Litter Processing of Exotic and Indigenous Leaves in Njoro River, Kenya

Abstract

The decomposition rate of riparian leaves can measure the potential of litter qualityas a food resource for aquatic organisms. This is valuable given the changing composition of riparian trees where exotic species are becoming more dominant. The core objective of this study was to estimate breakdown rates of 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, PittosporumviridiflorumandSyzygium cordatum in water. The classical decay coefficienct method was used after the leaves were immersed in water for 46 days. Syzygium cordatumand Eucalyptus salignarecorded the lowest decay rates (0.03). Decay rates for P. viridiflorumand G. robustawere 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. There was also a positive relationship between decay rate and macroinvertebrates for P. viridiflorum.Macroinvertebrate taxa favoredleaves of P. viridiflorumand G. robusta. Leaves of P. viridiflorum decayed faster, were softer and favoredby aquatic macroinvertebrates. ThusPittosporum viridiflorumleaves are of good quality and should notbe replaced by exotic species such as E. salignaand G. robustain riparian areas of streams. For aquatic and riparian management, planting of P. viridiflorum along river banks is encouraged to improve the qualityof food sources available for aquatic insects and the subsequent aquatic food web.