PROF.NGUGI ROBINSON KINUTHIA

Citation:

Kinuthia RK, Mureithi SM, Young TP, Njoka TJ, Otieno SG. "Aboveground Net Primary Productivity in Grazed and Ungrazed pastures: Grazing Optimisation Hypothesis or Local Extinction of Vegetation Species.". 2009.

Abstract:

The controversy that has surrounded herbivory studi es in the last few decades prompted our investigati on to establish the extent to which herbivore optimisatio n hypothesis or compensatory growth evidence is rea l. We used the traditional movable cage method to collect primary productivity data on herbage, functional g roups and key individual grass species in various controlled large herbivore treatments in an east African savan na. The herbivore treatments in triplicate blocks included cattle, wild herbivores with and without mega herbi vores and combinations of cattle and wild herbivores also wit h and without mega herbivores. The findings reveale d that at herbage level, most grazed treatments (four out of five) had higher productivity than the ungrazed con trol and three showed grazing optimisation curve at sixth po lynomial degree between monthly productivity and gr azing intensity (1-g/ng). At functional group level forbs productivity was higher in the ungrazed control th an in any of the grazed treatments while at individual grass spe cies level Themeda triandra productivity was higher in all grazed treatments than in ungrazed control. We conc lude against presence of herbivore optimisation hyp othesis at herbage, functional group and species level beca use of lack of attributable grazing effect in graze d treatments that matches complex ecological effects in the ungr azed treatment.