ASSESSMENT METHOD FOR ENVIRONMENTAL STRESSES IN TREES USING DELTA-C-13 RECORDS OF ANNUAL GROWTH RINGS

A method using delta(13)C records of annual growth rings has been prop osed for assessing environmental stresses in mature forest trees. Firs t, we calculate the change with time in the difference (C-a-C-i) betwe en the CO2 concentration in the atmosphere and the leaf intercellular spaces from the delta(13)C records in tree cellulose based on a carbon isotope fractionation model for C-3 plants. The C-a-C-i value is depe ndent primarily on the mesophyll capacity for photosynthesis and the s upply of CO2 through the stomata. Next, stomatal limitation of photosy nthesis is evaluated from the ratio of ring area to C-a-C-i which is p ossibly indicative of leaf conductance. These parameters for the trees from a declining grove of Japanese cedar (Cryptomeria japonica) in th e Kanto Plain, Japan were suggested to respond sensitively to the chan ges in air pollution (mainly SO2) and/or dry atmospheric conditions. T his method offers a potentially useful research tool for evaluating po ssible causes for forest decline.