LAND USE EFFECT ON PLANT SPECIES DIVERSITY AND SOIL MICROBIAL BIOMASS CARBON IN ALETA CHUKO OF SIDAMA REGION, ETHIOPIA

Background. There was a widespread conversion of species-diverse traditional agroforestry to monoculture land uses in Aleta Chuko, Ethiopia, particularly since 1990. However, the effect of such land use change on plant species diversity and soil microbial biomass in agroecosystems was not investigated. Objective. To investigate the effect of land use (LU) on plant species diversity and soil microbial biomass carbon (MBC), determine association between plant species diversity and MBC in Aleta Chuko district. Methodology. Three LU systems, namely, Coffee-Enset Agroforestry (CEA), Eucalyptus Woodlot (EW), and Chat Mono-cropping (CM), were aligned in three transect lines based on a spatial analog design; four (4) plots were used for each LU from individual transects, for a total of 36 plots (12 plot per LU), and then 108 soil samples were taken from three diagonal pits within 20 × 20 m, which was also used for species diversity assessment. The soil MBC was extracted via chloroform fumigation extraction and analyzed at plot level. Results. A total of 37, 16, and 8 plant species were recorded in the CEA, EW, and CM treatments, respectively. The Shannon diversity indices were 2.40, 0.40, and 0.03 for CEA, EW, and CM, respectively. Jaccard’s index indicated negligible similarity (0.15) among the three LUs. However, consistent similarity was observed between transects within each LU, with higher similarity (0.75) recorded for CEA among transects. MBC was 586.3, 298.2 and 313.8 µg g-1 soil in the CEA, CM and EW soils, respectively. MBC in CEA was significantly greater than that in the other two LUs, but there was no significant difference between CM and EW (p < 0.05). There was a strong positive correlation (r = 0.854) between MBC and plant richness. Implication. The strong positive association between MBC and plant diversity implies that decline in plant diversity result in associated degradation of MBC that impede the sustainability of agroecosystems. Conclusion. The expansion of monoculture has weakened plant diversity and soil microbial biomass carbon in agroecosystems. Further study on the plant species-specific association of microbial biomass is needed.