Traditional strategies used by pastoralists to cope with la nina induced drought in Kajiado, Kenya

Pastoralists traditionally relied on herd mobility to cope with drought. In the pastoral areas of Kajiado, Kenya this strategy is now threatened by increased individual land ownership as compared to communal access. Drought frequency as related to El-Nino and Southern Oscillation (ENSO) is predicated to increase with climate change. The aim of the study was investigate the use of herd mobility strategy in the ENSO related 1999/2000 la Nina induced drought under different land tenure types and varying household cattle wealth. The study found that despite changes in land tenure, herd mobility was used as a coping strategy. Households rich in livestock applied the herd mobility strategy more than the poorer ones by moving a larger proportion of their herds. Poorer households applied the strategy of keeping drought resistant animals more than richer ones by having a higher proportion of goats and sheep than cattle. Institutional land units of Kiboko Range Research Station and Chyulu National Reserve which had higher herbaceous biomass were the most favored refuge areas for livestock during the drought. In conclusion poorer families are likely to be impacted more from increased incidents of ENSO droughts due inability to use the herd mobility option.Key words: La-Nina, climate change, drought, pastoralist, herd mobility, land use type

Growth characteristics of two tropical forest species Warburgia ugandensis and Polyscias fulva seedlings grown under contrasting light conditions

Growth parameters for seedlings of two forest trees, Warburgia ugandensis and Polyscias fulva, were measured under various light growth conditions. Leaf area and plant height were significantly higher under low light (< 42% full sunlight) than high light (65% of sunlight) growth conditions (P<0.001). Plant leaf area ranged from 238 cm² under full sunlight to 376 cm² under dense shade in P. fulva and from 33 cm² under full sunlight to 178 cm² under dense shade in W. ugandensis. Plant heights ranged from about 20 mm under full sunlight to 38 mm under dense shade in P. fulva; and from about 36 mm under full sunlight to 89 mm under dense shade in W. ugandensis. P. fulva had more leaves than W. ugandensis but both species increased their leaf numbers from 28 (full sunlight) to 37 (dense shade) and 21 (full sunlight) to 29 (dense shade) respectively (P< 0.05). P. fulva accumulated more biomass (from 4 to about 9g) than W. ugandensis (from 0.6 to 2.4g) under all light conditions (P<0.05). The shoot/root ratios were highest (1.84 for P. fulva and 6.42 for W. ugandensis) under low light conditions in the two species (P<0.05). Highest specific leaf areas were recorded under low light growth conditions (198 cm² g-1 for P. fulva and 220 cm² g-1 for W. ugandensis). W. ugandensis was found to be more shade tolerant than P. fulva.Key words: Forest tree seedlings, Warburgia, Polyscias, light, growth

Influence of varying light regimes on photosynthesis and related variables on tree seedlings of Warburgia ugandensis Sprague and Polyscias fulva (Hiern) harms

The physiology of seedlings of Warburgia ugandensis and Polyscias fulva were studied at varying light levels. Photosynthesis was significantly higher in P. fulva (1.4 µmols CO2 m-2 s-1) than in W. ugandensis (0.3 µmols CO2 m-2s-1) when grown in full sunlight. However, photosynthesis was not significantly (P > 0.05) different under moderate and dense shades (PPFD about 600 µmols m-2s-1 and 350 µmols m-2s-1 respectively) for both species (and ranged between 0.4 and 0.5 µmols CO2 m-2s-1). Generally, P. fulva seedlings had significantly (P < 0.05) greater reductions (from 1.0 to 0.4 µmols CO2 m-2s-1) in photosynthetic rates in response to increasing shade than did W. ugandensis (0.6 to 0.4 µmols CO2 m-2s-1). However, W. ugandensis attained significantly (P < 0.05) higher photosynthetic rates under shade conditions (0.6 µmols CO2 m-2s-1) than full sunlight conditions (0.3 µmols CO2 m-2s-1). Leaf temperatures were highest (30°C) in full sunlight and lowest (27°C) in dense shade for both species. Generally, stomatal conductance, transpiration and water use efficiency showed significantly (P < 0.05) higher values for shade grown W. ugandensis and full sunlight grown P. fulva. Water use efficiency for P. fulva (2.3 µmols CO2 µmol-1 H2O) was significantly (P < 0.05) higher that for W. ugandensis (1.5 µmols CO2 µmol-1 H2O) in full sunlight than. It was concluded that P. fulva was also less adapted to growth at low light intensity while W. ugandensis was better adapted to growth at low light levels because of its significantly greater ability to maintain higher rates of photosynthesis in low light intensity. Therefore in East Africa P fulva can be a better agroforestry species than W. ugandensis.Key words: Net carbon exchange, forest tree seedlings, shade, Warburgia ugandensis, Polyscias fulv

Effects of prescribed seasonal burning on A combretum-commiphora plant community in South Central Kenya.

Studies of prescribed seasonal burning on a combretum-commiphora plant community were conducted in Kenya on the National Range Research Station, Kiboko, in 1980-81. Dry and early rainy season burns were applied in different months. Dry season burns were more effective in reducing woody plant canopy cover, height and increasing stem mortality for most species. Early season burns produced greater numbers of resprouts as compared to dry season burns. Numbers of plants for most species showed no significant change due to treatment. Composite plant canopy cover was highly significant (p .001)reduced by January (dry season)burn. Some species, however, had their canopy covers greatly reduced rainy season burns compared to dry season burns, notably, combrtum ariculatum.In some species, comretum apiculatum, Lannea processes and lantana vinbumoides, average plant heights were reduced more following early rainy season burns than after dry season burns. It is my pleasure to thank the rembers of my advisory committee, Dr. Fred E. Smeins, who directed this investigation, Dr. Murray H. Milford and Dr. Stephan L. Hatch. Thanks aslo to the staff of the National Range Research Sation, Kiboko, who provided their time and efforts in this study. Specifically I wish to thank Mr. James Ndemwa Ituli for his time in data colection. Again I want to thank Mr. Trey Richardson for his invaluable help in statistical data analysis and computer work. Finally, thanks to my wife, Kathi,

Human Population Growth, African Pastoralism, and Rangelands: A Perspective

Pastoral livestock production systems in Africa that have existed for centuries are now threatened by changing demographics, improved communications, increased availability of modern weapons, open rangeland shrinkage, global warming, and large-scale migration of people from rural areas to rapidly expanding cities. Human population increase coupled with globalization has led to major conflicts over natural resources in several African countries. If current growth rates persist, the population of Africa will double in 33 yr. Land resources available for farming are now fully used in several African countries. There is growing concern about the capability of these countries to feed their future projected populations. Africa's three most populous countries (Nigeria, Ethiopia, and Egypt) are all net food importers. Demand for meat and milk in Africa is projected to double by 2050. Roughly one-half of Africa can be classified as rangeland. Some form of pastoral grazing is the most efficient way to use most of these lands and sustain traditional cultures. Because most African rangelands are now stocked at or above grazing capacity, there is little potential to increase livestock production by increasing animal numbers. However, because offtake levels across Africa are much lower than in other parts of the world, considerable potential exists to increase meat and milk production. Local development projects oriented toward keeping people on the land and self-sufficiency have considerable potential to improve living and environmental conditions for small farmers and pastoralists. Improved and equal education opportunities for both genders, family planning assistance, renewable energy development, empowerment of women, improvement of soil and water resources, and wildlife conservation should be areas of development focus. Maintaining migration corridors, providing legal rights to historic grazing lands, and providing support services along migration corridors such as watering points, markets, schools, and health care are important strategies to sustain pastoralism. © Published by Elsevier Inc. on behalf of The Society for Range Management.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

Effects of human-livestock-wildlife interactions on habitat in an eastern Kenya rangeland

Human–livestock–wildlife interactions have increased in Kenyan rangelands in recent years, but few attempts have been made to evaluate their impact on the rangeland habitat. This study identified drivers of increased human–livestock–wildlife interactions in the Meru Conservation Area between 1980 and 2000 and their effects on the vegetation community structure. The drivers were habitat fragmentation, decline in pastoral grazing range, loss of wildlife dispersal areas and increase in livestock population density. Agricultural encroachment increased by over 76% in the western zone adjoining Nyambene ranges and the southern Tharaka area, substantially reducing the pastoral grazing range and wildlife dispersal areas. Livestock population increased by 41%, subjecting areas left for pastoral grazing in the northern dispersal area to prolonged heavy grazing that gave woody plant species a competitive edge over herbaceous life-forms. Consequently, open wooded grassland, which was the dominant vegetation community in 1980, decreased by c. 40% as bushland vegetation increased by 42%. A substantial proportion of agro pastoralists were encountered around Kinna and Rapsu, areas that were predominantly occupied by pastoralists three decades ago, indicating a possible shift in land use in order to spread risks associated with habitat alterations

THE EFFECT OF INTRODUCED FORAGE LEGUMES ON IMPROVEMENT OF SOIL FERTILITY IN NATURAL PASTURES OF SEMI-ARID RANGELANDS OF KAJIADO DISTRICT, KENYA

A two phase study was carried out from 2002 to 2005 in the semi-arid rangelands of Kajiado District, Kenya to determine the effect of introduced forage legumes on soil fertility improvement of natural pastures. During legume evaluation phase, Neonotonia wightii (Glycine), Macroptilium atropurpureum (Siratro), Lablab purpureus cv. Rongai (Dolichos), Mucuna pruriens (Velvet bean) and Stylosanthes scabra var. Seca (Stylo) were screened for adaptability and growth performance under the semi-arid conditions for two years. Results of soil analysis showed there were significant increases in soil pH (4.92 to 5.36), organic carbon (1.17 to 2.57%) , nitrogen (0.17 to 0.22%) and potassium (1.23 to 1.68 me%) probably due to the large amounts of organic residues produced by the legumes (particularly Glycine, Siratro and Stylo which are perennials). The calcium content decreased significantly from 7.97 to 4.50 me% (which was attributed to plant uptake) while the decrease of phosphorus was not significant. During the second phase of study for 1½ years Glycine, Siratro and Stylo were integrated into natural pastures. The results showed that only the soil pH significantly increased from 5.23 to 5.31 while all the other nutrients decreased results, which were attributed to production of less organic residues by the legumes compared to the residues produced during the legume evaluation phase. The study concluded that Glycine, Siratro and Stylo were capable of improving the soil fertility of semi-arid natural pastures only if the respective dry matter production was 10.31, 7.81 and 3.52 tha-1, amounts which were able to produce large amounts of organic residues. 

Phenology of <i>Avicennia marina</i> (Forsk.) Vierh. in a disjunctly-zoned mangrove stand in Kenya

Avicennia marina in Gazi Bay, Kenya, displays a disjunct zonation pattern across the intertidal zone with a seaward and a landward A. marina fringe. Earlier studies revealed significant differences in its vegetation structure, physiognomy, root system and leaf morphology, which can be attributed to salinity and tidal inundation differences that characterise the forest zones. The main objective of this study was to investigate the phenology of A. marina in the disjunctly zoned stands by direct shoot observation. Vegetative and reproductive phenology of A. marina was studied from January 2005 to December 2006. Four natural and one reforested sites were used for the study in the landward and the seaward intertidal zone. Randomly selected shoots (54 per site) were carefully tagged for direct shoot observation and sampling done every fortnight for leaf emergence and fall, and bud, flower and fruit production. Vegetative and reproductive attributes of the species were clearly seasonal in both zones with distinct patterns. However, shifts in peaks in leaf fall and emergence were observed in 2006. Unimodal and bimodal leaf fall patterns were respectively observed at the landward and seaward sites. Monthly leaf emergence and fall was significantly different (p0.05) between sites. Mean leaf longevity was 11 months with a significant difference (pA. marina across the intertidal zone are discussed