Proceedings of the BIOLOGY AND MANAGEMENT OF TRUE FIR IN THE PACIFIC NORTHWEST SYMPOSIUM

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1 Proceedings of the BOLOGY AND MANAGEMENT OF TRUE FR N THE PACFC NORTHWEST SYMPOSUM Edited by Chadwick Dearing Oliver and Reid M Kenady University of Washington USDA Forest Service College of Forest Resources Pacific Northwest Seattle, Washington Forest and Range Experiment Station nstitute of Forest Resources Contribution Number 45 Portland, Oregon

2 PATTERNS OF HEGHT GROWTH N WESTERN TRUE FRS Constance A Harrington and Marshall D Murray ABSTRACT Height growth of true firs in western North America can be characterized by: (1) an initial period of slow jufenile growth, 2) a fairly long period of rapid growth, and 3) an extended period of slower but still appreciable growth Data from younggrowth stands in western Washington were used to assess height growth of noble fir, Pacifc silver fir, and grand fir relative to height growth of Douglasfir as predicted by Douglasfir site index All three true firs are capable of excellent height growth on sites with high Douglasfir site indexes, but generally ha\'e slower ju Fenile growth than Douglas:fir On poor sites, noble fir can outgrow Douglasfir in height, primarily because Douglas:fir slows down in height growth more quickly on poor sites than does noble fir Based on its growth relatil'e to Douglasfir, the authors conclude noble fir warrants greater management consideration Pacific silver fir and grand fir also warrant more consideration, particularly as components of mixed stands NTRODUCTON The true firs (Abies spp) in western North America can easily be recognized by their distinctive silhouettes n addition to their common appearance, they also share similar patterns of height growth We first discuss the different phases of height growth during the lives of true firs and the seasonal progression of height growth We next present field data from younggrowth stands of noble fir (A procera Rehd ), Pacific silver fir (A amabilis [Doug!] Forbes), and grand fir (A grandis [Doug!] Lind!) which illustrate some specific patterns of height growth and the potential for height growth in these species The relationships between height growth of these true firs and predicted height growth of Douglasfir (Pseudotsuga menziesii [Mirb] Franco) are examined and the management implications discussed GENERAL PATTERNS OF HEGHT GROWTH Graphic representation of true fir height growth shows a characteristic Sshaped curve which can be divided into three phases: juvenile or early age; sapling to maturity; and mature to overmature old age The length of time a tree is in each phase varies with species, site, and stand conditions During the first or juvenile phase, height growth is characteristically slow n natural stands, it is not uncommon for many of the true firs to take up to years to reach breast height (table 1) Under favorable conditions, however, Pacific silver, grand, and noble firs are capable of reaching breast height in five to nine years Although most of the western true firs are fairly shade tolerant, in stands of mixed species their early height growth can be retarded by shade from those with greater juvenile height growth Regeneration in unevenaged stands can be severely suppressed; Williams (1968b) measured Pacific silver fir that took over 80 years to reach breast height Delays in growing out of the juvenile phase are still evident many years later Although most true firs can recover from early suppression or checks in height growth and show excellent subsequent height growth, they characteristically remain shorter than trees of the same age that emerged from the juvenile phase more rapidly Table Years to breast height for western true firs under conditions favorable for regeneration Species Pacific silver fir White fir Grand fir Subalpine fir California red fir Noble fir Years to breast height* * Sources include Fowells (1965), Hanzlik (1925), Stage ( 1959), Williams ( 1968b), and personal field observations

3 Height Growth Patterns n the second major phase, from the sapling stage to maturity, height growth is rapid, generally following a moreorless linear trend The linear portion of the heightgrowth curve is most extended on the best sites (Cochran 1979; Herman et al 1978; Schumacher 1926, 1928; Stage 1959) This period of rapid height growth is longer for the true firs than for many of their associates thus during this second phase the true firs often catch up with or surpass associated tree species (Herman 1967) Height growth slows as trees enter the third, mature to overmature, oldage phase of height growth The true firs are fairly longlived, however; on favorable sites, trees 0 to 0 years old continue to increase appreciably in height n many oldgrowth stands, the true firs are found in dominant or superdominant positions On good sites, most of the western Abies attain heights of to 60 m with maximum heights of Pacific silver, grand, and noble firs ranging from 75 to 85 m (table 2) True fir height growth is limited to a rather brief period during the growing season (figure 1 ) This is generally true of species with determinate height growth and is in contrast to species lacking large overwintering terminal buds, such as hemlock or cedar, which continue to grow in height as long as conditions are favorable during the growing season The western true firs, however, tend to have more rapid terminal expansion than any of their associates, with the possible exception of Douglasfir (Fowells 1941; Williams 1968a),, eo Olympia go Study locations Noble fir 0 Pacific silver fir Grand fir 0 : ;o M Rainier o M St Helens 0 '''p'' ',' '/ "Āā"" "'" :F ÿ/ Ă 90 /, ' 1 0, 80 / E, /,, / 2' 70,' ',,t; :: 60 : / c: t' : lj ' / " 0 i,'i / / 'E! if l/ May / / :, ' / // / //, / Figure 2 Location of true fir stands studied in western Washington western hemlock (Tsuga heterophylla [Raf] Sarg ) the most common tree associates Elevations ranged from to m with most of the stands occurring between 600 and 00 m / /, For each site, we determined aspect, elevation, soil series, and Douglasfir site index Elevation and soil series were deter / ' Douglas llr Western redcedar western hemlock Lodgepole pine Pacdlc s1lver hr Nobleflr f,' " Subalpme fir, site trees were measured in the older stands f not enough suit 0 ; t' Figure 1 Seasonal height growth of several northwestern conifers (Government Camp, Oregon, 00 m [3900 ft] adapted from Williams 1968) COLLECTON AND ANALYSS OF FELD DATA We collected height and age or annual height growth information in 49 true fir stands in western Washington (figure 2) Most of the stands were mixed species with Douglasfir and 2 mined from topographic and soil mapsdouglasfir site index was determine'd using King (1966); or more site trees were measured for height and age in the younger stands; at least five able Douglasfir trees were on the site to make an accurate site index determination, we used the Douglasfir site index for the appropriate soil series;' we used soil series to determine the Douglasfir site index for about onefifth of the sites On all sites, we determined total height and breastheight age of the true firs Some sites had more than one age class present; we used an average of three trees per species to determine an average height for each site and age class We also determined annual height growth of 17 true fir trees that came from 0 different stands The trees were felled, aged at breast height, and the distances between branch whorls measured The number of rings at breast height for each tree was verified to equal the number of whorls above breast height Based on Weyerhaeuser Company soil maps for their Washington tree farms

4 Harrington and Murray Table 2 Average and maximum heights of mature true firs on good sites (adapted from Fowells (1965) Species A1 erage Maximum Pacific silver fir 60 White fir Grand fir Subalpine fir Tala/ height (Meters) 1 ' ' ( ( Notif'' rxuq'' ''''"'"ll19e'' California red fir 57 Noble fir t nformation from Jerry F Franklin, Forestry Sciences Laboratory Corvallis, Oregon :17, 792;<23=25 1 =27=29>31?@35' 0 Breasl helght age (years) 0 0 When the trees were young enough to allow accurate determination, measurements were also made of interwhorl distances below breast height We avoided any trees of lower crown class or with obvious signs of past top damage, Cumulative height growth was plotted over age for each of the trees with annual height growth measurements The height growth patterns of the true firs on each site were compared with the expected height growth for Douglasfir on that site, as predicted by Douglasfir site index (King 1966) We wished to compare the relative heights of the true firs with those of Douglasfir on sites of varying Douglasfir site index Thus, for each age for which we had data, we regressed height of the true fir against Douglasfir site index The regression equations were computed individually for noble and Pacific silver firs; grand fir data were insuffcient for this analysis Data from the sites with annual height growth measurements were included in the regression analyses of each age for which other data were available The majority of the values used in the regression analyses, however, were independent for each age Douglasfir site index incorporates the effects of many site factors on height growth of Douglasfir The effects of some of these site factors may be speciesspecific To evaluate how well Douglasfir site index incorporates the effects of aspect and elevation on true fir height growth, the true fir heights predicted by the regression equations were compared to actual heights Sites having heights that deviated from the predicted values by more than percent (plus or minus) were tallied by aspect and elevation for each species RESULTS The plotted heightgrowth data illustrated the general trends of height growth during the juvenile phase and the early portion of the saplingtomaturity phase Delays in entering the period of rapid height growth are still evident in reduced height at later ages (figure 3a) Both minor top damage and rapid re Figure 3a Height growth of two noble firs compared with average height growth of Douglasfir on Douglasfir site index m (1 ft) (King 1966) :E 0 ' 0 ""!1 ' þ "' 1:: 72 {! 1B Q 0 0 GraM f" 1 DO<glash!Kmg P? 0 : LLAB37C,D 11 13E1F5GH, 179 2J,K3 2 Breast helght age (years) L5=27M2 9N31 O3'5 Figure 3b Height growth of three grand fir trees compared with average height growth of Douglasfir on Douglasfir site index m ( 1 ft) (King 1966) covery from top damage can be seen (figure 3b) All three species had excellent growth rates on areas with high Douglasfir site indexes; maximum annual height growth ranged from 0 to 1 2 meters (tabie 3) On the better sites most trees entered the linear phase of height growth at or just before reaching breast height; on the poorer sites, however trees did not begin rapid height growth until three or four years after passing breast height Once trees began rapid height growth, their growth rate was linear for as many years as we had data The regressions of true fir height against Douglasfir site index had correlation coefficients ranging from 0 85 to 0 98 (all significant at a= 01) All the regression lines (figures 4a and b) had positive slopes, indicating greater heights were associ 0 60 "8 [ ;? a 211

5 Height Growth Patterns 39 A 39 B Nobltllr Pacificsliver fir 1 1 JO 39, m Douglas flr site ndex (SO y8 Douglasflr site ndex (SO y8 JO 00[ (} :: 70 «:: 60 :::: === = =======, : ::: :,, _' :! _ 8, _G 60 H JoKLMNO1P00 QRST,U 1 V WX"Yo 70 eo:,a a 39 c 1 39 D 1 Douglasfir 0 36 Not>'elor PJc hcsderlor :, c ª 21 c {! :, c!221! eo (}!!!: :: : Douglas flr site ndex (SO y8 Douglas fir site ndex (SO Y E 36 0 F 1 PJC 'oerl r ooghr,, )} 1 Nobl('f,r 1 "" (} 24 :: 'a) c j e = 80 {! == d o BO Douglas lir site ndex ( Y8 Douglas lir site ndex (SO yr) Figure 4 Height by breastheight age and Douglasfir site index (King 1966) for: a) noble fir: b) Pacific silver fir; c) Douglasfir; d) noble fir and Pacific silver fir: e) Pacific silver fir and Douglasfir; and f) noble fir and Douglasfir 2

6 Harrington and Murray Table 3 Characteristics of study locations and best annual height growth in true fir stands in western Washington Meters Meters feet Meters GRAND FR Melbourne ,8 2 Melbourne ,22 PACFC SLVER FR 3 Astoria N Mal N , 17,22 5 Abiel sw ,, 1526 NOBLE FR 6 Boistfort NE Boistfort N ,7 8 Sugarloaf s Katula , 15,2 1,3 1 Katula , 16 17, Douglas:fir site index 85 Best a/1111/al height groh th Location Soil series Aspect E/e\'/ion ( year) Amount Breastheight age ated with higher Douglasfir site indexes The regression lines for Pacific silver and noble fir were compared with each other and with the lines for Douglasfir (figure 4c) developed from King (1966) When the regression lines for noble and Pacific silver firs were compared (figure 4d), the two species were seen to perform similarly on high Douglasfir sites, but the performance of Pacific silver fir fell off more sharply than that of noble fir at the lower site indexes Predicted height of Pacific silver fir was poorer than that of Douglasfir at all site indexes and for all ages; the greatest differences were on the poorest sites (figure 4e) The relationship between performance of noble fir and Douglasfir changed over time (figure 4f) Generally our analysis showed that Douglasfir outperforms noble fir on the higher Douglasfir site indexes; noble fir, however, grows better than Douglasfir on the poorer site indexes and its advantage increases with age At breastheight age 13 the regression lines cross at site index 23 m (74 ft); by breastheight age, the regression lines cross at site index 35 m (115 ft) Thus, by breastheight age, on sites where Douglasfir site index is less than 35 m, the predicted height of noble fir is greater than that of Douglasfir Cumulative height growth of noble fir can surpass that of Douglasfir because the period of maximum height growth in noble fir is longer than that in Douglasfir;2 this difference is most pronounced on poorer sites (figure 5 ) The extended period of good height growth in noble fir allows it to overtop all its associates eventuallyeven Douglasfir on good sites Douglasfir site index appears to incorporate the effect of elevation for the true firs as well as for Douglasfir; elevation by itself did not appear to account for any additional variation in height growth of noble or Pacific silver firs There was no 2 Douglasfir at high elevations have been shown to have slower height growth at early ages and greater height growth at later ages than trees at low elevations that have the same height at 0 years (Curtis eta/ 1974) Thus, differences in heightgrowth patterns of different species may vary with location consistent trend for either high or low elevations to be associated with deviations from the predicted values Aspect, however, did seem to have a greater influence on height growth of noble and Pacific silver fir than is accounted for by Douglasfir site index For noble fir, south and east aspects, especially at low to middle elevations, were associated with poorer performance than predicted For Pacific silver fir, north aspects were associated with better performance than predicted SUMMARY AND MANAGEMENT MPLCATONS Height growth of true firs that are free to grow can be characterized by a period of slow juvenile growth, an extended period of rapid growth that is almost linear, and a final phase in which slower but still appreciable growth continues up to very advanced ages These characteristics mean that juvenile true firs often appear at a disadvantage compared with their associated tree species Once past the juvenile phase, however, their relatively long period of rapid, uniform height growth often allows the true firs to catch up with or surpass their associates Seasonal height growth takes place during a fairly brief period Minor heightgrowth reductions may result if stand entries coincide with the period of rapid terminal expansion We found that true firs growing at low to middle elevations in western Washington performed better than most foresters probably would have predicted Pacific silver fir was fairly consistently outgrown by both noble fir and Douglasfir Height growth of Pacific silver fir was quite respectable though, and, with its shade tolerance and fairly narrow crown, it may warrant greater management considerationespecially as a component of mixed stands For the same reasons, grand fir should also be considered Any species capable of growing over 2 m a year should be evaluated seriously Both grand fir and noble fir have grown well in experimental plantings on several sites in Europe (Aldhous and Low 1974; McLean 1980;

7 1 Harrington and Murray Rohrig 1978) and have been recommended for wider use Noble fir tends to have a slower start than Douglasfir, but the superior performance of noble fir on poor sites (relative to Douglasfir), and its good performance on good sites suggest that the species should be considered more frequently for management on suitable lowland as well as upperslope locations Additional research is necessary to predict the productivity of these species under specific site conditions 0000 OQQQNoble!a Douqlast,rtK nb\9661, !! oo: l ;t so a L Breasl helghl age (years) Figure 5 Height growth of three noble fir trees compared with average height growth of Douglasfir on Douglasfir site index 26 m (85ft) (King 1966) REFERENCES Aldhous, J R Low A J 1974 The potential of \\'estem hemlock, westem redcedar, grand fir m lnoble fir in Britain For Comm Bull 49 London England: Her Majesty's Stationery Office Cochran, P H 1979 Site index and height growth cur\'es for managed, el'enaged stands of ll'hite or grand fir east of the Cascades in Oregon and Washington USDA For Serv Res Pap PNW252 Portland, OR: Pac Northwest For and Range Exp Sta Curtis Robert 0 Herman, Francis R and DeMars, Donald J 1974 Height growth and site index for Douglasfir in highelevation forests of the OregonWashington Cascades Forest Sci : 7316 Powells, H A 1941 The period of seasonal growth of ponderosa pine and associated species J For 39: compiler 1965 Sill'ics of forest trees of the United States USDA Agric Handb 271 Washington, DC Hanzlik, Edward J 1925 A preliminary study of the growth of noble fir]; Agric Res 31( 0): Herman, Francis R 1967 Growth comparisons of upperslope conifers in the Cascade Range Northll'est Sci 41:5152 Curtis, Robert 0 and DeMars, Donald J 1978 Height groll'th and site index estimates for noble fir in highelel'(ltion forests of the OregonWashington Cascades USDA For Serv Res Pap PNW243Portland, OR: Pac Northwest For and Range Exp Sta King, James E 1966 Site index curl'es for Douglasfir in the Pacifc Northwest Weyerhaeuser For Pap 8 Centralia, WA: Weyerhaeuser Co, For Res Cent McLean, C 1980 Abies in Scotland Report on the Silvicultural Group Scottish For 34:19 Rohrig, E ed 1978 Grundlagenjlir den Anbattl'on Abies grandis [Research on growing Abies grandis] Schr Forst! Fak Univ Gottingen und Niedersachs Forst! Versuchsanst 54 Schumacher, Francis X 1926 Yield, stand, and volume tables for ll'hite fir in the California pine region Agric Exp Sta Bull 7 Berkeley, CA: Univ Calif 1928 Yield, stand, and volume tables for red fir in California Agric Exp Stn Bull 491 Berkeley, CA: Univ Calif Stage, Albert E 1959 Site index cun es for grand fir in the nland Empire USDA For Serv Res Note 71 Ogden, UT: lntermt For and Range Exp Sta Williams, Carroll B, Jr 1968a Seasonal height growth of upperslope conifers USDA For Serv Res Pap PNW62 Portland, OR: Pac Northwest For and Range Exp Sta 1968b Juvenile height growth of four upperslope conifers in the Washington and northern Oregon Cascade Range USDA For Serv Res Pap PNW70 Portland, OR: Pac Northwest For and Range Exp Sta 214