Experimental design of open-field temperature and precipitation manipulation system to simulate summer extreme climate events for plants and soils

Extreme climate events are expected to occur very frequently and intensively with climate change, and such extreme events can induce irreversible damage to plants and soils, as well as ecosystems. Accordingly, there is a need to understand the effects of extreme climate events on ecosystems. Here, we designed a temperature and precipitation manipulation system to simulate extreme climate events of heat, drought, and heavy rainfall. We constructed three soil surface temperature manipulation levels (control, 3 °C, and 6 °C increases) and three precipitation manipulation levels (control, drought, and heavy rainfall) with six replicates, and operated these from day of year (DOY) 195 to 233 in 2020. Infrared heaters increased the soil surface temperature during the extreme heat treatments. For precipitation manipulation, the automatic rainout shelter excluded ambient rainfall to produce drought conditions and an artificial rainfall simulator with spray nozzles produced heavy rainfall conditions. As a result, the soil surface temperature (°C ± one standard deviation) was higher in the 3 °C and 6 °C heated treatments than in the control by 2.7 ± 0.2 and 5.7 ± 0.5, respectively. The mean soil water content (vol. %) was 12.9 ± 8.6 in the drought treatment, 14.1 ± 7.8 in the control, and 16.1 ± 8.3 in the heavy rainfall treatment during the precipitation manipulation period. The results showed that the system design and operation were as expected. The designed system can be effectively utilized to investigate the responses of plants and soils to extreme climate events.