Litter processing of Exotic and Indigenous leaves in Njoro River, Kenya
Keywords:allochthonous, aquatic, decomposition, exotic, indigenous, k-values
The decomposition rate of riparian leaves can measure the potential of litter quality as a food resource for aquatic organisms. The core objective of this study was to estimate breakdown rates of Kenyan riparian leaves and macroinvertebrates participation by examining four tree species common along the riparian areas of River Njoro, Kenya at Egerton University. The study assessed decay rates of the leaves of Grevillea robusta, Eucalyptus saligna, Pittosporum viridiflorum and Syzygium cordatum in water. Syzygium cordatum and Eucalyptus saligna recorded the lowest decay rates (0.03). Decay rates for P. viridiflorum and G. robusta were 0.19 and 0.05 respectively. There was a statistically significant difference in the decay rates for each sampling day (p>0.05) for all tree species except S. cordatum. The biological half-life for S. cordatum was highest while P. viridiflorum had the lowest. There was also a relationship between decay rate and macroinvertebrates for P. viridiflorum. Macroinvertebrate taxa favored leaves of P. viridiflorum and G. robusta. Leaves of P. viridiflorum decayed faster, were softer and favored by aquatic macroinvertebrates. Thus Pittosporum viridiflorum leaves are of good quality and cannot be replaced by exotic species such as E. saligna and G. robusta in riparian areas of streams. For aquatic and riparian management, planting of P. viridiflorum along river banks is encouraged to improve the quality of food sources available for aquatic insects and the subsequent aquatic food web.