Purchased by the r:·OI'f''. Service for official use
Pulpwood Section • Production • Management
LOBLOLLY STAND GROWING IN ARKANSAS
Highway 270 near Prattsville, Ark. The understory got started four This picture by PULP & PAPER'S Southern editor shows a heavy years before; overstory was partially thinned 2 years before shelter-wood of loblolly pine of sawtimber size alongside U. S. photographed.
The Loblolly Pine of the South Versus the Douglas Fir of Pacific Northwest
How DO THE YIELD and increment of By Norman Worthington est tree in the Puget Sound area, com natural, unmanaged young-growth prising 40% of the sawtimber volume. I,Jouglas fir compare with that of lob The tree grows in pure, even-aged lolly pine? This question often arises stands after fires, cutting, or any com in discussions of the pulp and paper plete removal of the forest. It is well industry of the Pacific Northwest and adapted to the shallow, coarse soils of the South. NORMAN WORTH- of the region and is the predominant INGTON'S Forest It provoked considerable interest Service career has species at lower elevations, except in at the American Paper and Pulp been divided be areas of high water table and shaded Association tour of Pacific Northwest tween South and north slopes. The h·ee produces little forests in Sept. 1953. To give a rea West. clear wood in the first 100 years be sonable and down-to-earth answer to cause of persistent branches, which the query, estimates have been made for Douglas fir in the Puget Sound Selected to write this article be region of Western Washington and cause of his long experience in for loblolly pine in Southwestern both Arkansas and Washington Arkansas. average forest and site conditions of States with U.S. Forest Service. Care has been taken to give a con the two regions. Now with Puget Sound Research servative estimate of potential and Douglas fir (Pseudotsuga menziesii Center, Pacific Northwest Forest & actual yields for both species under (Mirb.) Franco) is the principal for- Range Experiment Station. HOW DOUGI.AS FIR GROWS IN WEST range in ages from young 15 year old firs to 200 to 300 years old. this is view of 20 to 25 year old growth in the St. Helens Tree This has been naturally reseeded. MI. St. Helens-10,000 ft.-in Farm of Weyerhaeuser Timber Co., where Douglas fir farm plots background.
ling to the bole long after they are main reliance (84% of the harvest) is feet (height at age 50 years) for lob pead. Douglas fir is highly resistant on virgin timber. Hence, in Arkansas lolly. These site estimates are average to insects and decay. the rate and availability of increment for both species and areas. Loblolly pine (Pinus taeda L.) is are a critical concern of the forest Rotation, or time required to estab the most important of the Southern industry. Industry in the Puget Sound lish and grow timber crops to a yellow pines. It grows chiefly on the area, not yet dependent on young specified maturity, must be set for each more moist sites, where the water growth forests, places greater empha species. This period is not the same table is close to the surface or where sis on the current volume and accessi for the two species because growth soil moisture is readily available. The bility of stands that have attained habits are different. The rotation giv tree clears itself rapidly of dead merchantable size and quality. ing the greatest mean annual incre limbs; on rotations of 50 years at least However, the end of the virgin tim ment-:M.A.I. (total volume divided by one-quarter of the wood is knot-free. ber is in sight, and a shift to young total age)-is generally used in yield The tree springs up on exposed min growth stands of fairly recent incre comparisons. Yield tables indicate that eral soil, such as abandoned fields. It ment can be forecast. Soon the inter a rotation of 70 years for Douglas fir is subject to bark-beetle and sawfly ests of both regions will be identical. and 35 years for loblolly pine are most attacks, but not seriously so. An important consideration in any efficient for pulpwood, while 100 Douglas fir and loblolly pine reach yield comparison is a common unit of years and 50 years are best for savv full development in the areas com measurement. A cubic foot of wood timber. Rotation age for loblolly pine pared, namely, Puget Sound and should mean the same thing in all is one-half that of Douglas fir for both Southwest Arkansas. Management in regions, but, strangely, this is not cubic and board feet, chiefly because these two zones is more intensive always so. Pulpwood utilization to a loblolly pine has a faster initial growth than elsewhere within the respective 3-in. top is common in Arkansas, but rate and a shorter life expectancy. _ranges of the species, mainly because utilization is nearer a 6-in. top in the af application of research findings Puget Sound area. The disparities Fir vs. Pine-in No. of and existence of better markets. How between cubic and board foot meas Stems, Height, Diameter ever, Southwest Arkansas is consid urements of the two regions reflect erably ahead of Puget Sound in the the closer utilization of the tree in Douglas fir is more tolerant than .application of intensive forest man Arkansas. In this analysis, where yield loblolly pine, so that an acre will sup .agement. and increment are compared directly, port approximately twice as many all units have been adjusted to as stems. For example, at age 25 years What are Problems of Yield? near a common standard as possible. the normal stand of Douglas fir has These comparisons of growth and 1,160 stems of all sizes per acre com The two regions differ in the rela yield are meant to apply to average pared to 600 for loblolly. 1Iore signifi tive importance attached to forest conditions on average sites for each cant for a pulpwood rotation, how increment. In Southwest Arkansas all region. Cite index 140 feet (height of ever, would be a comparison using cutting is from second- or third trees at age 100 years) has been chosen only the trees 4 in. in diameter and :gwwth forests; on Puget Sound the for Douglas-fir, and site index 85 larger, drawn from standard yield 'tables for both species1 (Table 1). Table I.-Trees per acre 4 in. in di than pine, although growth rates for By this standard, Douglas fir out ameter and large•·, Douglas both species decrease steadily. At 70 numbers loblolly only 600 to 540 at fir vs, loblolly pine. years, the firrate is 1.6 in. per decade, Age Douglas fir Loblolly pine 25 years, but Douglas fir increases its compared to 1.1 for pine; at 100 years .advantage with increasing age. years number number it is 1. 1 in. compared to .8. Since 600 At 50 years it has 53% more trees 25 540 these rates are for dominant and ethan pine, and at 100 years it out 35 525 375 co-dominant trees they are higher than lmmbers loblolly 2 to 1. This ability 50 360 235 the average for all trees.
HOW HIGH THEY GROW HOW WIDE THEY GROW
Figure 1-Total height and annual height growth for South's lob Figure 2-Total diameter and diameter growth per decade for lolly Pine (dominant trees only) vs. Pacific Northwest's Douglas Fir South's loblolly Pine and Pacific Northwest's Douglas Fir. Data for (dominant and co.. dominant trees). Data from yield tables for both loblolly Pine from yield table. Data for Douglas Fir adjusted from species. yield table. regions covered in a nation-wide sur Table 3.-Yield in bd, ft. per acre of The difference between the two· vey made by the Forest Service. Douglas fir and loblolly pine species over large sawtimber areas for vat•ious forest conditions, Analysis of these yields should give sampled by the Forest Survey is the Type of Douglas Loblolly a good idea of the capabilities of the same as the theoretical difference in estimate fir pine two species. Different mensurational yield. Estimated increment of the Yield Table and utilization standards in the two average Douglas fir stand is 461 bel. Age years 100 50 regions, as well as inability to secure ft. per acre per year, of loblolly pine Total yield bd.ft. 85,703 30,318 data for the exact rotation age, make 327 bd. ft., an advantage of 41% in Annual in it impossible to compare the yields of favor of the Puget Sound species. crement bel.ft. 857 606 the two species precisely, but the Forest Survey1 figures given (Table 2) are reasonably Growing What It Adds Up To comparable. stock bd.ft. 27,685 5,396 Yield table examples show that the Comparison of cu. ft. and bd. ft. Annual in mean annual increment of Douglas fir yields shows that Douglas fir pro crement bel .ft. 461 327 over a 70-year rotation is 22% greater duces greater yield and increment than that of loblolly pine in a 35-year than the forests of Puget Sound, and than loblolly pine, but the pine pro rotation. The yields are theoretical in far too little growing stock is left upon duces earlier returns and more clear the sense that they would probably which growth may be added. lumber. not be achieved over a large area ex Bd. Ft. Volume-Rotations required The greater number and taller cept under a high level of manage to obtain maximum bd. ft. growth are stems per acre account for the greater ment. longer than for cu. ft. growth. The yield of Douglas fir. The larger Forest Survey data show the minimum-size tree required to pro diameter gained during its first 25 average volume of growing stock and duce sawlogs is larger, and hence years enables pine to produce a com the estimated current increment for older, than the smallest pulpwood mercial yield earlier than Douglas fir. large forest sawtimber areas in the tree. Since maximum increment by Pulpwood yields, based on the best two regions. Estimates indicate that any measure is not obtained until average annual increment, are 20 to existing stands of Douglas fir are nearly all trees pass the minimum-size 30% greater for Douglas fir. Bd. ft. growing at the rate of 1.06 cords per limit, it follows that bel. ft. rotations yields of Douglas fir are about 40% acre, which is 31% above the .81 cord are longer than cu. ft. rotations. more than Southern loblolly pine, estimated for loblolly. The actual The theoretical bd. ft. yield for growth of both species represented by Douglas fir at 100 years can be com these figures is far under the potential, pared with loblolly yield at 50 years yet anyone familiar with forest con (Table 3). These rotations are close to ditions of the two regions will agree the age of culmination of )nean an that such low productivity is only too nual increment. Standards of measure ARK. common. ment in this comparison are the same Although, potentially, Douglas fir for both species. In the comparison of LA. should out-produee loblolly only about Forest Survey data no attempt has 22%, actually the average Douglas fir been made to adjust either to theo WHERE LOBLOLLY PINE REACHES stands are growing over 31% faster retically best rotations or to strictly ITS FULL DEVELOPMENT than the pine stands. The chief reason comparable standards of measure for the poor showing of loblolly is, ment. The figures given, however, are Map shows Southern Arkansas area where data was obtained on Loblolly Pine. of course, that Southwest Arkansas representative of the perfmmance of forests have been more heavily cut the two species as they grow in their own regions. They also reflect the dif Table 2.-Yield in cords per acre of ferent degrees of utilization practiced Douglas fir and loblolly pine for various forest conditions. in the South and in the Northwest. Type of Douglas Loblolly Bel. ft. annual increment for Doug estimate fir pine las fir taken from the yield table ex Yield Table ceeds that of loblolly pine by 41%. This is in contrast to the 22% found Age years 70 35 for cu. ft. increment. The initial rapid Total yield cords 120 49 growth of pine brings its total· volume Annual in- productivity close to that of fir for crement cords 1.72 1.41 Forest Survey1 shorter rotations, but this advantage is largely lost in the longer bd. ft. Growing rotation. In fact, the ability of Doug stock cords 63 15 las fir to maintain a satisfactory Annual in- growth rate is another reason why it crement cords 1.06 .81 out-produces Southern pine.
1 Douglas fir: Average of Clark Cowlitz, Lewis, 1 Douglas fir: Average of Clark, Cowlitz, Lewis, WHERE DOUGLAS FIR REACHES Mason, Grays Harbor counties, \Vashington. Un Mason, Grays Harbor counties, Washington. Un published data from Forest Survey, Pacific North· published data from Forest Survey, Pacific North ITS FULL DEVELOPMENT west Forest and Range Experiment Station, Port· west Forest and Range Experiment Station, Port land, Ore, land, Ore. Map shows Western Washington area-the Loblolly: Forest Statistics for Southwest Loblolly: Forest Statistics for Southwest Arkansas, Forest Survey Release 65, Southern Arkansas, Forest Survey Release 65, <;outhern Shelton-McCleary area-where Douglas fir Forest Experiment Station, New Orleans. 1950. Forest Experiment Station, New Orleans. 1950. records were obtained.
Reprinted from PULP & PAPER, September 1954