ported by Steele and Worthington Old-Growth Douglas-Fir and (1955) and King (1961). This paper de scribes growth and mortality trends A 36- among species in a l,180-acre stand Western Hemlock: Year for the 36-year period 1947-1983. Record of Growth THE STAND The Thornton T. Munger Research Natural Area (RNA) is within the and Mortality Wind River Experimental Forest on the Gifford Pinchot National Forest, near Carson, Washington. The 1,180 Dean S. DeBell, Pacific Northwest Research Station, Olympia, ac tract lies on the lower eastern and 98502 Jerry F. Franklin, f southeastern slopes of Trout Creek Washington and Paci ic Northwest Hill, an extinct shield volcano in the Research Station, Corvallis, Oregon 973311 Cascade Range in southwestern Washington. Topography is gentle; the soils are well-drained shotty loams ABSTRACT. Growth and mortality were about esthetics, dependent wildlife and sandy loams of the Stabler series. measured at 6-year intervals in a 1,180 species, gene pools, and long-term The RNA has cool, wet winters and acre old-growth stand in southwestern productivity have been voiced in asso warm, periodically dry summers. Pre Washington. Principal tree species were ciation with the "old-growth" issue. cipitation averages 90 to 100 in. per Douglas-fir (Pseudotsuga menziesii), Resource managers are faced with de year, less than 10% of which falls in western hemlock (Tsuga heterophylla), cisions about the fate of old-growth summer; winter precipitation is often Pacific silver fir (Abies amabilis), stands and the future role of old snow, which accumulates in a modest western redcedar (Thuja plicata), and growth in long-term plans for man pack lasting several months. Mean an western white pine (Pinus monticola). agement of the forests. Information on nual temperature is 48°F. The1J composed 59, 27, 6, 6, and 1 %, re what is happening (stand dynamics) Vegetation is intermediate between spectively, of the total cubic volume in old-growth stands can be useful the Tsuga heterophylla and Abies ama (13,290 jr)in 1947. Gross volume growth background for such decisions. bilis Zones (Franklin and Dyrness averaged 94 jr per acre per year, and mor Thanks to an earlier generation of 1973). Overstory trees are Douglas-fir, tality averaged 86 jr per acre per year. Net foresters, we now have a relatively western hemlock, Pacific silver fir, growth was therefore minimal, and total long-term record of growth and mor grand fir (A. grandis), noble fir (A. pro stand volume remained nearly constant for tality in a 450-year-old, undisturbed cera), western redcedar, and western 36 years. Douglas-fir, which accounted for stand of Douglas-fir, western hem white pine. The understory is com only one-third of the gross growth and lock, and associated species in posed mostly of Pacific yew (Taxus nearly one-half of the mortality, is losing western Washington (Figure 1). Sum brevifolia), vine maple (Acer circil1 dominance to western hemlock, which pro maries of the first 6 and 12 years of atum), and Pacific dogwood (Comus vided nearly one-half the gross growth and measurement in this stand were re nutallii). Ground vegetation includes only 28% of the mortality. Pacific silver fir increased in importance in the lower canopy and composed 60% of the in growth. Thus, although net gain in timber volume was nil, substantial changes oc curred in stand characteristics during the 1947-1983 period. West. J. Appl. For. 2(4):111-114, October 1987.
Most of the old-growth Douglas-fir and western hemlock have been logged on private and industrial holdings in the Pacific Northwest; the remaining tracts, primarily on public lands, are therefore receiving in creased attention from users and man agers of forest resources. Concerns
1 The authors acknowledge the contribu tions of many individuals in the establish ment, maintenance, and remeasurement of the Thornton T. Munger RNA plots, partic ularly W. Bullard, R. E. Miller, D. 1. Reu kema, R. W. Steele, and W. I. Stein. We also thank G. W. Clendenen, M. D. Murray, and W. Pyott for assistance with data compilation and analysis. Financial support was provided by three National Science Foundation grants, as well as by Fig. 1. General view of Douglas-fir and western hemlock in Thornton T. Munger Re the USDA Forest Service. search Natural Area near Carson, Washington.
WJAF 2(4)1987 111 Reprinted from the WesternJournal of Applied Forestry, Vol. 2, No.4, October 1987 salal (Gaultheria shallon), Oregon-grape Table 1. Inventory of old-growth stand in Thornton T. Munger Research Natural Area in 1947 (Berberis nervosa), vanilla-leaf (Achlys {per-acre basis).1 triphylla), beargrass (Xerophyllum Volume tenax), and red whortleberry (Vac Species Trees Dq2 Cubic Scribner3 cinium parvifolium). Douglas-firs in the RNA are 230-460 years old, based on Number Inches Cunits4 mbfs Douglas-fir 24 ring counts on stumps in adjacent 37 78.3 53.2 Western hemlock 77 14 36.4 21.5 clearcuts (Franklin and Waring 1979), True firs6 43 9 8.4 3.8 suggesting that the stand originated Western redcedar 5 26 7.8 5.5 after a major disturbance more than Western white pine 1 26 1.4 0,'1 450 years ago. Douglas-fir site class Miscellaneous 25 5 0.6 varies from Site III to Site IV (McArdle Total or average 175 18 132.9 8L(. et al. 1961). 1 Includes all stems 2.5 in. dbh and larger. 2 Quadratic mean diameter. 3 Sixteen-foot logs. PROCEDURES 4 A cunit is equal to 100 ft3• S Thousand board feet. 6 Grand, noble, and Pacific silver firs combined. Inventory and gross growth data were gathered on 50 concentric plots, 1/20 ac and Vs ac in size. Plots were RESULTS Growth and Mortality (1947 to 1983) spaced systematically throughout the area at a rate of approximately two per Gross growth during the 36-year pe The Stand in 1947 40 ac. Trees 2.5 to 9.5 in. dbh were riod was nearly 3,400 ftJ per acre, rep tagged and tallied on the V2o-ac plots, The initial inventory showed an resenting an average annual incre and trees exceeding 9.5 in. dbh were average of 175 trees per acre, with es ment of 94 ftJ per acre (Table 2). Esti tagged and measured on the lfs-ac timated volumes of 13,290 ftJ or 93,000 mated Scribner gross volume growth plots. Sampling intensity was about bd ft (Table 1). Minor discrepancies was more than 20,000 bd ft or about 1% for the larger trees and 0.25% for between these data and earlier reports 565 bd ftlaclyr. Gross growth varied the smaller trees. Diameters of all (Steele and Worthington 1955, King considerably by period, however trees on these plots were measured by 1961) may be attributed to revised (Figure 2). During the 1947-1953 pe diameter tape to the nearest 0.1 in. ; height-diameter relationships and im riod, gross increment was twice that heights of 6 or more trees per plot proved volume equations. of the 1965-1971 period. Western were measured to the nearest foot by Douglas-fir and western hemlock hemlock accounted for nearly 50% of Abney level and chain. Mortality data constituted 80-90% of the stand gross volume growth, Douglas-fir con were collected on continuous cruise volume in 1947 (Table 1). There were tributed another 34%, and true firs strips, 2 chains wide, spaced 20 chains three times as many hemlock trees as provided two-thirds of the remaining apart. Diameters of trees that died Douglas-fir trees, but the latter were 16%. since the last measurement were esti substantially larger and contributed Mortality was an important process mated to the nearest 2 in. more than twice as much volume per in this stand (Table 2, Figure 2). About The plots have been measured acre as did the hemlock trees. True firs 3,100 ftJ/ac were lost during the 36-yr every 6 years since 1947. Mortality accounted for 25% of the stems, but period, or 86 ft3/ac/yr. Equivalent strips were checked every 2 years these were small and constituted only Scribner volume of the mortality was from 1947-1959, but since 1959 they 6% of the stand volume. Except for 19,360 bd ft/ac, or 538 bd ftlac/yr. Mor have been evaluated at the 6-year two swampy plots where western red tality also varied by period; losses measurement intervals. cedar dominated the stand, both red during the 1947-1953 period averaged Equations for estimating height cedar and western white pine were 650 bd ft/aclyr and were higher than from diameter were developed from scattered throughout the tract. Al losses in other periods. During the en our data for each tree species. The though few in number, individual tire 36-yr period, Douglas-fir ac measured diameter and estimated trees of these species were large, and counted for about 50% of the loss, height of each tree were then applied they contributed sizably to stand western hemlock for 28%. Western to appropriate regional volume equa volume (7% of cubic volume; 16% of white pirie wasa minor component of tions (Browne 1962) to obtain cubic board-foot volume). the stand, but it contributed dispro- foot volume per tree. These values were then summed for all trees on each plot to provide volume per unit area. Inventory and gross growth are Table 2. Gross growth, mortality, and net growth per acre (1947 -83) by species, Thornton T. estimated from data collected periodi Munger Research Natural Area. cally on the circular plots. Gross Conversion ratio1 growth includes increment on all trees Gross Net Gross tallied at the previous measurement Species growth Mortality growth growth Mortality plus ingrowth; i.e., volume of trees at taining measurable size for the first ...... Cubic-foot volume (total stem) ...... 1,531 -393 6.8 6.5 time during the growth period. Mor Douglas-fir 1,138 Western hemlock 1,670 854 +816 5.9 6.2 tality was calculated from the cruise True firs2 385 238 +147 4.5 4.7 strips and was subtracted from gross Western redcedar 137 80 +57 7.0 6.5 growth to provide estimates of net Western white pine 10 381 -371 7.0 6.5 growth. Board-foot volume (Scribner, Miscellaneous 39 18 +21 16-ft logs) and volume growth were Total 3,379 3,102 +277 estimated from ratios calculated from Per annum 94 86 +8 past measurements of cubic- and 1 Estimated board feet (16-ft logs) per ft3. board-foot volumes in the study plots. 2 Grand, noble, and Pacific silver firs combined.
112 WJAF 2(4)1987 160 o Live volume • Mortality of only 1 to 2% of 1947 volume and probably is not significantly different Gross growth > from zero. = 'i ...co Changes in Stand Structure 120 .. 1"11 o ...... nd Composition III ... E '2 10 (; Although growth and mortality are _G. essentially in balance for the stand as a - 80 8 :Sf u whole, major differences occurred e among individual species. Substantial 6 CI!l I g: '2 net losses occurred in Douglas-fir and western white pine, whereas net gains 40 4 e]. CI were achieved by western hemlock, ::i u true firs, and western redcedar (Ta 2 .;: ble 2) . Diameter distributions of principal o 1947 1953 1959 1965 1971 1977 1983 tree species in 1947 and 1983 provide Fig. 2. Live volume, gross growth, and mortality i old-growth Douglas-fir-western an indication of the changes occurring hemlock stand in Thornton T. Munger Research Natural Area (1947-1983). in stand structure (Figure 3). Douglas fir lost 3. 4 trees/ac, and surviving trees were generally in larger size classes. portionately to mortality because most has been a major cause of mortality of Diameters are distributed in the bell of the western white pine died. western hemlock and Pacific silver fir. shaped pattern typical of intolerant Causes of mortality varied by both Heavy mistletoe (Arceuthobium campy species in even-aged stands. There species and period. In the early 1950s, lopodum f. laricis) infections weaken were no Douglas-firs in the 6-in dbh Douglas-fir bark beetles (Dendroctonus and probably kill western hemlock class in either 1947 or 1983. Western pseudotsugae) were the principal cause and, to a lesser extent, Pacific silver hemlock and true fir also had fewer of Douglas-fir mortality, and white fir. trees (5.6 and 8.3, respectively) in 1983 pine blister rust (Cronartium ribicoZa) Net change in stand volume is than in 1947, and trees have grown and mountain pine beetle (D. ponder closer to zero for the 36-yr period be into larger diameter classes. The diam osae) killed most of the white pine. cause extensive mortality offset the eters of both western hemlock and the Root and butt rots have been a major large gross volume growth (Table 2, trueJirs were distributed in an in cause of mortality in Douglas-fir and Figure 2). Total net growth was 277 verse-} pattern, typical of uneven western hemlock the past two decades fr/ac or 990 bd ftlac; per annum equiv aged stands and tolerant species. and have often resulted in wind throw alents are 8 fr/ac and 28 bd ftlac. Such Western redcedar gained an average or windbreak of stems. Windthrow net growth resulted in a total increase of 1. 0 tree per acre during the period. More than half the western redcedar stems were in the smallest size class, but there was a normal distribution of the remaining trees in the larger size 6.0 Douglas-fir 60 Western hemlock classes. The changing importance of various species or species groups to stand 5.0 50 processes can be seen more clearly by
Q)... comparing species in terms of their g 4.0 40 relative contribution to initial inven ... tory, gross growth, ingrowth, and Q) Q. 3.0 30 mortality (Table 3). Douglas-fir consti If) tuted 59% of the stand volume in Q) 1947, but during the next 36 years con 2.0 20 I- tributed substantially less of the gross volume growth (34%), provided no in growth, and accounted for nearly half of all mortality. Western hemlock, on the other hand, contributed far more to gross growth on a percentage basis 4.0 Western redcedar 40 True fir than it did to original stand volume; relative contributions to ingrowth and Q) mortality are similar to each other and ;:; 3.0 30 10 to initial stand volume (26 to 28%). ... The true firs contributed 11 % of the Q) 01947 Q. 2.0 20 .1983 gross growth and 60% of all ingrowth, If) even though they accounted for only Q) 1.0 10 6% of initial stand volume. Western I- redcedar has more or less held its own in the stand. Western white pine was o essentially eliminated from the stand 12 24 36 48 60 72 12 24 36 48 60 by insects and disease. 6-inch dbh classes 6-inch dbh classes DISCUSSION AND CONCLUSIONS Fig. 3. Diameter distribution of principal species, by 6-in classes, in old-growth Douglas-fir-western hemlock stand in Thornton T. Munger Research Natural Area, 1947 This 36-yr record of growth and and 1983. mortality in a 450-yr-old stand illus-
WJAF 2(4)1987 113 Table 3. Species contributions to initial inventory, gross growth, ingrowth, and mortality be processes and changes are as dynamic tween 1947 and 1983. as those observed in many much
Inventory, Gross younger stands. Hence, characteristics Species 1947 growth Ingrowth Mortality or functions of old-growth stands cannot be guaranteed in perpetuity by ...... % of total cubic feet ...... simply preserving existing old-growth Douglas-fir 0 Western hemlock 27 49 26 28 tracts. Where desired old-growth True firs1 6 11 60 8 forests attributes are transient, long Western redcedar 6 4 6 3 term management strategies must in Western white pine 1 1 0 12 clude plans to recreate stands with Miscellaneous 1 1 8 1 those attributes. More information on ...... Cunits per acre ...... patterns and rates of change in old 132.9 33.8 0.1 31.0 Total growth forests is clearly essential for 1 Grand, noble, and Pacific silver firs combined. identifying the nature and intensity of such problems. D trates some patterns common to many Such net growth was probably not sig LITERATURE CITED old-growth Douglas-fir and western nificantly different from zero, espe hemlock stands in the Pacific North cially in view of the fact that losses in BROWNE, J. E. 1962. Standard cubic-foot volume west. Wood volume (and presumably usable volume caused by decay in tables for the commercial tree species of British total living biomass) have remained living trees were not evaluated in our Columbia. B.C. For. Serv., For. Servo & Inven tory Div., Victoria, B.C. 107 p. essentially constant, despite much ac study. In contrast, net growth of CURTIS, R. 0., ET AL. 1982. Yield tables for man tivity in growth and development pro Douglas-fir stands on rotations of 60 aged stands of coast Douglas-fir. USDA For. cesses. to 100 years averages about 150 fr/ae! Servo Gen. Tech. Rep. PNW-135. 182 p. Gross volume growth was larger yr (Curtis et al. 1982), nearly all of FRANKLIN, J. F., AND C. T. DYRNESS. 1973. Nat ural vegetation of Oregon and Washington. than many foresters might expect for which is recoverable. USDA For. Servo Gen. Tech. Rep. PNW-80. an old-growth stand (94 £t3/ac/yr). Important shifts have occurred (and 417 p. Such gross productivity is equivalent are continuing to occur) in the relative FRANKLIN, J. F., AND R. H. WARING. 1979. Dis to about one-half of that in 60- to 100 importance of various tree species. tinctive features of the northwestern conif erous forest: Development, structure, and yr-old Douglas-fir stands on sites of The stand is shifting gradually from function, P. 59-86 ill Forests: Fresh perspec similar quality. Mortality in the old Douglas-fir dominance in the upper tives from ecosystem analysis (R. H. Waring, growth stand was also very high canopy to western hemlock; simulta ed.). Oregon State Univ. Press, Corvallis. (86 ft3/ac/yr), and it essentially bal neously, true firs and western red KING, J. P. 1961. Growth and mortality in the Wind River Natural Area. J. For. 59(10):768 anced gross growth. Mortality losses cedar are increasingly represented in 769. in younger stands, even when un the lower crown classes. McARDLE, R. E., W. H. MEYER, AND D. BRUCE. thinned, on similar sites are much Demonstration of the ever-changing 1961. The yield of Douglas-fir in the Pacific lower. nature of old-growth stands is prob Northwest. USDA Tech. Bull. 201 (rev.), 74 p. STEELE, R. W., AND N. P. WORTHINGTON. 1955. Net volume growth resulted in a ably the most important contribution Increment and mortality in a virgin Douglas-fir 1983 stand volume that was only of this 36-yr record. Although the net forest. USDA For. Servo Pac. Northwest For. & 1-2% greater than the 1947 volume. change in timber volumes was nil, Range Exp. Stn. Res. Note 110. 6 p.
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114 WJAF 2(4)1987
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