Abstract
Key message Large differences were detected between genera and among species in chlorophyll pigment and macronutrient concentrations. Pines have greater variances than spruces and showed less downregulation of chlorophyll pigment concentrations than spruces in response to eCO 2 and DRT. There was strong genetic control of chlorophyll pigments and most macronutrients. Abstract Chlorophyll pigment and needle macronutrient concentrations were quantified for eight tree species in two commercially important genera, Pinus and Picea grown in a 2 × 2 factorial of atmospheric CO 2 (370 and 740 ppm) and soil moisture stress (− 0.1 to − 0.5 and − 0.7 to − 1.0 MPa) treatments. Four of the pines and three of the spruces are native to eastern North America, while a fourth spruce, Norway spruce (NS: Picea abies ), is from Europe but has been widely used for reforestation in northeastern North America. Overall, spruces had significantly greater chlorophyll a , b , (CHL a , CHL b ), and total chlorophyll concentration (TCC) and carotenoid concentration (CAR) than pines. Ambient CO 2 (aCO 2 ) had significantly greater TCC than in response to elevated CO 2 (eCO 2 ), and TCC and CAR was significantly downregulated more in spruces than in pines in response to eCO 2 . Pines had equal or greater TCC and CAR in response to drought treatment (DRT) than well-watered treatment, whereas spruces had significantly lower values in response to DRT. Needle N, P and Ca concentrations were greater for spruces than pines. Needle N concentrations declined in response to both eCO 2 and DRT. Needle P increased in response to eCO 2 but declined in response to DRT. Using total biomass as a covariate, needle N showed no response in pines; whereas spruces showed a slight positive response to increasing total biomass. Covariate analysis showed that TCC had a significant positive relationship to needle N and Mg, with greater TCC in spruces than in pines for a given needle N. Photosynthetic quantum efficiency (QE), derived from light response curves, had a significant positive relationship to TCC that was greater in pines than in spruces for a given TCC. Photosynthetic light convexity had a significant positive relationship to TCC that was also greater in pines than in spruces for a given TCC, indicating a sharper curvature compared to a more progressive curve for spruce. Pine species have greater variances than spruce species. While Pinus strobus (white pine, subgenus Strobus ) stands out as having greater chlorophyll and nutrient concentrations than the other three pines (subgenus Pinus ). Overall, pines showed less downregulation of chlorophyll pigment concentrations than spruces in response to eCO 2 and DRT. There was strong genetic control for chlorophyll pigments and most macronutrients.