© 2000 Heron Publishing—Victoria, Canada
Seasonal patterns of carbohydrate reserves in red spruce seedlings
P. G. Schaberg (1), M. C. Snyder (2), J. B. Shane (3) and J. R. Donnelly (3)
1. USDA Forest Service, Northeastern Research Station, P.O. Box 968, Burlington, VT 05403, USA (pschaberg/ne_bu@fs.fed.us) / 2. State of Vermont Department of Forests, Parks and Recreation, Essex Junction, VT 05452, USA / 3. School of Natural Resources, The University of Vermont, Burlington, VT 05405, USA / Received June 28, 1999
Summary
We studied seasonal dynamics of carbohydrate storage in red spruce (Picea rubens Sarg.) seedlings by measuring starch and sugar concentrations of old needles (≥ one year old), new needles (< one year old),
stems, and roots in two stands in the Green Mountains of Vermont. Although the two stands differed in many site characteristics
including percent slope, aspect, soil type, drainage, and 564 m in elevation, concentrations and seasonal patterns of carbohydrates
were similar for the two stands. For all tissues, starch concentrations peaked in late spring, declined through summer, and
reached a minimum in winter. Sugar concentrations were greater than starch concentrations in all months except May and June.
Sugar concentrations peaked in winter, and old needles showed a significant increase in sugar concentration between February
and March. This increase in sugar concentration occurred without any reduction in localized starch concentrations or reductions
in sugar or starch concentrations in new needles, stems or roots. Because March measurements were made toward the end of a
prolonged thaw, a time when increases in photosynthesis have been documented for red spruce, it is likely that the March increase
in sugar concentrations resulted from photosynthesis during the thaw. Compared with stems and roots, needles generally contained
the highest concentration of carbohydrates and exhibited the greatest seasonal change in carbohydrate concentration. Needles
were also the largest reservoir of carbohydrates throughout the year, especially during winter. Because of the critical roles
of needles in photosynthesis and storage of carbohydrates, we conclude that any factors that disrupt the accumulation or availability
of carbohydrates in red spruce needles will greatly alter plant carbon relations.
Keywords:
needles, Picea rubens, roots, sugars, starch, stems.
