Quantifications of annual soil respiration in switchgrass systems are limited to the\ngrowing season or coarse-scale temporal sampling. This study evaluates daily and seasonal soil\nCO2 respiration in switchgrass croplands. Hourly measurements during a 12-month period were\ntaken for soil CO2 flux, soil temperature, and soil moisture. Although both soil temperature and\nmoisture were positively correlated with soil CO2 flux rates, soil temperature was the primary\ndriver of soil respiration. During winter, lower soil temperatures corresponded with significant\ndecreases in average daily CO2 flux rates, however, CO2 pulses associated with precipitation events\nincreased flux rates up to three times the seasonal daily average. Soil temperature influenced both\ndaily and seasonal flux patterns where the highest flux rates, up to 31.0 kg CO2 haâË?â??1 hâË?â??1, were\nobserved during the warmest hours of the day (13:00 to 15:00) and during the warmest season\n(Summer). Summer and Spring emissions combined accounted for 80.1% of annual flux, indicating\nthat exclusion of non-growing season time periods may result in an underestimation of total annual\nCO2 efflux. Our results indicate that inclusion of the non-growing season and a fine-resolution\ntemporal sampling approach provides more accurate quantifications of total annual CO2 emissions\nin switchgrass croplands.
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