Diurnal and seasonal changes in soil respiration in a Japanese grapevine orchard and their dependence on temperature and rainfall

We determined diurnal and seasonal changes in the soil respiration rate in a grapevine orchard and clarified their dependence on temperature and rainfall, from autumn of 1998 to summer of 1999. Measurements were carried out at eight points using a multichannel dynamic closed chamber technique. Daily soil respiration rates were 2.6g CO2 m sup(-2) d sup(-1) in autumn, 0.9g CO2 m sup(-2) d sup(-1) in winter, 3.8g CO2 m sup(-2) d sup(-1) in spring, and 5.3g C02 m sup(-2) d sup(-1) in summer. There was significantly exponential relationship between summer soil respiration rate and the soil temperature, irrespective of dry or wet soil condition. Soil respiration rates in autumn, winter and spring did not significantly correlate with soil surface temperatures, except for a dry period before rain in spring. The relationship between the soil temperature at 5cm depth and the soil respiration rate was significant in winter, but not in autumn and spring. This significant relationship was not observed during a wet period with light rainfall (totally <=4.5mm over 6-12h) in autumn and spring, and was observed during a dry period in spring. Post-rainfall soil respiration bursts were observed after light rain in autumn and spring and the bursts disappeared at least within 12h after the rain. The bursts were not observed after heavy rain in summer. These results indicate that light rainfall accelerates the soil respiration rate. There was no difference in Q sub10 calculated for soil respiration through all seasons between the soil surface temperature and soil temperature at 5cm depth, while summer Q sub10 was larger at 5cm depth than at the soil surface. The estimated annual soil respiration in our grapevine orchard was 349.4g C m sup(-2) y sup(-1) . This value is lower than those in other agro-ecosystems because of lower content of the soil organic matter depending on the cultivation regime peculiar to the grapevine orchard.