Seasonal Changes in Soil Respiration Rate in a Mulberry Field

Abstract

Soil respiration rate was monitored during a period of one year from 1990 to 1991 in a mulberry field of volcanic ash soil containing 4.5% carbon in Central Japan, where 1.0kgm^-2 of fresh manure was supplied every year. Alkali absorption method using a sponge disc as absorbent holder (Sponge-AA method) was mainly adopted, but the energy budget method and open-flow chamber method were also applied because the Sponge-AA method has been reported to overestimate soil respiration.
It was found that when the Sponge-AA method was applied soil respiration was overestimated by 2.4 and 3.1 times in summer and winter respectively, compared with the other two methods. Calibrated annual soil respiration was 2.29kgCO₂m^-2.
Soil respiration rate was mainly affected by the air temperature. Both instantaneous and daily mean respiration rates increased approximately to 1.8 times when the air temperature increased by 10°C; except in summer. Soil respiration rate was sometimes considerably suppressed during or immediately after heavy precipitation, and enhanced from December to February due to manure supply and litterfall.
The estimated amount of decomposed organic materials was equivalent to, or slightly exceeded the amount of inputted materials.