The ability to monitor isotopic fractionation in terrestrial ecosystems is a challenge due to the 
presence of interacting variables. A laboratory-scale apparatus for controlled experiments could 
serve as a useful platform to deconvolute the variables that affect isotopic fractionation. Such a 
device could offer a powerful means to understand fractionation of carbon stocks in terrestrial 
ecosystems and to probe the effects of photosynthesis or interactions between the soil and plants 
on carbon fractionation. To this end, an enclosed and artificially-lit benchtop soil and plant 
chamber was constructed and equipped to monitor atmospheric isotopic composition. Fourier- 
transform infrared (FTIR) spectroscopy was employed for isotopic sensing since it enables in- situ 
measurements. The validity of FTIR for isotopic ratio determination was confirmed by comparing FTIR 
and isotope ratio mass spectrometry data for a series of CO2 gas samples with known quantities of 
¹³C and ¹²C. The greenhouse chamber was also equipped with an optically- based trace gas analyzer 
capable of continuously tracking CO2, CH4, and H2O concentrations and a residual gas analyzer mass 
spectrometer. Reflectance spectroscopy was also incorporated by way of sealed fiber optic 
feed-throughs coupled to a spectro-radiometer, for quantifying changes in leaf spectra induced by 
various environmental stressors. The resulting greenhouse chamber can be a useful tool for 
determining the effects of atmospheric trace gases on plant morphology and physiology as a function 
of concentration and isotopic composition. Microecosystems can be examined under controlled 
laboratory conditions and a wide variety of plant species can be accomodated. The bench-scale 
greenhouse should prove useful in assessing the impact of environmental variables and in guiding 
the design of field experiments.