Effect of a batericide-fungicide additive on the rates of decomposition of mature fresh leaves of four woody trees species.

摘要

A 3x4 factorial experimental design in a randomized complete block with 3 replications was used to investigate the influence of a potent fungicide-bactericide, mercuric chloride (HgCl), on the rates of decomposition of matured fresh leaves of 2 evergreen tree species, Dacryodes edulis and Irvingia gabonensis, and 2 deciduous species, Gmelina arborea and Ficus exasperata. The experiment, which lasted for 90 days, was performed under the canopy of the trees in the Arboretum of the University of Calabar, Nigeria. The HgCl significantly suppressed the rates of decomposition of the leaves. Thus, the mean percent decomposition of the four trees of 44.66 at 0.0 g HgCl differed significantly (P<0.05) from the other individual leaves in their mean percentage decomposition rates. Dacryodes edulis with 0.004 mean percent decomposition differed significantly from Irvingia gabonensis with the mean of 6.002, Gmelina arborea with 99.50 and Ficus exasperata with 98.10%. In general, the leaves of the evergreen tree species having a common mean percentage of 3.003 decomposed significantly slower than species with mean percent decomposition of 98.8. It is recommended that for greater humus accumulation, evergreen trees should be used to establish a forest stand. However, for soil fertility enrichment and maintenance within a short period of time, deciduous trees species are better since their leaves decompose faster even in the presence of a potent fungicide/bactericide in the soil. This ensures a quick turn over of soil nutrients.