No abstract

Interpretation of genetic variation associated with geographic origin must take into account the evolution and migratory history of the species being-studied. A literature survey was made to determine the probable origin of jack pine (pinus banksiana) and its migration from glacial refugia following the Wisconsin glacial maximum. Jack pine and contorta pine (Pinus contorta) became differentiated following cooling of the climate and crustal uplift in western North America in the late Tertiary. Modern hybrid swarms and introgression of jack pine and lodgepole pine (Pinus contorta var. lalifolia) east of the Rocky Mountains are of recent origin, dating from late post-glacial migration from the east and west respectively. Geological and paleobotanical evidence, particularly from fossil pollen depositions, indicate that jack pine survived glaciation in an extensive refugium centered on the Appalachian Highlands of eastern North America, and not in additional refugia south or west of the Great Lakes. This conclusion is consistent with the clinal pattern of geographic variation evident from genecological studies of the species.

Duration (D), rate of shoot elongation (RSE), number of stem units (NSU), and mean stem unit lengths (MSUL) of current year's (1987) leaders were analyzed in 18 jack pine (Pinusbanksiana Lamb.) full-sib progenies from nine inter- and nine intra-provenance crosses. The parent material consisted of selected "plus" trees from Ontario, Quebec, Wisconsin, and Michigan provenances. The average within-family variance (phenotypic) of D was on the average 186 days or twice as large as the among-family variance of 90 days. Duration was positively correlated with the number of growing degree-days at the place of parental origin. Tree height and height growth of several crosses significantly exceeded a local check lot, and the provenance effects on heights were predominantly additive (but not the luxuriance of hybrids). In determining annual height growth, it was discovered that D and RSE were roughly equally important, but large differences in RSE were observed among families with almost equal growth duration. The superior height growth of two interprovenance families was attributed to higher growth rates rather than a longer growth period. Although NSU was more important than MSUL in determining final shoot length, a negative correlation between NSU and MSUL complicated the overall significance of NSU. It was concluded that jack pine had sufficient variation in the examined height growth components to facilitate genetic improvement in height growth without adverse effects on periodicity. The provenance hybrids produced sufficiently promising results and additional exploitable phenotypic variation to warrant continued hybridization efforts.

Seedlings of six outcrossed jack pine (Pinus banksiana Lamb.) families from a diallel cross of jack pine were mainly larger than those of three selfed families at the time they were transplanted to the field in Ontario. Outcrossed families also exhibited a greater absolute and relative (percent) growth in total dry matter at the end of the first growing season. Outcrossed families exhibited a higher net photosynthesis, a lower transpiration rate, and a higher water use efficiency on hot, but not mild, days in mid-August. Stomatal conductance, transpiration rate, and net photosynthesis were greater in outcrossed families in September. There were significant, positive correlations between stomatal conductance, transpiration rate, and shoot and root growth in August and September. The results suggest that maintenance of a higher stomatal conductance and net photosynthesis until late in the growing season may contribute to the faster growth rates observed in outcrossed families.

Tree size and aboveground biomass in twelve 34-year-old Ontario jack pine (Pinusbanksiana Lamb.) provenances growing at Petawawa National Forestry Institute (Chalk River, Ontario) was negatively correlated with latitude of origin. The best provenance exceeded the local provenance in tree height and diameter by approximately 10%. The pattern of geographical variation was stable over time, making general and sound predictions of provenance growth based on juvenile performance feasible. Persistent differences among some geographically close provenances indicated the potential for genetic improvement by selecting the best populations within site regions. The results demonstrated have important implications for jack pine breeding and improvement strategies at the provenance level. The provenance averages of aboveground ovendry weight per tree ranged from 44 to 79 kg. The aboveground tree biomass was distributed as follows in seven analyzed provenances: stem wood, 78%; stem bark, 8%; branch wood, 8%; needles, 5%; cones, 1%. Variation in average stemwood mass among provenances was less than the variation in average stem volume because of a strong negative correlation on a single tree basis between stem volume and stem wood density. The mean annual volume and biomass accretion per hectare in the best provenances averaged 10 m3 and 4 t, respectively. Total stem volume production per hectare varied exponentially with tree height. Mean annual stem volume increment of the best provenances exceeded that of the slowest growing provenances by 22–40%.