Systematic review of yield responses of four North American conifers to forest tree improvement practices

Forest Ecology and Management 172 (2003) 29±51

Systematic review of yield responses of four North American conifers to forest tree improvement practices Peter F. Newton* Analytical Stand Dynamics Research, Great Lakes Forestry Centre, Canadian Forest Service, Natural Resources Canada, 1219 Queen Street, Sault Sainte Marie, Ont., Canada P6A 2E5 Accepted 2 December 2001

Abstract The objective of this review was to summarize the expected yield gains of black spruce (Picea mariana (Mill.) B.S.P.), jack pine (Pinus banksiana Lamb.), white spruce (Picea glauca (Moench) Voss) and red pine (Pinus resinosa Ait.), to correct provenance-progeny selection, ®rst generational selection strategies and second generational selection strategies, based on a systematic assessment of the scienti®c literature. The procedure consisted of four sequential steps: (1) searching electronic databases for relevant forest tree improvement studies employing a meta-analytical protocol; (2) attaining and assessing the identi®ed publications for their speci®c applicability; (3) collating the results of the resultant study subset in terms of relative height growth gains; and (4) estimating rotational consequences in terms of merchantable productivity via prediction models. The results of the systematic search indicated that documented long-term yield responses to tree improvement were paucity in nature. Speci®cally, the majority of the published studies consisted of short-term results pertaining to provenance-progeny experiments. Furthermore, studies reporting yield responses to ®rst and second generational selection strategies were practically non-existent. Consequently, expert opinion and unpublished preliminary results derived from ongoing tree improvement experiments were used to augment the limited published information available for these selection strategies. Overall, the results indicated that correct provenance-progeny selection could yield juvenile height growth gains of approximately 15% at 15 years for black spruce, 7% at 21 years for jack pine, 12% at 20 years for white spruce and 8% at 15 years for red pine. Corresponding merchantable productivity (mean annual merchantable volume increment) gains at rotation (50 years) for plantations established at nominal initial densities on medium-to-good quality sites were approximately 17, 15, 26 and 7%, respectively. Preliminary estimates derived from individual case-studies indicated that (1) ®rst generational selection strategies could increase merchantable productivity by approximately 13% at 50 years for black spruce, 28% at 40 years for jack pine, and 20% at 45 years for white spruce, and (2) second generational selection strategies could increase merchantable productivity by approximately 31% at 50 years for black spruce. Published by Elsevier Science B.V. Keywords: Black spruce; Jack pine; White spruce; Red pine; Correct provenance-progeny selection; First and second generational selection; Juvenile height growth response; Rotational yield consequences

* Tel.: ‡1-705-541-5615; fax: ‡1-705-541-5700. E-mail address: [email protected] (P.F. Newton).

0378-1127/02/$ ± see front matter. Published by Elsevier Science B.V. PII: S 0 3 7 8 - 1 1 2 7 ( 0 2 ) 0 0 3 2 7 - 4

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P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

1. Introduction Applied forest tree improvement is an important component of intensive forest management1 (Farnum et al., 1983). The basic objective of applied forest tree improvement is to increase forest productivity via the management of genetic variation (Daniels, 1984). This can include species selection through the introduction of exotic species as evident by the successful introduction of Monterey pine (Pinus radiata Mill.) in New Zealand, Sitka spruce (Picea sitchensis (Bong.) Carr.) in Great Britain, lodgepole pine (Pinus contorta Dougl.) in Sweden (Elfving et al., 2001) and Douglas-®r (Pseudotsuga menziesii (Mirb.) in Germany and France. Similarly, selecting superior inter-regional provenances across a species range is a method of managing genetic variation as illustrated by successful provenance selection programs for loblolly pine (Pinus taeda L.) in the USA (Li et al., 1998) and black spruce (Picea mariana (Mill.) B.S.P.) in Quebec (Beaulieu et al., 1989). Furthermore, propagation of superior intra-regional provenances within site regions is one of the most frequently used methods as exempli®ed by New Brunswick's plus tree selection program for black spruce and jack pine (Pinus banksiana (Lamb.)) (Simpson and Tosh, 1997; Simpson, 1998). Operationally, forest tree improvement consists of a set of ®ve sequential elements (sensu Fowler, 1975; Zobel and Talbert, 1984). The ®rst element is the identi®cation of the degree and nature of the genetic variability underlying commercially-important productivity determinates of inter-regional and (or) intra-regional provenances (e.g. survival, growth rate, developmental phenology, morphology (wood density, stem form) and disease resistance). Historically, this has been accomplished by partitioning a species phenotypic variation for a given trait into its additive 1

The underlying objective of intensive forest management is to increase the intrinsic productivity of the forest land base via the application of an integrated silvicultural regime involving the application of various temporal-spatial-specific treatment matrices encompassing intensive site preparation (e.g. mechanical scarification), plantation establishment including use of genetically improved stock, controlling competing vegetation (e.g. manual and/or chemical herbicides), continuous and active protection from insects and pathogens, and density management (e.g. maximizing product quality and quantity via precommercial and/or commercial thinning).

genotypic and environmental variance components through the use of provenance-progeny trials. The second element is the selection of the genotype(s) that will yield the largest genetic gain for a given trait based on the degree of heritability and selection differential (difference between the mean of the selected individuals and mean of the population for a given trait). The third element is the propagation of the selected genotype(s) via the establishment of seedling or clonal seed orchards followed by seed collection and subsequent seedling production of ®rst generation progeny. The fourth element consists of the assessment of ®rst generation progeny in nurserybased seedling experiments, experimental plantations or operational planting programs, in order to (1) guide roguing operations within ®rst generation orchards, (2) select progeny for the establishment of second generation orchards, and (3) identify genotypic candidates for controlled pollination. The ®fth element consists of repeating the second, third and fourth elements with the inclusion of enhanced selection procedures and advanced propagation procedures until cumulative genetic gains are maximized (e.g. breeding±cloning strategies, Morgenstern and Park, 1991). Forest tree improvement has been an important component of intensive forest management programs throughout central and eastern Canada (Simpson and Tosh, 1997). However, the systematic summarization of the yield consequences to tree improvement has not been completed for many of the commercially important coniferous species. Consequently, the degree of productivity gains associated with tree improvement and their implications in forest management planning, are largely unknown. The objective of this study was to summarize the expected yield gains of black spruce, jack pine, white spruce (Picea glauca (Moench) Voss) and red pine (Pinus resinosa Ait.) to tree improvement practices via a systematic review of the scienti®c literature and associated expert opinion. 2. Method Generally, the procedure consisted of four sequential steps: (1) systematically searching electronic databases for relevant forest tree improvement studies

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

employing a meta-analytical protocol; (2) attaining and assessing the identi®ed publications for their speci®c applicability; (3) collating the results of the selected studies in terms of height growth gains; and (4) subsequently estimating rotational consequences in terms of merchantable productivity arising from tree improvement practices. 2.1. Study identi®cation Electronic databases were keyword-searched for species-speci®c studies relating to (1) provenanceprogeny experiments, (2) ®rst generational selection and (3) second generational selection. The databases consisted of (1) WebSPIRS (#1997±2000 SilverPlatter Information N.V.) which includes Agricola, Biological Abstracts, CAB Abstracts and TreeCD, (2) Canadian Forest Service Library Network via the Metafore portal (Natural Resources Canada), and (3) ScienceDirect1 (Elsevier Science B.V.). Furthermore, the World Wide Web was searched employing the Google search engine (#2001 Google Inc., CA, USA). The coverage of the electronic database searches was approximately 71 years (1930±2001) and included consideration of all publications irrespective of language or location. 2.2. Study assessment The identi®ed publications were reviewed and assessed in terms of their study objectives, traits measured, response periods, and overall experimental design. Speci®cally, well-designed long-term studies in which the principal objective was to assess height growth responses to (1) inter-regional and intra-regional provenance-progeny variation, (2) ®rst generational selection strategies, or (3) second generational selection strategies, were selected by species. However, studies pertaining to ®rst and second generational selection programs were practically non-existent and hence expert opinion and unpublished preliminary results derived from ongoing tree improvement experiments were used to augment the limited documentation. 2.3. Quanti®cation of reported yield responses Species-speci®c quantitative gain estimates could not be ascertained for ®rst and second generational

31

selection strategies given the limited number of estimates available for analysis. Consequently, notional summaries of individual case-studies augmented by expert opinion and unpublished preliminary results are presented. Conversely, there were a large number of studies reporting yield variation among provenanceprogenies for each of the four species under evaluation. The results of these provenance-progeny studies were collated in terms of height growth responses. Speci®cally, gains achievable via correct provenanceprogeny selection were quanti®ed using relative percentage height growth as a response measure: mean percentage differential between the mean height of all the provenance-progenies tested and the mean height of those provenance-progenies within the tallest quartile (Eq. (1)). PI  Q…i† H  …i† H RH…i†  RH ˆ iˆ1 ; RH…i† ˆ 100  (1)  H …i† I  H is the species-speci®c mean relative height where R growth gain (%) achievable via correct provenanceprogeny selection based on I provenance-progeny experimental trials, RH…i† is the relative height growth gain (%) of the best performing provenance-progenies  Q…i† is the at the ith experiment trial (i ˆ 1; . . . ; I), H mean height of those provenance-progenies within the  …i† is tallest quartile at the ith experimental trial, and H the mean height of all the provenance-progenies tested at the ith experiment trial. Furthermore, given that the experiments vary by age and number of provenanceprogenies tested, weighted means were also calculated (Eqs. (2) and (3)). I X A…i†  HAW ˆ R RH…i† PI (2) iˆ1 iˆ1 A…i†  HAW is the species-speci®c age-weighted mean where R relative height growth gain (%) achievable via correct provenance-progeny selection based on I provenanceprogeny experimental trials, and A…i† is the age of the ith experimental trial.  HNW ˆ R

I X N…i† RH…i† PI iˆ1 iˆ1 N…i†

(3)

 HNW is the species-speci®c number-weighted where R mean relative height growth gain (%) achievable via correct provenance-progeny selection based on I provenance-progeny experimental trials, and N…i† is the

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P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

total number of provenance-progenies tested at the ith experimental trial. 2.4. Estimating rotational yields The consequences of correct provenance-progeny selection in terms of rotational yields were estimated employing a two-step procedure (sensu Talbert, 1982; Talbert et al., 1985; Buford and Burkhart, 1987; Li et al., 1998): (1) extrapolating height growth gains to rotation age via regression analysis; and (2) given (1), estimating associated merchantable productivity gains for a range of site qualities and initial planting densities. The assumptions underlying this approach included the following: (1) the observed juvenile height increase is maintained throughout the rotation (i.e. age-to-age correlations for height growth

increases are signi®cant, stable and consistent); (2) the shape of the site index function is invariant to genetic enhancement; (3) selection has minimal effects on overall stand dynamics except with respect to the rate of development; and (4) variation in height growth arising from the interaction between genetic and environmental effects is minimal on a given site at a ®xed stand density. 2.4.1. Height growth gain function The relationship between the mean height of the selected provenance-progenies and the mean height of the unselected provenance-progenies was quanti®ed employing ordinary least squares regression procedures (Eq. (4)) for each species  Q…i† ˆ b0 ‡ b1 H  US…i† ‡ e…i† H

(4)

Table 1 Relative percentage height growth gains of black spruce to correct provenance-progeny selection Experimental site location (i)

Agea (A(i)) (year)

Number of provenance-progenies testedb (N(i))

Relative height growth gainc (%) (RH…i† )

Source

Acadia Forest, New Brunswick Black Brook, New Brunswick Bartibog, New Brunswick Sabbies Brook, New Brunswick Dromore, Prince Edward Island East Bideford, Prince Edward Island Cape Breton, Nova Scotia Pleasant Valley, Nova Scotia Stanley, Nova Scotia East Dalhousie, Nova Scotia Dryden, Ontario Thunder Bay, Ontario Geraldton, Ontario Chapleau, Ontario Petawawa, Ontario Roddickton, Newfoundland Stag Lake, Newfoundland Big Falls, Newfoundland Sandy Brook, Newfoundland Newbay Pond, Newfoundland Cochrane Pond, Newfoundland Mont-Laurier, Quebec Lac St. Ignace, Quebec Chigougamau, Quebec Valcartier, Quebec

14 14 14 14 14 14 14 14 14 14 15 15 15 15 15 15 15 15 15 15 15 16 16 16 16

98 75 72 74 75 50 87 74 75 75 64 55 56 63 50 36 26 20 37 18 15 85 68 89 89

16.18 10.21 23.56 23.76 8.24 10.69 14.38 12.78 17.10 12.69 26.89 9.96 10.28 13.98 18.84 8.47 14.86 14.80 22.62 19.20 9.25 9.78 14.95 10.12 14.69

Table 1 in Park and Fowler (1988) Table 1 in Park and Fowler (1988) Table 1 in Park and Fowler (1988) Table 1 in Park and Fowler (1988) Table 1 in Park and Fowler (1988) Table 1 in Park and Fowler (1988) Table 1 in Park and Fowler (1988) Table 1 in Park and Fowler (1988) Table 1 in Park and Fowler (1988) Table 1 in Park and Fowler (1988) Appendix IV in Boyle (1985) Appendix IV in Boyle (1985) Appendix IV in Boyle (1985) Appendix IV in Boyle (1985) Appendix IV in Boyle (1985) Table 3 in Hall (1986a) Table 3 in Hall (1986a) Table 3 in Hall (1986a) Table 3 in Hall (1986a) Table 3 in Hall (1986a) Table 3 in Hall (1986a) Table 10 in Beaulieu et al. (1989) Table 10 in Beaulieu et al. (1989) Table 10 in Beaulieu et al. (1989) Table 10 in Beaulieu et al. (1989)

a

Total age from seed. Inter-regional provenance-progenies derived from stands located throughout central and eastern Canada. c  Q…i† H  …i† †=H  …i† , where H  Q…i† is the mean height of those provenance-progenies within the tallest quartile, at the ith RH…i† ˆ 100  …H  …i† is the mean height of all the provenance-progenies tested. experimental trial, and H b

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

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Table 2 Relative percentage height growth gains of jack pine to correct provenance-progeny selection Experimental site location (i)

Agea (A(i)) (year)

Number of provenance-progenies testedb (N(i))

Relative height growth gainc (%) (RH…i† )

Source

Superior National Forest, Minnesota Chippewa National Forest, Minnesota Pillsbury, State Forest, Minnesota General Andress Experiment Forest, Minnesota Clouquet Forestry Centre, Minnesota Burnett County Forest, Wisconsin Mosinee Industrial Forest, Wisconsin Chequamegon National Forest, Wisconsin Nepco Industrial Forest, Wisconsin Argonne Experimental Forest, Wisconsin Marinette County Forest, Wisconsin Ottawa National Forest, Michigan University of Michigan, Michigan Fife Lake State Forest, Michigan Northeastern Ontario Petawawa, Ontario

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 34

27 27 27 27 27 27 27 27 27 27 27 27 27 27 12 9

5.94 5.14 6.00 6.00 5.00 9.71 12.71 6.57 14.29 3.86 6.00 5.00 9.14 10.29 7.52 5.34

Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 4 in Jeffers and Jensen (1980) Table 1 in Skeates (1979) Fig. 2 in Magnussen et al. (1985) and Table 1 in Magnussen et al. (1986).

a

As de®ned in Table 1. Intra-regional provenance-progenies derived from stands located throughout Minnesota, Wisconsin and Michigan (Jeffers and Jensen, 1980), Ontario (Skeates, 1979; Magnussen et al., 1985, 1986). Note: Magnussen et al. (1985, 1986) results based on a subset of nine regional provenance-progenies for which height measurements were reported. c As de®ned in Table 1. b

 US…i† is the mean height of the unselected where H provenance-progenies at the ith experimental trial (unselected provenance-progenies are de®ned as those within the lower three height quartiles), b0 and b1 are intercept and slope parameters, respectively, and e…i† is an error term speci®c to the ith experimental trial. Ordinary least squares parameter estimates were obtained using simple linear regression procedures on the literature-derived data sets (Tables 1±4). 2.4.2. Prediction models Height growth gains were translated into rotational yield increases via the use of prediction models. Speci®cally, three base-line site qualities, which intrinsically represented the mean dominant height of the unselected provenance-progenies at 50 years (15, 18 and 21 m at 50 years), were used to predict the mean dominant height of the selected provenanceprogenies at 50 years, via Eq. (4). Prediction models were then used to estimate mean dominant height (m), quadratic mean diameter (cm), and mean annual

merchantable volume increment2 (m3 ha 1 per year) at 50 years for each site index across a range of conventional planting densities (1500, 2250 and 3000 stems ha 1). Black spruce yield estimates were obtained using a stand density management model (Newton and Weetman, 1994; Newton, 1998). However, in order to estimate rotational yields for jack pine, white spruce and red pine, empirical prediction equations were developed. Refer to Appendix A for a complete description of the data sets used and resulting prediction equations derived. Thus given estimates for both unselected and selected provenance-progenies, relative gains due to correct provenance-progeny selection could be calculated (Eqs. (5)±(7)). RH50 ˆ 100  2

^ H S

 US H  US H

(5)

Merchantable volume was defined as the stem volume between a stump height of 0.15 m and a top-diameter of approximately 7.62 cm of all trees greater than 9.1 cm in diameter at breast-height.

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P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

Table 3 Relative percentage height growth gains of white spruce to correct provenance-progeny selection Experimental site location (i)

Agea (A(i)) (year)

Number of provenance-progenies testedb (N(i))

Relative height growth gainc (%) (RH…i† )

Source

Lake DoreÂ, Ontario Harrington, Quebec St. Jacques des Piles, Quebec Grandes Piles, Quebec Casey, Quebec Chalk River, Ontario Drummondville, Quebec Harrington, Quebec Thunder Bay, Ontario Owen Sound, Ontario Dorset, Ontario Gander, Newfoundland Chalk River, Ontario Kapuskasing, Ontario Chalk River, Ontario Owen Sound, Ontario

12 14 14 14 14 19 20 20 23 25 25 25 25 25 27 30

12 16 18 20 20 53 11 15 48 24 25 32 25 25 25 25

9.48 6.66 6.65 15.20 9.35 6.79 6.67 16.63 9.46 15.29 9.20 11.53 31.39 19.49 7.75 16.89

Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix

E in Morgenstern and Copis 1 in Beaulieu (1996) 1 in Beaulieu (1996) 1 in Beaulieu (1996) 1 in Beaulieu (1996) E in Morgenstern and Copis 1 in Beaulieu (1996) 1 in Beaulieu (1996) E in Morgenstern and Copis E in Morgenstern and Copis E in Morgenstern and Copis II in Hall (1986b) D in Morgenstern and Copis E in Morgenstern and Copis E in Morgenstern and Copis D in Morgenstern and Copis

(1999)

(1999) (1999) (1999) (1999) (1999) (1999) (1999) (1999)

a

As de®ned in Table 1. Inter-regional provenance-progenies. Note that the estimates derived from Beaulieu (1986) results are based on a concentrated subset of range-wide provenance-progenies in which the Quebec-based provenance-progenies dominated. c As de®ned in Table 1. b

Table 4 Relative percentage height growth gains of red pine to correct provenance-progeny selection Experimental site location (i)

Agea (A(i)) (year)

Number of provenance-progenies testedb (N(i))

Relative height growth gainc (%) (RH…i† )

Source

Carlton, Minnesota Juneau, Wisconsin Chippewa, Michigan Kalamazoo, Michigan Allegan, Michigan Cass, Michigan Tippecanoe, Indiana Cass, Nebraska Pictou County, Nova Scotia Queens County, Prince Edward Island Cumberland County, Nova Scotia Kane, Pennsylvania Dryden, Ontario

11 11 11 11 11 11 11 11 17 17 21 25 30

48 38 85 63 89 60 18 52 24 16 16 47 12

10.00 12.00 8.73 8.44 13.26 10.80 12.20 7.77 4.12 4.92 3.24 4.14 4.78

Table 4 in Wright et al. (1972) Table 4 in Wright et al. (1972) Table 4 in Wright et al. (1972) Table 4 in Wright et al. (1972) Table 4 in Wright et al. (1972) Table 4 in Wright et al. (1972) Table 4 in Wright et al. (1972) Table 4 in Wright et al. (1972) Table 5 in Park and Fowler (1981) Table 5 in Park and Fowler (1981) Table 3 in Park and Fowler (1981) Fig. 4 in Hough (1967) Table 1 in Maley and Bowling (1993)

a

As de®ned in Table 1. Inter-regional provenance-progenies derived from stands located throughout central and eastern Canada. c As de®ned in Table 1. b

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

where RH50 is the relative height growth gain at 50 ^ S years due to correct provenance-progeny selection, H is the predicted mean dominant height (m) of the correctly selected provenance-progenies relative to the speci®ed mean dominant height (m) of the unse US ) at 50 years lected provenance-progenies (H (Eq. (4)).   DQS DQUS RD50 ˆ 100  (6) DQUS where RD50 is the relative diameter growth gain at 50 years due to correct provenance-progeny selection, DQS the predicted quadratic mean diameter of the correctly selected provenance-progenies at 50 years, and DQUS the quadratic mean diameter of the unselected provenance-progenies at 50 years.   MAIS MAIUS RMAI50 ˆ 100  (7) MAIUS where RMAI50 is the relative mean annual merchantable volume increment gain at 50 years due to correct provenance-progeny selection, MAIS is the predicted mean annual merchantable increment diameter of the correctly selected provenance-progenies at 50 years, and MAIUS is the mean annual merchantable increment of the unselected provenance-progenies at 50 years.

35

3. Results and discussion Generally, the systematic search of the tree improvement literature indicated that documented long-term yield responses to tree improvement was scarce. Speci®cally, the majority of the published studies consisted of short-term results derived from provenance-progeny experiments. Furthermore, studies pertaining to ®rst and second generational selection programs were practically non-existent. Consequently, results for these selection strategies were limited to notional summaries of individual case-studies augmented by expert opinion and unpublished preliminary results derived from ongoing tree improvement experiments. 3.1. Correct provenance-progeny selection Height growth gains attributable to correct provenance-progeny selection for black spruce, jack pine, white spruce and red pine for each individual trial are given in Tables 1±4, respectively. Additionally, trial location, age from seed, number of provenance-progenies tested and source publication are listed. Table 5 lists the species-speci®c mean relative height growth gains (Eqs. (1)±(3)). Table 6 lists the resultant parameter estimates and associated regression statistics by species for the height growth gain function (Eq. (4)).

Table 5 Species-speci®c relative percentage height growth gains achievable via correct provenance-progeny selection Species

Mean agea  (year) (A)

Relative height growth gains (%) Arithmetic mean H) Mean (R b

Weighted means 95% CI Lower

Upper

Age-basedc  HAW ) (R

N-basedd  HNW ) (R

Black spruce 14.73 12.57 16.89 14.75 14.69 15 Jack pine 7.41 5.81 9.00 7.32 7.50 21 White spruce 12.40 8.88 15.92 12.89 12.24 20 Red pine 8.03 5.92 10.14 6.99 9.05 15 PI a  A ˆ iˆ1 A…i† =I, where A(i) is the species-speci®c age of the ith experimental trial (Tables 1±4). P b  RH ˆ Iiˆ1 RH…i† =I, where RH…i† is the species-speci®c relative percentage height growth gain derived from the ith experimental trial (i ˆ 1; . . . ; I; I ˆ species-speci®c total number of experimental trials (I ˆ 25, 16, 16 and 13 for black spruce, jack pine, white spruce and red pine, respectively, Tables 1±4).
P P c  RHAW ˆ Iiˆ1 RH…i† A…i† = Iiˆ1 A…i† .
P P d  RHNW ˆ Iiˆ1 RH…i† N…i† = Iiˆ1 N…i† , where N…i† is the species-speci®c total number of provenance-progenies tested at the ith experimental trial (Tables 1±4).

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P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

Table 6 Parameter estimates and associated regression statistics for the height growth gain function (Eq. (4); Fig. 1) Species

Parameter estimatesa ^ b 0

Black spruce Jack pine White spruce Red pine

0.214 0.535 0.233 0.240

^ b 1

1.095 1.033 1.127 1.038

Regression statisticsb ^ 95% CI for b 1 Lower

Upper

1.014 0.997 0.956 1.022

1.177 1.099 1.297 1.055

SEE (m)

r2

F-statistic

I

0.122 0.284 0.530 0.096

0.971 0.988 0.935 0.999

768 1122 210 18674

25 16 16 13

a

Parameter estimates obtained by ordinary least squares regression procedures. Standard error of estimate (SEE); coef®cient of determination (r2); F-statistic for the overall regression relationship, where () denotes a signi®cant (P  0:05) relationship; and total number of experiments (I) utilized. b

Fig. 1 graphically illustrates the height growth gain function including the data sets used by species. Furthermore, residual analysis of the regression relationships indicated that there was insuf®cient evidence to reject the principal assumptions underlying ordinary least squares estimation (e.g. model speci®cation, normality, and constant error variance). Consequently, the functions were considered adequate describers of the linear relationship between the mean height of the selected and unselected provenance-progenies. Table 7 lists the species-speci®c relative percentage productivity gains at rotation arising from correct provenance-progeny selection by site class and initial planting density. 3.1.1. Black spruce The scienti®c literature pertaining to black spruce provenance-progeny research was characterized by inter-regional and intra-regional range-wide experiments established throughout the species range (Khalil, 1981; Boyle, 1985; Hall, 1986a; Park and Fowler, 1988; Beaulieu et al., 1989; Morgenstern and Mullins, 1990). Morgenstern and Mullins (1990) summarized the results of 34 of the range-wide provenance-progeny experiments that were established during the 1973±1977 period. These experiments were located in Newfoundland (n ˆ 3), Prince Edward Island (n ˆ 2), Nova Scotia (n ˆ 4), New Brunswick (n ˆ 4), Maine (n ˆ 3), Quebec (n ˆ 6), Ontario (n ˆ 5), Wisconsin (n ˆ 1), Minnesota (n ˆ 2), Manitoba (n ˆ 1), Saskatchewan (n ˆ 1), Alberta (n ˆ 1) and Alaska (n ˆ 1). The progeny were derived from 218 provenances selected across the species range: latitudinally from Connecticut (418N) to Alaska

(618N) and longitudinally from Newfoundland (538W) to Alaska (1568W). In 1985, 15 years from seed, 29 of the trials were evaluated in which the mean height and survival differences among the provenance-progenies were assessed employing cluster analysis (8 regional-based provenance-progeny clusters were formulated and assessed: Newfoundland; New Brunswick, Prince Edward Island and Nova Scotia; Maine; Eastern Quebec; Ottawa River; Northern Ontario; Wisconsin and Minnesota; Manitoba, Saskatchewan and Alberta). Morgenstern and Mullins (1990) collectively assessed 29 of the trials for mean height and survival differences at approximately 15 years from seed employing cluster analysis. Furthermore, they related these differences to geographic and climatic variables. Their results indicated (1) negative height growthÐlatitude correlation suggesting movement of provenance-progeny northward may enhance growth response, (2) negative survivalÐlatitude correlation for temperate regions suggesting movement of provenance-progeny northward may enhance survival, (3) positive survivalÐlatitude correlation for boreal regions suggesting movement of provenanceprogeny southward may enhance survival, (4) trials established in Newfoundland had the greatest survival rates but low height growth rates, and (5) trials established in the Great Lakes States had the greatest height growth rates but low survival rates. These results con®rmed the north-south clinal nature of genetic variation in black spruce for height and survival traits. Park and Fowler (1988) reported 14 years height growth responses for the 10 provenance-progeny trials established throughout Prince Edward Island, Nova Scotia, and New Brunswick (Table 1). Their results

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

37

Fig. 1. Graphical illustration of the linear relationship between the mean height of the unselected and selected provenance-progenies by species: the solid line illustrates the height growth gain function arising from correct provenance-progeny selection (Eq. (4); Table 6) and the diagonal broken line denotes equivalence.

38

Table 7 Estimated relative percentage productivity gains at rotation arising from correct provenance-progeny selection Plantation density (stems ha 1)

Site index ˆ 15

Site index ˆ 18

Site index ˆ 21

Relative height growth gaina (%) (RH50 )

Relative diameter growth gainb (%) (RD50 )

Relative MAI gainc (%) (RMAI50 )

Relative height growth gaina (%) (RH50 )

Relative diameter growth gainb (%) (RD50 )

Relative MAI gainc (%) …RMAI50 †

Relative height growth gaina (%) (RH50 )

Relative diameter growth gainb (%) (RD50 )

Relative MAI gainc (%) (RMAI50 )

Black spruce

1500 2250 3000

10.95

9.88 11.18 11.61

24.52 21.83 19.28

10.71

10.78 11.80 12.63

19.28 15.67 13.10

10.54

12.08 13.36 13.97

14.40 11.13 9.26

Jack pine

1500 2250 3000

6.86

3.51 3.62 3.73

21.30 20.08 18.99

6.27

3.49 3.59 3.68

14.41 13.89 13.40

5.85

3.48 3.56 3.65

11.33 11.03 10.75

White spruce

1500 2250 3000

14.21

19.37 18.40 17.43

32.15 30.06 28.22

13.95

22.78 21.82 20.85

26.08 24.88 23.80

13.77

12.55 13.09 13.68

22.89 22.08 21.33

Red pine

1500 2250 3000

5.43

2.70 2.92 3.19

7.51 7.40 7.28

5.17

2.80 3.01 3.26

6.72 6.63 6.55

5.0

2.89 3.08 3.31

6.20 6.14 6.08

a

RH50 is de®ned by Eq. (5). RD50 is de®ned by Eq. (6). c RMAI50 is de®ned by Eq. (7). b

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

Species

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

indicated that progeny derived from local provenances out performed the progeny derived from non-local provenances. Khalil (1981) and Hall (1986a) reported 10 and 15 years height growth responses, respectively, for six provenance-progeny trials established throughout insular Newfoundland. These trials were based on a randomized complete block design involving 6 replicates and 39 provenance-progenies (31 from Newfoundland and 8 from the Canadian mainland) planted in four tree-plots spaced at 1:8 m  1:8 m. Results from the remeasurement in 1979 (10 years from seed) indicated that the best provenance-progenies, as de®ned as those within the ®rst height quartile at each location, out performed the mean trail value, by 14.81% (Big Falls), 8.40% (Cochrane Pond), 15.59% (Little George's Lake), 10.24% (New Bay Pond), 8.99% (Roddickton), 16.87% (Sandy Brook) and 9.49% (South Brook). Corresponding results derived from a subsequent remeasurement of six of the trials at 15 years from seed are given in Table 1. Hall (1986a) noted that the best performance provenance-progenies varied across trials and subsequently recommended localizing seed-sources within reforestation programs (i.e. using progeny derived from the best performing provenance-progenies within the nearest trial). Beaulieu et al. (1989) reported 16 years height growth responses of four of the provenance-progeny trials established in Quebec (Table 1). These trials were based on a randomized complete block design involving six replicates. Provenance-progeny were planted in 16 tree plots at 3:05 m  2:45 m or 2:45 m  2:45 m spacing. Statistical analyses indicated that 5±17% of the height growth variation was attributed to seed origin whereas survival was invariant to seed origin. Based on the best 25 provenance-progenies at each test site ®ve breeding zones were delineated for Quebec: Abitibi; Lower North Shore; High Laurentian and Gaspe Plateau; Ottawa ValleyÐLaurentian; and Saguenay-Appalachian. The analyses also indicated that using the best ®ve provenance-progenies could result in relative height growth gains of approximately of 12.21%. Boyle (1985) reported 15 years height growth responses of ®ve provenance-progeny trials established in Ontario (Table 1). Results indicated that among the 76 range-wide provenance-progenies tested, those from Ontario and Quebec performed

39

the best. Furthermore, among this group of superior provenances, progeny derived from Nipissing, Ontario was the best overall. This result is similar to that reported in the Newfoundland and the Maritimes experiments (i.e. Khalil (1984) and Fowler and Park (1982), respectively). 3.1.2. Jack pine Twenty-year results from 14 intra-regional provenance-progeny trials which were established throughout Minnesota, Wisconsin, and Michigan during the 1950s, were reported on by Jeffers and Jensen (1980; Table 2). Speci®cally, these trials consisted of randomized complete block experimental designs and included approximately 29 provenance-progenies planted in 64 tree-plots spaced at 1:52 m  1:52 m with four replications. The mean of the best performing provenance-progeny which corresponds to the 97.5% percentile (plantation mean ‡ 2 S.D.) within each trial in terms of relative height growth, was calculated as follows: RH ˆ ((97.5% percentile height mean height of the plantation)/mean height of the plantation)  100. The mean height growth differential due to correct provenance-progency selection was approximately 10.49% (CI 95%: 7.26  mean height growth percentage increase 13.73). Corresponding estimates for volume per unit area, which implicitly combines both survival and stem volume growth gains, indicated a mean volume growth differential due to provenance selection of 30.52% (CI 95%: 20.90  mean volume growth percentage increase  40:13). In a subsequent study, in which the biomass production (t ha 1 per year) among the best four provenances within three of the trials was compared at approximately 25 years (Zavitkovski et al., 1981), the best performing provenance within each trial out performed the other three by 11.54, 13.64 and 12.12%. Skeates (1979) reported 20 years pooled results for two intra-provincial provenance-progeny trials established within site regions (Hills, 1961) 4E (Kirkland Lake) and 5E (Algonquin Park) in 1955 (Table 2). The differential between the height of 12 provenanceprogenies and the mean height of the tallest quartile suggested that correct provenance selection could result in a 7.62% increase in height at 20 years. Magnussen et al. (1985) reported 34 years results for a single intra-provincial provenance-progeny trial established at Petawawa in 1954 (Table 2). The 12

40

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

Ontario-based progenies (2 ‡ 1 transplants) were initially planted at a 1:2 m  1:2 m spacing employing a randomized complete block design involving four replicates. The trial was subsequently thinned at 18 years (1969) and 28 years (1979) resulting in a ®nal spacing of 1:6 m  1:6 m. The differential between the mean volumetric yield of the 12 provenance-progenies and the mean volumetric yield of the most productive quartile, indicated that correct provenance selection with randomized roguing (thinning) could result in a 17.20% increase in volumetric yield at 34 years. 3.1.3. White spruce Morgenstern and Copis (1999) summarized the height growth and survival responses of over 300 provenance-progenies in Ontario via the assessment of 20 ®eld experiments established across seven site regions (6E, 5E, 3E, 3W, 4W and 4S; Hills, 1961) (Table 3). The results indicated that very few substantial changes in rank occurred after 20 years and non-local provenance-progenies moved 2±48N outperformed local provenances in terms of height. Summarizing the results for the differential between the height of all of the provenance-progenies tested and the mean height of the tallest quartile for experiments >20 years of age, indicated that correct provenance selection could result in a 14.0% increase in height at approximately 24 years (CI 95%: 7.9  mean height growth percentage increase 20.0; Source: Appendices D and E, Morgenstern and Copis, 1999). Beaulieu and Corriveau (1985) reported 20 years results for a range-wide provenance-progeny trial established at the Harrington Forest Farm in Quebec (Table 3). The resultant differential between the height of all of the provenance-progenies tested and the mean height of the tallest quartile, indicated that correct provenance selection could result in a 32.71% increase in volume per hectare (m3 ha 1) at 20 years (source: Table 5, Beaulieu and Corriveau, 1985). Furthermore, Beaulieu (1996) compared the performance of intraprovincial provenance-progenies against those derived from provenances located across the species range within six trials throughout Quebec (Table 3). Speci®cally, comparing the median height of the best provenance-progenies with the median height of the Quebec-based provenance indicated that correct provenance-progeny selection could result in a 14.8% increase in height at approximately 16 years (CI 95%:

8.7  mean height growth percentage increase 21.0; n ˆ 9; Source: Appendix 1, Beaulieu, 1996). In a subsequent analysis of two of the trials (Drummondville and Harrington Forest Station) in which the volumetric production of eight Quebec-based provenance-progenies were compared against the seven recommended Ontario-based provenance-progenies, Beaulieu et al. (1997) reported a mean gain of 42.64% (59 m3 ha 1) in total volume yield at 25 years (source: Table 4, Beaulieu et al., 1997). Hall (1986b) reported 25 years results for a rangewide provenance-progeny trial established in Newfoundland (Table 3). Speci®cally, the differential between the height of all of the provenance-progenies tested and the mean height of the tallest quartile, indicated that correct provenance selection could result in a 11.53% increase in height at 25 years (source: Appendix II, Hall, 1986b). 3.1.4. Red pine Historically, forest tree improvement activities in red pine have largely consisted of attaining an understanding of the species genetic variability via interregional provenance-progeny trials (Rudolf, 1948; Buckman and Buckman, 1962). Results from these trials have indicated that the degree of genetic variability underlying most of the commercially-important traits is minimal (e.g. survival, phenology, lammas growth, and wood quality). However, gains in juvenile height growth has been attributed to correct provenance-progeny selection (Hough, 1967; Wright et al., 1972; Park and Fowler, 1981; Maley and Bowling, 1993). Hough (1967) reported 25 years results for a single provenance-progeny trial established in Pennsylvania in 1937 (Table 4). The 47 progeny were planted at a 1:83 m  1:83 m square spacing within a randomised north±south 50 trees per provenance row design employing seven replicates. The trial was systematically thinned at 15 years to a residual spacing of approximately 2:73 m  2:73 m (thinning simulated a height-based roguing operation in which inferior phenotypes were removed). The differential between the mean height of the 47 provenance-progenies tested and the mean height of those within the tallest quartile, indicated that correct provenance selection could result in a 4.14% increase in height at 25 years (source: Fig. 4, Hough, 1967).

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

Wright et al. (1972) reported 11 years results for eight wide-range provenance-progeny trials established throughout Nebraska, Minnesota, Wisconsin, Michigan and Indiana (Table 4). Speci®cally, 94 progenies, established at 2:44 m  2:44 m or 2:44 m  3:66 m spacing, were evaluated employing randomized complete block designs involving 4±10 replicates. The resultant differential between the mean height of all of the provenance-progenies tested and the mean height of the tallest quartile due to correct provenance-progeny selection was approximately 10.40% (CI 95%: 8.73  mean height growth percentage increase 12.07). Park and Fowler (1981) reported results for three wide-range provenance-progeny trials established in Cumberland County, Nova Scotia; Pictou County, Nova Scotia; and Queens County, Prince Edward Island (Table 4). The data obtained from the Cumberland trial consisted of 21 years height growth measurements derived from the 16 range-wide progenies which were planted at a 1:2 m  1:2 m spacing within a randomized complete ®ve-block design (source: Table 3, Park and Fowler, 1981). The trial was systematically thinned at 15 years to a residual spacing 1:2 m  2:4 m. The data obtained from the Pictou trial consisted of 17 years height growth measurements derived from the 24 range-wide progenies which were planted at a 1:8 m  1:8 m spacing within a randomized complete three-block design (source: Table 5, Park and Fowler, 1981). The data obtained from the Queens trial consisted of 17 years height growth measurements derived from the 16 progenies which were planted at a 1:8 m  1:8 m spacing within a randomized complete ®ve-block design (source: Table 5, Park and Fowler, 1981). The differential between the mean height of the all the provenanceprogenies tested and the mean height of those within the tallest quartile for the Cumberland, Pictou and Queens trials was 3.24, 4.12 and 4.92%, respectively. These results suggest that correct provenance-progeny selection could result in a 4.09% increase in height at 18 years. Maley and Bowling (1993) reported 30-year results for a single inter-regional provenance-progeny trial established in northwestern Ontario (Table 4). Experimentally, a randomized complete block design consisting of three replicates involving 12 progenies planted at a 1:8 m  1:8 m spacing was used. The

41

differential between the mean height of the 12 provenance-progenies tested and the mean height of the tallest quartile, indicated that correct provenance selection could result in a 4.78% increase in height at 30 years (source: Table 1, Maley and Bowling, 1993). 3.1.5. Species-speci®c yield gain summaries Results indicated that correct provenance-progeny selection yielded juvenile height growth gains of approximately 14.7% at 15 years for black spruce, 7.4% at 21 years for jack pine, 12.4% at 20 years for white spruce and 8.0% at 15 years for red pine (Table 5). The 95% con®dence intervals suggested that these correct provenance-progeny selection resulted in signi®cant juvenile height growth gains (Table 5): the lower 95% con®dence limit was greater than zero, irrespective of species. Means weighted by age, and number of provenance-progeny tested, were approximately equivalent to the arithmetic means suggesting relatively stable responses across trials (Table 5). Extrapolating these results to rotational age suggest that substantial productive gains could be achieved via correct provenance-progeny selection (Table 7). Speci®cally, plantations established at densities of 1500, 2250 and 3000 stems ha 1 on site indices 15, 18 and 21 using planting stock derived from the best performing provenances could be expected to outperform plantations established with unimproved stock as follows (Table 7): (1) gains in mean dominant height at 50 years of 10.73% …S:D: ˆ 0:21) for black spruce, 6.33% (S:D: ˆ 0:51) for jack pine, 13.98% (S:D: ˆ 0:22) for white spruce, and 5.20% (S:D: ˆ 0:22) for red pine; (2) gains in quadratic mean diameter at 50 years of 11.92% (S:D: ˆ 1:27) for black spruce, 3.59% (S:D: ˆ 0:09) for jack pine, 17.77% (S:D: ˆ 3:87) for white spruce, and 3.02% (S:D: ˆ 0:21) for red pine; and (3) gains in mean annual merchantable volume increment at 50 years of 16.50% (S:D: ˆ 5:08) for black spruce, 15.02% (S:D: ˆ 4:08) for jack pine, 25.72% (S:D: ˆ 3:73) for white spruce, and 6.73% (S:D: ˆ 0:55) red pine. 3.2. First and second generational selection The limited number of published results pertaining to ®rst and second generational selection strategies negated the calculation of literature-based species-level

42

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

gain estimates. Although expert opinion was used to augment the limit documentation, consensus gain estimates could not be realistically calculated on a species-level basis. Alternatively, notional summaries of case-studies are provided by species. There was insuf®cient information regarding red pine and hence no summary is provided. Note, unless otherwise stated, a classical phenotypic selection strategy based on superior height growth was the dominant criterion used in selecting ®rst and second generational progenies. 3.2.1. Black spruce Simpson and Tosh (1997) described the forest tree improvement program for black spruce in the Province of New Brunswick. The program was initiated under the auspices of the New Brunswick Tree Improvement Council consisted of collecting seed from approximately 1233 phenotypic plus-trees and subsequently establishing open-pollinated family test plantations and seedling seed orchards throughout the province in 1978. Approximately 80 ha of seedling seed orchards spaced at 1:0 m  2:0 m spacing on average and above average sites have been established The orchards consisted of seed tree plots in which each family was represented by about 100 trees randomized throughout. These orchards started producing seed in 1986 and have been rogued twice using information attained from the parallel series of family test plantations. Orchards were rogued at 10 years in which >50% of the poorest (smallest) families were removed, then second-rogued at 15 years with a further >50% of the poorest (smallest) families removed. Furthermore, trees were selected for second breeding in 1989 based height growth performance using 10-year family test data. Speci®cally, scions were obtained, grafted and treated with gibberellic acid to promote ¯owering. Clonal seed orchards established using the 40 top-ranking families with seed production initiating in 1992. A series of realized gain tests were established for each species in 1991: the test design consisted of six seedlots planted in four replicates using 64-tree plots at ®ve locations (seedlots consisted of rogued and unrogued orchard and unimproved stand checklots). Although, improved seed is available for all reforestation programs in New Brunswick, the quantitative assessment of gain in terms of yield parameters is

currently in progress and hence undocumented. Consequently, preliminary unpublished results were used to estimate expected gain. Speci®cally, 20 years results derived from replicated experiments located throughout New Brunswick were used to estimate yield gains from tree improvement (source: McInnis personal communication). These results were based on experiments established by the New Brunswick Tree Improvement Council during the mid-to-late 1970s and consisted of stand tests (zeroth generational experiments), family tests (®rst generational experiments) and progeny tests (second generational experiments). Speci®cally, the zeroth generational experiments consisted of ®ve stand tests and included approximately 13,000 progenies derived from phenotypically superior natural stands. The ®rst generational experiments consisted of 12 family tests and included approximately 27,000 half-sib progenies derived from plus trees. The second generational experiments consisted of ®ve progeny tests grown from ®rst generation polycrossed progenies. Projected merchantable volume differences between the zeroth and ®rst generational experiments, as estimated employing the STAMAN Stand Growth Model using the tallest 25% of the trees within the ®rst generational experiment indicated a 11% gain at 40 years. Measured height growth differences between the zeroth and second generational experiments using the tallest 25% of the trees within the second generational experiments, indicated a 49% gain at 10 years. Additionally analyses of these initial results employing a stand density management model (Newton and Weetman, 1994; Newton, 1998) are described in Appendix B. Speci®cally, the preliminary 20 years results derived from 12 ®rst generational tree improvement experiments (family tests) indicated a gain of approximately 13% (0.8 m) in height based on the tallest quartile (Table 8). Extrapolating this increase to a rotational age of 50 years for plantations established at 1500, 2000, 2500 and 3000 stems ha 1 on mediumgood quality sites (17 m) in New Brunswick, suggest a mean 13% (34 m3 ha 1) increase in merchantable volume, 10% (1.9 cm) increase in quadratic mean diameter, and 10% (4 years) decrease in the time to operability status, are attainable via a ®rst generational selection strategy (Table 8). Similarly, estimated 20 years results derived from second generational tree improvement experiments (progeny tests) indicated a

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

43

Table 8 Simulated 50-year rotational yield and operability gains resulting from ®rst and second generation black spruce plantations established on medium to good quality sites within the Province of New Brunswick Generationa

Mean dominant heightb (m)

Merchantable volumec (m3 ha 1)

Quadratic mean diameter (cm)

Minimum time to operabilityd (year)

20 years

Initial density (stems ha 1)

Initial density (stems ha 1)

Initial density (stems ha 1)

1500

3000

1500

2000

2500

3000

1500

2000

2500

3000

235 260 277 290 272 296 311 321 326 344 355 362 15.7 13.9 12.3 10.7 38.7 32.3 28.2 24.8

20.4 22.2 25.4 8.8 24.5

19.7 21.6 24.9 9.6 26.4

19.3 21.2 24.6 9.8 27.5

19.0 21.0 24.4 10.5 28.4

45 40 33 11.1 26.7

41 37 31 9.8 24.4

39 35 29 10.3 25.6

40 36 30 10.0 25.0

Zeroth 6.4 First 7.2 Second 8.4 % Gain first/zeroth 12.5 % Gain second/zeroth 31.3

50 years

17.3 18.6 20.6 7.5 19.1

2000

2500

Note: Rotational yield estimates and operability times were derived from an algorithmic stand density management model for managed black spruce stands (Newton and Weetman, 1994; Newton, 1998). a De®ned in Appendix B. b Mean height for second generation is an extrapolated regression estimate based on 5 and 10 years height measurements (Eq. (B.2)). Note that the mean total age at a height of 1.3 m for the zeroth generation was approximately 7-year and hence the intrinsic site index (mean dominant height of 17.3 m at a breast-height of 50 years) of the experimental sites was calculated using the 20 years (13 breast-height age) height measurements of the zeroth generation progenies via Ker and Bowling's (1991) site index function for black spruce in New Brunswick. c Merchantable volume computations based on a 0.15 m stump and 7.62 cm top diameter for all stems >9.1 cm in diameter at breast-height. d Minimum number of total years which are required for the plantation to achieve both a merchantable volume and piece-size target: speci®cally, set at 200 m3 ha 1 and 10 stems m 3, respectively.

gain of approximately 31% (2.0 m) in height based on the tallest quartile (Table 8). Extrapolating this increase to a rotational age of 50 years for plantations established at 1500, 2000, 2500 and 3000 stems ha 1 on medium-good quality sites in New Brunswick, suggest a mean 31% (81 m3 ha 1) increase in merchantable volume, 27% (5.2 cm) increase in quadratic mean diameter and a 25% (11 years) decrease in the time to operability, are attainable via a second generational selection strategy (Table 8). Example trajectories for merchantable volume, quadratic mean diameter and stems m 3 for plantations established at 2500 stems ha 1 are graphically illustrated in Figs. 2±4, respectively. 3.2.2. Jack pine Simpson and Tosh (1997) described the forest tree improvement program for jack pine in the Province of New Brunswick. First-generational selection consisted of identifying and propagating progeny from superior plus-trees via progeny testing. Speci®cally, superior phenotypic open-pollinated plus tree progeny were selected and propagated via seedling seed orchards. Although improved seed is available for jack pine reforestation programs in New Brunswick, the

quantitative assessment of gain in terms of yield parameters is currently in progress and hence undocumented. Consequently, preliminary unpublished results were used to estimate expected gain. Speci®cally, 20 years results derived from replicated experiments located throughout New Brunswick were used to estimate yield gains from tree improvement. These results were based on experiments established under the auspices of the New Brunswick Tree Improvement Council during the mid-to-late 1970s and consisted of stand tests (zeroth generational experiments) and family tests (®rst generational experiments). The four zeroth generational experiments were established in 1976 and included approximately 7000 progenies grown from seed which was collected from phenotypically superior natural stands. The 12 ®rst generational experiments were established during the 1979± 1982 period and included approximately 17,000 halfsib progenies grown from seed collected from plus trees. Projected merchantable volume differences between the zeroth and ®rst generational experiments, as estimated employing the STAMAN Stand Growth Model, using the tallest 25% of the trees within the ®rst generational experiments indicated a 28% gain at 40 years. Preliminary results derived from research in

44

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

Fig. 2. Temporal yield trajectories for merchantable volume for zeroth (triangle), ®rst (square) and second (diamond) generational selection strategies for black spruce plantations established at 2500 stems ha 1 on medium-good quality sites within the Province of New Brunswick.

Quebec based on quantitative genetic theory suggest height gains of approximately 9% if only elite (tallest) trees are selected during the ®rst generational selection (source: Beaulieu personal communication). 3.2.3. White spruce Magnussen (1993a) assessed the potential of improving white spruce growth by 20% using a restricted selection of growth curve parameters in parent trees. The experiment involved selection of provenance-progenies derived from dominant and co-dominant parent trees situated in ®ve stands throughout the Ottawa Valley. Results indicated (1) crop tree selection based upon juvenile height growth responses (<40 years) is not advisable, (2) growth curve selection is advantageous to selection based on single stem growth metrics given it re¯ects the full integration of the entire growth history, and (3) a 20% increase in size (volume) may be achievable in 0.5 and

1.5 generations of mass and family selection, respectively. Preliminary results derived from research in Quebec based on quantitative genetic theory suggest height gains of approximately 26% if only elite (tallest) trees are selected from half-sib superior provenance-progenies (Beaulieu, 1996). Furthermore, rotational increases in merchantable volume are predicted to be approximately 20% greater with genetically improved stock than with unimproved stock at 45 years (Beaulieu, 2001). 3.2.4. Species-speci®c yield gain summaries Results for the literature search indicated that although a number of innovative ®rst and second generation selection programs are currently underway throughout central and eastern Canada (Fowler, 1986; Beaulieu et al., 1997; Simpson and Tosh, 1997; Park et al., 1998; Boysen et al., 2000), quantitative responses had yet to be documented in the literature.

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

45

Fig. 3. Temporal yield trajectories for quadratic mean diameter for zeroth (triangle), ®rst (square) and second (diamond) generational selection strategies for black spruce plantations established at 2500 stems ha 1 on medium-good quality sites within the Province of New Brunswick.

Preliminary results derived from the tree improvement program for black spruce in New Brunswick, suggests that for plantations established at nominal densities on medium-good site qualities, increases of approximately 13 and 31% in MAI at 50 years are attainable via a ®rst and second generational selection strategy, respectively. Results for jack pine indicated that gains in MAI of approximately 28% at 40 years are possible via a ®rst genenrational selection strategy (source: McInnis personal communication). Similar values have been estimated for white spruce: gains of approximately 20% at 45 years are possible via a ®rst generational selection strategy (Beaulieu, 2001). 3.3. Concluding notes Overall, the results of this study indicated that documented long-term yield responses of black

spruce, jack pine, white spruce, and red pine to tree improvement were paucity in nature. Consequently, preliminary unpublished results derived from ongoing tree improvement programs were used to augment the limited published results. Collectively, these results indicated that correct provenance-progeny selection yielded juvenile height growth gains of approximately 14.7% at 15 years for black spruce, 7.4% at 21 years for jack pine, 12.4% at 20 years for white spruce and 8.0% at 15 years for red pine. Corresponding rotational merchantable productivity gain estimates at 50 years for plantations established at nominal densities on medium-to-good quality sites were approximately 16.5, 15.0, 25.7 and 6.7%, respectively. Preliminary results from ongoing tree improvement programs suggest that employment of a ®rst and second generational selection strategy could increase black spruce merchantable productivity at rotation (50 years) by

46

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

Fig. 4. Temporal yield trajectories for stems per cubic metre for zeroth (triangle), ®rst (square) and second (diamond) generational selection strategies for black spruce plantations established at 2500 stems ha 1 on medium-good quality sites within the Province of New Brunswick.

approximately 13 and 31%, respectively. Similarly, results for jack pine indicated rotational (40 years) increases of approximately 28% are achievable via a ®rst generational selection strategy. Results for white spruce suggest that merchantable productivity at rotation (45 years) could be increased by approximately 20% via a ®rst generational selection strategy. These results suggest that substantial productivity gains are achievable through correct provenance-progeny selection, and ®rst and second generational selection strategies. However, the selected subset of studies from which height growth estimates could be obtained were characterized by the following attributes: (1) largely interregional and intra-regional provenance related trials; (2) minimal ®rst generation results; (3) limited response periods (pre-crown closure); and (4) narrow range density stress levels within trials. Furthermore, translating these individual-tree genetic height gains to increases in population-level productivity within

the context of operational forest management planning is problematic given that: (1) tree improvement is relatively new in Canada and hence observed genetic gains are applicable to pre-crown closure stand conditions under a relatively narrow range of density conditions; (2) given (1), genetic gains are largely projected using the unknown applicability of the ageto-age correlation concept nor are the potential genotypic  environmental interactions well understood when the genetic improved stock is outplanted; (3) the nature of the correlation among traits is largely unknown (e.g. breeding for increased growth may concurrently reduce wood quality); and (4) environmental heterogeneity and variation in competitive stress within genetic ®eld experiments reduces the sensitive of the results (Magnussen, 1993b). Consequently, additional experimentation and analyses including the assessment of the impact of the problematic factors identi®ed above are required before the yield consequences of tree improvement will be fully ascertained.

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

Acknowledgements The author would like to express his appreciation to: (1) Bryce McInnis and Kathleen Tosh of the New Brunswick Department of Natural Resources and Energy, Jean Beaulieu of the Laurentian Forestry Centre (Canadian Forest Service), Dale Simpson of the Atlantic Forestry Centre (Canadian Forest Service), and Dennis Joyce of the Ontario Forest Research Institute (Ontario Ministry of Natural Resources), for provision of expert opinion and associated preliminary gains estimates for black spruce, jack pine and white spruce; (2) Nancy-Jean Dukes and Leo May of the Great Lakes Forestry Centre (Canadian Forest Service) for provision of literature searching and retrieval assistance; and (3) Forestry Research Partnership and the Ontario Living Legacy Trust for ®scal support.

Appendix A In order to estimate rotational yield estimates for quadratic mean diameter (DQ; cm) and mean annual merchantable increment (MAI; m3 ha 1 per year), prediction equations were developed for jack pine, white spruce and red pine. Speci®cally, species-speci®c multi-regression functions were parameterized employing ordinary least squares regression procedures (Eq. (A.1)). Y ˆ b0 ‡ b1 A ‡ b2 D ‡ b3 S ‡ e

(A.1)

where Y is either DQ or MAI (dependent variable), A is total age (years), D initial spacing density (stem ha 1), and S is site index (mean dominant height (m) at 50 years) (independent variables), bj, j ˆ 0; . . . ; 3 are parameters speci®c to the ith dependent variable, and e is an error term speci®c to the ith dependent variable. Note, merchantable volume was de®ned as the stem volume between a stump height of 0.15 m and a top-diameter of approximately 7.62 cm of all trees >9.1 cm in diameter at breast-height. The databases used to parameterized the equations were selected from representative initial spacing experiments and empirical yield tables. Speci®cally, long-term initial spacing studies and empirical yield tables reporting rotational yield estimates (50 years) for a range of representative site conditions and initial

47

spacing regimes were selected. The jack pine database consisted of 24 sets of DQ, MAI, A, D and S estimates: (1) 18 sets of yield table estimates at 50 years for initial spacings of 1.25, 1.50, 1.75, 2.00, 2.25, 2.50, 2.75 and 3.0 m established on sites qualities of 13.8, 16.9 and 20.0 m (source: Appendix D in Bell et al., 1990); (2) four set of measured yield responses at 20 years for initial spacings of 1.2, 1.8, 2.4 and 3.0 m established on a 16.4 m site quality (source: Tables 1 and 2 and Fig. 3 in Bella, 1986); and (3) two sets of measured yield responses at 21 years for initial spacings of 2.13 m and 4.27 m established on site qualities of 22 and 19 m, respectively (source: Table 1 in Janas and Brand, 1988). The white spruce database consisted of 28 sets of DQ, MAI, A, D and S estimates: (1) 24 sets of yield table estimates at 50 years for initial spacings of 1.25, 1.50, 1.75, 2.00, 2.25, 2.50, 2.75 and 3.0 m established on site qualities of 15, 18, 21 and 24 m (source: Appendix B in Bell et al., 1990); (2) 3 sets of measured yield responses at 37 years for initial spacings of 1.8, 2.7 and 3.6 m established on site qualities 15.0, 15.0 and 14.6 m, respectively (Table 1 in McClain et al., 1994); and (3) 1 set of measured yield responses at 53 years for an initial square spacing of 1.6 m established a 18 m site quality (source: Tables 1 and 2 in Stiell, 1980). The red pine database consisted of 54 sets of DQ, MAI, A, D and S estimates: (1) 40 sets of yield table estimates at 50 years for initial square spacings of 1.25, 1.50, 1.75, 2.00, 2.25, 2.50, 2.75 and 3.0 m established on 15, 18, 21, 24 and 27 m site qualities (source: Appendix E in Bell et al., 1990); (2) three sets of measured yield responses at 37 years for initial spacings of 1.8, 2.7 and 3.6 m established on 20.5, 20.9 and 19.9 m site qualities, respectively (source: Table 1 in McClain et al., 1994); (3) four set of measured yield responses at 20 years for initial spacings of 1.2, 1.8, 2.4 and 3.0 m established on a 20.8 m site quality (source: Tables 1 and 2 and Fig. 3 in Bella, 1986); (4) one set of measured-based yield responses at 50 years for an initial spacing of 1.8 m established on a 26.2 m site quality (source: Tables 1 and 2 in von Althen and Stiell, 1990); and (5) six sets of yield table estimates at 50 years for an initial spacing of approximately 1.80 m established on 16, 18, 20, 22, 24 and 26 m site qualities (source: Table 2 in Beckwith et al., 1983). Resultant parameter estimates and associated regression statistics are given in Table 9 by dependent

48

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

Table 9 Parameter estimates and associated regression statistics for prediction equations (Eq. (A.1)) Parameter estimatesa

Species

^ b 0 Jack pine White spruce Red pine

DQ MAI DQ MAI DQ MAI

1.416 8.495 9.023 2.646 1.641 5.572

^ b 1

Regression statisticsb ^ b 2

0.182 0.048 0.101 0.145 0.134 0.072

^ b 3

0.0007 0.0002 0.0013 0.0003 0.0020 0.0001

SEE

0.656 0.566 1.010 0.494 0.660 0.440

0.822 0.577 0.922 0.393 2.257 1.940

R2 0.937 0.886 0.953 0.954 0.817 0.461

F-statistic

N



99 52 163 165 74 16

24 24 28 28 54 54

a

Parameter estimates obtained by ordinary least squares regression procedures. Standard error of estimate (SEE; units speci®c to dependent variable); multiple coef®cient of determination (R2); F-statistic for the overall regression relationship, where () denotes a signi®cant (P  0:05) relationship; and total number of sets (N). b

variable and species. Residual analysis indicated that there was insuf®cient evidence to reject the principal assumptions underlying ordinary least square estimation (e.g. model speci®cation, normality, and constant error variance). Consequently, the functions were considered adequate for prediction within the scope of this study. Appendix B Yield gains of black spruce to ®rst and second generational selection strategies were derived from the extrapolation of preliminary results obtained from unpublished sources (source: McInnis personal communication). Speci®cally, periodic height growth measurements derived from stand tests (zeroth generational experiments), family tests (®rst generational experiments) and progenies tests (second generational experiments) situated throughout New Brunswick were used. These experiments were established under the auspices of the New Brunswick Tree Improvement Council during the late 1970s. The zeroth generation results were based on ®ve stand tests which were established in 1977 and consisted of 13,616 progenies which were derived from phenotypically superior natural stands. The ®rst generation results were based on 12 family tests that were established during 1979± 1980 period and consisted of 26,756 half-sib progenies which were derived from plus trees. The second generation results were based on ®ve progeny tests consisting of approximately 2259 ®rst generation polycrossed progenies. In order to estimate the

expected gains from ®rst and second generational selection, the mean height of the tallest quartile at each measurement was calculated. Consequently, the mean height at age 20 for the second generational experiments was estimated empirically (Eq. (B.1)).  …ij† ˆ b0 ‡ b1 I1 A0…j† ‡ b2 I2 A1…j† ‡ b3 I3 A2…j† ‡ e…ij† H (B.1)  …ij† is the mean height (cm) of the all trees where H within the zeroth generational experiments (i ˆ 0) at the jth measurement, the mean height (cm) of the tallest quartile within the ®rst generational experiments (i ˆ 1) at the jth measurement, or the mean height (cm) of the tallest quartile within the second generational experiments (i ˆ 2) at the jth measure …0j† ment, I1 is an indicator variable equal to 1 when H is non-zero, zero otherwise, I2 is an indicator variable  …1j† is non-zero, zero otherwise, I3 is equal to 1 when H  …2j† is non-zero, an indicator variable equal to 1 when H zero otherwise, A0(j) is the age of the trees within the zeroth generational experiments at the jth measurement, A1(j) is the age of the trees within the ®rst generational experiments at the jth measurement, A2(j) is the age of the trees within the second generational experiments at the jth measurement, bk, k ˆ 0, 3 are parameter estimates obtained by ordinary least squares regression procedures, and e…ij† is the error term speci®c to the ith generation and jth measurement. The resultant prediction equation was derived (Eq. (B.2)). ^ ˆ H …ij†

79:70 ‡ 35:95I1 A0…j† ‡ 40:55I2 A1…j† ‡ 45:84I3 A2…j†

(B.2)

P.F. Newton / Forest Ecology and Management 172 (2003) 29±51

Associated regression statistics were as follows: multiple coef®cient of determination (R2) ˆ 0.98; standard error of the estimate (SEE; cm) ˆ 33.93; F-statistic ˆ 124.2 (P  0:05); and n ˆ 10. Residual analysis indicated the there was insuf®cient evidence to reject the hypotheses of normal and independently distributed residuals with constant variance. Thus the mean height of the tallest quartile at age 20 for the second generational experiments was estimated via Eq. (B.2) (Table 8). The selection strategies were compared in terms of increased productivity as re¯ected by dominant height differentials at a speci®c site index age. Speci®cally, a site index function for black spruce in New Brunswick was used to obtain extrapolated mean dominant height values for each selection strategy based on the observed mean height values at 20 years (Table 8, Ker and Bowling, 1991). Consequently, the height differential of 0.8 m (12.5%) at 20 years for a ®rst generational selection strategy translates into a 1.3 m gain at 50 years (breast-height age). Similarly, the height differential of 2.0 m (31.3%) at 20 years for a second generational selection strategy translates into a 3.3 m gain at 50 years (breast-height age). Comparable estimates based on expert opinion suggest that these estimates are within expectation. Speci®cally, ®rst generation gain estimates for black spruce in Quebec suggest that increases ranging from 3% to 8% are plausible at 12 years and up to 12% if only elite (tallest) trees are selected (source: Beaulieu personal communication). Estimating the rotational consequences of these dominant height differentials was accomplished via the use of the stand density management model (Newton and Weetman, 1994; Newton, 1998). Speci®cally, for plantations established at 1500, 2000, 2500 and 3000 stems ha 1 on medium-good quality sites (17.3 m) in New Brunswick, suggest a mean 13% (34 m3 ha 1) increase in merchantable volume, 10% (1.9 cm) increase in quadratic mean diameter, and 10% (4 years) decrease in the time to operability status, are attainable via a ®rst generational selection strategy (Table 8). Similarly, a mean 31% (81 m3 ha 1) increase in merchantable volume, 27% (5.2 cm) increase in quadratic mean diameter and a 25% (11 years) decrease in the time to operability status, are attainable via a second generational selection strategy (Table 8).

49

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