Comparative Effects of Dominant Forest Tree Species on Soil Characteristics and Microbial Biomass

Tree species differ in litter quality and belowground biomass, thereby exerting species-specific impact on soil properties and microbial biomass. A study was conducted to find out the comparative effects of Podocarpus falcatus and Croton macrostachys on basic soil characteristics and microbial biomass, in the Munessa forest, Ethiopia. Four experimental plots under the canopies the respected tree species (two from each) were established for sample collection. From these plots, soil samples were collected from a depth 0-10 cm and 10-25 cm. The results showed that, from the depth 0-10 cm, concentration of organic carbon (C) and nitrogen (N) was larger under C. macrostachys and from the depth 10-25 cm these values were greater under P. falcatus. There was significant difference (p < 0.05) in cation exchange capacity being larger under C. macrostachys. There were no differences in microbial composition between the plots. However, the total phospholipid fatty acids (PLFA) concentration as an entry for microbial biomass determination tended to be significantly larger in soil under Podocarpus plots (382.7 +/- 60.9 nmol PLFA g(-1) dry soil) vs. 262.2 +/- 32.8 nmol PLFA g(-1) dry soil (Croton plots). The varying impacts of tree species on soil characteristics and microbial biomass may be partly explained by differences in functional traits related to life-history strategy of the respected species.