Determining ecosystem responses to stress requires careful control of the environment while measuring biological effects. Technologically advanced sun-lit closed chambers at WED were found to provide appropriate environmental control and measurement compared to chamberless controls. Chamber impacts on the ecosystems were documented so that treatment effects could be interpreted. Differences in growth can likely be attributed to less soil moisture and lower light intensities, and possibly slightly greater vapor pressure deficits in chamber vs. outside during parts of the year. Because of the advance control system, the effects of these sunlit chambers on plant growth appears to be negligible.