Table 3 Comparison of The Linear and Non-Linear Effects of CO2 on Crops in Selected Elevated CO2 - Plants Relationship Studies.
Studies | Time Period | Regions | Comparison of Results | ||
|---|---|---|---|---|---|
Method | Corn (C4 Crop) | Soybean (C3 Crop; Legume) | |||
Linear: The percentage increase in crop yields per ppm | |||||
Kimball (1983) | Various years | Various Countries | Review enclosure studies | 0.039–0.13% | |
Cure & Acock (1986) | Various years | Various Countries | Review enclosure studies | −0.10–0.27% | 0.062–0.11% |
Long et al. (2006) | 1992–2005 (Short-term for each crop) | Various Countries | Free-Air Concentration Enrichment Experiment (FACE) | 0% | 0.082% |
Ziska & Bunce (2007) | Various years | Various Countries | Review enclosure and FACE studies | −0.00012–0.28% | |
This Paper | 1959–2013 | Ontario, Canada | Bio-Economic Crop Yield Response Model (BECYR) | 0.04% ± 0.80% | 0.32% ± 1.26% |
Nonlinear: The direction and turning point of CO2 effect on plants | |||||
Andresen et al. (2017) | 1998–2014 | Hesse, German | Giessen Free-Air Concentration Enrichment Experiment (GiFACE) | The biomass of legumes at elevated CO2 (+20% above ambient) is less than that at ambient CO2 for 1998–2006. After 2006, the biomass at elevated CO2 is more than that at ambient. | |
Reich et al. (2018) | 1998–2017 | Minnesota, US | Free-Air Concentration Enrichment Experiment (FACE) | The biomass of C4 grasses was not markedly raised at elevated CO2 (+180ppm) in the first 12 years, but markedly raised in the subsequent 8 years. | The biomass of C3 grasses was markedly raised at elevated CO2 (+180ppm), but not in the subsequent 8 years |
This Paper | 1959–2013 | Ontario, Canada | Bio-Economic Crop Yield Response Model (BECYR) | Corn yield decreases in the beginning. When CO2 reaches 353ppm (the value in 1994), yield starts to increase | Soybean yield decreases in the beginning. When CO2 reaches 360ppm (the value in 1998), yield starts to increase |
