Soil biological activity under different land-uses in Leyte Philippines

On seven sites in Western Leyte, Philippines, different land-uses, namely reforestation with indigenous tree species (`rainforestation`), reforestation with exotic tree specie Gmelina arborea, and traditional fallow / grassland use were compared with respect to soil biological activity. Analysed parameters were Basal Respiration (BR), microbial carbon (Substrate-Induced Respiration method, SIR) and leaf litter decomposition. Correlations between BR, SIR, metabolic quotient (qCO2), soil organic carbon (Corg) soil N (NT) and pH were assessed. BR and Cmic, SIR as well as the metabolic quotient qCO2 (BR/SIR) proved to be sensitive parameters and the methods gave reproducible values to distinguish sites and land-uses in most cases. However, due to differences among fallow /grassland treatments, a uniform tendency between these and rainforestation was not observed. On the other hand, BR and Cmic SIR were significantly higher under Gmelina than under either of the other land-uses. Correlations between parameters were strongest for BR vs. Corg, and BR vs. pH as well as for Cmic SIR vs. Corg and qCO2 vs. Corg