A controlled environmental facility is necessary for investigation of the interaction between above-ground and below-ground components in microcosm experiments. The Earthtron is a simple computer-controlled chamber simulating natural environments: diurnal light/dark cycles, and separately controlled soil and air temperature, humidity and CO2 concentration. In soil core incubation experiments, the Earthtron was able to simulate the dynamics of soil temperature field conditions. Environmental control also affects the dynamics of soil water and distribution patterns of nutrients in the microcosm, linking to the distribution of plant roots and soil biota. The Earthtron can not only reproduce field conditions but also predict the effects of global climatic change on terrestrial ecosystems.