Changes in microclimate induced by experimental warming and clipping in tallgrass prairie

In order to facilitate interpretation and comparison of warming effects on ecosystems across various habitats, it is imperative to quantify changes in microclimate induced by warming facilities. This paper reports observed changes in air temperature, soil temperature and soil-moisture content under experimental warming and clipping in a tallgrass prairie in the Great Plains, USA. We used a factorial design with warming as the primary factor nested with clipping as the secondary factor. Infrared heater was used in order to simulate climatic warming and clipping to mimic mowing for hay or grazing. The warming treatment significantly increased daily mean and minimum air temperatures by 1.1 and 2.3 °C, respectively, but had no effect on daily maximum air temperature, resulting in reduced diurnal air-temperature range. Infrared heaters substantially increased daily maximum (2.5 and 3.5°C), mean (2.0 and 2.6°C) and minimum (1.8 and 2.1°C) soil temperatures in both the unclipped and clipped subplots. Clipping also significantly increased daily maximum (3.4 and 4.3°C) and mean (0.6 and 1.2°C) soil temperatures, but decreased daily minimum soil temperature (1.0 and 0.6°C in the control and warmed plots, respectively). Daily maximum, mean and minimum soil temperatures in the clipped, warmed subplots were 6.8, 3.2 and 1.1°C higher than those in the unclipped, control subplots. Infrared heaters caused a reduction of 11.0% in soil moisture in the clipped subplots, but not in the unclipped subplots. Clipping reduced soil-moisture content by 17.7 and 22.7% in the control and warmed plots, respectively. Experimental warming and clipping interacted to exacerbate soil-moisture loss (26.7%). Overall, infrared heaters simulated climate warming well by enhancing downward infrared radiation and by reducing the diurnal air-temperature range.