Browsing by Author "Calatayud, P. A."

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    Can Climate-Driven Change Influence Silicon Assimilation by Cereals and Hence the Distribution of Lepidopteran Stem Borers in East Africa?
    (Elsevier, 2016) Calatayud, P. A.; Njuguna, E.; Mwalusepo, Sizah; Gathara, Mary; Okuku, G.; Kibe, A.; Musyoka, B.; Williamson, David; Ong’amo, Georges; Gerald, Juma; Johansson, Tino; Subramanian, Sevgan; Gatebe, E.; Le Ru, Bruno P.
    In East Africa, lepidopteran stemborers such as Chilo partellus and Busseola fusca are major constraints to production of maize, which is the main staple food crop in the region. Cereals depend on silicon (Si)-based defences to fight off herbivores. Using altitudinal ranges in the East African highlands as ecological surrogates for inferring climate change, it was shown that Si concentrations in soil and maize decreased with altitude. This was attributed, in part, to low temperatures at high altitudes, which negatively affected Si assimilation by maize. Experiments showed that B. fusca was more susceptible to Si than C. partellus. Hence the predominance of B. fusca in the highlands and of C. partellus in the lowlands could be partly explained by altitudinal differences in Si concentrations in maize plants. Therefore, a rise in temperature due to climate change should enhance the plants’ Si assimilation and as a result C. partellus might move into the higher altitudes and increasingly displace B. fusca.
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    Predicting the Impact of Temperature Change on the Future Distribution of Maize Stem Borers and Their Natural Enemies along East African Mountain Gradients Using Phenology Models
    (2015) Mwalusepo, Sizah; Tonnang, Henri E. Z.; Massawe, Estomih S.; Okuku, Gerphas O.; Khadioli, Nancy; Johansson, Tino; Calatayud, P. A.; Le Ru, Bruno P.
    Lepidopteran stem borers are among the most important pests of maize in East Africa. The objective of the present study was to predict the impact of temperature change on the distribution and abundance of the crambid Chilo partellus, the noctuid Busseola fusca, and their larval parasitoids Cotesia flavipes and Cotesia sesamiae at local scale along Kilimanjaro and Taita Hills gradients in Tanzania and Kenya, respectively. Temperature-dependent phenology models of pests and parasitoids were used in a geographic information system for mapping. The three risk indices namely establishment, generation, and activity indices were computed using current temperature data record from local weather stations and future (i.e., 2055) climatic condition based on downscaled climate change data from the AFRICLIM database. The calculations were carried out using index interpolator, a sub-module of the Insect Life Cycle Modeling (ILCYM) software. Thin plate algorithm was used for interpolation of the indices. Our study confirmed that temperature was a key factor explaining the distribution of stem borers and their natural enemies but other climatic factors and factors related to the top-down regulation of pests by parasitoids (host-parasitoid synchrony) also played a role. Results based on temperature only indicated a worsening of stem borer impact on maize production along the two East African mountain gradients studied. This was attributed to three main changes occurring simultaneously: (1) range expansion of the lowland species C. partellus in areas above 1200 m.a.s.l.; (2) increase of the number of pest generations across all altitudes, thus by 2055 damage by both pests will increase in the most productive maize zones of both transects; (3) disruption of the geographical distribution of pests and their larval parasitoids will cause an improvement of biological control at altitude below 1200 m.a.s.l. and a deterioration above 1200 m.a.s.l. The predicted increase in pest activity will significantly increase maize yield losses in all agro-ecological zones across both transects but to a much greater extent in lower areas.
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    Smallholder Farmers' Perspectives on Climatic Variability and Adaptation Strategies in East Africa: The Case of Mount Kilimanjaro in Tanzania, Taita and Machakos Hills in Kenya
    (2015) Mwalusepo, Sizah; Massawe, Estomih S.; Affognon, H.; Okuku, G.; Kingori, Sarah; Mburu, Peter D. M.; Ong’amo, Georges; Muchugu, Eric; Calatayud, P. A.; Landmann, Tobias; Muli, Eliud; Raina, Suresh K.; Johansson, Tino; Le Ru, Bruno P.
    Climate change is expected to have serious economic and social impacts in East Africa, particularly on rural farmers whose livelihoods largely depend on rain-fed agriculture, hence adaptation is required to offset projected drawbacks of climate change on crop productivity. This paper examines farmers' perceptions and understanding of climatic variability, coping strategies adopted and factors that influence the choice of a particular adaptation. The study uses cross section data collected from 510 farmers in three mountain gradients sites, namely; Mount Kilimanjaro of Tanzania, Taita and Machakos Hills of Kenya. Farmers’ perceptions were compared to actual trend in meteorological records over the last thirty years (1981-2010). The result revealed that farmers in East Africa were partly aware of climate variability, mainly in temperature and rainfall patterns. Many respondents reported that conditions are drier and rainfall timing is becoming less predictable. The perception of farmers on temperature and rainfall were in line with recorded meteorological data, but contrary with that of recorded rainfall in Machakos which was perceived to be decreasing by the farmers. Farmers perceived changes in rainfall and temperature to have negative effects on the production and management of crops. The common adaptation strategies used by farmers include water harvesting, soil conservation techniques and shifting of planting periods. The most important variables affecting farmers choices in regards to adaptation option were, lack of access to credit, farming experience and household size. As a conclusion, there is a need for these factors to be taken into account in the development and implementation of smallholder farmers’ adaptation strategies to climate variability in East Africa. Additionally, dedicated capacity building and extensive outreach initiatives on adaptation through governments, researchers, policy-makers and the farmers groups themselves are needed to achieve large scale success.
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    Variation of Soil Nutrients in Maize Growing Areas along the Altitudinal Gradient of Taita Hills Transect in Kenya
    (2015) Njuguna, Elijah; Le Ru, Bruno P.; Okuku, G.; Gathara, Mary; Mwalusepo, Sizah; Juma, Gerald; Sambai, K.; Johansson, Tino; Ong’amo, Georges; Gatebe, E.; Calatayud, P. A.
    Maize is the main staple food crop in Kenya but its yield is being affected by biotic and abiotic factors which reduce maize yield while soil nutrient elements increase the yield. Most plants grow by absorbing nutrients from the soil depending on the nature of the soil. Soil texture affects how well nutrients and water are retained in the soil. Clays and organic soils hold nutrients and water much better than sandy soils. As water drains from sandy soils, it often carries nutrients along with it through leaching. When nutrients leach into the soil, they are not available for plants to use thus affecting the plant health. This study evaluated several physical and chemical properties of soil along the altitudinal gradients of Taita hills which is characterized by graded changes in climatic conditions. Both nitrogen and carbon increased with increase in altitude while Potassium, phosphorus and pH deceased with increase in altitude. Moisture and temperature appear to be important drivers in soil parameter and therefore biological patterning along the transect.