Molecular characterization of some bacteria and fungi associated with the decomposition of leaf litters of Eucalyptus camaldulensis and Tectona grandis

Abstract

Eucalyptus camaldulensis and Tectona grandis, have the characteristics of fast growth rate. The decomposition of litter biomass of these exotic plants is necessary in order to return the nutrients taken up by the plants. Some of the major nutrients include nitrogen, carbon, phosphorus, potassium, calcium and magnesium. To have a better understanding of the decomposition of leaf litters of E. camaldulensis and T. grandis, bacteria and fungi associated with their decomposition were investigated. Soil and leaf litters of these exotic plant species were collected from six sampling sites of each plantation designated as E1 – E6 for E. camaldulensis and T1 – T6 for T. grandis, respectively. Litterbag technique was employed for the decomposition study which lasted for 60 days. Using standard methods, analysis of carbon (IV) oxide evolution and microbial population were done at day 1, 30 and 60 of the decomposition period. Results showed that there was a general decrease in the percentage mass loss of E. camaldulensis and T. grandis leaf litter samples, which ranged from 71-85% and 40-61% respectively. The amount of carbon, nitrogen, phosphorus, potassium, calcium and magnesium decreased in the leaf litter but increased in the soil during decomposition. The evolution of CO₂ was highest in E4 on day 60 (554.4 μg/g/day) among E. camaldulensis samples, whereas the evolution of CO₂ was highest in T2 on day 30 with a value of 516.5 μg/g/day among T. grandis samples. The bacteria isolated during the decomposition periods were Bacillus licheniformis, Pseudomonas putida, Bacillus subtilis, Micrococcus luteus, Proteus vulgaris while fungi were Aspergillus niger and Penicillium notatum. Bacillus licheniformis was the most prevalent bacteria isolated. There is need to molecularly establish the specific capability of each microbial isolate with the view to identifying those that sequentially elaborate enzymes that can completely metabolize the leaf litters to their elemental form for adequate enrichment of the soil. This will enhance rapid recovery of the composite undergrowth and also promote diverse microbial colonization.

Keywords: Decomposition, leaf litters, Eucalyptus camaldulensis, bacteria, fungi, and Tectona grandis