Heat-crater: A passive structure to induce local heatwaves in the field for plant and soil science

The frequency and intensity of extreme weather events have increased under current climate change. Heatwaves are extreme weather events characterized by high temperatures and high vapor pressure deficit (VPD) over several consecutive days. However, the in-situ simulation of heatwaves remains a challenge in plant and soil sciences, as the currently available structures either do not adequately mimic heatwave conditions or are too expensive for ecological studies, which significantly relies on replications in field. Here, we present a solar-powered structure designed to create local heatwaves in the field, allowing the impacts of heatwaves on low herbaceous and small shrub communities to be analysed. This structure, called the heat-crater, is low-cost and easily replicable. We carried out a pilot test by using it and inducing a spring heatwave during a 14-day period in May 2026 in a semiarid area with sparse herbaceous vegetation in Spain. We extrapolated the results using historical weather records from an automatic weather station located near the pilot-test site. The heat-crater successfully induced a local heatwave characterized by daytime temperatures averaging 4 °C higher and by VPD averaging 0.63 kPa higher, while nighttime temperatures and VPD were not significantly different from those of ambient conditions. When extrapolated to the historical record, this artificial heatwave exceeded the P95 threshold for at least seven consecutive days. This methodological manuscript presents the heat-crater and the pilot test, and suggests the steps required to properly validate the system. Our aim is to provide a robust and low-cost technique for inducing heatwaves in the field and improving our understanding of the effects of heatwaves on plants and soils in in- situ conditions.