© 2007 Heron Publishing—Victoria, Canada
Controls of growth phenology vary in seedlings of three, co-occurring ecologically distinct northern conifers
D. Scott Green
Ecosystem Science and Management, University of Northern British Columbia, Prince George, BC V2N 4Z9, Canada (greens@unbc.ca) / Received January 31, 2006; accepted October 28, 2006; published online May 1, 2007
Summary
The objective of this study was to investigate the effects of temperature and seed-source elevation on height-growth phenology
of three co-occurring and ecologically distinct northern conifers (Pinus contorta Dougl. ex Loud. var. latifolia (lodgepole pine), Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm. (interior spruce) and Abies lasiocarpa (Hook.) Nutt. (subalpine fir)). Seed from populations of the three indigenous and co-occurring species was collected across
an elevational transect on the southwestern slope of McBride Peak, near Prince George, BC. Collection sites were at elevations
of 750 to 1850 m, the latter being close to the tree line. In 2003, seeds were germinated and seedlings raised under favorable
growing conditions in a temperature-controlled glasshouse. In 2004, seedlings of each population were grown in natural daylengths
at a location within 50 km of the seed collection site both in a temperature-controlled glasshouse and at a nearby field site,
and height growth was recorded twice a week throughout the growing season. Species differed in both the date and the accumulated
heat sum above 5 °C for the initiation and cessation of shoot extension. Growth durations (which integrate growth initiation
and growth cessation) were more similar among species in the field than in the glasshouse. This suggests that different mechanisms
of phenological control among co-occurring species can result in adaptive “equivalence” under a particular set of climatic
conditions.
Keywords:
adaptation, co-occurring tree species, photoperiod, temperature.
