Soil CO2 Flux Measurements -- Addressing Spatial Variability: Determining the Number of Readings Required


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Soils can be highly variable in terms of CO2 flux values. Even at a seemingly uniform site, the soil CO2 flux might range from 2 μmol/m2/s at one location to over 4 mol/m2/s just a few meters away. To obtain reliable site mean flux values, it is important to determine how many readings might be required so that time and resources can be properly allocated before starting an investigation. In addition to spatial heterogeneity, soils also exhibit both diurnal and seasonal patterns of variation in CO2 evolution due to changes in soil water content, temperature, soil organic carbon resources, etc. To accurately obtain site CO2 fluxes, it is often necessary to take readings with adequate spatial as well as temporal resolution.


The LI-8100 Automated Soil CO2 Flux System is designed to satisfy both the temporal and spatial resolution requirements of soil CO2 flux monitoring. When connected to the 8100-101 or 8100-104 Long Term Chamber, the LI-8100 system can take frequent CO2 flux readings automatically at user-defined intervals.  When not taking a reading, the chamber moves up and away from the measurement collar. This enables ambient CO2 concentrations to prevail between measurement intervals and also allows the collar area to be fully exposed to elements of wind, rain, sunlight, etc.


When equipped with the LI-8150 Multiplexer, the LI-8100 System is able to control and obtain flux data from up to 16 Long Term Chambers. With either the 10 cm or 20 cm Survey Chamber, the system can be used to rapidly obtain flux readings at many different locations. The Survey Chambers move down over the measurement area to take a flux reading and then move up a short distance to allow ambient CO2 concentrations to be re-established. The survey chambers can also be used for automatic, unattended measurements suitable for intermediate periods. Thus, various user-defined high temporal resolution as well as high spatial resolution monitoring is possible with the LI-8100 System.

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