co2_hi

Elevated CO2 atmospheric concentration corresponding the 2nd point on the radiation use efficiency curve

The 1st point on the radiation use efficiency curve is comprised of the ambient CO2 concentration, 330 μL CO2/L air, and the biomass-energy ratio reported for bm_e.

In order to assess the impact of climate change on agricultural productivity, SWAT+ incorporates equations that adjust RUE for elevated atmospheric CO2 concentrations. Values must be entered for co2_hi and bm_e_hi in the plant database whether or not the user plans to simulate climate change.

For simulations in which elevated CO2 levels are not modeled, co2_hi should be set to some number greater than 330 ppmv and bm_e_hi should be set to some number greater than bm_e.

To obtain radiation-use efficiency values at elevated CO2 levels for plant species not currently in the database, plants should be established in growth chambers set up in the field or laboratory where CO2 levels can be controlled. RUE values are determined using the same methodology described in the explanation of bm_e.