual reproduction (number of flowers, fruits and seeds) was determined for different sized trees subjected to three experimental tapping intensities (no, normal and heavy tapping). 3. At the stand level, non-tapped trees produced three times as many healthy and filled seeds as tapped trees. Germination success was highest in stands with non-tapped trees (> 80%) and lowest for those with tapped trees (<16%). 4. At the tree level, sexual reproduction decreased with increasing tapping regime irrespective of tree size. Overall, large trees tended to produce slightly heavier seeds than small trees, and seeds from non-tapped trees were heavier than those from tapped trees. In the stands where tapping was prohibited changes in tapping regimes had the greatest effect on sexual reproduction. Trees subjected to annual tapping always showed the lowest sexual reproduction. 5. Synthesis and applications. Tapping for frankincense results in limited flower and fruit production, and low production of mainly non-viable seeds in B. papyrifera. We argue that tapping causes competition for carbohydrates between frankincense production, and fruit and seed setting. Consequently, the current tapping regimes will cause tree exhaustion and eventually a decline in vitality. Tapping may potentially reduce natural regeneration of the species. New tapping regimes are suggested that include periods of time in which tapping is prohibited in order for trees to recover and replenish their stored carbon pool, and a reduction in the number of tapping points per tree. This is important in view of the long-term sustainability of frankincense production, an internationally highly valued resource.
Population structure and morphology of the frankincense tree Boswellia papyrifera along an altitude gradient in Eritrea
Ogbazghi, W. ; Bongers, F.J.J.M. ; Rijkers, A.J.M. ; Wessel, M. - \ 2006
Journal of the Drylands 1 (2006)1. - ISSN 1817-3322 - p. 85 - 94.
In Eritrea, the frankincense tree Boswellia papyrifera is a multipurpose plant. Human induced factors such as land clearing for agriculture, overgrazing by livestock and overtapping of resin are threatening its distribution. Against this background, a study was carried out to investigate the species current population structure and tree morphology in five Boswellia areas along an altitude gradient (range 800 - 2000 m a.s.l.). In each area sample plots of 20 by 20 m were inventoried; a total of 144 plots were studied. The population structure analysis showed that there was an overall absence of juvenile trees between 1 and 8 cm DBH. Natural regeneration was found only in two areas in which trees were not tapped for resin and inaccessible to livestock. Tree height, DBH, crown depth and crown diameter decreased with increasing altitude. In the lowland areas trees were about two times taller (10 to 12 m) with deeper crowns than those growing in the highland areas. This indicates that the species grows better in the warm moist lowlands than in the moist and dry highlands. To promote natural regeneration and seedling establishment in existing Boswellia woodlands control measures are needed including proper tapping procedures and controlled grazing.
The distribution of the frankincense tree Boswellia papyrifera in Eritrea: the role of environment and land use
Ogbazghi, W. ; Rijkers, A.J.M. ; Wessel, M. ; Bongers, F.J.J.M. - \ 2006
Journal of Biogeography 33 (2006)3. - ISSN 0305-0270 - p. 524 - 535.
Aim We determined the present and past distribution, and the abundance, of Boswellia papyrifera in Eritrea, and the environmental and land-use factors determining its distribution limits. Location Eritrea, in the Horn of Africa. Methods In 1997 a Boswellia field survey was conducted in 113 village areas covering four administrative regions. Species occurrence was related to rainfall, air temperature and length of growing period. Additionally, the relationship between the abundance of Boswellia trees and selected physical and chemical soil factors, topography and land-use types was determined for five study areas (with a total of 144 plots) situated along an altitude gradient of 800¿2000 m a.s.l. Results The geographical distribution of B. papyrifera was limited to the southwestern and southern parts of the country between 800 and 1850 m altitude receiving a mean annual rainfall of 375¿700 mm, with a growing period of 45¿100 days. Species abundance was affected by, in order of importance: altitude, land-use intensity and soil organic matter. Most trees were found in hilly areas; tree density increased from the foot slope to the hill summit; no trees occurred in valleys. Land-use intensity, especially agriculture, fallow and grazed areas, had a profound negative effect on tree abundance. Natural regeneration of the species was promoted in areas where grazing by livestock was not allowed or regulated. Main conclusions The distribution of B. papyrifera in Eritrea has decreased during past decades, mainly due to an increasing human population, resulting in the conversion of woodlands into agricultural fields and increasing livestock pressure hindering natural regeneration. Consequently, Boswellia trees are found mainly in hilly areas on steep slopes with shallow soils of low fertility. The species appears to be able to adapt to these harsh growing conditions: in adjacent countries it was also found in comparable growth habitats.
Workshop closure
Struik, P.C. - \ 2003
In: Proceedings of the Research Development Workshop, University of Asmara - College of Agriculture, Asmara 2003 / Woldeselassie Ogbazghi & Paul E. Loth Wageningen/Asmara : Wageningen University/University of Asmara - p. 76 - 77.
Research management : How to create optimum output of high quality with minimum input and maximum satisfaction?
Struik, P.C. - \ 2003
In: Proceedings of the Research Development Workshop, University of Asmara - College of Agriculture, Asmara 2003 / Woldeselassie Ogbazghi & Paul E. Loth Wageningen/Asmara : Wageningen University/University of Asmara - p. 63 - 67.
Developing research at the College of Agriculture: The role of foreign universities
Struik, P.C. - \ 2003
In: Proceedings of the Research Development Workshop, University of Asmara - College of Agriculture, Asmara 2003 / Woldeselassie Ogbazghi & Paul E. Loth Wageningen/Asmara : Wageningen University/University of Asmara - p. 18 - 23.
The distribution and regeneration of Boswellia papyrifera (Del.) Hochst. in Eritrea
Ogbazghi, W. - \ 2001
Wageningen University. Promotor(en): M. Wessel; F. Bongers. - S.l. : S.n. - ISBN 9789058083685 - 131
boswellia - gomleverende planten - plantengeografie - distributie - verjonging - eritrea - boswellia - gum plants - phytogeography - distribution - regeneration - eritrea

Boswellia papyrifera (Del.) Hochst. is a deciduous gum-producing multipurpose perennial tree species growing in Sudanian and Sahelian regions. The tree is tapped on the stem for oleo-gum called olibanum (true frankincense). Land clearing for agriculture and un-regulated grazing are threatening the future of the natural Boswellia woodlands in Eritrea. Against this background, a study was carried out to investigate the distribution of the species and the factors determining its distribution in Eritrea, to study the structure and dynamics of Boswellia populations, including the natural regeneration, and to identify the factors causing the decline of Boswellia woodlands and measures which can reverse this situation. At macro-level, the distribution of the species was found to be limited to the southwestern and southern parts of the country between 800-1850 m altitude receiving a mean annual rainfall of 375-700 mm with a dependable length of growing period of 45-100 days. At micro-level, the abundance and distribution of the species was found to be affected in order of importance by altitude, land use intensity, soil organic matter, and to a lesser extent by silt and pH. Tree development studies showed that trees in the lowlands were twice as high as those in the highlands. The most important outcome of the population structure study is the lack of regeneration. Out of five areas investigated regeneration was only found at two sites where trees were not tapped and which were not accessible to livestock. Further research showed that the present system of intensive annual tapping throughout the dry season leads to low production of non-viable seeds and that where viable seeds are produced, seedlings and saplings are usually destroyed by livestock. Establishment of enclosures in which tapping and grazing is not allowed were found to be an effective measure to promote natural regeneration. Further research is needed to refine this system and to investigate the feasibility of replanting former Boswellia areas.

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