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Response of wheat growth, grain yield and water use to elevated CO 2 under a Free ‐ Air CO 2 Enrichment ( FACE ) experiment and modelling in a semi ‐ arid environment

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ABSTRACT

The response of wheat crops to elevated CO2 (eCO2) was measured and modelled with the Australian Grains Free‐Air CO2 Enrichment experiment, located at Horsham, Australia. Treatments included CO2 by water, N and temperature. The location represents a semi‐arid environment with a seasonal VPD of around 0.5 kPa. Over 3 years, the observed mean biomass at anthesis and grain yield ranged from 4200 to 10 200 kg ha−1 and 1600 to 3900 kg ha−1, respectively, over various sowing times and irrigation regimes. The mean observed response to daytime eCO2 (from 365 to 550 μmol mol−1CO2) was relatively consistent for biomass at stem elongation and at anthesis and LAI at anthesis and grain yield with 21%, 23%, 21% and 26%, respectively. Seasonal water use was decreased from 320 to 301 mm (P = 0.10) by eCO2, increasing water use efficiency for biomass and yield, 36% and 31%, respectively. The performance of six models (APSIM‐Wheat, APSIM‐Nwheat, CAT‐Wheat, CROPSYST, OLEARY‐CONNOR and SALUS) in simulating crop responses to eCO2 was similar and within or close to the experimental error for accumulated biomass, yield and water use response, despite some variations in early growth and LAI. The primary mechanism of biomass accumulation via radiation use efficiency (RUE) or transpiration efficiency (TE) was not critical to define the overall response to eCO2. However, under irrigation, the effect of late sowing on response to eCO2 to biomass accumulation at DC65 was substantial in the observed data (~40%), but the simulated response was smaller, ranging from 17% to 28%. Simulated response from all six models under no water or nitrogen stress showed similar response to eCO2 under irrigation, but the differences compared to the dryland treatment were small. Further experimental work on the interactive effects of eCO2, water and temperature is required to resolve these model discrepancies.

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Response of biomass at stem elongation (DC31) to elevated CO2 compared to daytime ambient conditions (365 μmol mol−1) from six crop models; APSIM‐Wheat (a), APSIM‐Nwheat (b), CAT‐Wheat (c), CROPSYST (d), OLEARY‐CONNOR (e) and SALUS (f). The simulated response to elevated CO2 (● and solid fitted lines) compared to the observed response to elevated CO2 (○ and dotted fitted lines slope = 1.21). The 1 : 1 unity dashed line is the line of zero response to elevated CO2. CROPSYST does not simulate stage DC31, but simulated biomass was outputted on the observed date of DC31 for comparison.
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gcb12830-fig-0002: Response of biomass at stem elongation (DC31) to elevated CO2 compared to daytime ambient conditions (365 μmol mol−1) from six crop models; APSIM‐Wheat (a), APSIM‐Nwheat (b), CAT‐Wheat (c), CROPSYST (d), OLEARY‐CONNOR (e) and SALUS (f). The simulated response to elevated CO2 (● and solid fitted lines) compared to the observed response to elevated CO2 (○ and dotted fitted lines slope = 1.21). The 1 : 1 unity dashed line is the line of zero response to elevated CO2. CROPSYST does not simulate stage DC31, but simulated biomass was outputted on the observed date of DC31 for comparison.

Mentions: The observed increase in growth of wheat, up to stem elongation, due to eCO2 was 21% (using regression) (Table S10). This early growth response was not captured well by all the models where APSIM‐Wheat, APSIM‐Nwheat, CAT‐Wheat, CROPSYST, OLEARY‐CONNOR and SALUS produced a predicted response to eCO2 of 29%, 18%, 25%, 40%, 45% and 9%, respectively (Fig. 2 and Table S10). The models: APSIM‐Wheat, CAT‐Wheat and SALUS substantially oversimulated early biomass (stem elongation), whereas the OLEARY‐CONNOR model undersimulated the amount of biomass but oversimulated the response to eCO2 for the same period. Wheat growth up to anthesis increased on average (using regression) by 23% due to eCO2 (Fig. 3 and Table S10). In comparison, simulated response was 22%, 21%, 20%, 28%, 25% and 16% for the APSIM‐Wheat, APSIM‐Nwheat, CAT‐Wheat, CROPSYST, OLEARY‐CONNOR and SALUS models, respectively. All the six models performed within or close to the 95% confidence limits of observed slope. However, in contrast to the oversimulation of early growth, SALUS was not able to capture the observed range of biomass. The simulated increase in LAI at DC65 from eCO2 was 19% for both APSIM‐Wheat and APSIM‐Nwheat and 13%, 7%, 24% and 8% for PAI for CAT‐Wheat, CROPSYST, OLEARY‐CONNOR and SALUS models, respectively (Fig. 4 and Table S10). For both APSIM models, the range of both observed and simulated data matched, whereas the CAT‐Wheat, CROPSYST, OLEARY‐CONNOR and SALUS did not match well the observed range of PAI. The observed and simulated biomass and LAI response to eCO2 at DC65 (50% anthesis) under irrigation was generally increased despite irrigation not fully preventing stress (Table S10). Under irrigation, the effect of late sowing on response to eCO2 to biomass accumulation at DC65 was substantial in the observed data (~40%), but the simulated response ranged from 17% from SALUS to 28% from CROPSYST (Table 4). Simulated response from all the six models under no water or nitrogen stress showed similar response to eCO2 under irrigation, but the differences compared to the dryland treatment were small.


Response of wheat growth, grain yield and water use to elevated CO 2 under a Free ‐ Air CO 2 Enrichment ( FACE ) experiment and modelling in a semi ‐ arid environment
Response of biomass at stem elongation (DC31) to elevated CO2 compared to daytime ambient conditions (365 μmol mol−1) from six crop models; APSIM‐Wheat (a), APSIM‐Nwheat (b), CAT‐Wheat (c), CROPSYST (d), OLEARY‐CONNOR (e) and SALUS (f). The simulated response to elevated CO2 (● and solid fitted lines) compared to the observed response to elevated CO2 (○ and dotted fitted lines slope = 1.21). The 1 : 1 unity dashed line is the line of zero response to elevated CO2. CROPSYST does not simulate stage DC31, but simulated biomass was outputted on the observed date of DC31 for comparison.
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gcb12830-fig-0002: Response of biomass at stem elongation (DC31) to elevated CO2 compared to daytime ambient conditions (365 μmol mol−1) from six crop models; APSIM‐Wheat (a), APSIM‐Nwheat (b), CAT‐Wheat (c), CROPSYST (d), OLEARY‐CONNOR (e) and SALUS (f). The simulated response to elevated CO2 (● and solid fitted lines) compared to the observed response to elevated CO2 (○ and dotted fitted lines slope = 1.21). The 1 : 1 unity dashed line is the line of zero response to elevated CO2. CROPSYST does not simulate stage DC31, but simulated biomass was outputted on the observed date of DC31 for comparison.
Mentions: The observed increase in growth of wheat, up to stem elongation, due to eCO2 was 21% (using regression) (Table S10). This early growth response was not captured well by all the models where APSIM‐Wheat, APSIM‐Nwheat, CAT‐Wheat, CROPSYST, OLEARY‐CONNOR and SALUS produced a predicted response to eCO2 of 29%, 18%, 25%, 40%, 45% and 9%, respectively (Fig. 2 and Table S10). The models: APSIM‐Wheat, CAT‐Wheat and SALUS substantially oversimulated early biomass (stem elongation), whereas the OLEARY‐CONNOR model undersimulated the amount of biomass but oversimulated the response to eCO2 for the same period. Wheat growth up to anthesis increased on average (using regression) by 23% due to eCO2 (Fig. 3 and Table S10). In comparison, simulated response was 22%, 21%, 20%, 28%, 25% and 16% for the APSIM‐Wheat, APSIM‐Nwheat, CAT‐Wheat, CROPSYST, OLEARY‐CONNOR and SALUS models, respectively. All the six models performed within or close to the 95% confidence limits of observed slope. However, in contrast to the oversimulation of early growth, SALUS was not able to capture the observed range of biomass. The simulated increase in LAI at DC65 from eCO2 was 19% for both APSIM‐Wheat and APSIM‐Nwheat and 13%, 7%, 24% and 8% for PAI for CAT‐Wheat, CROPSYST, OLEARY‐CONNOR and SALUS models, respectively (Fig. 4 and Table S10). For both APSIM models, the range of both observed and simulated data matched, whereas the CAT‐Wheat, CROPSYST, OLEARY‐CONNOR and SALUS did not match well the observed range of PAI. The observed and simulated biomass and LAI response to eCO2 at DC65 (50% anthesis) under irrigation was generally increased despite irrigation not fully preventing stress (Table S10). Under irrigation, the effect of late sowing on response to eCO2 to biomass accumulation at DC65 was substantial in the observed data (~40%), but the simulated response ranged from 17% from SALUS to 28% from CROPSYST (Table 4). Simulated response from all the six models under no water or nitrogen stress showed similar response to eCO2 under irrigation, but the differences compared to the dryland treatment were small.

View Article: PubMed Central - PubMed

ABSTRACT

The response of wheat crops to elevated CO2 (eCO2) was measured and modelled with the Australian Grains Free‐Air CO2 Enrichment experiment, located at Horsham, Australia. Treatments included CO2 by water, N and temperature. The location represents a semi‐arid environment with a seasonal VPD of around 0.5 kPa. Over 3 years, the observed mean biomass at anthesis and grain yield ranged from 4200 to 10 200 kg ha−1 and 1600 to 3900 kg ha−1, respectively, over various sowing times and irrigation regimes. The mean observed response to daytime eCO2 (from 365 to 550 μmol mol−1CO2) was relatively consistent for biomass at stem elongation and at anthesis and LAI at anthesis and grain yield with 21%, 23%, 21% and 26%, respectively. Seasonal water use was decreased from 320 to 301 mm (P = 0.10) by eCO2, increasing water use efficiency for biomass and yield, 36% and 31%, respectively. The performance of six models (APSIM‐Wheat, APSIM‐Nwheat, CAT‐Wheat, CROPSYST, OLEARY‐CONNOR and SALUS) in simulating crop responses to eCO2 was similar and within or close to the experimental error for accumulated biomass, yield and water use response, despite some variations in early growth and LAI. The primary mechanism of biomass accumulation via radiation use efficiency (RUE) or transpiration efficiency (TE) was not critical to define the overall response to eCO2. However, under irrigation, the effect of late sowing on response to eCO2 to biomass accumulation at DC65 was substantial in the observed data (~40%), but the simulated response was smaller, ranging from 17% to 28%. Simulated response from all six models under no water or nitrogen stress showed similar response to eCO2 under irrigation, but the differences compared to the dryland treatment were small. Further experimental work on the interactive effects of eCO2, water and temperature is required to resolve these model discrepancies.

No MeSH data available.


Related in: MedlinePlus