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PLEASE NOTE: Publications listed in this catalog are available for viewing, printing, and downloading from this site. Just click on the "View and Print this Publication Now" link under the abstract. Please send e-mail to rdm@srs.fs.usda.gov if you have any problems viewing or printing these publications.
The seven publications that are published by the Southern Research Station are also available in hard copy through the mail. To order Station publications in hard copy, print the Publications Order Form that is at the "Order This Publication" link. You may request more than one title per form, up to two copies of the same title. The number at the beginning of the citation is the number to circle on the form; i.e., to order: Rosson, James F., Jr. 2001. "Forest Resources of Mississippi, 1994" you would circle "21".
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Swimming with the Fishes The spotted bass swims toward the creamy colored object to score a quick bite. At the last second, he realizes he’s fallen for the bait. As the fish turns, the deceptive mussel releases her larvae; the cloudy mass of parasites attaches to the gills of the retreating bass. After a few weeks, freshwater mussels emerge and return to their free-living, filter-feeding lifestyle. Wendell R. Haag and Melvin L. Warren, Jr., Southern Research Station scientists in Oxford, MS, found that Villosa nebulosa and V. vibex, which live in upland streams in Alabama’s Mobile Basin and in Georgia, Mississippi, and Tennessee, use similar methods to facilitate transmittal of their larvae to fish. But V. nebulosa, with a pale to white mantle, releases primarily at night. V. vibex displays her inky–black to rusty–orange mantle primarily during daylight hours. Both mussels will release larvae in the presence of host and non-host fish, though V. vibex demonstrates more discretion. V. vibex further attempts to ensure transfer of her larvae by releasing large numbers only when physical contact with a host fish is possible. Haag and Warren report field and laboratory results in Effects of Light and Presence of Fish on Lure Display and Larval Release Behaviours in Two Species of Freshwater Mussels. The displayed mantle margins of V. nebulosa and V. vibex strongly resemble small fish, caterpillars, or large aquatic insect larvae, all major favorites of bass. The authors state that having bass and sunfish as host fish contributes significantly to Villosa species distribution, abundance, and speciation. In Dynamics in Species Composition of Stream Fish Assemblages: Environmental Variability and Nested Subsets, co-authors Christopher M. Taylor, Mississippi State University, and Mel Warren examine how species migration and abundance relate to extinction rates. Taylor, an assistant professor in the Department of Biological Sciences, and Warren sampled 30 species of fish in 9 stream sites in the Alum Fork of the Saline River system and 3 sites in the Little Glazypeau Creek of the Ouachita River over a two-year period. Strongly folded, uplifted sedimentary rock and pine-oak upland forest characterize both river systems. The authors used seasonal matrices rather than the traditional, "snapshot" spatial matrices assembled across sites. Taylor and Warren found that nestedness increased with an increasing extinction rate and decreased with an increasing immigration rate. Further, at high extinction rates, an increase in nestedness was less likely to occur by chance. Taylor and Warren’s study demonstrates the importance of maintaining natural flow regimes. Road culverts and poor watershed management practices may influence local immigration and extinction, affecting distribution and abundance of fish species. The authors conclude by saying, "If our results represent general ecological phenomena, it may be possible to better understand and predict the community-level effects of disturbance (such as fragmentation) in a variety of systems."
Assessing Effects of Climate Change Events on Earth startle us daily. If we could "put time in a bottle," we might want to reserve a portion to give humans more time to adapt to climate changes. Planet Earth will evolve, but how fast can humans modify lifestyles and political and economic structures? Climate and land use primarily control biological diversity, and what happens to forests includes the big landscape picture with an internal focus not always recognized for its overarching significance. In U.S. National Climate Change Assessment on Forest Ecosystems: An Introduction, Steven G. McNulty, Southern Research Station, and John D. Aber, University of New Hampshire, state that " . . . ecosystems are complex communities and current models only associate biodiversity with existing environmental conditions. If climate change occurs faster than new ecosystem structure and function can be developed, then the historical relationships between plant, animal, and climatic conditions may not be reestablished and biological diversity will be reduced." The Southern Appalachians—and the world—could well lose its tiny salamanders, one species that marks the area’s rich biodiversity. Add the anticipated natural disturbances of fire, drought, introduced species, insect and pathogen outbreaks, hurricanes, windstorms, and ice storm. Now we enter an arena where little research has been done—interactions of climate and disturbance. Climate change will probably shift forest ecosystem distribution across much of the Nation. During climate transition, forests may be more predisposed to other disturbance factors, such as insect and disease outbreaks. The amount of forest area burned may increase by 25 to 50 percent as increased forest productivity initially builds fuel loads and subsequent droughts fuel fire occurrence. Mandated by the 1990 Global Change Research Act, the U.S. Global Change Research Change Program published the first National Assessment of the Potential Consequences of Climate Variability and Change (visit http://www.usgcrp.gov/) arlier this year. The assessment addresses water resources and availability, agriculture and food production, human health, coastal areas, and forests. These sectors represent important or politically sensitive United States resources that could be adversely affected by climate change. The September 2001 issue of BioScience focuses on a summary of research findings from the forest sector and regional findings of the 2001 national assessment. The impacts of climate change on the forest sector are divided into four categories: (1) forest processes, (2) biodiversity change, (3) disturbance interactions, and (4) socioeconomic change. These categories represent key interactions between a changing climate, forest structure or function, and human interactions with forests. The Southern Global Change Program in Raleigh, NC, led by Steve McNulty, sponsored the research published in BioScience.
On the Bookshelf The Red-Cockaded Woodpecker: A Resilient Bird in a Tough Spot In The Red-cockaded Woodpecker—Surviving in a Fire-maintained Ecosystem, Richard N. Conner, D. Craig Rudolph, and Jeffrey R. Walters present the complex situation of the endangered species perhaps best known in the Southeastern United States. This small woodpecker needs an old-growth pine ecosystem to survive. Many private, industrial, State, and Federal landowners struggle to balance uses and maintain habitat. Conversion of forests to agricultural uses and commercial development consumes vast amounts of land daily. The authors discuss the bird’s history, its relationship with prey and predators, management options, and its uncertain future. Conner, wildlife biologist, and Rudolph, ecologist, conduct research with the Southern Station’s Integrated Management of Wildlife Habitat and Timber Resources research unit, Nacogdoches, Tx. Walters is Bailey Professor of Biology at Virginia Tech in Blacksburg. To purchase a copy of The Red-cockaded Woodpecker—Surviving in a Fire-maintained Ecosystem, visit the University of Texas Press online at http://www.utexas.edu/utpress or send your request to University of Texas Press, P.O. Box 7819, Austin, TX 78713-7819. The hardcover book costs $60, plus shipping. For a quick read about the strong parenting behaviors red-cockaded woodpeckers demonstrate, check out the publication listed below. Conner and Rudolph team up with Richard R. Schaefer and Daniel Saenz, also with the Southern Station’s Nacogdoches research unit, and James R. McCormick, Stephen F. Austin State University, Nacogdoches.
Natural Lands Dynamic: Place, Population, Economics, Recreation, and the American Experience Footprints on the Land: An Assessment of Demographic Trends and the Future of Natural Resources in the United States examines the changes occurring between us and our natural resources. Ken Cordell, project leader for the Assessing Trends, Values, and Rural Community Benefits from Outdoor Recreation and Wilderness in Forest Ecosystems unit in Athens, GA, and Christine Overdevest, social scientist in Cordell’s unit, edited this Sagamore Publishing book. Footprints on the Land: An Assessment of Demographic Trends and the Future of Natural Resources in the United States addresses the dynamics of place and how socioeconomic trends intersect with natural land and water, public or private. To purchase a copy for $38.95, contact Sagamore Publishing at 800-327-5557 or http://www.sagamorepub.com. Measured Impacts of Forest Roads Hermann Gucinski, Southern Station assistant director for Integrated Assessments, co-edited Forest Roads: A Synthesis of Scientific Information. Published by the Pacific Northwest Research Station, Portland, OR, as General Technical Report 509, this publication examines the multiple effects of roads. Co-editors Gucinski, Michael J. Furniss, Robert R. Ziemer, and Martha H. Brookes address physical and ecological effects, such as geomorphic and hydrological; indirect and landscape level changes, including aquatic habitat, terrestrial vertebrates, and biodiversity conservation; and socioeconomic changes, ranging from passive-use value, economic effects on development, and range management) Forest Roads: A Synthesis of Scientific Information recognizes that road effects take place in the contexts of environmental settings, their history, and the state of engineering practices, and must be evaluated in those contexts for best management approaches. Southern Station scientists Michael Bowker, Don English, and Ken Cordell, Athens, GA, contributed to the chapter on resource-based outdoor recreation. Jennifer Knoepp and Lloyd Swift, Coweeta Hydrologic Laboratory, Otto, NC, provided expertise about geomorphologic and hydrologic effects. Knoepp wrote chapters on habitat, habitat fragmentation, aquatic habitat, road kill, predation, and water quality. Gucinski contributed research on biological invasions, forest inventory and monitoring, and Forest Service roadless areas while managing the Ecosystem Processes Research Program, Pacific Northwest Station, Corvallis, OR. To request a copy of Forest Roads: A Synthesis of Scientific Information, write to Publications Distribution, Pacific Northwest Station, P.O. Box 3890, Portland, OR 97208-3890. You can e-mail desmith@fs.fed.us or call (503) 808-2138 to ask for a copy. To print or download this publication, log on to http://www.fs.fed.us/pnw/. Station News Dan Schmoldt has traded in his Forest Service uniform to work for the Cooperative State, Research, Education, and Extension Service in Washington, DC. Though stationed in Madison, WI, Dan was connected to the Integrated Life Cycle of Wood: Tree Quality, Processing, and Recycling research unit. Phil Araman leads this Blacksburg, VA project. Several selections of related research appear in this issue of Compass.
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Southern Pines Research
Conner, Richard N.; McCormick, James M.; Schaefer, Richard R.; and others. 2001. A red-cockaded woodpecker group with two simultaneous nest trees. Wilson Bulletin. 113(1): 101-104.
During a study of red-cockaded woodpecker (Picoides borealis) nesting in eastern Texas, we discovered a single breeding pair of woodpeckers with two simultaneous nests in nest trees that were 24 m apart. Incubation of eggs in each nest tree was at least 13 d and may have been as long as 16 d. The breeding male incubated and fed a nestling in one nest tree, and the breeding female incubated and fed a nestling in the other nest tree until the nestlings were ³24 d old. Prior to fledging, both the breeding male and female were observed feeding both nestlings in both nest trees. The pair successfully fledged the two nestlings, a single fledging from each nest tree, during one nesting cycle. After the nestlings were fledged, both the male and female woodpeckers were observed feeding both fledglings about 350 m from the pair of nest trees. Our observations indicate that there are exceptions to the current theory that the contribution by the breeding male and female to incubation and feeding of nestlings is essential and that neither the male nor the female can normally rear young birds without the contribution of the other.
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Haywood, James D.; Harris, Finis L.; Grelen, Harold E.; Pearson, Henry A. 2001. Vegetative response to 37 years of seasonal burning on a Louisiana longleaf pine site. Southern Journal of Applied Forestry. 25(3): 122-130.
From1962 through 1998, 20 prescribed bums were applied in a natural stand of longleaf pine (Pinus palustris Mill.) to determine the effects of various fire regimes on the forest plant community. The original longleaf seedlings regenerated from the 1955 seed crop and were growing in a grass-dominated cover when the study began. By 1999, prescribed burning in March and May resulted in a significantly greater stocking of longleaf pine (203 trees/ac) than on the unburned and July-burned treatments (72 trees/ac) (a = 0.05). Fire arrested the growth of natural loblolly pine (P. taeda L.) and hardwoods, but loblolly pines and hardwoods of at least 4 in. d.b.h. added 70 ft2/ac of basal area on the unburned plots. Thus, total woody basal area was significantly greater on the unburned (117 ft2/ac) and May-burned (132 ft2/ac) treatments than on the July-burned treatment (66 ft2/ac); basal area was intermediate on the March- burned treatment (97 ft2ac). Pine volume was 4,315; 2, 870; 2,652; and 1,970 ft3 inside-bark/ac on the May-burned, March-burned, unburned, and July-burned treatments, respectively, but these differences were not statistically significant (P = 0.06). There were only 11 lb/ac of herbaceous plants on the unburned plots. Herbaceous plants averaged 993 lb/ac on the three burned treatments, with pinehill bluestem (Schizachyrium scoparium var. divergens [Hack] Gould) being the most common herbaceous plant. We believe the chief influence of burning in this natural longleaf pine forest was not on pine yield but how fires influenced overall stand structure and species composition.
Loeb, Susan C.; Chapman Gregg L.; Ridley, Theodore R. 2001. Sampling small mammals in southeastern forests: the importance of trapping in trees. Proceedings of the annual conference of the Southeastern Association of Fish and Wildlife Agencies. 53: 415-424.
Because estimates of small mammal species richness and diversity are strongly influenced by sampling methodology, 2 or more trap types are often used in studies of small mammal communities. However, in most cases, all traps are placed at ground level. In contrast, we used Sherman live traps placed at 1.5 m in trees in addition to Sherman live traps and Mosby box traps placed on the ground to sample small mammals in pine stands in the Upper Coastal Plain of South Carolina. To determine the importance of placing traps in trees, we compared estimates of small mammal (primarily rodent) species richness and diversity based on data from all traps (ground and tree) with estimates based on data from ground traps only. Estimates of species richness based on data from ground traps only did not differ from estimates based on data from all traps. However, 4 other diversity indices (Simpson Index, Shannon-Wiener Index, Shannon Evenness Index, and Brillouin Index) based on data from both tree and ground traps were significantly greater than indices based on data from ground traps only. The increase in the diversity estimates when data from all traps were used was primarily due to the large number of southern flying squirrels (Glaucomys volans) captured in tree traps. When data from ground traps only were considered, the community was highly dominated by cotton mice (Peromyscus gossypinus), but, when data from all traps were considered, cotton mice and southern flying squirrels were co-dominant (567 and 580 individuals, respectively). Our data suggest that studies of forest small mammal communities which do not include tree traps are biased because one of the most common and potentially important species, the southern flying squirrel, is highly underrepresented. We recommend that future studies of forest mammal communities, particularly those designed to test the effects of forest management practices on small mammal communities, include arboreal traps.
Strom, B.L.; Goyer, R.A.; Shea, P.J. 2001. Visual and olfactory disruption of orientation by the western pine beetle to attractant-baited traps. Entomologia Experimentalis et Applicata. 100: 63-67.
Olfactory deterrents have been proposed as tree protectants against attack by bark beetles, but their development has been hindered by a lack of knowledge of host selection behavior. Among the primary tree-killing (aggressive) Dendroctonus, vision appears to be an integral part of the host selection process. We evaluated the importance of vision in host finding by D. brevicomis LeConte, and our ability to affect it by modifying the visual stimulus provided by attractant-baited multiple-funnel traps. White-painted traps caught ~42 percent fewer D. brevicomis than black traps in California, USA (P < 0.05). Visual treatments were less effective (P < 0.0001) than olfactory disruptants (verbenone with ipsdienol), which reduced catch by about 78 percent. When combined, olfactory and visual disruptants resulted in ~89 percent fewer D. brevicomis being caught, but this combination was not more effective than olfactory disruptants alone (P > 0.05). Our results demonstrate that the visual component of D. brevicomis host finding behavior can be manipulated, but that D. brevicomis may be more affected by olfactory than visual disruptants. In contrast, visual disruption is more pronounced in the southern pine beetle, Dendroctonus frontalis Zimmermann, suggesting that non-insecticidal tree protection strategies for these related species should differ.
Wetlands, Bottomland Hardwoods, and Streams Research
Devall, Margaret; Schiff, Nathan; Boyette, Douglas. 2001. Ecology and reproductive biology of the endangered pondberry, Lindera melissifolia (Walt) Blume. Natural Areas Journal. 21:250-258.
Lindera melissifolia [Walt] Blume (pondberry) is an endangered woody plant that grows in seasonally flooded wetlands and on the edges of sinks and ponds in six States of the Southern United States: Arkansas, Georgia, Mississippi, Missouri, North Carolina, and South Carolina. It is a stoloniferous, clonal shrub up to 2 m in height and is dioecious, with small yellow flowers that bloom in spring. Information on its ecology and reproductive biology is sparse. The species has been affected by habitat destruction and alteration, especially timber cutting, clearing of land, and drainage or flooding of wetlands. Stem dieback was noted in populations in five States, but populations monitored for three years do not appear to be declining. Three fungal pathogens were isolated from stems. Flowers covered with mesh bags produced no fruit, and flowers that received supplemental pollination did not set more fruit than open-pollinated flowers. Seed production was erratic in populations in Mississippi and Arkansas, and no seedlings were noted even after seed production was high. Individual ramets can be easily transplanted and multiply rapidly. Successful dispersal is very limited now due to restrictive land use in areas surrounding pondberry populations and to changes in hydrology. Introduction of plants to new areas may be necessary if the species is to recover.
Gardiner, Emile S.; Krauss, Ken W. 2001. Photosynthetic light response of flooded cherrybark oak (Quercus pagoda) seedlings grown in two light regimes. Tree Physiology. 21: 1103-1111.
Two-year-old cherrybark oak (Quercus pagoda Raf.) seedlings raised in full or partial (27 percent) sunlight were flooded for 30 days to study the effects of light availability and root inundation on photosynthetic light response. Compared with seedlings receiving full sunlight, seedlings receiving partial sunlight developed leaves with 90 percent greater blade area, 26 percent less mass per unit volume, and 35 percent lower nitrogen (N) concentration per unit area, leading to a 15 percent reduction in leaf photosynthetic capacity when carbon exchange rates were based on blade area. However, when carbon exchange rates were based on leaf mass, leaves acclimated to partial sunlight exhibited a 15 percent greater photosynthetic capacity realized primarily through an increased initial slope of the photosynthetic light response (A/PPFD) curve and increased net photosynthesis at leaf saturation (Amax). Short-term flooding increased leaf mass per unit area more than 19 percent, reduced foliar N concentrations per unit dry mass by 19 percent, and initiated reductions in Amax and apparent quantum yield (F) of seedlings in both light regimes. Greatest impairment of Amax (56 percent area basis, 65 percent mass basis) and F (40 percent) were observed in leaves receiving full sunlight, and the declines were concomitant with a 35 percent decrease in chlorophyll concentration. Flooding also depressed instantaneous photosynthetic N-use efficiency (PPNUE) such that Amax decreased 54 percent, and the initial slope of PPNUE/PPFD curves decreased 33 and 50 percent for leaves acclimated to partial and full sunlight, respectively. The A/PPFD patterns indicated that the magnitude of flood-induced inhibition of the photosynthetic mechanism of cherrybark oak seedlings is determined partly by the light environment.
Gardiner, Emile S.; Schweitzer, Callie J.; Stanturf, John A. 2001. Photosynthesis of Nuttal oak (Quercus nuttallii Palm.) seedlings interplanted beneath an eastern cottonwood (Populus deltoides Bartr. Ex Marsh.) nurse crop. 2001. Forest Ecology and Management. 149: 283-294.
An afforestation system which utilizes the pioneer species eastern cottonwood (Populus deltoides Bartr. ex Marsh.) as a nurse for slower growing, disturbance-dependent species is under evaluation as a forest rehabilitation tool on former agricultural land in the Lower Mississippi River Alluvial Valley, USA. The primary objectives of this study were to quantify understory light availability in the eastern cottonwood plantation, and describe the photosynthetic light response of interplanted Nuttall oak (Quercus nuttallii Palm.) seedlings. Photosynthetic photon flux density (PPFD) measured in the understory of a 3-year-old cottonwood plantation was 43 percent of full sunlight, and was sufficient to meet leaf saturation requirements over 29 percent of the diurnal cycle. Oak seedlings established in the cottonwood understory showed no change in blade area, and minimal shifts (<19 percent) in dry mass per unit area relative to open grown seedlings. A 19 percent decrease in dark respiration rate (Rd) was measured on a leaf area basis; but gross photosynthesis (Pg–sat), net photosynthesis (Pn–sat), quantum yield (Q), light compensation point (LCP), and the saturation constant (K) of Nuttall oak leaves were not influenced by the presence of the cottonwood canopy, regardless of leaf area, mass, or N content. (Pn–sat) was strongly determined by foliar N concentration of seedlings in understory and open environments, increasing 1.2 µmol m-2 s-1 for each 0.1 percent increase in N concentration. Our data indicate that Nuttall oak seedlings established beneath an eastern cottonwood canopy developed leaves with a capacity for carbon assimilation similar to open-grown plants. However, carbon assimilation by Nuttall oak may be sub-optimal on degraded sites where intensive row cropping has depleted soil N.
Haag, Wendell R.; Warren, Melvin L., Jr. 2000. Effects of light and presence of fish on lure display and larval release behaviours in two species of freshwater mussels. Animal Behaviour. 60: 879-886.
We investigated how two sympatric species of freshwater mussels transmit their parasitic larvae to fish hosts. We found that Villosa nebulosa and V. vibex both display large mantle lures to attract potential host fish, but V. nebulosa displayed only at night and V. vibex displayed mostly by day. Display periods were similar in the laboratory and in the field. In two laboratory experiments, we found that the frequency of lure display in both mussel species was unrelated to the presence of fish or to the species of fish present. However, both species released more larvae in the presence of a suitable host fish (Micropterus spp.) and a nonhost species (Cyprinella camura) than in the absence of fish. In all treatments, females released low numbers of larvae on a daily basis throughout the experiment. We also observed several, irregularly occurring major release events in which numbers of larvae released were from one to three orders of magnitude larger than minor, daily releases. In V. nebulosa, major releases occurred with suitable and nonsuitable host species; in V. vibex major releases occurred mostly with suitable host species. In an additional laboratory experiment, we found that V. vibex released large numbers of larvae only when the host fish was able to make physical contact with the mussel. Few larvae were released when no fish were present or when host fish were present but physical access to the mussel was restricted. These results show that, in mussel species that display lures, physical interaction with a fish is necessary to stimulate large releases of larvae and suggest that interactions with a suitable host species stimulate larger and more frequent releases than with nonhosts.
9 Hamel, Paul B.; Foti, Thomas L., tech. eds. 2001. Bottomland hardwoods of the Mississippi Alluvial Valley: characteristics and management of natural function, structure, and composition. 1995 October 28. Fayetteville, AR. Gen. Tech. Rep. SRS-42. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 109 p.
A symposium entitled "Bottomland Hardwoods of the Mississippi Alluvial Valley: Characteristics and Management of Natural Function, Structure, and Composition" convened on October 28, 1995, as part of the Natural Areas Conference, October 25-28, 1995 in Fayetteville, AR. The symposium’s goal was to provide information that managers need to begin restoring the composition, structure, and function of forest ecosystems in the Mississippi Alluvial Valley (MAV). Included in the proceedings from that symposium are 8 of 13 presentations. These peer-reviewed contributions address historical conditions of forests in the MAV (two papers), historical changes that are reflected in today’s forests (one paper), the effect of historic and prehistoric rainfall patterns (one paper), forest fauna in the region (two papers), the effect of herbivory on forest vegetation (one paper), and management of bottomland hardwood forests for multiple outputs (one paper). A ninth paper, concerning characteristics of old-growth forests, is a posthumous submission authored by Dr. James T. Tanner; and the tenth paper was published in another venue. The intended audience of these proceedings includes managers of private, State, and Federal lands, as well as land management planners from a range of jurisdictions.
Meadows, James S.; Burkhardt, E.C. 2001. Epicormic branches affect lumber grade and value in willow oak. Southern Journal of Applied Forestry. 25(3): 136-141.
A case study was conducted in a 50-yr-old bottomland oak stand in central Alabama to investigate the relationship between epicormic branches and lumber grade and value in willow oak (Quercus phellos L.). The stand had been thinned from below 7–10 yr earlier, resulting in a wide variety of epicormic branch conditions on the residual trees. A sample of 41 willow oak trees was selected before the stand was clearcut in late 1991. All merchantable logs in each tree were graded prior to felling. Average d.b.h. of sampled trees was 19.1 inches. Each tree averaged 9.5 epicormic branches on the sawlog portion of the bole. From these 41 trees, a random sample of 57 logs (31 butt logs and 26 upper logs) was shipped to a sawmill where they were sawn into lumber and graded. Epicormic branching had a large detrimental effect on log grade of individual trees. In general, as few as five epicormic branches somewhat evenly distributed on a 16 ft log were enough to cause a reduction in log grade. More importantly, defects caused by epicormic branches had a serious effect on lumber grade, particularly in the higher grades. Over 50 percent of the lumber volume that would have been graded as either first and seconds or select in the absence of epicormic branches was downgraded to no. 1 common or below due to defects caused by epicormic branches. Based on lumber prices prevailing at the time of the study, defects caused by epicormic branches resulted in a 13 percent reduction in the value of the lumber produced in the final harvest.
Sun, Ge; McNulty, Steven G.; Shepard, James P.; and others. 2001. Effects of timber management on the hydrology of wetland forests in the Southern United States. Forest Ecology and Management. 143. 227-236.
The objectives of this paper are to review the hydrologic impacts of various common forest management practices that include harvesting, site preparation, and drainage. Field hydrological data collected during the past 5–10 years from ten forested wetland sites across the Southern United States are synthesized using various methods, including hydrologic simulation models and Geographic Information Systems. Wetland systems evaluated include red river bottoms, black river bottoms, pocosins, wet mineral flats, cypress domes, and pine flatwoods. Hydrologic variables used in this assessment include water table level, drainage, and storm flow on different spatial and temporal scales. Wetland ecosystems have higher water storage capacity and higher evapotranspiration than uplands. Hydrologic impacts of forest management are variable, but generally minor, especially when forest best management practices are adopted. A conceptually generalized model is developed to illustrate the relative magnitude of hydrologic effects of forest management on different types of wetlands in the Southern United States. This model suggests that in addition to soils, wetland types, and management practice options, climate is an important factor in controlling wetland hydrology and the magnitude of disturbance impacts. Bottomland wetlands, partial harvesting, and warm climate usually offer conditions that result in low hydrologic impact.
Taylor, Christopher M.; Warren, Melvin L., Jr. 2001. Dynamics in species composition of stream fish assemblages: environmental variability and nested subsets. Ecology. 82(8): 2320-2330.
Stream landscapes are highly variable in space and time and, like terrestrial landscapes, the resources they contain are patchily distributed. Organisms may disperse among patches to fulfill life-history requirements, but biotic and abiotic factors may limit patch or locality occupancy. Thus, the dynamics of immigration and extinction determine, in part, the local structure of assemblages. We sampled fishes and stream habitat at 12 localities for two years (96 samples) to examine the deterministic nature of immigration and extinction processes in stream fish assemblages. Mean immigration rates for assemblages were highest at large stream localities, where the pool of potential immigrants was largest. Mean extinction rates were highest where variability in the flow regime was high, though local refugia appeared to modify the extinction process at one locality. Significant nested subset patterns in species composition occurred over time for 7 of the 12 localities. The strength of the nesting was associated with mean immigration and extinction rates. Higher extinction rates corresponded to stronger nestedness, whereas higher immigration rates were associated with weaker nestedness. Across all species, both immigration and extinction rates were strongly associated with mean abundance. Species with high local abundances had higher immigration rates and lower extinction rates than did species with low local abundances. There were no significant associations between trophic guild or body size and immigration and extinction rate. This work supports the hypothesis that immigration and extinction rates for assemblages are predictable along environmental gradients, and that species are less prone to local extinction and more prone to colonize areas when they maintain high local abundances. The extinction process in local assemblages can be a highly ordered event leading to strong nested subset patterns, but immigration appears to be more stochastic.
Southern Appalachians Research
Beckage, Brian; Clark, James S.; Clinton, Barton D.; Haines, Bruce L. 2000. A long-term study of tree seedling recruitment in Southern Appalachian forests: the effects of canopy gaps and shrub understories. Canadian Journal of Forest Research. 30: 1617-1631.
We examined the importance of intermediate-sized gaps and a dense shrub layer on tree seedling recruitment in a Southern Appalachian deciduous forest. We created 12 canopy gaps under two contrasting understory conditions: 6 gaps were dominated by the dense, shade-producing shrub, Rhododendron maximum L., while the remaining gaps were relatively open. Density of first-year and >first-year seedlings was monitored for 5 years in transects extending from adjacent undisturbed forest through the experimental gaps. We concurrently measured the understory light environment, soil moisture, litter biomass, and seed rain. Neither species diversity nor richness consistently increased following gap formation. Acer rubrum L. responded consistently to canopy gaps with increased seedling densities while most other species, including both shade-tolerant and shade-intolerant species, did not. Seedling densities were especially low and unresponsive to gap formation in areas dominated by R. maximum. Understory light levels were consistently low beneath R. maximum and did not increase with canopy gap formation. Our results suggest that dense shrub cover can neutralize recruitment opportunities in canopy gaps, that seed rain often limits recruitment in gaps, and that canopy gaps that are larger or include understory disturbance are needed to maintain diversity in these forests.
Greenberg, Cathryn H. 2001. Response of reptile and amphibian communities to canopy gaps created by wind disturbance in the Southern Appalachians. Forest Ecology and Management. 148: 135-144.
Reptile and amphibian communities were sampled in intact gaps created by wind disturbance, salvage-logged gaps, and closed canopy mature forest (controls). Sampling was conducted during June–October in 1997 and 1998 using drift fences with pitfall and funnel traps. Basal area of live trees, shade, leaf litter coverage, and litter depth was highest in controls and lowest in salvaged gaps. Percent cover, length, and diameter of coarse woody debris (CWD) were significantly greater in intact gaps than in salvaged gaps or controls. Coarse woody debris was more decayed and had less bark in controls than gaps. The relative abundance of salamanders and American toads, and species richness and diversity of amphibians did not differ among treatments. In contrast, relative abundance of two lizard species and (marginally) snakes, and species richness and diversity of reptiles was higher in both gap treatments than in controls. Results suggest that higher light in gaps positively influenced reptile abundance, but CWD at the tested levels was not an important determinant of habitat quality. The presence of a partial canopy and other forest features in both gap treatments may have adequately retained the microclimatic conditions required by moisture-sensitive amphibians. Xeric study sites and an associated assemblage of species that are pre-adapted to relatively warm, dry conditions also might partially explain the absence of any significant response by amphibians. In the closed canopy forests of the Southern Appalachians, I suggest that salamanders were historically dominant, whereas many reptile species occurred at low densities and depended upon infrequent natural disturbance to create ephemeral patches of suitable habitat. Further study is required to determine what parameters of disturbance influence reptile and amphibian communities, and how these effects might differ along a moisture gradient and among species.
Sponseller, R.A.; Benfield, E.F. 2001. Influences of land use on leaf breakdown in Southern Appalachian headwater streams: a multiple-scale analysis. Journal of North American Benthological Society. 20(1): 44-59. [Editor’s note: The Evaluation of Watershed Ecosystem Responses to Natural, Management, and Other Human Disturbances research unit provided funding for this research.]
Stream ecosystems can be strongly influenced by land use within watersheds. The extent of this influence may depend on the spatial distribution of developed land and the scale at which it is evaluated. Effects of land-cover patterns on leaf breakdown were studied in 8 Southern Appalachian headwater streams. Using a GIS, land cover was evaluated at several spatial scales, including the watershed, riparian corridor, and subcorridors that extended upstream in 200-m increments for 2 km. Breakdown rate for American sycamore (Plantanus occidentalis) leaf packs varied significantly among sites (k = 0.0051–0.0180/d), but fell within the range reported in the literature for sycamore. Leaf breakdown rate increased at sites with high shredder density and biomass. Further, breakdown rate and shredder density and biomass were positively related to mean substrate particle size. Several instream variables were related to watershed-scale features, but leaf breakdown rate was not related to land cover at the watershed scale. Leaf breakdown rate was inversely related to percent nonforested land within riparian subcorridors of 1 km. Results suggest that the distribution of shredders is critical to leaf processing in these streams. In some streams, increased sediment inputs resulting from agricultural activity or residential development in riparian corridors may limit the distribution of shredders and thus influence leaf breakdown rates. Alternatively, near-stream development may alter the quality of allochthonous inputs to streams, and thus indirectly influence the distribution of shredders and instream processing.
Interior Highlands Research
16 Guldin, James M., comp. 2001. Proceedings of the symposium on Arkansas forests: a conference on the results of the recent forest survey of Arkansas; 1997 May 30–31; North Little Rock, AR. Gen. Tech. Rep. SRS–41. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 125 p.
The proceedings include 14 papers on the status of Arkansas forests, based on data from the 1995–96 Forest Survey of Arkansas conducted by the Southern Research Station of the USDA Forest Service. Authors reviewed the State’s forest history, current conditions and changes over time, implications for different resource values and ownerships, and current issues that affect the sustainability of Arkansas forests.
17 Guldin, James M.; Heath, Gerald. 2001. Underplanting shortleaf pine seedlings beneath a residual hardwood stand in the Ouachita Mountains: results after seven growing seasons. Res. Note SRS-09. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 8 p.
An unreplicated demonstration was established in the Ouachita Mountains in which shortleaf pine (Pinus echinata Mill.) trees were harvested and overstory hardwoods were retained. A new stand was established by underplanting shortleaf pine seedlings. After the third growing season, five 0.5-acre plots were established, and one of five overstory hardwood retention treatments—0, 10, 20, 30, or 40 square feet per acre of residual basal area (RBA)—was randomly assigned to each. Pine seedlings were measured after the third, fifth, and seventh growing seasons. Over time, pine seedling density changed very little by treatment, but seedling basal area varied inversely with increasing overstory retention. After the fifth and seventh growing seasons, the basal area of the average tree in the RBA 0 treatment was greater than in any other treatment, and differences in height among treatments were also observed. Between the third and seventh growing seasons, average annual growth of pine in both height and basal area declined with increasing overstory hardwood basal area. The decline in height growth occurred uniformly from the RBA 0 through the RBA 40 treatments; but the decline in seedling basal area growth occurred between the RBA 0 and RBA 10 treatments. To date, seedlings have survived and growth has increased across all treatments. Future monitoring will determine if and when growth rates cease on any of the plots.
Large Scale Assessment and Modeling Research
18 Aber, John; Neilson, Ronald P.; McNulty, Steve; and others. 2001. Forest processes and global environmental change: predicting the effects of individual and multiple stressors. BioScience. 51(9): 735-751.
The purpose of this article is to review the state of prediction of forest ecosystem response to envisioned changes in the physical and chemical climate. These results are offered as one part of the forest sector analysis of the National Assessment of the Potential Consequences of Climate Variability and Change. This article has three sections. The first offers a very brief review of the literature on the effects of environmental factors on forest ecosystem function. The second and largest part of the article is a summary of results from the Vegetation/Ecosystem Modeling and Analysis Project (VEMAP), an integrated effort to predict ecosystem response to climate change. The third is a brief review of other regional modeling efforts that have addressed climate change or have looked at the possible effects of other components of global change, using tropospheric ozone and nitrogen deposition as examples, or both.
Dale, Virginia H.; Joyce, Linda A.; McNulty, Steve; and others. 2001. Climate change and forest disturbances. BioScience. 51(9): 723-734.
This article examines how eight disturbances influence forest structure, composition, and function, and how climate change may influence the severity, frequency, and magnitude of disturbances to forests. We focus on examples from the United States, although these influences occur worldwide. We also consider options for coping with disturbance under changing climate. This analysis points to specific research needs that should improve the understanding of how climate change affects forest disturbances.
Hansen, Andrew J.; Neilson, Ronald P.; Dale, Virginia H.; and others. 2001. Global change in forests: responses of species, communities, and biomes. BioScience. 51(9): 765-779. [Editor’s note: The Southern Global Change Program provided funding for this research.]
This article serves as a primer on forest biodiversity as a key component of global change. We first synthesize current knowledge of interactions among climate, land use, and biodiversity. We then summarize the results of new analyses on the potential effects of human-induced climate change on forest biodiversity. Our models project how possible future climates may modify the distributions of environments required by various species, communities, and biomes. Current knowledge, models, and funding did not allow these analyses to examine the population processes (e.g., dispersal, regeneration) that would mediate the responses of organisms to environmental change. It was also not possible to model the important effects of land use, natural disturbance, and other factors on the response of biodiversity to climate change. Despite these limitations, the analyses discussed herein are among the most comprehensive projections of climate change effects on forest biodiversity yet conducted. We conclude with discussions of limitations, research needs, and strategies for coping with potential future global change.
Irland, Lloyd C.; Adams, Darius; Alig, Ralph; and others. 2001. Assessing socioeconomic impacts of climate change on U.S. forests, wood-product markets, and forest recreation. BioScience. 51(9): 753-764.
In this paper we discuss the problems of projecting social and economic changes affecting forests and review recent efforts to assess the wood-market impacts of possible climate changes. To illustrate the range of conditions encountered in projecting socioeconomic change linked to forests, we consider two markedly different uses: forest products markets and forest recreation. In the case of forest products, we use an existing forest-sector model to arrive at new simulation results concerning the impacts of climate change. The impact of climate change on recreation has received less attention; here we consider a case study of downhill skiing. Other important forest values were not treated explicitly in this research. Our primary emphasis is on methods and issues in the socioeconomic assessment process. Our efforts may be viewed as an exercise in human ecology, studying complex interactions between human societies and their forests. We close with suggestions for future research.
McNulty, Steven G.; Aber, John D. 2001. U.S. national climate change assessment on forest ecosystems: an introduction. BioScience. 51(9): 720-722.
The 1990 Global Change Research Act mandates that an assessment be conducted periodically to summarize research findings. Begun in 1997, the first National Assessment of the Potential Consequences of Climate Variability and Change was published in 2001. The assessment is divided into five sectors: (1) water resources and availability, (2) agriculture and food production, (3) human health, (4) coastal areas, and (5) forests. These sectors represent important or politically sensitive United States resources that could be adversely affected by climate change. The assessment also includes over 20 regional studies, which examine the impacts of climate change for specific geographical areas of the United States. This special section of BioScience focuses on a summary of research findings from the forest sector and regional findings of the 2001 national assessment. The impacts of climate change on the forest sector are divided into four categories: (1) forest processes, (2) biodiversity change, (3) disturbance interactions, and (4) socioeconomic change. These categories represent key interactions between a changing climate, forest structure or function, and human interactions with forests.
Inventory and Monitoring Research
23 Conner, Roger C.; Sheffield, Raymond M. 2001. Forest statistics for the Southern Coastal Plain of North Carolina. 1999. Resour. Bull. SRS-59. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station, 61 p.
This report summarizes a 1999 inventory of the forest resources of a 21-county area of North Carolina. Major findings are highlighted in text and graphics; detailed data are presented in 49 tables.
24 Cooke, William H. 2001. Development of a methodology for predicting forest area for large-area resource monitoring. Res. Pap. SRS-24. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 11 p.
The U.S. Department of Agriculture, Forest Service, Southern Research Station, appointed a remote-sensing team to develop an image-processing methodology for mapping forest lands over large geographic areas. The team has presented a repeatable methodology, which is based on regression modeling of Advanced Very High Resolution Radiometer (AVHRR) and Landsat Thematic Mapper (TM) data. It is a methodology that Forest Inventory and Analysis (FIA) survey personnel can implement in any region or area. The term repeatable implies objectivity. Studies in the conterminous United States, Central America and Mexico, and west Texas and Oklahoma have provided valuable insights that address the subjective nature of some of the steps taken in mapping large forest areas. The team has identified seven such steps. They have reduced or eliminated subjectivity in four of the steps and identified two steps in which objectivity can be enhanced.
25 Hartsell, Andrew J.; Vissage, John S. 2001. Forest statistics for west-central Alabama, 1999. Resour. Bull. SRS-60. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 52 p.
This report summarizes a 1999 inventory of the forest resources of a nine-county area of Alabama. Major findings are highlighted in text and graphics; detailed data are presented in 49 tables.
Parresol, Bernard R. 2001. Additivity of nonlinear biomass equations. Canadian Journal of Forest Research. 31: 865-878.
Two procedures that guarantee the property of additivity among the components of tree biomass and total tree biomass utilizing nonlinear functions are developed. Procedure 1 is a simple combination approach, and procedure 2 is based on nonlinear joint-generalized regression (nonlinear seemingly unrelated regressions) with parameter restrictions. Statistical theory is given for construction of confidence and prediction intervals for the two procedures. Specific examples using slash pine (Pinus elliottii Engelm. var. elliottii) biomass data are presented to demonstrate and clarify the methods behind nonlinear estimation, additivity, error modeling, and the formation of confidence and prediction intervals. Theoretical considerations and empirical evidence indicate procedure 2 is generally superior to procedure 1. It is argued that modeling the error structure is preferable to using the logarithmic transformation to deal with the problem of heteroscedasticity. The techniques given are applicable to any quantity that can be disaggregated into logical components.
27 Rosson, James F., Jr. 2001. Forest Resources of East Oklahoma, 1993. Resour. Bull. SRS-58. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 75 p.
The principal findings of the sixth forest survey of east Oklahoma (1993) and changes that have occurred since the previous survey are presented. Topics examined include forest area, ownership, forest-type groups, stand structure, basal area, timber volume, growth, removals, mortality, harvesting, and management.
28 Rosson, James F., Jr. 2001. Forest Resources of Mississippi, 1994. Resour. Bull. SRS-61. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 78 p.
The principal findings of the seventh forest survey of Mississippi and changes that have occurred since the previous survey are presented. Topics examined include forest area, ownership, forest-type groups, stand structure, basal area, timber volume, growth, removals, mortality, harvesting, and management activity.
Foundation Programs Research
Bragg, Don C.; Bragg, Hope A. 2001. Woody plants of North America [product review]. Bulletin of the Ecological Society of America. 82(3): 191-192.
The authors review a 2-CD set created to aid in identifying woody plants. The product is intended to supplement (rather than replace) field instruction for identifying 470 of the most common native and introduced trees and shrubs in North America.
Kabir, Firoz; Schmoldt, Daniel; Schafer, Mark. 2001. Detection of defects in red oak deckboards by ultrasonic scanning. In: Kline, D. Earl; Abbott, A. Lynn., tech. eds. Proceedings: 4th international conference on image processing and scanning of wood; IPSW 2000; 2000 August 21-23; Mountain Lake, VA. Blacksburg, VA: Virginia Tech, Department of Wood Science and Forest Products: 89-96.
Experiments were conducted to detect defects in red oak (Quercus rubra L.) deckboards by ultrasonic scanning. Scanning of the deckboards was carried out with two rolling transducers in a pitch-catch arrangement with pallet parts moving between the transducers at 70 ft/m and 220 ft/m. Data were collected, stored, and processed using LabViewTM software. The defects examined were sound and unsound knots, bark pockets, holes, decay, and wane. Three deckboard samples (fresh cut and unplaned condition) were scanned for each defect type. Defects were characterized on the basis of time of flight, pulse energy, and pulse duration of the received signals. Results demonstrated that defected wood can be distinguished from clear wood by observing the variation in received signals. Ultrasonic signal parameters are more sensitive to unsound knots, decay, bark pockets, holes, and wane, compared to sound knots. This study demonstrates the feasibility of on-line inspection of green (high moisture content) and rough (unplaned) red oak deckboards.
Kline, Earl; Surak, Chris; Araman, Philip. 2001. Evaluation of a multi-sensor machine vision system for automated hardwood lumber grading. In: Kline, D. Earl; Abbott, A. Lynn., tech. eds. Proceedings: 4th international conference on image processing and scanning of wood; IPSW 2000; 2000 August 21-23; Mountain Lake, VA. Blacksburg, VA, Department of Wood Science and Forest Products: Virginia Tech: 75-87.
Over the last 10 years, scientists at the Thomas M. Brooks Forest Products Center, the Bradley Department of Electrical Engineering, and the USDA Forest Service have been working on lumber scanning systems that can accurately locate and identify defects in hardwood lumber. Current R&D efforts are targeted toward developing automated lumber grading technologies. The objective of this work is to evaluate hardwood lumber grading accuracy based on current state-of-the-art multiple sensor scanning technology which uses laser profile detectors, color cameras, and an x-ray scanner. Eighty-nine red oak boards were scanned and graded using Virginia Tech's multiple sensor scanning system. A certified National Hardwood Lumber Association (NHLA)–employed lumber inspector then graded the lumber and the boards were manually digitized and mapped for defects.
The lumber grading system was found to be 63 percent accurate in classifying board grade on a board-by-board basis. While this accuracy may seem low, the automated lumber grading system was found to be 31 percent more accurate than the line graders. Further, the automated lumber grading system estimated the lumber value to be within 6 percent of the NHLA certified value, whereas the line grader overestimated the lumber value by close to 20 percent. Most automated lumber grading discrepancies resulted from board geometry related issues (e.g., board crook, surface measure rounding, calculation of cutting units, etc.). Concerning the multiple sensor scanning system, defect recognition improvements should focus on better methods to differentiate surface discoloration from critical grading defects. These results will help guide the development of future scanning hardware and image processing software to more accurately identify lumber grading features.
Lee, Sang-Mook; Abbott, A. Lynn; Schmoldt, Daniel L. 2000. Wane detection on rough lumber using surface approximation. In: Kline, D. Earl; Abbott, A. Lynn., tech. eds. Proceedings: 4th international conference on image processing and scanning of wood; IPSW 2000; 2000 August 21-23; Mountain Lake, VA. Blacksburg, VA: Virginia Tech, Department of Wood Science and Forest Products: 89-96.
The initial breakdown of hardwood logs into lumber produces boards with rough surfaces. These boards contain wane (missing wood due to the curved log exterior) that is removed by edge and trim cuts prior to sale. Because hardwood lumber value is determined using a combination of board size and quality, knowledge of wane position and defects is essential for selecting cuts that maximize profit. We have developed a system that uses a structured light system to obtain profile (thickness) images of unplaned boards, in addition to gray-scale images for defect detection. The focus of this paper is to describe a new approach for detecting wane boundaries through the analysis of these profile images. The problem is difficult because bark and other debris adversely affect the laser-based imaging process, and because variations in surface reflectance also cause inaccuracies in the resulting images. The problem is compounded by the need to perform wane detection rapidly in a manufacturing environment. The method that we have developed relies on a combination of column-wise image statistics, selective smoothing, and the analysis of surface shape. Initial wane edge estimates that are obtained using the smoothed image are then refined by analysis of the original image data. Based on visual assessment, the current method appears to improve dramatically on traditional thresholding techniques.
Moss, Patricia A.; Groom, Les. 2001. Microscopy. In: Borch, Jens; Lyne, M. Bruce; Mark, Richard E.; Habeger, Charles C., Jr. Handbook of Physical Testing of Paper. New York: Marcel Dekker, Inc.: 149-265.
This chapter discusses the applications of microscopy to pulp and paper research. Conventional optical and electron microscopical techniques are covered only briefly, because these are well documented elsewhere. Novel forms of microscopy—confocal laser scanning microscopy (CLSM), low temperature scanning electron microscopy (LTSEM), and atomic force microscopy (AFM)—are presented in detail. As yet, there are no official or standard methods pertaining to their use.
Sarigul, Erol; Abbott, Lynn; Schmoldt, Daniel. 2001. Rule-driven defect detection in CT images of hardwood logs. In: Kline, D. Earl; Abbott, A. Lynn., tech. eds. Proceedings: 4th international conference on image processing and scanning of wood; IPSW 2000; 2000 August 21-23; Mountain Lake, VA. Blacksburg, VA: Virginia Tech, Department of Wood Science and Forest Products: 37-49.
This paper deals with automated detection and identification of internal defects in hardwood logs using computed tomography (CT) images. We have developed a system that employs artificial neural networks to perform tentative classification of logs on a pixel-by-pixel basis. This approach achieves a high level of classification accuracy for several hardwood species (northern red oak, Quercus rubra L.; water oak, Q. nigra L.; yellow poplar, Liriodendron tulipifera L.; and black cherry, Prunus serotina Ehrh.) and three common defect types (knots, splits, and decay). Although the results are very satisfactory statistically, a subjective examination reveals situations that could be refined in a subsequent post-processing step. We are currently developing a rule-based approach to region refinement to augment the initial emphasis on local information. The resulting rules are domain dependent, utilizing information that depends on region shape and type of defect. For example, splits tend to be long and narrow, and this knowledge can be used to merge smaller, disjoint regions that have tentatively been labeled as splits. Similarly, image regions that represent knots, decay, and clear wood can be refined by removing small, spurious points and by smoothing the boundaries of these regions. Mathematical morphology operators can be used for most of these tasks. This paper provides details concerning the domain-dependent rules by which morphology operators are chosen, and for merging results from different operations.
Schmoldt, Daniel L. 1996. CT imaging, data reduction, and visualization of hardwood logs. In: Meyer, Dan A., ed. Putting research to work for the hardwood industry: new technology available today: Proceedings of 24th annual hardwood symposium; 1996 May 8-11; Cashiers, NC. Memphis, TN: National Hardwood Lumber Association: 69-80.
Computer tomography (CT) is a mathematical technique that, combined with noninvasive scanning such as x-ray imaging, has become a powerful tool to nondestructively test materials prior to use or to evaluate materials prior to processing. In the current context, hardwood lumber processing can benefit greatly by knowing what a log looks like prior to initial breakdown. Previous research has indicated that CT imaging of logs can pay for itself in medium- and high-volume sawmills. Nevertheless, numerous implementation issues remain. This paper discusses several of these. First, x-ray imaging parameters for various species, defect resolutions, and defect contrasts need to be better understood. Second, the CT data collected is voluminous and needs to be condensed for application to subsequent decisionmaking. Third, because CT imaging produces spatial information, there needs to be some way to visualize that information to allow saw operators to improve lumber value recovery.
Thawornwong, Suraphan; Occena, Luis; Schmoldt, Daniel. 2001. Investigation of the effect of reducing scan resolution on simulated information-augmented sawing. In: Kline, D. Earl; Abbott, A. Lynn., tech. eds. Proceedings: 4th international conference on image processing and scanning of wood; IPSW 2000; 2000 August 21-23; Mountain Lake, VA. Blacksburg, VA: Virginia Tech, Department of Wood Science and Forest Products: 51-62.
In the past few years, computed tomography (CT) scanning technology has been applied to the detection of internal defects in hardwood logs for the purpose of obtaining a priori information that can be used to arrive at better log breakdown or sawing decisions. Since today sawyers cannot even see the inside of the log until the log faces are revealed by sawing, there is no perceived need to obtain scan images as fine and as high a resolution as those obtained in medical CT imaging. The resolution in which the CT scan data is collected is a factor of physical pixel size, thickness, and pitch. A 23 factorial experiment with two levels for each of the three factors was designed. Three hypothetical logs corresponding to the three hardwood log grades were simulation-scanned and studied. The results showed that the effect of reducing CT resolution factors (doubling pitch, thickness, and pixel size) in a simulated log processing experiment did not significantly reduce the lumber values produced from the logs.
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