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University of Nairobi (1991)

Preferences of livestock on semi-arid range in South-Eastern Kenya

Ekaya, Wellington N

Titre : Preferences of livestock on semi-arid range in South-Eastern Kenya

Auteur : Ekaya, Wellington N

Université de soutenance : University of Nairobi, Kenya

Grade : MSc 1991

Résumé
A study was conducted to estimate and characterize the structure and function of a rangeland ecosystem on the Njemps flats of Baringo District, Kenya. Herbaceous primary production and productivity were estimated, and energy flow and nitrogen cycling characterized over a two-year period. Total aboveground standing crop ranged from 84.6 g m-2 to 295.4 g m-2, with a mean of 162.3 ?60.6 g m-2. Mean monthly aboveground standing crop for 1992 and 1993 was 142.8 ?53.8 and 178.5 ?63.3 g m-2 respectively. The two values were significantly different (P<0.10). Aboveground biomass yield ranged from 17.7 g m-2 to 242.7 g m-2, with a mean of 104.3 ?58 g m-2 and a coefficient of variation of 58%. Mean aboveground standing crop was 59 ?24 g m-2. Monthly values ranged from 28.8 g m-2 to 120 g m-2, with a 38% coefficient of variation. The range for total belowground standing crop was from 83.3 g m-2 to 232.7 g m-2, and a mean of 155.2 ?46 g m-2. The values had a coefficient of variation of 30%. Mean total monthly belowground plant material yield for 1992 and 1993 was 137.6 ?41 g m-2 and 169.9 ?46 g m-2. The coefficients of variation were 59% and 28% respectively. The mean monthly belowground biomass yield was 51.6 ?33 g m-2 with a coefficient of variation of 64%. Mean monthly yield for belowground dead material was 103.7 ?32 g m-2, with a coefficient of variation of31 %. There was no significant difference (p>0.01) in the mean belowground dead material yield between 1992 and 1993. Aboveground:Belowground plant material ratios ranged from 0.55 to 2.31. Ratios greater than 1.00, thus indicating higher quantity of plant material aboveground than belowground, were observed in March and October of 1992 and July and October of 1993. Monthly litter production spread from 31.4 g m-2 to 130 g m-2. Mean monthly yield was 92.5 ?26 g m-2, with a 28% coefficient of variation. There was no significant difference (P>O.OI) in litter yield between 1992 and 1993. Rate of decomposition for aboveground material ranged from 0.005 g g-1 day-l to 0.084 g g-1 day-I. The mean annual rate of decomposition was 0.026 g g-1 day-I. Belowground plant material rates of decomposition spread from 0.009 g g-1 day ! to 0.062 g g-1 day-I, with a mean annual rate of 0.041 g g-1 day-I. Belowground material consistently decomposed faster than aboveground material. Peaks in both aboveground and belowground material decomposition rates coincided with rainfall peaks. In 1992, annual NPP was 439.2 g m-2, giving a net primary productivity of 1.22 g m-2day-l. MonthlyNPP ranged from 17.2 g m-2 to 90.1 g m-2. In 1993, annual NPP was 944.5 g m-2, equivalent to a net primary productivity of 2.62 g m-2 day l. Monthly NPP was between 27.4 g m-2 and 548.6 g m-2. Over the 1992-1993 period, NPP was 1383.7 g m-2, equivalent to a productivity of 1.92 g m-2day-l. Trends in monthly NPP closely followed the trend in rainfall. Turnover rates and times varied between years and compartments. Highest turnover rate was for aboveground biomass (0.40), which was closely followed by the grass litter and belowground biomass compartments with 0.32 and 0.30 respectively. Lowest turnover rate (0.13) was recorded from the aboveground dead compartment. The turnover times for the aboveground biomass, grass litter, and belowground biomass compartments were 2.5 years, 3.1 years and 3.3 years respectively. The dead aboveground biomass had a turnover time of 4.5 -7.7 years. High turnover rates were associated with higher rainfall. Energy contents in the aboveground and belowground plant materials during both seasons were 17.9 KJ g-1 and 21.6 KJ g-1 respectively. Aboveground live and dead plant material compartments had one and a half times more standing crop of energy during the dry season compared to the wet season. During the dry season there was net loss of energy from the aboveground dead compartment. The litter compartment had a net loss of energy during both seasons. Energy content in the belowground live compartment was 113

Mots clés : Livestock / Pastures / South Eastern Kenya

Présentation (Research Kenya)

Page publiée le 22 septembre 2010, mise à jour le 23 février 2018