# Net Carbon Exchange

At the ecosystem level, carbon (CO2) is fixed through photosynthetic carbon metabolism, and then fixed carbon is used for growth and development of plants. Some of fixed carbon will be lost through respiration. Net Carbon Exchange (NCE) is defined as the net carbon exchange between an ecosystem and the atmosphere, which is the Gross Primary Production (GPP) minus the ecosystem respiration (Reco). It is a key variable for understanding the carbon balance of an ecosystem. NCE can be readily measured with the eddy covariance method or with the chamber-based method (for short and small canopy).

Example of time series of Cc' (water vapor dilution corrected CO2 concentration) from one observation from the clear chamber over a short grassland on the LI-COR campus. Values for various fitted parameters (to, Cm, and N) from the equation below are also shown. The observation length was 120 s with deadband of 20 s. The net carbon exchange (NCE) for this example is -13.0 µmol m-2s-1, showing the ecosystem is taking up CO2.

The following equation is used to fit the time series of Cc':
${C}_{c}\prime \left(t\right)={C}_{m}\prime +\left({C}_{o}\prime -{C}_{m}\prime \right){e}^{-N\left(t-{t}_{o}\right)}$

## LI-8100-NCE Net Carbon Exchange Package

The LI-8100-NCE Net Carbon Exchange Package is designed for scientists interested in quantifying the net carbon exchange between an ecosystem and the atmosphere using the chamber based method. This package includes the LI-8100A Analyzer Control Unit, 8100-104C Clear Chamber, LI-190 Quantum Sensor, 8100-202 Soil Moisture Probe, 8100-203 Thermistor Probe, 8100-564 Wireless package, 8100-604 Leveling Stake, and an Amplifier.

This package is a one chamber option for computing NCE. This system can be used in both a long-term and survey mode depending on their research objectives. Options are also available for multiple chambers.

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