CO2 FLUX FROM A SINGLE MAPPED SOIL UNIT UNDER DIFFERENT MANAGEMENT PRACTICES

Soil has been identified as a major source of CO₂ flux to the atmosphere, and has been increased by human activities that increase disturbance of the soil. Previous studies have shown that increases in disturbance from agriculture and related activities including fertilization and manure application are correlated with increased CO₂ flux from the soil surface. In this study, we investigate the rate of CO₂ flux from a single contiguous mapped soil unit. Within the unit, three management practices exist. A portion of the area is a tilled field that has been managed in this way for over a decade. A second area was previously tilled, but has been planted with alfalfa for the past 4 years with no tillage. The third area is wooded with mature maple trees. In each area, 8 sampling sites were established with 10 cm diameter by 10 cm high PVC sampling rings inserted 5 cm into the soil surface. Soil samples were collected adjacent to each of the sampling location for determination of soil organic matter content. A vented 1.5 liter chamber is coupled to the sampling rings and CO₂ concentration is determined every 15 seconds for 2 minutes. Soil temperature, air temperature and soil moisture were determined at each location for all sampling events. Results to date show a wide range of CO₂ flux rates that may be associated with ambient air temperature. Soil temperature does not fluctuate to that same degree as air temperature. Soil moisture varies by management type and by sampling date, but does not appear to be related to flux rates. Flux rates do correlate with management type and organic matter content. Contrary to previous studies, the forested site has the highest flux rate, followed by the alfalfa field with the tilled field having the lowest flux rate. This is the same relative relationship for soil organic matter with the forest having an average of 5.1%, the alfalfa field at 3.8% and the tilled field at 2.8%. These represent three distinct soil organic matter contents which appear to be the strongest influence on CO₂ flux rate.