Contrasting Modes of Survivial by Jack and Pitch Pine at a Common Range Limit

Greenwood, Michael; Livingston, William; Day, Michael; Kenaley, Shawn; White, Alan; Brissette, John

A description of freezing tolerance, reproductive development, and seed germination of jack pine and pitch pine. 'Freezing tolerance, reproductive development, and seed germination of jack pine (Pinus banksiana Lamb.) and pitch pine (Pinus rigida Mill.) were compared in a small sympatric population in Acadia National Park in Maine, at the southern range limit of the former and the northern range limit of the latter. Freezing tolerances of vegetative shoots and roots were similar for both species. Both species flower prolifically, and there was no evidence of differences in either pollen viability, cone survival, or proportion of viable seed (65-70% of the total). Regeneration success (established seedlings ranging from 1 to 13 years old) was similar overall for both species, but success by species varied greatly in some years. Jack pine regeneration was significantly associated with thinner soils, while pitch pine regeneration was associated with thicker soils in hallows. Jack pine seed germinated significantly faster than pitch pine seed, especially when day-night temperature was reduced. Pitch pine seedlings always exhibited a significantly higher root-shoot ratio than those of jack pine. The most northerly provenances of jack pine germinated significantly faster than those form the most southerly provenances. Jack pine also germinated at a significantly higher percentage than pitch pine in exposed granite sand. Thus relatively cool, dry conditions may favor establishment of jack pine seedlings, while pitch pine establishment may be favored in warmer, wetter conditions. ' 'We did not find any obvious developmental or physiological factors that would explain what determines the range limits of either jack or pitch pine in Maine. The failure of jack and pitch pine to extend beyond their current ranges may be the outcome of a complex interaction between differences in germination responses...with a variety of environmental conditions, including temperature, moisture, and competing vegetation.' Coordinates and description of study location are provided. /STUDY LOCATIONS:/ /ACADIA NATIONAL PARK/Cadillac Mountain/

Contrasting Modes of Survivial by Jack and Pitch Pine at a Common Range Limit

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