GENECOLOGICAL
VARIATION CORRESPONDING
TO FOREST ECOSYSTEM CLASSIFICATION VEGETATION AND SOIL TYPES FOR JACK PINE AND BLACK SPRUCE FROM NORTHWESTERN
ONTARIO
WILLIAM H. PARKER, ANNETTE VAN NIEJENHUIS and JOELL WARD Faculty of Forestry, Lakehead University, Thunder Bay, Ontario, P7B 5E1, Canada
Abstract. A preliminary study was undertaken to reveal ecotypic differentiation in jack pine and black spruce corresponding to ecological land classification groups. Seed sources of jack pine (64) and black spruce (68) from northwestern Ontario were classified according to Vegetation Types (VTypes) and Soil Types (S-Types) defined by the Forest Ecosystem Classification (FEC) developed by the Ontario Ministry of Natural Resources and Forestry Canada for northwestern Ontario. Two short-term common garden field trials and a greenhouse trial were established for each species. Significant differences were present among ecological groupings of seed sources for both species. These differences were expressed according to V-Types and S-Types based on first, second, and third year heights as well as needle flushing dates for jack pine and second year growth increments for black spruce. Rank differences among the groups based on FEC V-Types and S-Types were generally consistent for each of the two species although certain groups showed rank reversals at the two field trials. Apparently, selection pressures corresponding to different FEC V-Types and S-Types have resulted in a detectable pattern of adaptive variation for both jack pine and black spruce in northwestern Ontario. However, the management implications for these two species are uncertain since additional tests are required to verify these results.
I. Introduction Black spruce ( P i c e a m a r i a n a (Mill.) B.S.E) and jack pine (Pinus b a n k s i a n a Lamb.) are two o f the most widespread conifers growing in the boreal forest o f Ontario. In this region, considerable environmental variation is seen in the climate, Soil Types, and plant associations (Hosie, 1979; Sims et al., 1990). Provenance tests have revealed patterns o f adaptive variation corresponding to geographic and climatic trends for both jack pine (Steiner, 1979; Rudolph and Yeatman, 1982) and for black spruce (Khalil and Douglas, 1979; Park and Fowler, 1988; Morgenstern and Mullen, 1990). The influence o f plant association and Soil Type on patterns o f adaptive variation are less well understood. These environmental variations almost certainly generate differential selection pressures, particularly for black spruce (Parker et al., 1983), a species that occupies distinct upland and lowland sites. These pressures may have given rise to ecotypic differentiation in one or both o f these species although so far there has been little evidence to support this contention (O'Reilly et al., 1985; Boyle et al., 1990). In spite of these negative findings, edaphic ecotypic variation has been shown for other associated conifers Environmental Monitoring and Assessment 39: 589-599, 1996. (~) 1996 Kluwer Academic Publishers. Printed in the Netherlands.
590
WILLIAM H. PARKER ET AL.
including white spruce (Picea glauca (Moench) Voss) (Teich and Hoist, 1974) and eastern white cedar (Thuja occidentalis L.) (Habek, 1958). The genecology of jack pine and black spruce is of interest to forest managers in northwestern Ontario because of the commercial importance of these species and their extensive artificial regeneration programs. For this reason, numerous studies have been completed which investigate differences in upland-lowland stand pairs of black spruce. While seedling traits differed between the upland and lowland types (Lee, 1984), actual field trials showed little to no differentiation (Fowler and Mullin, 1977). However the advisability of using upland or lowland seed sources for reforestation of the inappropriate site type is still considered uncertain or in some cases inadvisable (Haavisto, personal communication). The goal of this study was to reveal ecotypic differentiation of jack pine and black spruce corresponding to environmental variation at seed origin, based on the Forest Ecosystem Classification (FEC) for northwestern Ontario devised by Sims et al. (1989). Our intent was to test the use of the FEC as a tool to classify geographically diverse seed sources into groups having common selection pressures resulting from the same plant associations (V-Types) or Soil Types (S-Types). Our hypothesis was that black spruce and jack pine stands belonging to a common V-Type or S-Type could be distinguished from other stands belonging to other FEC classification units, regardless of their collection location, when grown in a common environment.
2. Methods Intensive short-term provenance trials were established in the Ontario Ministry of Natural Resources Northwest Region of Ontario. This involved collection of seed from 64 jack pine stands and 68 black spruce stands in an area extending from Geraldton to Atikokan (Figure 1). Seed from a minimum of ten trees was bulked to constitute each seed source. Details of the collection procedures for jack pine and black spruce, respectively, have been reported by Maley and Parker (1993) and Parker et al. (1994). FEC data were collected at each of the jack pine and black spruce sites from which seed was collected. FEC V-Types and S-Types were determined for each site following the procedures described by Sims et al. (1989). Jack pine seed was collected from sites classified to 8 V-Types and black spruce seed was collected from sites classified to 13 V-Types; species groupings overlapped in 3 of the 18 V-Types (Table I). Similarly, jack pine and black spruce seed was collected from sites classified to 12 and 14 S-Types respectively; there was overlap in 7 of the 19 S-Types (Table II). Unfortunately, the distribution of seed sources among the Vand S-Types was uneven with a few categories represented by few or only one seed collection.
59l
GENECOLOGICAL VARIATION OF TREE SPECIES
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Fig. 1. Locations of 64 seed sources of jack pine (open circles) and 68 seed sources of black spruce (solid circles) from northwestern Ontario. Locations of the two field trials are indicated as open squares.
Seedlings from each of the seed sources were started in a greenhouse. Field trials and a potted greenhouse trial were established from this stock. The greenhouse trials contained 10 seedlings from each seed source arranged in a completely randomized block. The field trials for each species consisted of 3 completely randomized blocks. Each block contained 10 replicate seedlings (single tree plots) from each of the 64 jack pine seed sources and each of the 68 black spruce seed sources. The 2 field trials were established in 2 contrasting environments: at the Leo Vidlak Demonstration Forest, located north of the town of Raith (Raith forestry trial -48~ N, 890581 W) and at Lakehead University (LU field trial - 480261 N, 89~ ~ W) (Figure 1). The forestry trial was established on a site from which an upland jack pine/black spruce stand had previously been harvested (V32 and S1 FEC Types). The field trial was established on an abandoned hay field that probably supported a poplar/white birch/white spruce mixed wood stand before it was cleared (probably V8 and S1 FEC Types). Eleven growth and phenological variables were determined for jack pine (van Niejenhuis, 1995) and 3 growth variables for black spruce (Ward, 1992). Annual heights of jack pine were measured at the end of each of the first 3 growing seasons (1988, 1989 and 1990) at the 2 field trials, and after the first growing season (1988) at the greenhouse trial. Height increment was also measured after the second growing season (1989) at the greenhouse trial. Needle flushing dates
592
WILLIAM H. PARKER ET AL.
TABLE I Number of seed sources according to FEC Vegetation Type. (V-Types as described in Sims et al. (1989).) V-Type
Vegetation type name
Jack pine
V10 VII V17 V18 V19 V20 V25 V28 V29 V30 V31 V32 V33 V34 V35 V36 V37 V38
Trembling Aspen-Black Spruce-Jack Pine/Low Shrub Trembling Aspen-Conifer/Blueberry/Feathermoss Jack Pine Mixedwood/Shrub Rich Jack Pine Mixedwood/Feathermoss Black Spruce Mixedwood/Herb Rich Black Spruce Mixedwood/Feathermoss White Spruce-Balsam Fir/Feathermoss Jack Pine/Low Shrub Jack Pine/Ericaceous Shrub/Feathermoss Jack Pine-Black Spruce/Blueberry/Lichen Black Spruce-Jack Pine/Tall Shrub/Feathermoss Jack Pine-Black Spruce/Ericaceous Shrub/Feathermoss Black Spruce/Feathermoss Black Spruce/Labrador Tea/Feathermoss (Sphagnum) Black Spruce/Speckled Aider/Sphagnum Black Spruce/Bunchberry/Sphagnum Black Spruce/Ericaceous Shrub/Sphagnum Black S pruce/Leatherleaf/Sphagnum
Total
Black spruce
3 7 2 4 1 5 8 8 5 27
64
9 4 5 6 11 11 3 8 3 68
of jack pine were recorded during the second growing season (1989) at the 2 field trials. Second year (1991) height increments were measured at each of the 3 black spruce trials (Ward, 1992). Data for each variable were analyzed using one-way Analysis of Variance (ANOVA) to determine the differences among groups of seed sources classified according to FEC V-Types and FEC S-Types. V-Type and S-Type groups of seed sources were ranked and the group means were compared by Least Significant Difference (LSD) tests (p < 0.05) to further examine group differences. This mean comparison test is appropriate for planned comparisons between any 2 group means (Sokal and Rohlf, 1981) but other procedures intended for multiple mean comparisons would have produced more conservative results.
3. Results One-way ANOVA results for the jack pine trials showed that significant differences were expressed among groups of seed sources classified according to FEC category,
GENECOLOGICALVARIATIONOF TREESPECIES
593
TABLE II Number of seed sources according to FEC Soil Type. (S-Types as described in Sims et al. (1989).) S-Type
Soil type name
S1 $2 $3 $4 $5 $6 $7 $9 S 10 S 11 S12F S12S SS 1 SS2 SS3 SS4 SS5 SS6 SS7
Dry/Coarse Sandy Fresh/Fine Sandy Fresh/Coarse Loamy Fresh/Silty-Silt Loamy Fresh/Fine Loamy Fresh/Clayey Moist/Sandy Moist/Silty-Silt Loamy Moist/Fine Loamy-Clayey Moist/Peaty Phase Wet/Organic[Feathermoss] Wet/Organic[Sphagnum] Discontinuous Mat on Bedrock Extremely Shallow Soil on Bedrock Very Shallow Soil on Bedrock Very Shallow Soil on Boulder Pavement Shallow-Moderately Deep/Sandy 4 Shallow-Moderately Deep/Coarse Loamy Shallow-Moderately Deep/Silty-Fine Loamy--Clayey
Total
Jack pine
Black spruce
30 7 3 1 3 3
7
5 2 2
3 2 8 5 3 5 1 23 2
1 5 3 1
1 2
64
68
whether for V-Type or S-Type (Table III). This effect was observed for all o f the 11 variables determined for jack pine, and the effect was particularly pronounced for the groups determined by S-Type. Significant differences were also observed a m o n g groups o f black spruce seed sources grouped according to V-Type and SType when grown at the field trials but were not evident for the greenhouse trial (Table III). Further examination o f these group differences using L S D tests revealed a number o f significant differences expressed among FEC groups. The results o f six o f these mean comparison tests are presented as representative examples (Figures 2 7). The remaining twenty-two tests that are not presented are either similar to the six shown here or demonstrated fewer or no significant differences among groups. Figures 2 and 3, 4 and 5, and 6 and 7 are pairs that compare growth at the L U field trial and the Raith forestry trial. Growth rates were two to three times higher at the L U trial and the number o f significant differences expressed among the FEC V- and S-Types reflects this differential growth rate; i.e., more significant comparisons were present among faster growing seedlings.
594
WILLIAMH. PARKERET AL.
TABLE III Analyses of variance results for jack pine and black spruce trials according to FEC Vegetation and Soil Type. Species
Variable*
Degrees Vegetationtype of F-value Significance freedom
Soil type F - v a l u e Significance
Jack Pine
GH88HT GH89EL GH89FL LU88HT LU89HT LU90HT LU89FL RA88HT RA89HT RA90HT RA89FL
630 624 625 1917 1904 1895 1909 1087 1311 1269 1217
3.50 3.86 4.26 14.99 17.13 7.77 2.16 3.00 3.28 1.98 2.46
0.001 0.000 0.000 0.000 0.000 0.000 0.035 0.004 0.002 0.054 0.017
3.86 4.14 2.08 5.71 15.40 12.41 4.29 4.69 7.26 5.97 2.42
0.0000 0.0000 0.0200 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0056
Black Spruce
GH90EL LU90EL RA90EL
678 2019 1977
1.53 5.36 1.71
0.107 0.000 0.059
0.76 3.15 3.01
0.7058 0.0001 0.0002
*GH88HT = Greenhouse First Year Height GH89EL = Greenhouse Second Year Height Increment GH89FL = Greenhouse Needle Flushing Date LU88HT = LU First Year Height LU89HT = LU Second Year Height LU90HT = LU Third Year Height LU89FL = LU Needle Flushing Date RA88HT = Raith First Year Height RA89HT = Raith Second Year Height RA90HT = Raith Third Year Height RA89FL = Raith Needle Flushing Date GH90EL = Greenhouse Second Year Height Increment LU90EL = LU Second Year Height Increment RA90EL = Raith Second Year Height Increment
Figures 2 and 3 depict the results o f the mean comparison tests for third year heights o f jack pine seedlings classified into V-Types. The rank order o f certain groups is similar at both sites; V25 had the shortest and V30 had the second tallest trees at both sites. Certain V-Types perform relatively differently at the two test sites: V32 ranked fourth at the forestry trial (also a V32 site), while it ranked sixth at the field trial; V29 ranked first at the forestry trial and fourth at the field trial. Figures 4 and 5 show the results of the L S D tests for third year heights o f jack pine seedlings classified into S-Types. A few of the S-Types showed consistent
595
GENECOLOGICAL VARIATION OF TREE SPECIES
V V V V V V V Mean V- 2 1 3 3 2 1 3 (mm) Type 5 8 2 1 9 7 0 634.0 25 744.7 18 ~/ 746.5 32 779.4 31 786.2 29 ~/ ~/ 798. l 17 ~ ~/ 801.7 30 4 ~ 4
Fig. 2. Results of Least Significant Difference (LSD) test for the effect of jack pine V-Types on third year height at the Lakehead University field trial. Check marks indicate a significant difference between group means (p < 0.05).
Mean (ram) 589.3 704.8 731.0 756.5 778,1 778.3 787.2 794.9 808.4 831.1 870.7 914.7
SType $4 $2 $3 SI SS5 SS1 $5 SS7 $6 SS3 SS2 SS6
SS S SS S S S S S S S S S SS 4 2 3 1 5 1 5 7 6 3 2 -4 -4 -4 -4 -4 "4 -4
-4-4 -4
q -4 -4 -4
Fig. 4. Results of LSD test for the effect of jack pine S-Types on third year height at the Lakehead University field trial.
V Mean V- 2 (mm) Type 5 218.5 25 248.5 31 272.0 18 275.7 17 279.1 32 q 285.0 28 4 292.8 30 ~/ 296.0 29 q
V V V V V V 3 1 1 3 2 3 1 8 7 2 8 0
~/ ~/
Fig. 3. Results of LSD test for the effect of jack pine V-Types on third year height at the Raith forestry trial.
Mean (ram) 215,8 231,8 238.6 249,4 258,5 264.5 268.0 268,3 273,8 286.3 317,6 385,7
SType $4 SS2 $2 SS5 SS6 SS7 $6 $3 $5 SI SS1 SS3
S S S S S S S S S S S S S S S S 4 2 2 5 6 7 6 3 5 1 1
-4 q q q q q ~/ ~/ "4 q -4 -4 "4 -4 q ~ 4 4 -4 4 4 -4 q .4
Fig. 5. Results of LSD test for the effect of jack pine S-Types on third year height at the Raith forestry trial.
performance for the two tests; for example, $ 4 and $2 were the worst performers at both sites and SS-3 was the best and third from the best. Many of the remaining S-Types showed rank reversals between the two test sites including SS2, $3, S1 and SS 1. It is o f particular interest that the sources classified as S 1 performed well on the S 1 soil at the forestry trial, and performed poorly on the S 1 soil at the field trial. Figures 6 and 7 present the L S D test results of black spruce seed sources classified according to S-Type. As for jack pine, some S-groups performed consistently while others showed rank reversals. SS7 seed sources grew slowly at the Raith forestry trial and rapidly at the LU field trial while SS1 and $9 sources did the opposite. Unlike the situation for jack pine, the S 1 group performed at mid-rank at both locations.
596
Mean (mm) 17.4 17.8 t8.7 19.0 19.1 19.4 19.4 19.4 19.5 19.5 197 20.4 20.5 21.5
WILLIAM
SType S10 SSI SII $9 SS6 SS4 S1 SS5 S125 $6 $12S SS7 s7 $4
H. P A R K E R E T A L .
S S SS S1 IS S S S l S 1 S S S S S 2 S 2 S S 0 1 1 9 6 4 1 5 F 6 S 7 7
"4 %/ %/ "~ %/ %/ %/ %/
%/ %/ %/ %/ %/ %/ %/ %/
%/%/
4-I
Fig. 6. Resultsof LSD test for the effect of black spruce S-Types on second year elongation at the Lakehead University field trial.
Mean (mm) 4.23 5.20 5.28 5.38 5.42 5.76 5.78 5.95 6.05 6.20 6.24 6.26
SType SS7 S10 S12F SS4 SS6 SS5 Sl S6 Sll S12S $4 SSI
6.28
$7
6.34
$9
S S S S 1 S S S S 1 S S 1 2 S S S S S 1 2 S S S 7 0 F 4 6 5 1 6 1 S 4 1 7
%/ "4 %/ %/ %/ %/ %/
%/ %/ %/ %/
%/ %/ `/ %l
Fig. 7. Resultsof LSD test for the effect of black spruce S-'l~pes on second year elongation at the Raith forestry trial.
4. Discussion Throughout much of this century, common garden tests of seed sources gathered from diverse habitats throughout a species range have provided an invaluable source of information regarding genecological differentiation (Turesson, 1922; Clausen et al., 1940). Much of the variation expressed among seed sources correlates with the environment and thus is accepted to be the result of natural selection operating at the population level to eliminate less well adapted individuals from genetically variable species (Heslop-Harrison, 1964). In the forestry context, provenance tests are an essential preliminary step to understand intraspecific variation and to guide successful seed transfers (Langlet, 1962; Rehfeldt, 1984). Previously noted patterns of adaptive variation for black spruce and jack pine have shown correlations with climatic trends or with geographic trends that reflect climate changes. The results of this study indicate that seed sources of jack pine and black spruce from northern Ontario are differentiated according to plant association type and Soil Type. Thus, patterns of adaptive variation of these 2 species may have also been shaped by non-climatic factors. These results are to be expected since changes in association type and Soil Type should result in differential selection pressures; but they are novel in that the FEC system provided the means to reveal the differentiation. Earlier work with black spruce in the Maritimes showed some similarity to our results. Khalil (1975) found that the ecotypic nature of juvenile height growth in Newfoundland corresponded to Rowe's (1972) forest section boundaries. However, geographic areas provide the basic framework for Rowe's system, not plant or soil associations. Studies with western conifers also have indicated that variation expressed among seed sources of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) could be partly accounted for by habitat type (Campbell and Franklin, 1981; Rehfeldt, 1979). These habitat types are based on indicator species as are the
GENECOLOGICAL VARIATION OF TREE SPECIES
597
FEC V-Types but the western habitat types also closely correspond to elevational zones which represent distinct climatic changes. Although elevation probably does not play much of a role in our results, it is possible that the differences we have observed among seed sources based on V-Types may also result, at least in part, from subtle climatic differences that produced the different plant associations. The significant differences expressed among jack pine and black spruce seed sources classified according to V-Type and S-Type that we observed are evidence pointing to the existence of ecological races in both species. Both the consistency in performance and the rank reversals of seed sources at the forestry trial and at the field trial may be interpreted as support for genecological differentiation. Certain categories of FEC Types could be better adapted for growth at both test sites while others might be well adapted for growth at only one of the sites. The differential performance of S 1 Type jack pine seed sources at the two trials each with S 1 Soil Type (Figures 4 and 5) is of interest. Intuitively, one would expect S 1 Type seed sources to do well on S 1 soils if, as our results suggest, ecotypic differentiation has occurred. However, the forestry trial formerly supported a jackpine stand while the field trial probably supported a hardwood-dominated mixed-wood stand. Thus, although the texture was similar, the pH of the two soils was different - acidic at the forestry trial, and essentially neutral at the field trial. It is possible that this pH difference caused the relatively poorer growth at the field trial. In contrast, black spruce S 1 sources showed consistent average performance at both test sites. With regard to the possible differentiation of upland/lowland ecotypes for black spruce, the results are not particularly supportive. Seed sources grouped into the S 12S Soil Type corresponding to lowland stands produced above average growth at each of the test sites, both having coarse sandy soils (S 1). To help resolve this issue of edaphic ecotypes in black spruce, at least one test site would need to be established on an organic, poorly drained soil. Although preliminary, the results presented here are definitely provocative. They suggest that the categories of the FEC classification system produced for northwestern Ontario correspond to natural selection units. If repeatable, these results could well have implications for seed transfers; i.e., best growth in reforestation efforts would not only depend upon matching the climates of seed source and planting site but also upon matching FEC V-Types and S-Types. There are implications for tree improvement programs as well. Breeding for production gains may be lost if seedlings are poorly adapted to the planting site. Although it is remarkable that essentially the same pattern emerged for both jack pine and black spruce, these results are inconclusive for several reasons. The location of seed origin is affecting the tests to an unknown extent. The geographical distribution of seed sources classified to various V-Types and S-Types did not, in some cases, display an even distribution throughout the study area. When seed sources of a given FEC Type are grouped geographically, the results become confounded. A further problem is that many of the V-Types and S-Types
598
WILLIAMH. PARKERET AL.
are represented by very few or only one seed source. M a n y o f the significant c o m parisons between F E C groups indicated in Figures 2 - 7 , involve relatively few seed sources (cf. Tables I and II). In these cases there is a distinct possibility that the d e m o n s t r a t e d differences arise just by chance. We have begun additional tests to further investigate the causes o f the significant differences observed a m o n g F E C groups. I f our results are repeatable, the utility of the F E C system as a m a n a g e m e n t tool for northwestern Ontario would be broadened. However, the results presented here require verification before any F E C V-Type or S-Type matches are contemplated. Further tests are required with balanced sampling designs o f seed sources that are r a n d o m l y located within a geographic area. T h e s e tests need to be replicated at c o m m o n garden sites having contrasting S-Types.
References Boyle, T.J.B., Liengsiri, C. and Piewluang, C.: 1990, 'Genetic structure of black spruce on two contrasting sites', Heredity 65, 393-399. Campbell, R.K. and Franklin J.F.: 1981, 'A comparison of habitat type and elevation for seed-zone classification of Douglas-fir in western Oregon', Forest Sci. 27, 49-59. Clausen, J., Keck, D.D. and Hiesey, W.M.: 1940, Experimental Studies on the Nature of Species, L The Effect of Varied Environments on Western North American Plants, Carnegie Institute of Washington Publication No. 520, 452 pp. Fowler, D.P. and Mullin, R.E.: 1977, 'Upland-lowland ecotypes not well developed in black spruce in northern Ontario', Can. J. For. Res. 7, 35-40. Habek, J.R.: 1958, 'White cedar ecotypes in Wisconsin', Ecology 39, 547-563. Heslop-Harrison, J.: 1964, 'Forty years of genecology', Advances in Ecological Research 2, 159-247. Hosie, R.C.: 1979, Native Trees of Canada (8th ed.), Fitzhenry and Whiteside Ltd., Don Mills, Ontario, 380 pp. Khalil, M.A.K.: 1975, 'Genetic variation in black spruce in Newfoundland', Silvae Genet. 24, 88-96. Khalil, M.A.K. and Douglas, A.W.: 1979, 'Correlation of height growth in black spruce provenances with site factors of the provenances', Silvae Genet. 28, 122-124. Langlet, O.: 1962, 'Ecological variability and taxonomy of forest trees', in: T.T. Kozlowski (ed.), Tree Growth, Ronald Press, New York, 442 pp. Lee, D.: 1984, 'Genetic variation in progeny of upland and peatland black spruce from northern Ontario', B.Sc.E Thesis, Lakehead University, Thunder Bay, Ontario, 50 pp. Maley, M.L. and Parker, W.H.: 1993, 'Phenotypic variation in cone and needle characters of Pinus banksiana (jack pine) in northwestern Ontario', Can. J. Bot. 71, 43-51. Morgenstern, E.K. and Mullen, T.J.: 1990, 'Growth and survival of black spruce in the range-wide provenance study', Can. J. For. Res. 20, 130-143. O'Reilly, G.L, Parker, W.H. and Cheliak, W.M.: 1985, 'Isozymedifferentiation of upland and lowland Picea mariana stands in northern Ontario', Silvae Genet. 34, 214-221. Park, Y.S. and Fowler, D.P.: 1988, 'Geographic variation of black spruce tested in the Maritimes', Can. J. For. Res. 18, 106-114. Parker, W.H., Knowles, P., Bennett, E, Gray, A. and Krickl, T.: 1983, 'Habitat-dependent morphological and chemical variation in Picea mariana from northwestern Ontario', Can. J. Bot. 61, 1573-1579. Parker, W.H., van Niejenhuis, A. and Charrette, P.: 1994, 'Adaptive variation in Picea mariana from northwestern Ontario determined by short-term common environment tests', Can. J. For. Res. 24, 1653-1661.
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Rehfeldt, G.E.: 1979, 'Patterns of first-year growth in populations of Douglas-fir (Pseudotsuga menziesii vat. glauca)', Research Note No. INT-255, US Dep. Agric., For. Serv., Washington, DC, 7 pp. Rehfeldt, J.: 1984, 'Microevolution of conifers in the northern Rocky Mountains: a view from common gardens', in: R.M. Lanner (ed.), Proceedings, 8th North American Forest Biology Workshop, 30 July-1 Aug. 1984, Utah State Univ., Logan, Utah, pp. 132-146. Rowe, J.S.: 1972, 'Forest regions of Canada', Publ. No. 1300, Can. For. Serv., Ottawa, Ontario. Rudolph, T.D. and Yeatman, C.W.: 1982, 'Genetics of jack pine', Res. Pap. No. WO-38, US Dep. Agric., For. Serv., Washington, DC, 60 pp. Sims, R.A., Towill, B.D., Baldwin, K.A. and Wickware, G.M.: 1989, 'Field guide to the forest ecosystem classification for northwestern Ontario', Ont. Min. Nat. Resour., Thunder Bay, Ontario, 191 pp. Sims, R.A., Kershaw, H.M. and Wickware, G.M.: 1990, 'The autecology of major tree species in the North Central Region of Ontario', COFRDA Report No. 3302, Can. For. Serv., Sault Ste. Marie, Ontario, 126 pp. Sokal, R.R. and Rohlf, EJ.: 1981, Biometry (2nd ed.), W.H. Freeman and Co. San Francisco, California, 859 pp. Steiner, K.C.: 1979, 'Patterns of variation in bud-burst timing among populations in several Pinus species', Silvae Genet. 28, 185-194. Teich, A.H. and Hoist, M.J.: 1974, 'White spruce limestone ecotypes', Forestry Chronicle 50, 110lll. Turesson, G.: 1922, 'The genotypical response of the plant species to the habitat', Hereditas 3, 211-350. van Niejenhuis, A.: 1995, 'Genecology of jack pine in north central Ontario', M.Sc. Thesis, Lakehead Univ., Thunder Bay, Ontario. Ward, J.: 1992, 'Genecological variation in two-year height growth for provenances of black spruce from the Northwest Region of Ontario', H.B.Sc. Thesis, Lakehead Univ., Thunder Bay, Ontario, 59 pp.
VARIATION CORRESPONDING
TO FOREST ECOSYSTEM CLASSIFICATION VEGETATION AND SOIL TYPES FOR JACK PINE AND BLACK SPRUCE FROM NORTHWESTERN
ONTARIO
WILLIAM H. PARKER, ANNETTE VAN NIEJENHUIS and JOELL WARD Faculty of Forestry, Lakehead University, Thunder Bay, Ontario, P7B 5E1, Canada
Abstract. A preliminary study was undertaken to reveal ecotypic differentiation in jack pine and black spruce corresponding to ecological land classification groups. Seed sources of jack pine (64) and black spruce (68) from northwestern Ontario were classified according to Vegetation Types (VTypes) and Soil Types (S-Types) defined by the Forest Ecosystem Classification (FEC) developed by the Ontario Ministry of Natural Resources and Forestry Canada for northwestern Ontario. Two short-term common garden field trials and a greenhouse trial were established for each species. Significant differences were present among ecological groupings of seed sources for both species. These differences were expressed according to V-Types and S-Types based on first, second, and third year heights as well as needle flushing dates for jack pine and second year growth increments for black spruce. Rank differences among the groups based on FEC V-Types and S-Types were generally consistent for each of the two species although certain groups showed rank reversals at the two field trials. Apparently, selection pressures corresponding to different FEC V-Types and S-Types have resulted in a detectable pattern of adaptive variation for both jack pine and black spruce in northwestern Ontario. However, the management implications for these two species are uncertain since additional tests are required to verify these results.
I. Introduction Black spruce ( P i c e a m a r i a n a (Mill.) B.S.E) and jack pine (Pinus b a n k s i a n a Lamb.) are two o f the most widespread conifers growing in the boreal forest o f Ontario. In this region, considerable environmental variation is seen in the climate, Soil Types, and plant associations (Hosie, 1979; Sims et al., 1990). Provenance tests have revealed patterns o f adaptive variation corresponding to geographic and climatic trends for both jack pine (Steiner, 1979; Rudolph and Yeatman, 1982) and for black spruce (Khalil and Douglas, 1979; Park and Fowler, 1988; Morgenstern and Mullen, 1990). The influence o f plant association and Soil Type on patterns o f adaptive variation are less well understood. These environmental variations almost certainly generate differential selection pressures, particularly for black spruce (Parker et al., 1983), a species that occupies distinct upland and lowland sites. These pressures may have given rise to ecotypic differentiation in one or both o f these species although so far there has been little evidence to support this contention (O'Reilly et al., 1985; Boyle et al., 1990). In spite of these negative findings, edaphic ecotypic variation has been shown for other associated conifers Environmental Monitoring and Assessment 39: 589-599, 1996. (~) 1996 Kluwer Academic Publishers. Printed in the Netherlands.
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WILLIAM H. PARKER ET AL.
including white spruce (Picea glauca (Moench) Voss) (Teich and Hoist, 1974) and eastern white cedar (Thuja occidentalis L.) (Habek, 1958). The genecology of jack pine and black spruce is of interest to forest managers in northwestern Ontario because of the commercial importance of these species and their extensive artificial regeneration programs. For this reason, numerous studies have been completed which investigate differences in upland-lowland stand pairs of black spruce. While seedling traits differed between the upland and lowland types (Lee, 1984), actual field trials showed little to no differentiation (Fowler and Mullin, 1977). However the advisability of using upland or lowland seed sources for reforestation of the inappropriate site type is still considered uncertain or in some cases inadvisable (Haavisto, personal communication). The goal of this study was to reveal ecotypic differentiation of jack pine and black spruce corresponding to environmental variation at seed origin, based on the Forest Ecosystem Classification (FEC) for northwestern Ontario devised by Sims et al. (1989). Our intent was to test the use of the FEC as a tool to classify geographically diverse seed sources into groups having common selection pressures resulting from the same plant associations (V-Types) or Soil Types (S-Types). Our hypothesis was that black spruce and jack pine stands belonging to a common V-Type or S-Type could be distinguished from other stands belonging to other FEC classification units, regardless of their collection location, when grown in a common environment.
2. Methods Intensive short-term provenance trials were established in the Ontario Ministry of Natural Resources Northwest Region of Ontario. This involved collection of seed from 64 jack pine stands and 68 black spruce stands in an area extending from Geraldton to Atikokan (Figure 1). Seed from a minimum of ten trees was bulked to constitute each seed source. Details of the collection procedures for jack pine and black spruce, respectively, have been reported by Maley and Parker (1993) and Parker et al. (1994). FEC data were collected at each of the jack pine and black spruce sites from which seed was collected. FEC V-Types and S-Types were determined for each site following the procedures described by Sims et al. (1989). Jack pine seed was collected from sites classified to 8 V-Types and black spruce seed was collected from sites classified to 13 V-Types; species groupings overlapped in 3 of the 18 V-Types (Table I). Similarly, jack pine and black spruce seed was collected from sites classified to 12 and 14 S-Types respectively; there was overlap in 7 of the 19 S-Types (Table II). Unfortunately, the distribution of seed sources among the Vand S-Types was uneven with a few categories represented by few or only one seed collection.
59l
GENECOLOGICAL VARIATION OF TREE SPECIES
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Fig. 1. Locations of 64 seed sources of jack pine (open circles) and 68 seed sources of black spruce (solid circles) from northwestern Ontario. Locations of the two field trials are indicated as open squares.
Seedlings from each of the seed sources were started in a greenhouse. Field trials and a potted greenhouse trial were established from this stock. The greenhouse trials contained 10 seedlings from each seed source arranged in a completely randomized block. The field trials for each species consisted of 3 completely randomized blocks. Each block contained 10 replicate seedlings (single tree plots) from each of the 64 jack pine seed sources and each of the 68 black spruce seed sources. The 2 field trials were established in 2 contrasting environments: at the Leo Vidlak Demonstration Forest, located north of the town of Raith (Raith forestry trial -48~ N, 890581 W) and at Lakehead University (LU field trial - 480261 N, 89~ ~ W) (Figure 1). The forestry trial was established on a site from which an upland jack pine/black spruce stand had previously been harvested (V32 and S1 FEC Types). The field trial was established on an abandoned hay field that probably supported a poplar/white birch/white spruce mixed wood stand before it was cleared (probably V8 and S1 FEC Types). Eleven growth and phenological variables were determined for jack pine (van Niejenhuis, 1995) and 3 growth variables for black spruce (Ward, 1992). Annual heights of jack pine were measured at the end of each of the first 3 growing seasons (1988, 1989 and 1990) at the 2 field trials, and after the first growing season (1988) at the greenhouse trial. Height increment was also measured after the second growing season (1989) at the greenhouse trial. Needle flushing dates
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WILLIAM H. PARKER ET AL.
TABLE I Number of seed sources according to FEC Vegetation Type. (V-Types as described in Sims et al. (1989).) V-Type
Vegetation type name
Jack pine
V10 VII V17 V18 V19 V20 V25 V28 V29 V30 V31 V32 V33 V34 V35 V36 V37 V38
Trembling Aspen-Black Spruce-Jack Pine/Low Shrub Trembling Aspen-Conifer/Blueberry/Feathermoss Jack Pine Mixedwood/Shrub Rich Jack Pine Mixedwood/Feathermoss Black Spruce Mixedwood/Herb Rich Black Spruce Mixedwood/Feathermoss White Spruce-Balsam Fir/Feathermoss Jack Pine/Low Shrub Jack Pine/Ericaceous Shrub/Feathermoss Jack Pine-Black Spruce/Blueberry/Lichen Black Spruce-Jack Pine/Tall Shrub/Feathermoss Jack Pine-Black Spruce/Ericaceous Shrub/Feathermoss Black Spruce/Feathermoss Black Spruce/Labrador Tea/Feathermoss (Sphagnum) Black Spruce/Speckled Aider/Sphagnum Black Spruce/Bunchberry/Sphagnum Black Spruce/Ericaceous Shrub/Sphagnum Black S pruce/Leatherleaf/Sphagnum
Total
Black spruce
3 7 2 4 1 5 8 8 5 27
64
9 4 5 6 11 11 3 8 3 68
of jack pine were recorded during the second growing season (1989) at the 2 field trials. Second year (1991) height increments were measured at each of the 3 black spruce trials (Ward, 1992). Data for each variable were analyzed using one-way Analysis of Variance (ANOVA) to determine the differences among groups of seed sources classified according to FEC V-Types and FEC S-Types. V-Type and S-Type groups of seed sources were ranked and the group means were compared by Least Significant Difference (LSD) tests (p < 0.05) to further examine group differences. This mean comparison test is appropriate for planned comparisons between any 2 group means (Sokal and Rohlf, 1981) but other procedures intended for multiple mean comparisons would have produced more conservative results.
3. Results One-way ANOVA results for the jack pine trials showed that significant differences were expressed among groups of seed sources classified according to FEC category,
GENECOLOGICALVARIATIONOF TREESPECIES
593
TABLE II Number of seed sources according to FEC Soil Type. (S-Types as described in Sims et al. (1989).) S-Type
Soil type name
S1 $2 $3 $4 $5 $6 $7 $9 S 10 S 11 S12F S12S SS 1 SS2 SS3 SS4 SS5 SS6 SS7
Dry/Coarse Sandy Fresh/Fine Sandy Fresh/Coarse Loamy Fresh/Silty-Silt Loamy Fresh/Fine Loamy Fresh/Clayey Moist/Sandy Moist/Silty-Silt Loamy Moist/Fine Loamy-Clayey Moist/Peaty Phase Wet/Organic[Feathermoss] Wet/Organic[Sphagnum] Discontinuous Mat on Bedrock Extremely Shallow Soil on Bedrock Very Shallow Soil on Bedrock Very Shallow Soil on Boulder Pavement Shallow-Moderately Deep/Sandy 4 Shallow-Moderately Deep/Coarse Loamy Shallow-Moderately Deep/Silty-Fine Loamy--Clayey
Total
Jack pine
Black spruce
30 7 3 1 3 3
7
5 2 2
3 2 8 5 3 5 1 23 2
1 5 3 1
1 2
64
68
whether for V-Type or S-Type (Table III). This effect was observed for all o f the 11 variables determined for jack pine, and the effect was particularly pronounced for the groups determined by S-Type. Significant differences were also observed a m o n g groups o f black spruce seed sources grouped according to V-Type and SType when grown at the field trials but were not evident for the greenhouse trial (Table III). Further examination o f these group differences using L S D tests revealed a number o f significant differences expressed among FEC groups. The results o f six o f these mean comparison tests are presented as representative examples (Figures 2 7). The remaining twenty-two tests that are not presented are either similar to the six shown here or demonstrated fewer or no significant differences among groups. Figures 2 and 3, 4 and 5, and 6 and 7 are pairs that compare growth at the L U field trial and the Raith forestry trial. Growth rates were two to three times higher at the L U trial and the number o f significant differences expressed among the FEC V- and S-Types reflects this differential growth rate; i.e., more significant comparisons were present among faster growing seedlings.
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WILLIAMH. PARKERET AL.
TABLE III Analyses of variance results for jack pine and black spruce trials according to FEC Vegetation and Soil Type. Species
Variable*
Degrees Vegetationtype of F-value Significance freedom
Soil type F - v a l u e Significance
Jack Pine
GH88HT GH89EL GH89FL LU88HT LU89HT LU90HT LU89FL RA88HT RA89HT RA90HT RA89FL
630 624 625 1917 1904 1895 1909 1087 1311 1269 1217
3.50 3.86 4.26 14.99 17.13 7.77 2.16 3.00 3.28 1.98 2.46
0.001 0.000 0.000 0.000 0.000 0.000 0.035 0.004 0.002 0.054 0.017
3.86 4.14 2.08 5.71 15.40 12.41 4.29 4.69 7.26 5.97 2.42
0.0000 0.0000 0.0200 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0056
Black Spruce
GH90EL LU90EL RA90EL
678 2019 1977
1.53 5.36 1.71
0.107 0.000 0.059
0.76 3.15 3.01
0.7058 0.0001 0.0002
*GH88HT = Greenhouse First Year Height GH89EL = Greenhouse Second Year Height Increment GH89FL = Greenhouse Needle Flushing Date LU88HT = LU First Year Height LU89HT = LU Second Year Height LU90HT = LU Third Year Height LU89FL = LU Needle Flushing Date RA88HT = Raith First Year Height RA89HT = Raith Second Year Height RA90HT = Raith Third Year Height RA89FL = Raith Needle Flushing Date GH90EL = Greenhouse Second Year Height Increment LU90EL = LU Second Year Height Increment RA90EL = Raith Second Year Height Increment
Figures 2 and 3 depict the results o f the mean comparison tests for third year heights o f jack pine seedlings classified into V-Types. The rank order o f certain groups is similar at both sites; V25 had the shortest and V30 had the second tallest trees at both sites. Certain V-Types perform relatively differently at the two test sites: V32 ranked fourth at the forestry trial (also a V32 site), while it ranked sixth at the field trial; V29 ranked first at the forestry trial and fourth at the field trial. Figures 4 and 5 show the results of the L S D tests for third year heights o f jack pine seedlings classified into S-Types. A few of the S-Types showed consistent
595
GENECOLOGICAL VARIATION OF TREE SPECIES
V V V V V V V Mean V- 2 1 3 3 2 1 3 (mm) Type 5 8 2 1 9 7 0 634.0 25 744.7 18 ~/ 746.5 32 779.4 31 786.2 29 ~/ ~/ 798. l 17 ~ ~/ 801.7 30 4 ~ 4
Fig. 2. Results of Least Significant Difference (LSD) test for the effect of jack pine V-Types on third year height at the Lakehead University field trial. Check marks indicate a significant difference between group means (p < 0.05).
Mean (ram) 589.3 704.8 731.0 756.5 778,1 778.3 787.2 794.9 808.4 831.1 870.7 914.7
SType $4 $2 $3 SI SS5 SS1 $5 SS7 $6 SS3 SS2 SS6
SS S SS S S S S S S S S S SS 4 2 3 1 5 1 5 7 6 3 2 -4 -4 -4 -4 -4 "4 -4
-4-4 -4
q -4 -4 -4
Fig. 4. Results of LSD test for the effect of jack pine S-Types on third year height at the Lakehead University field trial.
V Mean V- 2 (mm) Type 5 218.5 25 248.5 31 272.0 18 275.7 17 279.1 32 q 285.0 28 4 292.8 30 ~/ 296.0 29 q
V V V V V V 3 1 1 3 2 3 1 8 7 2 8 0
~/ ~/
Fig. 3. Results of LSD test for the effect of jack pine V-Types on third year height at the Raith forestry trial.
Mean (ram) 215,8 231,8 238.6 249,4 258,5 264.5 268.0 268,3 273,8 286.3 317,6 385,7
SType $4 SS2 $2 SS5 SS6 SS7 $6 $3 $5 SI SS1 SS3
S S S S S S S S S S S S S S S S 4 2 2 5 6 7 6 3 5 1 1
-4 q q q q q ~/ ~/ "4 q -4 -4 "4 -4 q ~ 4 4 -4 4 4 -4 q .4
Fig. 5. Results of LSD test for the effect of jack pine S-Types on third year height at the Raith forestry trial.
performance for the two tests; for example, $ 4 and $2 were the worst performers at both sites and SS-3 was the best and third from the best. Many of the remaining S-Types showed rank reversals between the two test sites including SS2, $3, S1 and SS 1. It is o f particular interest that the sources classified as S 1 performed well on the S 1 soil at the forestry trial, and performed poorly on the S 1 soil at the field trial. Figures 6 and 7 present the L S D test results of black spruce seed sources classified according to S-Type. As for jack pine, some S-groups performed consistently while others showed rank reversals. SS7 seed sources grew slowly at the Raith forestry trial and rapidly at the LU field trial while SS1 and $9 sources did the opposite. Unlike the situation for jack pine, the S 1 group performed at mid-rank at both locations.
596
Mean (mm) 17.4 17.8 t8.7 19.0 19.1 19.4 19.4 19.4 19.5 19.5 197 20.4 20.5 21.5
WILLIAM
SType S10 SSI SII $9 SS6 SS4 S1 SS5 S125 $6 $12S SS7 s7 $4
H. P A R K E R E T A L .
S S SS S1 IS S S S l S 1 S S S S S 2 S 2 S S 0 1 1 9 6 4 1 5 F 6 S 7 7
"4 %/ %/ "~ %/ %/ %/ %/
%/ %/ %/ %/ %/ %/ %/ %/
%/%/
4-I
Fig. 6. Resultsof LSD test for the effect of black spruce S-Types on second year elongation at the Lakehead University field trial.
Mean (mm) 4.23 5.20 5.28 5.38 5.42 5.76 5.78 5.95 6.05 6.20 6.24 6.26
SType SS7 S10 S12F SS4 SS6 SS5 Sl S6 Sll S12S $4 SSI
6.28
$7
6.34
$9
S S S S 1 S S S S 1 S S 1 2 S S S S S 1 2 S S S 7 0 F 4 6 5 1 6 1 S 4 1 7
%/ "4 %/ %/ %/ %/ %/
%/ %/ %/ %/
%/ %/ `/ %l
Fig. 7. Resultsof LSD test for the effect of black spruce S-'l~pes on second year elongation at the Raith forestry trial.
4. Discussion Throughout much of this century, common garden tests of seed sources gathered from diverse habitats throughout a species range have provided an invaluable source of information regarding genecological differentiation (Turesson, 1922; Clausen et al., 1940). Much of the variation expressed among seed sources correlates with the environment and thus is accepted to be the result of natural selection operating at the population level to eliminate less well adapted individuals from genetically variable species (Heslop-Harrison, 1964). In the forestry context, provenance tests are an essential preliminary step to understand intraspecific variation and to guide successful seed transfers (Langlet, 1962; Rehfeldt, 1984). Previously noted patterns of adaptive variation for black spruce and jack pine have shown correlations with climatic trends or with geographic trends that reflect climate changes. The results of this study indicate that seed sources of jack pine and black spruce from northern Ontario are differentiated according to plant association type and Soil Type. Thus, patterns of adaptive variation of these 2 species may have also been shaped by non-climatic factors. These results are to be expected since changes in association type and Soil Type should result in differential selection pressures; but they are novel in that the FEC system provided the means to reveal the differentiation. Earlier work with black spruce in the Maritimes showed some similarity to our results. Khalil (1975) found that the ecotypic nature of juvenile height growth in Newfoundland corresponded to Rowe's (1972) forest section boundaries. However, geographic areas provide the basic framework for Rowe's system, not plant or soil associations. Studies with western conifers also have indicated that variation expressed among seed sources of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) could be partly accounted for by habitat type (Campbell and Franklin, 1981; Rehfeldt, 1979). These habitat types are based on indicator species as are the
GENECOLOGICAL VARIATION OF TREE SPECIES
597
FEC V-Types but the western habitat types also closely correspond to elevational zones which represent distinct climatic changes. Although elevation probably does not play much of a role in our results, it is possible that the differences we have observed among seed sources based on V-Types may also result, at least in part, from subtle climatic differences that produced the different plant associations. The significant differences expressed among jack pine and black spruce seed sources classified according to V-Type and S-Type that we observed are evidence pointing to the existence of ecological races in both species. Both the consistency in performance and the rank reversals of seed sources at the forestry trial and at the field trial may be interpreted as support for genecological differentiation. Certain categories of FEC Types could be better adapted for growth at both test sites while others might be well adapted for growth at only one of the sites. The differential performance of S 1 Type jack pine seed sources at the two trials each with S 1 Soil Type (Figures 4 and 5) is of interest. Intuitively, one would expect S 1 Type seed sources to do well on S 1 soils if, as our results suggest, ecotypic differentiation has occurred. However, the forestry trial formerly supported a jackpine stand while the field trial probably supported a hardwood-dominated mixed-wood stand. Thus, although the texture was similar, the pH of the two soils was different - acidic at the forestry trial, and essentially neutral at the field trial. It is possible that this pH difference caused the relatively poorer growth at the field trial. In contrast, black spruce S 1 sources showed consistent average performance at both test sites. With regard to the possible differentiation of upland/lowland ecotypes for black spruce, the results are not particularly supportive. Seed sources grouped into the S 12S Soil Type corresponding to lowland stands produced above average growth at each of the test sites, both having coarse sandy soils (S 1). To help resolve this issue of edaphic ecotypes in black spruce, at least one test site would need to be established on an organic, poorly drained soil. Although preliminary, the results presented here are definitely provocative. They suggest that the categories of the FEC classification system produced for northwestern Ontario correspond to natural selection units. If repeatable, these results could well have implications for seed transfers; i.e., best growth in reforestation efforts would not only depend upon matching the climates of seed source and planting site but also upon matching FEC V-Types and S-Types. There are implications for tree improvement programs as well. Breeding for production gains may be lost if seedlings are poorly adapted to the planting site. Although it is remarkable that essentially the same pattern emerged for both jack pine and black spruce, these results are inconclusive for several reasons. The location of seed origin is affecting the tests to an unknown extent. The geographical distribution of seed sources classified to various V-Types and S-Types did not, in some cases, display an even distribution throughout the study area. When seed sources of a given FEC Type are grouped geographically, the results become confounded. A further problem is that many of the V-Types and S-Types
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WILLIAMH. PARKERET AL.
are represented by very few or only one seed source. M a n y o f the significant c o m parisons between F E C groups indicated in Figures 2 - 7 , involve relatively few seed sources (cf. Tables I and II). In these cases there is a distinct possibility that the d e m o n s t r a t e d differences arise just by chance. We have begun additional tests to further investigate the causes o f the significant differences observed a m o n g F E C groups. I f our results are repeatable, the utility of the F E C system as a m a n a g e m e n t tool for northwestern Ontario would be broadened. However, the results presented here require verification before any F E C V-Type or S-Type matches are contemplated. Further tests are required with balanced sampling designs o f seed sources that are r a n d o m l y located within a geographic area. T h e s e tests need to be replicated at c o m m o n garden sites having contrasting S-Types.
References Boyle, T.J.B., Liengsiri, C. and Piewluang, C.: 1990, 'Genetic structure of black spruce on two contrasting sites', Heredity 65, 393-399. Campbell, R.K. and Franklin J.F.: 1981, 'A comparison of habitat type and elevation for seed-zone classification of Douglas-fir in western Oregon', Forest Sci. 27, 49-59. Clausen, J., Keck, D.D. and Hiesey, W.M.: 1940, Experimental Studies on the Nature of Species, L The Effect of Varied Environments on Western North American Plants, Carnegie Institute of Washington Publication No. 520, 452 pp. Fowler, D.P. and Mullin, R.E.: 1977, 'Upland-lowland ecotypes not well developed in black spruce in northern Ontario', Can. J. For. Res. 7, 35-40. Habek, J.R.: 1958, 'White cedar ecotypes in Wisconsin', Ecology 39, 547-563. Heslop-Harrison, J.: 1964, 'Forty years of genecology', Advances in Ecological Research 2, 159-247. Hosie, R.C.: 1979, Native Trees of Canada (8th ed.), Fitzhenry and Whiteside Ltd., Don Mills, Ontario, 380 pp. Khalil, M.A.K.: 1975, 'Genetic variation in black spruce in Newfoundland', Silvae Genet. 24, 88-96. Khalil, M.A.K. and Douglas, A.W.: 1979, 'Correlation of height growth in black spruce provenances with site factors of the provenances', Silvae Genet. 28, 122-124. Langlet, O.: 1962, 'Ecological variability and taxonomy of forest trees', in: T.T. Kozlowski (ed.), Tree Growth, Ronald Press, New York, 442 pp. Lee, D.: 1984, 'Genetic variation in progeny of upland and peatland black spruce from northern Ontario', B.Sc.E Thesis, Lakehead University, Thunder Bay, Ontario, 50 pp. Maley, M.L. and Parker, W.H.: 1993, 'Phenotypic variation in cone and needle characters of Pinus banksiana (jack pine) in northwestern Ontario', Can. J. Bot. 71, 43-51. Morgenstern, E.K. and Mullen, T.J.: 1990, 'Growth and survival of black spruce in the range-wide provenance study', Can. J. For. Res. 20, 130-143. O'Reilly, G.L, Parker, W.H. and Cheliak, W.M.: 1985, 'Isozymedifferentiation of upland and lowland Picea mariana stands in northern Ontario', Silvae Genet. 34, 214-221. Park, Y.S. and Fowler, D.P.: 1988, 'Geographic variation of black spruce tested in the Maritimes', Can. J. For. Res. 18, 106-114. Parker, W.H., Knowles, P., Bennett, E, Gray, A. and Krickl, T.: 1983, 'Habitat-dependent morphological and chemical variation in Picea mariana from northwestern Ontario', Can. J. Bot. 61, 1573-1579. Parker, W.H., van Niejenhuis, A. and Charrette, P.: 1994, 'Adaptive variation in Picea mariana from northwestern Ontario determined by short-term common environment tests', Can. J. For. Res. 24, 1653-1661.
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Rehfeldt, G.E.: 1979, 'Patterns of first-year growth in populations of Douglas-fir (Pseudotsuga menziesii vat. glauca)', Research Note No. INT-255, US Dep. Agric., For. Serv., Washington, DC, 7 pp. Rehfeldt, J.: 1984, 'Microevolution of conifers in the northern Rocky Mountains: a view from common gardens', in: R.M. Lanner (ed.), Proceedings, 8th North American Forest Biology Workshop, 30 July-1 Aug. 1984, Utah State Univ., Logan, Utah, pp. 132-146. Rowe, J.S.: 1972, 'Forest regions of Canada', Publ. No. 1300, Can. For. Serv., Ottawa, Ontario. Rudolph, T.D. and Yeatman, C.W.: 1982, 'Genetics of jack pine', Res. Pap. No. WO-38, US Dep. Agric., For. Serv., Washington, DC, 60 pp. Sims, R.A., Towill, B.D., Baldwin, K.A. and Wickware, G.M.: 1989, 'Field guide to the forest ecosystem classification for northwestern Ontario', Ont. Min. Nat. Resour., Thunder Bay, Ontario, 191 pp. Sims, R.A., Kershaw, H.M. and Wickware, G.M.: 1990, 'The autecology of major tree species in the North Central Region of Ontario', COFRDA Report No. 3302, Can. For. Serv., Sault Ste. Marie, Ontario, 126 pp. Sokal, R.R. and Rohlf, EJ.: 1981, Biometry (2nd ed.), W.H. Freeman and Co. San Francisco, California, 859 pp. Steiner, K.C.: 1979, 'Patterns of variation in bud-burst timing among populations in several Pinus species', Silvae Genet. 28, 185-194. Teich, A.H. and Hoist, M.J.: 1974, 'White spruce limestone ecotypes', Forestry Chronicle 50, 110lll. Turesson, G.: 1922, 'The genotypical response of the plant species to the habitat', Hereditas 3, 211-350. van Niejenhuis, A.: 1995, 'Genecology of jack pine in north central Ontario', M.Sc. Thesis, Lakehead Univ., Thunder Bay, Ontario. Ward, J.: 1992, 'Genecological variation in two-year height growth for provenances of black spruce from the Northwest Region of Ontario', H.B.Sc. Thesis, Lakehead Univ., Thunder Bay, Ontario, 59 pp.
