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.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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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.
Observed and model simulated twenty-first century hydro-climatic change of Northern Ethiopia
Tesfaye, Samuale ; Taye, Gebeyehu ; Birhane, Emiru ; Zee, Sjoerd E.A.T.M. van der - \ 2019
Journal of Hydrology: Regional Studies 22 (2019). - ISSN 2214-5818
Artificial neural networks - Climate change - GCM - Precipitation - Streamflow - Temperature

Study region: This study focuses on Tekeze river basin of northern Ethiopia, and it is characterized by a typical dry biogeophysical environment. Study focus: In recent years, recurrent droughts are having an adverse impact on agricultural production and water resources in northern Ethiopia. Climate change through changes on temperature, precipitation and streamflow, may further strain this critical situation. This study has investigated the observed (1961–2014) and potential (2006–2099) hydro-climatic changes in Tekeze river basin of northern Ethiopia. Artificial Neural Networks (ANNs) are used to downscale temperature and precipitation predicated by 30 General Circulation Models (GCMs) as well as the projected streamflow changes for two Representative Concentration Pathways (RCP4.5 and RCP8.5) scenario. New hydrological insights for the region: Results indicate that the variability of climatic factors as temperature and precipitation was observed to be both spatially and temporally diverse for the considered Tekeze river basin. Accordingly, the response of streamflow was also spatiotemporally complex. GCMs were evaluated with several performance indictors regarding patterns in hydro-climatic variables. The analysis showed the superiority of the multimodel ensemble means compared with individual GCM output. GCM projections for the 21century indicate a gradual reductions in streamflow attributed to the combined effect of increasing temperature and decreasing precipitation. The persistent increase of temperature and decrease of precipitation will have negative impacts on water availability and agriculture, hence site specific adaptation strategies are necessary.

Climatic controls of ecohydrological responses in the highlands of northern Ethiopia
Tesfaye, Samuale ; Birhane, Emiru ; Leijnse, Toon ; Zee, S.E.A.T.M. van der - \ 2017
Science of the Total Environment 609 (2017). - ISSN 0048-9697 - p. 77 - 91.
Ecosystem model - Land use - Precipitation - Primary productivity - Semi-arid - Streamflow
Climate variability and recurrent droughts have a strong negative impact on agricultural production and hydrology in the highlands northern Ethiopia. Since the 1980s, numerous mitigation and land rehabilitation measures have been implemented by local and national authorities to reduce these impacts, are often poorly effective. As underlying reason may be that controlling relationships between climate and ecohydrology at medium-sized catchments (10–10,000 km2) of semi-arid highlands are not well known. We investigated trends and relationships in precipitation, temperature, streamflow, and net primary productivity (NPP). The results were mixed, with both significant increasing and decreasing trends for temperature and streamflow. Precipitation time series did not show a significant trend for the majority of stations, both over the years and over each season, except for a few stations. A time series indicated a significant abrupt increase of NPP in annual, seasonal and monthly timescale. Cross-correlation and regression analysis indicate precipitation and maximum temperature were the dominant climatic variables in the Geba catchment for streamflow and NPP. In view of these results, also land use and land cover change over the past three decades was analysed as a possible factor of importance, as human intervention, may affect streamflow and NPP. Factors that mainly correlate with streamflow and NPP are precipitation and maximum temperature. Important interventions that appear beneficial for these responses are construction of micro-dams, soil and water conservation and ecological restoration measures. The awareness that interactions can be quite different in semi-arid and semi-humid regions, as well as in upstream and downstream areas, should be reflected in management aimed at sustainable water and land resources use.
Arbuscular mycorrhiza and water and nutrient supply differently impact seedling performance of dry woodland species with different acquisition strategies
Emiru Birhane, E.B. ; Kuyper, T.W. ; Sterck, F.J. ; Gebrehiwot, K. ; Bongers, F. - \ 2015
Plant Ecology & Diversity 8 (2015)3. - ISSN 1755-0874 - p. 387 - 399.
Background: Arbuscular mycorrhizal (AM) fungi increase seedling survival and performance through enhancement of nutrient and water uptake under stress conditions. Acacia etbaica, A. senegal and Boswellia papyrifera dominate large areas in African drylands where both moisture and nutrients are limited. Aims: We evaluated the effects of AM, drought and soil quality on carbon gain (growth), gas exchange and nutrient contents of seedlings of these three dry woodland species. Methods: We used a greenhouse experiment with a fully factorial design of two levels of AM, two levels of soil and four levels of water availability, on the carbon gain, gas exchange and nutrient content of seedlings of the three species. Results: AM symbiosis enhanced the acquisition of water and nutrients and increased gas exchange resulting in increased Acacia and Boswellia seedling biomass. The rapidly growing Acacia species (acquisitive strategy) showed larger mycorrhizal benefit at higher water availability. The slow-growing Boswellia (conservative strategy), in contrast, showed larger mycorrhizal benefit at lower water availability. Conclusions: This study showed that different species of dry woodlands benefit from AM in different ways depending on the resource use strategy under stress conditions. The inclusion of the mycorrhizal habit in trait-based approaches increases understanding of functional differences of coexisting tree species.
Arbuscular mycorrhizal impacts on competitive interactions between Acacia etbaica and Boswellia papyrifera seedlings under drought stress
Birhane, E. ; Sterck, F.J. ; Bongers, F. ; Kuyper, T.W. - \ 2014
Journal of Plant Ecology 7 (2014)3. - ISSN 1752-9921 - p. 298 - 308.
interspecific competition - plant-growth - trade-offs - fungi - frankincense - infection - traits - associations - populations - coexistence
Aims Arbuscular mycorrhizal fungi can have a substantial effect on the water and nutrient uptake by plants and the competition between plants in harsh environments where resource availability comes in pulses. In this study we focus on interspecific competition between Acaia etbaica and Boswellia papyrifera that have distinctive resource acquisition strategies. We compared the extent of interspecific competition with that of intraspecific competition. Methods In a greenhouse study we examined the influence of Arbuscular Mycorrhiza (AM) and pulsed water availability on competitive interactions between seedlings of the rapidly growing species A. etbaica and the slowly growing species B. papyrifera. A factorial experimental design was used. The factors were AM, two water levels and five species combinations Important Findings Seedlings of both species benefitted from AM when grown alone, and the positive growth response to pulsed water availability in B. papyrifera seedlings was in contrast with the negative growth response for A. etbaica seedlings. AM also affected the competitive performance of both species. B. papyrifera was not affected by intraspecific competition, whereas A. etbaica was negatively affected compared to the seedlings grown alone. This effect was stronger in the presence of AM. In interspecific competition, A. etbaica outcompeted B. papyrifera. Mycorrhiza and pulsed water availability did not affect the outcome of interspecific competition, and the aggressivity index of A. etbaica remained unchanged. The extent to which AM influences plant competition in a drought-stressed environment may depend on belowground functional traits of the species. AM and pulsed water availability could modify the balance between intraspecific and interspecific competition. By affecting the balance between intraspecific and interspecific competition, both factors could impact the establishment and survival of seedlings.
Arbuscular mycorrhizal fungi enhance biomass, photosynthesis and water use efficiency of frankincense seedlings in a drought -pulse environment
Emiru Birhane, E.B. ; Sterck, F.J. ; Fetene, M. ; Bongers, F. ; Kuyper, T.W. - \ 2012
Oecologia 169 (2012)4. - ISSN 0029-8549 - p. 895 - 904.
boswellia-papyrifera - semiarid environment - northern ethiopia - resource pulses - tree - ecosystems - infection - colonization - adaptations - delta-c-13
Under drought conditions, arbuscular mycorrhizal (AM) fungi alter water relationships of plants and improve their resistance to drought. In a factorial greenhouse experiment, we tested the effects of the AM symbiosis and precipitation regime on the performance (growth, gas exchange, nutrient status and mycorrhizal responsiveness) of Boswellia papyrifera seedlings. A continuous precipitation regime was imitated by continuous watering of plants to field capacity every other day during 4 months, and irregular precipitation by pulsed watering of plants where watering was switched every 15 days during these 4 months, with 15 days of watering followed by 15 days without watering. There were significantly higher levels of AM colonization under irregular precipitation regime than under continuous precipitation. Mycorrhizal seedlings had higher biomass than control seedlings. Stomatal conductance and phosphorus mass fraction in shoot and root were also significantly higher for mycorrhizal seedlings. Mycorrhizal seedlings under irregular watering had the highest biomass. Both a larger leaf area and higher assimilation rates contributed to higher biomass. Under irregular watering, the water use efficiency increased in non-mycorrhizal seedlings through a reduction in transpiration, while in mycorrhizal seedlings irregular watering increased transpiration. Because assimilation rates increased even more, mycorrhizal seedlings achieved an even higher water use efficiency. Boswellia seedlings allocated almost all carbon to the storage root. Boswellia seedlings had higher mass fractions of N, P, and K in roots than in shoots. Irregular precipitation conditions apparently benefit Boswellia seedlings when they are mycorrhizal
Replication data for: Management, use and ecology of medicinal plants in the degraded dry lands of Tigray, Northern Ethiopia (version 4)
Hizikias, Emiru-Birhane ; Aynekulu, E. ; Mekuria, W. ; Endale, D. - \ 2011
ecology - medicinal crops - Dead standing stem - Elevation gradient - Juniperus procera - Olea europaea subsp. cuspidata - restoration - semiarid
An ethnomedicinal study was conducted to document the indigenous medicinal plant knowledge on the management, use, and ecology of locally important medicinal plants in Tigray, Northern Ethiopia. Ethnobotanical data were collected from 250 people, using semi-structured questionnaires, field observation and informal discussion. The ethnomedicinal use of 259 plant species mainly herbs (31 to 51%), shrubs (31 to 46%) and trees (13 to 39%) used to treat 147 human and livestock ailments were documented in the study area. The most frequently used plant part were roots (49%), followed by leaves (37%) and bark (14%)... Crushing (59%), homogenizing with ingredients (17%) and chewing (14%) were the commonly used forms of herbal preparation. Drinking (45%), smoke inhalation (12%) and tie and hold on (10%) were the most frequently used methods of application. Most of the medicinal plants are collected from the wild. The use of more than one species was reported for remedy preparations and some health problems were treated by more than one medicinal plant. Our result showed that the local communities give less attention for the management of medicinal plants as local communities consider medicinal plants as wild, have unattractive market value and lack of knowledge. The mismanagement together with loss of habitat showed that ethnomedicinal plant species used by healers are under serious threat which indicates the need for urgent attention towards their documentation, conservation and sustainable utilization.
Arbuscular mycorrhizal associations in Boswellia papyrifera (frankincense-tree) dominated dry deciduous woodlands of Northern Ethiopia.
Emiru Birhane, E.B. ; Kuyper, T.W. ; Sterck, F.J. ; Bongers, F. - \ 2010
Forest Ecology and Management 260 (2010)12. - ISSN 0378-1127 - p. 2160 - 2169.
monocultural coffee systems - tropical rain-forest - southwestern ethiopia - soil fertility - fungi spores - land-use - plants - colonization - agroforestry - infection
This study assessed the arbuscular mycorrhizal (AM) status of Boswellia papyrifera (frankincense-tree) dominated dry deciduous woodlands in relation to season, management and soil depth in Ethiopia. We studied 43 woody species in 52 plots in three areas. All woody species were colonized by AM fungi, with average root colonization being relatively low (16.6% – ranging from 0% to 95%). Mean spore abundance ranged from 8 to 69 spores 100 g-1 of dry soil. Glomus was the dominant genus in all study sites. Season had a strong effect on root colonization and spore abundance. While spore abundance was higher (P <0.001) in the dry season in all three study sites, root colonization showed a more variable response. Root colonization was reduced in the dry season in the site that was least subject to stress, but increased in the dry season in the harshest sites. Management in the form of exclosures (that exclude grazing) had a positive effect on spore abundance in one of the two sites considered. Spore abundance did not significantly differ (P = 0.17) between the two soil depths. Our results show that in this arid region all trees are mycorrhizal. This has profound consequences for rehabilitation efforts of such dry deciduous woodlands: underground processes are vital for understanding species adaptation to pulsed resource availability and deserve increasing attention.
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