In a changing climate, extreme events such as heatwaves and extreme droughts become more frequent and more severe, but the impact on plant communities is poorly understood. In PLECO we investigate among others how the tolerance of plant communities to climate extremes is related to species diversity and ecosystem complexity. Droughts are simulated with rainout shelters and heatwaves with infrared radiation (in free-air conditions in the field). On the left, the first heating prototype is shown as deployed in arctic tundra. Nowadays we use larger devices irradiating plots up to 3 m diameter with more advanced regulation systems.