Impacts of Burning and Herbicide Disturbances on Soil Animals and Organic Matter Decomposition in Terraced Paddy Field Levees in Japanese Satoyama

Terraced paddy field landscapes in valleys have linear seminatural grasslands on surfaces adjacent to forest and paddy fields. Paddy levees are traditionally managed by regular mowing and burning, and such landscapes are important habitat for biological communities. Furthermore, these biological communities may contribute to organic matter decomposition in paddy levees. However, seminatural grasslands on paddy levees have recently decreased in Japan due to the use of herbicides. Therefore, we investigated the effects of burning and herbicide disturbances on microenvironmental factors, soil animal communities, and organic matter decomposition. Nine experimental belt transects were set up at paddy levees located on Sado Island, Japan. The burning and herbicide experiments were performed three times per year. The investigations were performed before the experiments and after the first and third experiments. The soil moisture, litter amount, pH, and electrical conductivity were measured as microenvironmental factors. Soil animals were collected and were classified into soil macrofauna and mesofauna. The organic matter decomposition rate was measured using the Bait-Lamina test. In the burning plot, the litter amount and the soil macrofauna abundance decreased after the first experiment. In the herbicide plot, the litter amount, the soil macrofauna abundance, and organic matter decomposition rate increased after the first experiment. Furthermore, with repeated herbicide spraying, the values of these parameters decreased. However, soil mesofauna abundance after the third experiment was not significantly different between all experimental plots. The change in the litter amount was different for each experiment. Furthermore, the changes in litter amount and the soil macrofauna abundance tended to coincide. Additionally, the current paper suggested that soil mesofauna community was less affected by burning and herbicide spraying compared to soil macrofauna.