Biological Soil Invertebrate Activity in a Tropical Rainforest : A comparison of soil invertebrate activity in two tropical rain forests in Borneo

Logging of tropical forests is increasing worldwide. Logging alters the forest conditions such as temperature, soil water content and litter input into the soil. This study explored how soil invertebrate activity in Borneo differs between pristine forests and two secondary forests, with 10 and 40 years of recovery time since the last logging. To measure the soil fauna feeding activity, the bait lamina stick method was applied. The study was conducted in Sabah, Malaysian Borneo, during April and May 2019. 33 forest plots were examined with ten lamina sticks placed in each of the three replicas per forest plot. The sticks were kept in the soil for four weeks before being removed. Upon removal, the soil invertebrate activity was determined by assessing how many holes of the bait lamina sticks were eaten and at what depth. The activity was related to the above-ground carbon density (ACD, a density measure for amount of above-ground carbon), as well as depth-specific activity in the different plots. Moreover, further relationships with the invertebrate activity and environmental conditions such as cumulative throughfall during the study time as well as the soil water content were studied. The results showed that the soil activity slightly decreased with increased ACD, but no statistical significance was found. This study also suggests that the activity was higher in the upper 0-5cm of the soil than in the lower 5-10 cm. Lastly, the results showed that the activity was highest in the forest with the shortest recovery time (10 years). This implies that it might be possible to regain the original soil activity since the activity of the 40-year-old forest was closer to the pristine forest than that of the 10- year-old forest.