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Nanyuki, Kenya

Wahungu G.M.,Moi University | Wahungu G.M.,Olpejeta Research Center | Wahungu G.M.,Earthwatch Institute | Mureu L.K.,Olpejeta Research Center | And 8 more authors.
African Journal of Ecology | Year: 2011

Survival and recruitment of the whistling thorn (Acacia drepanolobium Sjøstedt) seedlings was studied in Olpejeta Conservancy, Kenya, between 1999 and 2009. Seedlings were monitored for damage by drought and herbivores as well as survival and recruitment into adult trees. We determined variability in seedling damage, survival and recruitment before and after two management interventions; the elephant translocation in 2001 and the expansion of the reserve in 2007. Seedling survival over 8years was low, with mortalities being initially high between 2000 and 2001. Reduction in elephant numbers was followed by a gradual reduction in seedling mortality. We recorded a 47% survival over 8years; 63% of the mortality having been caused by browsers, drought or other factors. Only 8 (0.75%) of the seedlings had grown into trees. Seedlings experienced greater damage at higher densities and exhibited a storage effect underneath grass cover. Survival and recruitment of A. drepanolobium seedlings is very low and of concern. The expansion of conservation area and the opening of wildlife migration corridors have, however, resulted in a steady recovery for seedlings. We recommend enclosing sections of the conservancy to exclude grazers and browsers such as elephants and to allow seedling survival and recruitment. © 2011 Blackwell Publishing Ltd.

Wahungu G.M.,Moi University | Wahungu G.M.,Olpejeta Research Center | Mureu L.K.,Moi University | Mureu L.K.,Olpejeta Research Center | And 2 more authors.
African Journal of Ecology | Year: 2010

Mortalities to Acacia drepanolobium, a main item in the diet of the eastern black rhino (Diceros bicornis Michaeli) in Olpejeta conservancy, Kenya, are caused by three main factors: drought, browsers and fire. The effect of controlled fires on A. drepanolobium was examined by monitoring survival and growth in experimental plots before and after fire episodes between 2003 and 2007. Density, survival and growth in A. drepanolobium trees were compared eighteen months before and after burning. Tall trees were more likely to die from fire compared to short trees (R2 = 0.575; df = 6; P = 0.048), while seedling densities increased after fire (Χ2 = 36.57; df = 1; P = 0.001). Even with increased seedling densities, burned areas attracted large numbers of seedling predators, lowering the possibility of seedling recruitment into adult, as mean seedling heights reduced significantly (ANOVA, F = 204.42; df = 1; P = 0.036). Fires also significantly lowered flowering (F = 346; df = 1; P < 0.05) in A. drepanolobium, thereby affecting fruit production. Although fires caused mortalities to adult A. drepanolobium, the most significant effect was tree reversals into seedling height class as trees resprouted. Although fire may increase browse biomass of A. drepanolobium available for black rhino, it is not an appropriate black rhino habitat management tool because burnt areas attract many seedling predators that lower seedling recruitment into adult trees. © 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Ltd.

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