Influence of Buffer Zone Regimes on Treespecies Health, Richness, Abundance and Density in Kakamega Forest, Kakamega County, Kenya

Abstract

Worldwide, Buffer zone regimes (BZRs) have been established as designated areas to protect tropical forests from human activities. In Kenya, Nyayo Tea Zone (NTZ) was established around all gazetted forests as BZR. In areas where soil was not ideal for tea, Exotic Tree Plantations (ETP) was established though some parts Open Edge (OE) still exist. However, there are minimal studies on how the BZRs (OE, ETP, and NTZ) area influences tree species; health; richness; abundance and density in Kakamega forest. The purpose of this study was to examine the influence of BZRs area on tree species health, richness, abundance and density in Kakamega forest. The objectives of the study were to: establish the relationship between BZRs (OE, ETP, NTZ) area and the health of individual trees protected from (debarking, exposure of roots to soil surface, storm breakage, poaching for wood collection); assess the influence of BZRs (OE, ETP, NTZ) area on tree species richness; and establish the influence of BZRs (OE, ETP, NTZ) area on tree species relative abundance and density in Kakamega forest. Cross-sectional descriptive research design was employed. Study population of BZR area and that for trees was unknown. Saturated sampling was used where 40 plots in adjacent BZRs along a string placed 100m from forest edge to interior was studied. OE acted as a control site assuming all the forest conditions were similar. Study sites were located using hand held GPS. Trees were identified visually and counted. Spearman rank correlation coefficient was used to establish the relationship between BZRs (OE, ETP, NTZ) area and the health of individual trees protected from debarking, exposure of roots to soil surface, storm breakage and poaching for wood collection. Simple linear regression was used to assess the influence of BZRs (OE, ETP, and NTZ) area on tree species richness, species abundance and tree density. The results showed that the relationship between BZRs area and the health of individual trees protected from: debarking, exposure of roots to soil surface, storm breakage, and poaching for wood collection in that order positive and moderately strong in the OE(r= 0.57, r=0.54, r=0.59, r=0.62; strong in ETP(r=0.88, r= 0.75, r=0.78, r=0.74); and very strong in NTZ (r= 0.98, r=0.93, r=0.96, r=0.88). Further, results demonstrated that 68% (r2 = 0.68), 82% (r2 = 0.82), 93% (r2= 0.93) variation of tree species richness can be explained by BZRs area in OE, ETP, NTZ respectively. Moreover, 72% (r2 = 0.72), 83 % (r2 = 0.83), 93% (r2= 0.93) variation of tree species abundance and that 53 % (r2 = 0.53), 76 % (r2 =0.76,), 95 % (r2 = 0.95) variation of tree species density can be explained by BZR area in OE, ETP, NTZ respectively. It was concluded that BZRs area (ETP and NTZ) have higher influence on the health of individual trees protected from (debarking, exposure roots to soil surface, storm breakage, poaching for wood collection); tree species richness, tree species abundance and density than OE. It was recommended that BZRs area (ETP and NTZ) should be extended to OE in order to protect more tree species.