1e:T546,Greenhouse-cultured, container-grown ponderosa pine (Pinus ponderosa var. scopulorum Engelm.), interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), and Engelmann spruce (Picea engelmannii (Parry) Engelm.) were cold acclimated and deacclimated in growth chambers over 19 weeks. Cold hardiness was measured weekly by a whole-plant freeze test and by two quick tissue tests: freeze-induced electrolyte leakage of needles, and differential thermal analysis of buds. The whole-plant freeze test provided results in 7 days, and indicated differences in cold hardiness among stems, buds, and needles. Although the whole-plant freeze test could accurately measure cold hardiness, it was not precise, and it required destructive sampling. Results from freeze-induced electrolyte leakage and differential thermal analysis were available in 2 days and 1 hour, respectively. The freeze-induced electrolyte leakage test was a precise, sensitive and objective predictor of changes or differences in tissue cold hardiness. To determine actual cold hardiness, results could be calibrated to the response of the same tissue in the whole-plant freeze test. The speed and objectivity of differential thermal analysis made this test useful for rapid, general assessment of cold hardiness status, but calibration was difficult, and precision varied.1f:T523,• Temperature and light responses of CO₂ efflux of Fagus sylvatica (beech) current-year stems were measured for 1 yr to estimate their annual carbon balance. • Gas exchanges were determined using infrared gas analysis. Seasonal patterns of a fluorescence parameter ((F_v /F_m )_max ), nitrogen and chlorophyll contents were also assessed in stems and leaves, using standard techniques. • Basal respiration rates at 20°C (R²⁰ ) were very high during the growing season, reaching a maximum of 17 170 µmol m^-3 s^-1 . Light-saturated assimilation followed the same seasonal pattern as R²⁰ . During the winter, chlorophyll content was undiminished compared with the summer, N content was slightly increased, and despite low (F_v /F_m )_max values, instantaneous maximum assimilation could account for 80-110% of the respiration. • For an average-size stem (4 mm diameter), the estimated annual respiration was 0.5 g carbon with 55% of this amount attributed to maintenance respiration. The potential assimilation contributed 0.2 g carbon and approximately compensated for the growth respiration. Information on older branches and trunks is now needed for estimations at the tree and stand levels.20:T565,

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