Manipulating natural heatwaves in AmbControl chambers: bridging controlled and field conditions for warming studies in plant–soil systems

Quantifying the impact of natural heatwaves on crop productivity requires direct comparison with a no-heatwave control. Yet conventional growth chambers, which rely on artificial lighting and stepwise heating–cooling programs, fail to capture natural sunlight and temperature variability, often leading to biased estimates of heatwave effects. Field-based experiments, on the other hand, provide realistic growing conditions but lack precise temperature control, especially air cooling, making it technically and economically infeasible to establish no-heatwave controls when extreme events occur. Heatwaves are increasingly unavoidable in rice-growing regions, but localized air cooling, under natural sunlight, on a small scale, is technically feasible. To address this gap, AmbControl was developed, a sunlit field chamber system designed to manipulate air temperature without altering natural light dynamics. The results showed that AmbControl successfully replicated the dynamics of natural heatwaves recorded in 2021 and 2022, enabling precise control of air temperature from +1.5 to −4 °C relative to ambient, as well as maintaining a fixed 28.9 °C treatment. Under +1.5 °C warming, daytime and nighttime temperatures were maintained within Δ1.8 °C and Δ1.0 °C of target values, respectively. Relative humidity and vapor pressure deficit co-varied with temperature treatments, highlighting RH as a potential confounding factor in warming studies. By combining environmental precision with field realism, AmbControl offers a versatile, field-relevant platform for directly quantifying plant–soil responses to extreme heat, with the objective of generating field-validated data that can be integrated into crop and climate models, to improve projections of crop resilience under future climate scenarios.