EVIDENCE THAT LONGER NEEDLE RETENTION OF SPRUCE AND PINE POPULATIONS AT HIGH ELEVATIONS AND HIGH-LATITUDES IS LARGELY A PHENOTYPIC RESPONSE

There is abundant evidence that evergreen conifers living at high elev ations or at high latitudes have longer-lived needles than trees of th e same species living elsewhere. This pattern is likely caused by the influence of low temperature in combination with related factors such as a shea growing season and low nutrient availability. Because it is not known to what degree such patterns result from phenotypic versus g enotypic variation, we evaluated needle longevity for common-garden-gr own lowland populations of European Scots pine (Pinus sylvestris L.) o f wide latitudinal origin and Norway spruce (Picea abies L.) of wide e levational origin. Nine-year-old trees of 16 Scots pine populations ra nging in origin from 47 degrees to 60 degrees N were studied in Kornik , Poland (52 degrees N) and 18-year-old trees of 18 Norway spruce popu lations ranging in origin from 670 to 1235 m elevation in southwestern Poland were studied near Morawina, Poland (51 degrees N, 180 m elevat ion). There was no tendency in either species for populations from nor thern or high elevation origins to retain needles longer than other po pulations. All of the Scots pine populations had between 2.5 to 3.0 ne edle age cohorts and all of the Norway spruce populations had between 6.4 and 7.2 needle age cohorts. Thus, extended needle retention in Sco ts pine and Norway spruce populations in low-temperature habitats at h igh elevations and high latitudes appears to be largely an environment ally regulated phenotypic acclimation.