A METHOD FOR THE IN-SITU MEASUREMENT OF FINE-ROOT GAS-EXCHANGE OF FOREST TREES

A new method is described for measuring in situ carbon dioxide release of fine roots of trees under field conditions. The method was used on Quercus rubra L., Prunus serotina Ehrh. and Acer rubrum L. The system facilitates repeated in situ measurements of gas exchange on roots < 5 mm in diameter living in flexible polyethylene cuvettes. Intact fine roots were excavated and enclosed in: the prefabricated cuvettes. The cuvettes were then reburied to their original location. The enclosed root segments were approximately 15 cm long and their dry weights rang ed from 0.04 to 3.0 g. Root carbon exchange rates were sampled at the end of the growing season with an open gas exchange system; then the r oot segments were excised and their gas exchange was remeasured with a different, closed gas exchange system. The measurement with the close d system was repeated after approximately 30 min. Gas exchange rates o btained with the three consecutive measurements corresponded well, alt hough the first measurement with the closed system showed, for all thr ee species, a significantly (P < 0.05) higher rate than the other two measurements. (C) 1997 Elsevier Science B.V.