The Influence of Species on Site Selection and Timber Removal in West Virginia. William Luppold 1 and Delton Alderman 2 USDA Forest Service

Transcription

1 The Influence of Species on Site Selection and Timber Removal in West Virginia William Luppold 1 and Delton Alderman 2 USDA Forest Service 1 Project Leader, USDA Forest Service, Northeastern Research Station, 241 Mercer Springs Road, Princeton, WV wluppold@fs.fed.us; (v); (fax) 2 Research Forest Products Technologist, USDA Forest Service, Northeastern Research Station, 241 Mercer Springs Road, Princeton, WV daldeman@fs.fed.us ; Phone: (v); (fax)

2 Abstract During the past 50 years, the composition and structure of eastern hardwood forests have been influenced through harvest site selection based on relative species value and selective harvesting of larger diameter trees. In recent years, new markets for hardwood roundwood have emerged possibly changing the type of timber removed. One state in which harvesting practices may have changed is West Virginia, where new industries have created additional roundwood markets. To determine the impact of new and traditional markets on timber removals and residual-stand attributes, we examined roundwood harvests on 28 sites in West Virginia during The composition of the sample sites generally was not statistically different from overall composition within the state except for yellow-poplar and chestnut oak. More than 21% of the basal area (BA) on the sampled sites was yellow-poplar, nearly twice the proportion of this species BA statewide. Removals of yellow-poplar and black cherry were greater than those of red and sugar maple, hickory, and American beech. While the demand for yellow-poplar roundwood by multiple users (sawmills, peeler mills, engineered-wood products plants, and split-rail fencing manufacturers) seems to influence harvest site selection, the continuation of diameter-limit cutting and value seems to have the greatest affect on which trees are removed. This pattern of partial harvests favors the regeneration of shade-tolerant species such as red and sugar maple. Key words Hardwood markets, forest composition, harvesting, yellow-poplar 24

3 Introduction Harvesting has influenced the composition and structure of eastern hardwood forests though overstory removal and by perturbing regeneration processes (Carvell 1986). In turn, relative species prices influence which stands are harvested and the criteria (e.g., for timber management or diameter-limit cutting) used to determine which trees are removed. Currently, there are large differences in the price of different hardwood species. Black cherry (Prunus serotina) and sugar maple (Acer saccharum) are higher value species while American beech (Fagus grandifolia) is of low value (Hardwood Mark. Rep ). In addition, there has been increased demand for engineered wood products manufactured from low-density hardwoods (Schuler and Adair 2003; Schuler et al. 2001). Understanding the impact of current markets on harvest site and tree selection will provide insight into the composition and structure of future stands West Virginia is one state in which roundwood markets have changed. By 1997, the state s sawmilling industry was dominated by large mills producing more than 5 million board feet per year. In addition, there were oriented strand board (OSB) mills and two peeler mills (WV, Bureau of Commer. 1997). To determine the impact of these multiple markets on timber removals and residual-stand attributes, we examined 28 harvest sites in West Virginia during With these data we examined the attributes of sites selected for harvesting and the characteristics of trees removed from these sites. Markets for West Virginia Hardwoods The value of individual hardwood species varies considerably and has changed over time. The existence of markets also influences the value of specific portions of the tree (butt log, upper logs, limbs, etc.) that can be merchandized profitably. Therefore, it is useful to examine the markets and value for the 10 most important species (focus species) in West Virginia 1 (Tables 1-2). Yellow-poplar (Liriodendron tulipifera) roundwood is used by several industries in West Virginia. Butt logs are processed by sawmills, smaller diameter logs are peeled for plywood or laminated veneer lumber, or processed into fence rails, and low-grade roundwood is consumed by oriented strand board (OSB) mills. In 2001, yellow-poplar lumber was of relatively low value (Hardwood Mark. Rep. 2001). Chestnut oak (Quercus prinus) roundwood is converted into sawlogs and pulpwood. The price of chestnut oak lumber and white oak (Q. alba) lumber usually is the same yet the grade yield from chestnut oak logs is poorer than from white oak logs (Hanks et al. 1980). Chestnut oak can be interchanged for white oak, though the export markets prefer true white oak. There have been periods in which white oaks were considered a higher value species, but white oak were a midvalued species in 2001 (Hardwood Mark. Rep. 2001). 1 Based on growing-stock volume (USDA For. Ser. 2004). In 2000, these species comprised 75% of the growingstock volume for all species and 79% of the growing-stock volume for hardwoods. 25

4 Table 1 -- Proportional basal area, average diameter, and percent of grades 1 and 2 hardwood trees in West Virginia compared to trees on sampled sites. Focus Proportion of all Diameter of live Proportion of species live trees greater trees greater than sawtimber in than 5 inches 5 inches grades 1 and 2 1 Statewide 2 Sites Statewide 2 Sites Statewide 2 Sites ---Percent Inches-- ---Percent--- Yellow-poplar Chestnut oak Red maple White oak Northern red oak Sugar maple Hickory American beech Black oak Black cherry All trees NA NA Weighted by basal area. 2 See USDA For. Ser. (2004). 3 Significantly different from state average as developed from USDA For. Serv at 0.1 probability level for two-tailed test. 4 Significantly different from state average as developed from USDA For. Serv at 0.5 probability level for two-tailed test. Table 2 Number of sites harvested by harvesting criteria and average change in basal area, average number of markets, and average number of low-grade markets associated with these sites. Harvest Number Average percentage Average criteria of sites removal of basal number area of markets 1 Diameter-limit cutting 2 Unspecified Managed Clearcut Includes sawlogs, peeler logs, tie logs, low-grade sawlogs, fence materials, pulpwood, OSB roundwood, alloy chips, and firewood. 2 Includes one site that was an apparent 18-inch diameter-limit cut. 26

5 Red maple (A. rubrum) timber is used for lumber production, but this species also has limited use in OSB, pulp, and fence rail production. In the lumber market, red maple is sold as soft maple. In 2001, soft maple was an emerging species in the lumber market having crossed the threshold from a low-value to a mid-value species in the late 1990s. Northern red oak (Q. rubra) is processed into sawlogs, veneer logs, and pulpwood. Red oak has emerged as a high-value species over the last 25 years. The high-value and the lack of regeneration of this species has resulted in cut exceeding growth during the 1989 to 2000 survey cycle (USDA For. Ser. 2004). Black oak (Q. velutina) is sold as red oak and is virtually identical to northern red oak when sawn into lumber. Sugar maple is processed into sawlogs, veneer logs, and pulpwood. Hard maple became increasingly valuable in the 1990s and was a high-value species by Hickory species (Carya spp.) are used in the production of lumber and paper, but the high density of hickory makes it difficult to process in modern band mills. The value of hickories has increased in recent years despite highly variable wood characteristics, (e.g. color, grain consistency, and bird peck). American beech can be processed into lumber and pulpwood but its historic low-value and poor grade have resulted in an large growth-to-removal ratio (USDA For. Ser. 2004). Black cherry is a traditional high-value species in the production of lumber and veneer. In recent years black cherry has surpassed black walnut (Juglans nigra) as the most expensive species in the U.S. lumber market. Data Collection Selection of the 30 harvest sites examined was based on the distribution of primary wood processors in West Virginia. Since the state has three of the USDA Forest Service s Forest Inventory and Analysis Survey Units that differ in species composition, we stratified the sample based on the proportion of sawtimber volume in these regions. Thus of the 30 sites, 12 should be in the Northeastern Unit, 10 in the Southern Unit, and 8 in the Northwestern Unit. To ensure that all potential roundwood markets were represented in each unit, the population of purchasing mills was stratified by product and mill size. Data on mill size were provided by the West Virginia Division of Forestry. We focused on larger mills because small and part-time mills have limited markets and in West Virginia tend to purchase logs rather than stumpage. The final sample was constrained by the number of willing participants and contained 13 sites in the Northeastern Unit, 9 in the Southern Unit, and 8 in the Northwestern Unit. One site in the latter unit was excluded from the analysis because entrance restrictions prevented a full post harvest observation. A second site also was excluded because it was a pine pulpwood harvest. On each harvest site, five standard 1/5-acre plots were selected randomly from a grid drawn from the area expected to be harvested and merchandized the next day. Before harvest, the diameter and height of all trees equal to or greater than 5 inches in diameter at breast height (DBH) were measured and current and potential future tree grades were determined. Trees that did not meet criteria for grades 1, 2, or 3 were classified as grade 4. Loggers were questioned as to the harvesting criteria they used (management plan, diameter-limit, etc.) as well as the number of 27

6 markets they used in merchandizing timber. Each plot was revisited immediately after harvest to classify trees as harvested, not harvested, or destroyed during harvest. Because it was difficult to estimate cubic volume for all species without detailed information on cull portions of the trees, we examined the surveyed sites in terms of BA. Characteristics of Sites Harvested In Table 1, the composition, diameter, and quality characteristics of growing-stock trees measured on the sample plots are compared to estimates for these characteristics for the entire state as developed for the 2000 forest inventory (USDA For. Ser. 2004). In general, the composition of the sites was not statistically different from the overall composition for West Virginia except for yellow-poplar and chestnut oak. More than 21% of the BA on the sampled sites was yellow-poplar, or nearly twice the proportion of this species BA statewide (11.2%). 2 By contrast, only 4.6% of the BA on the sample sites was chestnut oak, or less than half of the proportion statewide (10.2%). The relative volume of yellow-poplar on the survey sites apparently is the result of multiple markets for this species. Peeler logs and OSB logs were merchandized on 82% and 79% of the sites, respectively. The relatively low proportion of chestnut oak on these sites may reflect its tendency to grow on dry upland sites that are not sought out by industry (Burns and Honkala 1990) and the relatively low lumber yield for this species. The average diameter of growing-stock trees on the sample sites was greater than the average diameter of all similar trees reported in the 2000 West Virginia inventory (Table 1). However, there was some variation to this finding when examining individual species. The shadeintolerant and mid-tolerant species, including yellow-poplar, the oaks, and black cherry were larger in diameter on the sample sites than reported in the 2000 statewide inventory. By contrast, the average diameters of red and sugar maple were similar to the statewide averages. American beech was the only shade-tolerant species whose diameter was greater on the sample sites than in the state inventory. To compare the relative quality of timber measured on the sample sites to that of timber throughout West Virginia, we compared the proportional BA of sawtimber size trees for tree grades 1 and 2. Although the proportion of all trees of these grades was higher on the sample sites than for the state, yellow-poplar was the only species that had a statistically significant higher proportion. The quality of chestnut oak measured on the sites was significantly lower than the average for West Virginia. The shade-tolerant species generally had the lowest proportion of BA in tree grades 1 and 2. For red and sugar maple, part of this reduced grade is associated with smaller diameter trees. However, American beech had the lowest percentage of grades 1 and 2 trees compared to other species tallied on the sample sites. 2 Because the average estimates of BA were developed from estimates of number of trees of various diameters, it is impossible to develop an accurate variance estimate for BA. Thus, we treat this estimate as a constant in our analysis. 28

7 Harvesting and Basal Area Removed The harvesting criteria used, BA removed, and average number of markets for the 28 sites examined are presented in Table 2. Diameter-limit cutting (DLC) was the most commonly observed harvesting method. However, the data indicated several instances in which largediameter beech were left uncut even though they exceeded the target diameter-limit and several instances in which black cherry and sugar maple were cut even though they did not meet the target diameter-limit. The use of DLC is motivated by operational efficiency and profitability goals of sawmills and logging operations. Hardwood lumber grades are based on long, wide, clear board sections (Smith 1967), that usually result from large-diameter timber. Larger diameter logs also require less sawing time per board foot of lumber produced (Rast 1974). Loggers are paid for volume of timber produced and can make more money by cutting larger trees. These economic realities will continue to dictate residual-stand attributes so long as there is no incentive to change. Loggers at six sites did not specify logging criteria but a combination DLC and cutting for value apparently was used. The five stands that were cut with a stated management criteria had lower BA removed, but we could not determine whether this lower removal rate was significant because of the limited number of observations. We expected that an increase in the number of markets would increase the frequency of managed cuts or clearcut, but no such trend was discerned. In Table 3 the number of sites on which specific focus species were found is listed and the average percentage of BA harvested of focus species is compared to the average BA of all trees removed from those sites. The oaks and other mid-tolerant or shade-intolerant species generally were harvested at greater levels, but only yellow-poplar and black cherry had significantly higher removal rates (Table 3). Because shade-intolerant and mid-tolerant species tend to be larger in diameter, a greater volume of these species usually would be removed by DLC. The relatively high BA of yellow-polar harvested appears to be the result of multiple markets for this species. This high rate of cherry harvest is consistent with the higher value, quality, and yield of that species. By contrast, the maples, American beech, and hickory were harvested at significantly lower levels. Both DLV and the small average diameter of the maple species on nearly all sites examined contributed to the low BA harvested. The average diameter of the American beech tallied on the survey sites was fairly large, but the proportional BA of beech removed was small. Hickory species were the least harvested with less than 3% of the BA removed on 13 sites containing these hickories. The diameter of the hickory species was only slightly greater than that of the maples. The relatively high volume of small-diameter hickory on the measured sites was one factor that influenced the low volume of these species harvested (Table 3). Also, hickory is difficult to process due to its high specific gravity. Mills that process this species are mid-size and small circle mills that may not have been adequately accounted for in the survey due to our focus on larger operations. 29

8 Table 3-- Number of sites where focus species were found, average basal (BA) area cut of focus species versus all species on sites containing focus species, and average diameter of focus species versus all trees on sites containing focus species. Focus Number Average BS cut of: Average DBH of trees of: species of sites where Focus Sites Focus Sites focus species species containing species containing were found 1 focus species focus species Number percent inches Yellow-poplar Chestnut oak Red maple White oak Nor. red oak Sugar maple Hickory Beech Black oak Black cherry On sites where focus species accounted for at least 5% of total basal area. 2 Significantly different from site average at 0.1 probability level for a t-test: paired two sample for means. 3 Significantly different from site average at 0.05 probability level for a t-test: paired two sample for means. 4 Significantly different from site average at 0.01 probability level for a t-test: paired two sample for means. Conclusion Our objective was to determine how multiple markets influence the selection of harvest sites and the characteristics of trees removed from these sites. The results of our study were mixed. Although the addition of multiple markets for yellow-poplar roundwood seems to have influenced site selection and the removal of this species, the continued dominance of DLC and/or a combination of DLC and value cutting seem to dominate the type of timber harvested. This resulting pattern of partial harvests will continue to favor the regeneration of shade-tolerant species such as red and sugar maple. 30

9 Literature Cited Burns, R.M. and B.H. Honkala Silvics of North America, Vol. 2, Hardwoods. Washington DC: USDA Forest Service Agriculture Handbook Carvell, K.L Effect of past history on present stand composition and condition. In: Smith, H.C. and M.C. Eyer, eds. Guidelines for managing immature Appalachian hardwood stands: workshop proceedings. May 28-30, Morgantown WV. SAF Publ West Virginia University Books, Morgantown, WV. p. 1-7 Hanks, L.F., G.L. Gammon, R.L. Brisbin, and E.D. Rast Hardwood log grades and lumber grade yields for factory lumber logs. For. Ser. Res. Pap. NE-468. USDA For. Serv., Northeast For. Exp. Stn. Broomall, PA 92 p. Hardwood Market Report to H. Jones (ed). Memphis, TN. Rast, E. D Log and tree sawing times for hardwood mills. For. Serv. Res. Pap. NE-304. Northeastern For. Exp. Stn. Upper Darby, PA: 10 p. Schuler, A, and C. Adair Demographics, the housing market, and demand for building materials. Forest Prod. J. 53(5):9-17. Schuler, A, C. Adair, and E. Elias Engineered lumber products, taking their place in the global market. Journal of For. 99(12): Smith, W.R Simplified guidelines to hardwood lumber grading. USDA Forest Serv., Southeastern For Exp. Stn. Asheville, NC. 26 p. USDA Forest Service Forest inventory mapmaker Version 1.0 USDA Forest Service, North Central Res. Stn., St. Paul, MN. West Virginia Bur. of Comm The forest industry of West Virginia. Division of Forestry, WV Bur of Comm. Charleston, WV. 75 p. 31