Speaker
Description
- Introduction
Future crop production depends on plant plasticity to the increase in atmospheric CO2 concomitant to an increase in mean temperatures as well as more frequent and intense events of heat waves and droughts (Zscheischler et al., 2018; Wang et al., 2023). Thus, it is necessary to better understand the effects of these different climatic variables and their interactions on crops, particularly wheat. These climatic effects have been studied experimentally using different types of facilities, but few studies have focused on the interactions between elevated CO2 (eCO2), warming and water deficit. Indeed, the outcome of these interactions is uncertain as these three variables have opposite effects on two main processes: photosynthesis is increased by elevated CO2 but decreased by high temperatures and water deficit while stomatal conductance (and hence transpiration) is reduced by elevated CO2 and water deficit but increased by high temperatures (Kadam et al., 2014). We thus aimed to synthesize current experimental knowledge on the effects of combined stress under eCO2 on production and water related traits.
- Materials, methods
A literature search was carried out to identify 63 experiments quantifying the interaction effects between these variables. Based on this data, we studied the evolution of wheat production and water related traits between current non-limiting conditions (ambient CO2 and temperature, no stress) and the future stressed conditions tested in experiments (eCO2, warming and water deficit). We also studied the hypothesis according to which the fertilizing effect of elevated CO2 on crop production is stronger under dry than wet conditions. Relative reaction norms have been used to summarize the available data as far as possible.
- Results
Highly variable trends were observed, especially for crop production, due to the heterogeneity of the experimental protocols applied. Despite this variability, crop production tends to decrease under future conditions, despite the fertilizing effect of increased CO2 and this decrease is emphasized by the intensity of water deficit, the increase in temperature and the duration of heat wave events. Conversely, water consumption also tends to decrease under these conditions despite the antagonist effect of high temperatures. We also tested the hypothesis that the fertilizing effect of CO2 on yield is greater under drought conditions and on the basis of the data collected, this hypothesis was only verified in 56% of cases.
- Discussion
The studied experimental results mostly show that the fertilizing effect of elevated CO2 on wheat crop performance is not able to offset the negative effects of high temperatures and water deficit. Water consumption is another key aspect of plant functioning under climate change with contrasted plastic responses to the different climatic variables. However, the effects of elevated CO2 and water deficit are predominant over warming, resulting in a decreasing trend under future climatic conditions. Indeed, experiments combining interactions between CO2, temperature and water deficit are not numerous enough and very heterogeneous, mainly because of the diversity in experimental protocols. Besides, a better characterization of stress factors could be achieved with the conception of ecoclimatic indices (Caubel et al., 2015) which would enable better inter-comparison of existing heterogeneous experiments, and the design of future experiments that better represent future multiple stresses. The acquisition of experimental data under future climatic conditions is all the more important as the calibration and validation of crop models depend on them and their range of validity should be more thoroughly tested under interacting climatic variables.
- References
Caubel, J. et al. (2015) ‘Broadening the scope for ecoclimatic indicators to assess crop climate suitability according to ecophysiological, technical and quality criteria’, Agricultural and
Forest Meteorology, 207, pp. 94–106. Available at: https://doi.org/10.1016/j.agrformet.2015.02.005.
Kadam, N.N. et al. (2014) ‘Agronomic and Physiological Responses to High Temperature, Drought, and Elevated CO2 Interactions in Cereals’, in Advances in Agronomy. Elsevier, pp. 111–156. Available at: https://doi.org/10.1016/B978-0-12-800131-8.00003-0.
Wang, E. et al. (2023) ‘Modelling the impact of climate change on agriculture in Australia and Oceania’, in Leibniz Centre for Agricultural Landscape Research (ZALF), Germany and C. Nendel (eds)
Burleigh Dodds Series in Agricultural Science. Burleigh Dodds Science
Publishing, pp. 481–540. Available at: https://doi.org/10.19103/AS.2022.0115.17.
Zscheischler, J. et al. (2018) ‘Future climate risk from compound events’, Nature Climate Change, 8(6), pp. 469–477. Available at: https://doi.org/10.1038/s41558-018-0156-3.
| Keywords | plasticity;climate change;wheat;elevated CO2;high temperature |
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