Soil temperature and moisture-based estimation of rates of soil aggregate formation by the endogeic earthworm Eisenia japonica (Michaelsen, 1892)

Ecological importance of earthworm via aggregate production has been well studied in Europe, but much less is known for Asian species. Assessing the effects of temperature and moisture on the soil aggregate formation by earthworms is a logical step towards the quantification of earthworm’s function in ecosystem. Here, we estimated soil temperature and moisture-based rate of aggregate formation by the earthworm Eisenia japonica (Michaelsen, 1892), which is distributed widely in Japan and South Korea. Based on the data obtained from 1-week laboratory incubations, we developed a model describing the aggregate formation rate by earthworm as a function of body mass, soil temperature, and soil moisture. We then applied the model to a field mesocosm experiment. While the aggregate production rates predicted by the model were slightly underestimated, the estimated values showed significant positive correlation with the measured field data (P < 0.001). The empirical model developed here was therefore applicable to the field condition studied, implying that our approach would help to quantify and predict the ecological function of earthworm.