Day and night soil respiration from a grassland

Abstract

Day and night soil respiration from a tallgrass prairie in north-east Kansas were compared using the static chamber method with alkali absorption. On each of 18 days and nights in the summer of 1987. 20 observations were made with chambers inserted into the soil on bare spots between plants. The average day and night soil respiration rates were 120 and 100μg CO 2m −2s −1, respectively. Under drier soil conditions soil respiration was greater during the day than during the night. However, day and night soil respiration rates were not significantly different when the volumetric soil water content was > 0.22 m 3m −3. More similar day and night soil respiration rates under wetter soil conditions were attributed to two factors. First, reduced diurnal variability in soil temperature and second, relatively less day root respiration and relatively more night surface soil microbial respiration compared to dry soil conditions. The portion of variability in soil respiration rate explained by soil water content was greater for nocturnal soil respiration than for day soil respiration, indicating that factors other than soil water content have more influence on soil respiration rate during the day than during the night. Day respiration rates were not precisely predicted by using the previous night's respiration rate and soil water content. Day and night soil respiration may both need to be measured to completely and accurately determine the soil respiration component of the carbon balance. Whether day soil respiration rates exceed those during the night depends upon the interactive effects of temperature and water on soil biological activity.