GROWTH, SHOOT PHENOLOGY AND PHYSIOLOGY OF DIVERSE SEED SOURCES OF BLACK SPRUCE .1. SEEDLING RESPONSES TO VARIED ATMOSPHERIC CO2 CONCENTRATIONS AND PHOTOPERIODS

We conducted a greenhouse experiment to determine: (1) if diverse prov enances of black spruce (Picea mariana (Mill.) B.S.P.) respond similar ly in growth, phenology and physiology to an approximately 300 ppm inc rease in atmospheric CO2 concentration, and (2) the influence of photo period on both provenance and provenance x CO2 interaction effects. Se edlings from provenances that originated from the Yukon (63 degrees 34 ' N, 135 degrees 55' W), British Columbia (58 degrees 47' N, 123 degre es 38' W), Alberta (52 degrees 22' N, 115 degrees 15' W), Newfoundland (50 degrees 54' N, 56 degrees 06' W) and Ontario (48 degrees 59' N, 8 0 degrees 38' W and 45 degrees 10' N, 77 degrees 10' W) were subjected to growth analysis in greenhouse growth chambers supplied with 712 +/ - 93 (SD) ppm CO2 (elevated) or 394 +/- 59 ppm CO2 (ambient). Seedling s from Provenances 7000 and 6901 were also subjected to an extended ph otoperiod treatment and periodically measured for shoot and root gas e xchange. In response to a natural photoperiod, southern provenances gr ew more, broke and set bud later, and partitioned more biomass to shoo t versus root than northern provenances. These differences among prove nances were influenced by the extended photoperiod treatment but not b y the elevated CO2 treatment. Averaged across all provenances, elevate d CO2 increased seedling final weights by 55%; however, the elevated C O2 treatment had no effect on the provenance differences in any measur ed trait. We conclude that the large differences in physiology, phenol ogy and growth among these diverse provenances of black spruce were ex pressed similarly in both ambient and elevated atmospheric CO2 concent rations.