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[ACG37-P01] Change in soil respiration rate and soil organic matter for three years after clear-cutting in a Cryptomeria japonica plantation
Keywords:litter, dead root, soil carbon
Clear-cutting of forests significantly alters the carbon dynamics in soil, with the large temporary supply of litter and dead roots, followed by significant decline. In this study, we measured soil respiration rates, amount of litter on soil surface, dead root, and soil carbon contents at 20 measurement points in a sugi (Cryptomeria japonica) plantation of Tokyo University of Agriculture Okutama Forest from May 2017 (just before clear-cutting) to August 2019. Litter and soil at 0-5 cm in depth were collected at soil respiration measurement points approximately every three months. After soil sampling, the measurement points were reestablished at new locations. Weeding had been done once a year in the study site, and the herbaceous vegetation that entered the measurement points was removed.
Soil respiration rate at 20 °C (R20) was estimated using the exponential functions of soil respiration rate and soil temperature at 5 cm in depth. The mean R20s of 20 measurement points in 2018 and 2019 were not significantly different from that of 2017. The dead root amount of sugi fine root in measurement points did not decreased until May 2018 compared to the fine root biomass before clear-cutting (0.33 ± 0.27 t ha-1) significantly. After that, the dead root amount from September 2018 to August 2019 decreased significantly to 35.7-52.0% before clear-cutting. The amount of sugi leaf litter was 6.24±1.98 t ha-1 before clear-cutting, but decreased significantly to 2.03±1.74 t ha-1 three months after clear-cutting, which may have been affected by the ground preparation after clear-cutting. The amount of sugi leaf litter after March 2018 has decreased significantly compared to August 2017, and it was 20.9-54.9% in August 2017. The fact that the soil respiration rate in the third year after clear-cutting did not decrease compared to the first year after clear-cutting could be due to the continuous supply of organic matter to the soil by litter and dead roots.
Soil respiration rate at 20 °C (R20) was estimated using the exponential functions of soil respiration rate and soil temperature at 5 cm in depth. The mean R20s of 20 measurement points in 2018 and 2019 were not significantly different from that of 2017. The dead root amount of sugi fine root in measurement points did not decreased until May 2018 compared to the fine root biomass before clear-cutting (0.33 ± 0.27 t ha-1) significantly. After that, the dead root amount from September 2018 to August 2019 decreased significantly to 35.7-52.0% before clear-cutting. The amount of sugi leaf litter was 6.24±1.98 t ha-1 before clear-cutting, but decreased significantly to 2.03±1.74 t ha-1 three months after clear-cutting, which may have been affected by the ground preparation after clear-cutting. The amount of sugi leaf litter after March 2018 has decreased significantly compared to August 2017, and it was 20.9-54.9% in August 2017. The fact that the soil respiration rate in the third year after clear-cutting did not decrease compared to the first year after clear-cutting could be due to the continuous supply of organic matter to the soil by litter and dead roots.