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A comparison of Grand fir and Douglas-fir growth performance in the Elk River Tree Farm Klinka, Karel 2008

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Scientia  Silvica Extension Series, Number  16, 1998 A Comparison of Grand Fir and Douglas-Fir Growth Performance in the Elk River Tree Farm Introduction The superior growth of grand fir (Abies grandis) compared to Douglas-fir (Pseudostuga menziesii) on suitable coastal sites has previously been recognized on the basis of qualitative observations with little empirical evidence.  For example, D.E. McMullan (1977, pers. comm.) reported 18% higher volume for a grand fir tree of the same height and age as a 108-year- old Douglas-fir plus tree (No. 622) This study was undertaken by Bernardy (1988) to examine possible differences in the growth of grand fir  and Douglas- fir growing in a mixed 40-year-old plantation of unknown origin.  Trends in height, diameter and annual volume increment between the two species over time were examined.  Expected growth performance (i.e. volume and form) of each species was inferred from trends identified at time of sampling. Methods The plantation is located in the Elk River Tree Farm on the Quinsam River flats,  Vancouver  Island.  The site had a strongly fluctuating water table, the soil moisture regime (SMR) was estimated as winter-wet and summer-fresh, and the soil nutrient regime was estimated as rich.  Such special SMRs have not been considered in characterizing the quality of coastal forest sites until recently. Stem analysis was carried out on ten trees of each species with sample trees chosen to represent dominant and codominant trees.  Height and diameter at breast height was measured for 20 trees of each species and the average calculated. Annual height increment for each of the last 15 years (1973- 1987) and length of live crown were also recorded.  The trees were then sectioned and disks collected at 30, 60, and 130 cm above germination point with another eight disks sampled at equal spacing between 130 cm and the top of the tree. Bark thickness and the width of all rings were measured on each disc.  These measurements were then used to calculate annual diameter and volume increments. Results Mean growth performance data and standard deviations for each species are given in Table 1. No significant differences were identified in total height, diameter at breast height, or length of live crown.  Significant differences were also not apparent when these variables were examined over the 1973-1987 period Figure 1. Trends in cumulative annual height increment between Douglas-fir and grand fir (1972 - 1987). Figure 2. Trends in cumulative annual diameter increment between Douglas-fir and grand fir (1972 - 1987). 14 16 18 20 22 24 26 28 30 '72 '73 '74 '75 '76 '77 '78 '79 '80 '81 '82 '83 '84 '85 '86 '87 Grand fir Douglas- fir H ei gh t (m ) Date 22 24 26 28 30 32 34 36 38 core '75 '76 '77 '78 '79 '80 '81 '82 '83 '84 '85 '86 Grand fir Douglas- fir D ia m et er  (c m) Date seicepS thgieH )m( retemaiD tsaerbta thgieh )mc( fohtgneL evil nworc )m( fo.oN sehcnarb lrohwrep hcnarB retemaid )mm( latoT emulov m( 3) rif-salguoD 4.72 )4.2( 3.83 )2.4( 5.41 )1.3( 3.7 )8.1( 6.91 )9.3( 81.1 )03.0( rifdnarG 9.82 )2.2( 2.04 )0.3( 0.51 )5.2( 5.5 )5.0( 6.51 )4.1( 33.1 )13.0( Table 1. Mean (std. dev.) growth performance measures for Douglas-fir and grand fir. using repeated-measures analysis of variance (ANOVA).  The slightly greater height and diameter of grand fir appears to represent a continuing trend (Figures 1 and 2).  The similar live crown lengths in both species may imply that shade tolerance in this environment is comparable between the two species. Scientia Silvica is published by the Forest Sciences Department, The University of British Columbia, ISSN 1209-952X Editor: Karel Klinka ( Research: Paul Bernardy ( Production and design: Christine Chourmouzis ( Financial support: Natural Science and Engineering Council of Canada Copies available from:  or K. Klinka, Forest Sciences Department, UBC, 3036-2424 Main Mall, Vancouver, BC, V6T 1Z4 Changes in diameter with height were evaluated in each species. Taper was found to be approximately the same.  Regression of diameter against height showed Douglas-fir decreased in diameter by 1.33 cm for each meter of height and grand fir decreased an average of 1.30 cm for each meter of height.  When the average diameter of each species was plotted against sampling height the two species were indistinguishable. Discussion Estimates of growth performance prior to this stand reaching age 28 would have led to different results.  The early success of Douglas-fir on this site appears to be in decline whereas grand fir appears to be performing consistently well.  Grand fir now has a greater total height and diameter (not significant) and total volume (p <0.01).  Grand fir growth rate continues to increase at a greater rate than Douglas-fir growth rate.  Grand fir also had better general form, with smaller and fewer branches than Douglas-fir.  Therefore, the growth of grand fir prior to 30 years of age does not appear to give a reliable prediction of its potential productivity. It must be noted that this study has investigated growth performance on only one site, using a small sample size. Caution should be exercised when considering other sites and stand conditions.  However, in the absence of growth data for the coastal population of grand fir, these results represent a valuable initial contribution to tree species selection and suggest further investigation is warranted, particularly on sites where grand-fir may be a more productive tree than Douglas- fir. References Bernardy, P. 1988. Classification and rehabilitation interpretations of hardwood ecosystems in the Elk River Tree Farm. M.Sc. thesis, University of  British Columbia, Vancouver, BC. 101 pp. Grand fir had a consistently greater annual volume increment since 1974.  If this trend continues grand fir will soon have a much greater volume than Douglas-fir on an individual tree basis (Figure 4).  The greater current annual volume increment of grand fir relative to Douglas-fir was significantly different over time based on repeated measures ANOVA (p <0.001).  The contribution of each year was relatively consistent over the 12 year period. Douglas-fir trees had significantly poorer branching characteristics than grand fir.  Douglas-fir has a significantly greater number of branches per whorl (p <0.006) and branches of larger diameter (p <0.003). Mean total volume for grand fir was approximately 12% higher than that of Douglas-fir at time of sampling.  However, the mean total volume in 1974 was 24% greater for Douglas-fir than grand fir (Figure 3). Figure 3. Trends in cumulative volume increment between Douglas- fir and grand fir (1972 - 1987). Figure 4. Trends in annual increment between Douglas-fir and grand fir (1972 - 1987). 0.2 0.4 0.6 0.8 1.0 1.2 1.4 core '75 '76 '77 '78 '79 '80 '81 '82 '83 '84 '85 '86 Grand fir Douglas- fir Vo lu m e (m 3 ) Date 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 core '75 '76 '77 '78 '79 '80 '81 '82 '83 '84 '85 '86 Vo lu m e (m 3 ) Date Grand fir Douglas-fir


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