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Temporal Variability of Soil Carbon Dioxide Flux

Effect of Sampling Frequency on Cumulative Carbon Loss Estimation

USDA-ARS, National Soil Tilth Lab., 2150 Pammel Dr., Ames, IA 50011

View larger version (61K): [in a new window]   Fig. 1. Hourly measurements of soil water content, rainfall, air temperature, and CO2 flux. Soil water content data is average for each site. Carbon dioxide fluxes for each individual chamber are presented. Two chambers were located on the Clarion site and two chambers were located at the Canisteo site.

View larger version (43K): [in a new window]   Fig. 2. Influence of time between measurements on estimated cumulative CO2–C flux for each chamber.

View larger version (27K): [in a new window]   Fig. 3. Influence of sampling interval on deviation of estimated cumulative flux from the best estimate obtained from all the hourly fluxes. Duplicate chambers at each site were combined.

View larger version (21K): [in a new window]   Fig. 4. Variances associated with the spread of percentage deviations observed at different sampling intervals.

View larger version (29K): [in a new window]   Fig. 5. Probabilities of obtaining estimates of cumulative CO2–C flux at a given precision as a function of sampling intervals.

View larger version (28K): [in a new window]   Fig. 6. Time series cross correlation of rainfall and average daily CO2 flux. Both chambers from each site are represented.

View larger version (18K): [in a new window]   Fig. 7. Deviation of estimated cumulative CO2–C flux determined by sampling after days receiving rainfalls of different intensities. Squares are results from the Canisteo site, circles are from the Clarion site.