CO2 response curves can be measured with a field-portable closed-loop photosynthesis system D.K. McDermitt, J.M. Norman, J.T. Davis, T.M. Ball, T.J. Arkebauer, J.M. Welles and S.R. Roerner Ann. For. Sci., 46 Supplement (1989) 416s-420s DOI: 10.1051/forest:19890593