Family differences in height growth and photosynthetic traits in three conifers.

We investigated variation in height growth, gas exchange, chlorophyll fluorescence and leaf stable carbon isotope ratio among wind-pollinated progenies of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca), ponderosa pine (Pinus ponderosa Dougl. ex Laws.) and western white pine (Pinus monticola Dougl. ex D. Don) from a small group of contiguous stands on the Priest River Experimental Forest in northern Idaho. Photosynthetic variables differed between height classes in the pines, but not in Douglas-fir. Among species and families, tall families of ponderosa pine regained photosynthetic capacity earliest in the spring and maintained it latest in the growing season. Tall families of western white pine had higher instantaneous water-use efficiencies and lower photosynthetic rates than short families on warm days in August.