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Chapter 6.

Productivity

The South is blessed with abundant anddiverse forest resources. Today, forestscover approximately 215 million acres in

the South, which represents 29 percent of theforest land in the United States (Conner andHartsell 2002). Maintaining the productivityof these forests is essential to the economic,environmental, and social well being of the Southand the Nation. The forest products industryranks among the top industries in most SouthernStates and is the largest industry in several. Thewood products sector contributed 770,000 directjobs and over $120 billion in total industry outputin 1997 (Abt and others 2002).

The diversity of forest ecosystems in the Southis also large, ranging from mixed, mesophytichardwood forests of the Southern Appalachians,to the planted pine forests of the Coastal Plainand Piedmont, to the bottomland hardwoodforests along major rivers throughout the region.In 1999 there were 65 million acres of uplandhardwood forests, 30 million acres of lowlandhardwoods, 29 million acres of mixed pine-hardwood forests, 33 million acres of naturalpine, and 30 million acres of pine plantationsin the South excluding Kentucky (Conner andHartsell 2002). These forests provide a widevariety of goods and services other than timber,including a diverse range of habitat for wildlife,recreational opportunities, and clean air andwater. These goods and services contributeto an improved quality of life for an increasingpopulation that has become more urbanized.Modern forest management regimes mustprovide these noncommodity benefits.

Management practices have been developedand refined for each of the major forest types inthe South since the advent of scientific forestry at

the Biltmore Estate led by the work of Olmstead,Pinchot, and Schenck in the 1890s. Althoughtremendous strides have been made in themanagement of most forest types, progress hasbeen uneven. Economic factors associated withthe development of southern pine-based pulp andpaper industry, which started in the 1920s and1930s, fostered the development of pine plantationmanagement using an agronomic approach.The work of research scientists and practicingforesters in the U.S. Department of AgricultureForest Service (Forest Service), southern forestryschools and universities, State forestry agencies,and private industry in pine tree improvementand intensive silvicultural practices has greatlyimproved the productivity of southern pineplantations. Similar but less sustained effortswere periodically directed toward intensivemanagement of plantation hardwoods, generallywith mixed results. The research efforts directedtoward the management of natural hardwood,pine, and mixed hardwood-pine stands have beenless concerted than that associated with intensivepine plantation silviculture. However, individualresearch programs within the Forest Serviceand at several southern forestry schools havemaintained a strong and consistent focus on theseforest types. Most notable are the Forest Serviceresearch units at Bent Creek and Coweeta focusedon upland hardwoods, the program at MississippiState University on silviculture of bottomlandhardwoods, the industry-sponsored HardwoodResearch Cooperative at North Carolina StateUniversity, which has strong programs in bothupland and bottomland hardwoods, and the ForestService Research Work Unit at Crossett, AR, thathas developed uneven-aged silvicultural systemsfor southern pines.

Six chapters are included in this section onproductivity. Three of these chapters review andhighlight the progress made on silviculture of themajor forest types in the South. This is followedby a chapter on the history and accomplishmentsof tree improvement programs in both southernpine and hardwoods. The final chapter discussesthe links that exist between silviculture andremote sensing, specifically focusing on the useof remote sensing as a mensurational technique.

Thomas R. Fox andRay R. Hicks, Jr.1

1 Associate Professor of Forestry, Virginia PolytechnicInstitute and State University, Department of Forestry,Blacksburg, VA 24061; and Professor of Forestry, WestVirginia University, Division of Forestry, Morgantown, WV26506, respectively.

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The second chapter of this section “Silvicultureand Management Strategies Applicable toSouthern Hardwoods” by Ray R. Hicks, Jr.,William H. Conner, Robert C. Kellison, and DavidVan Lear addresses the management of uplandand bottomland hardwood forests in the South.Hardwoods comprise a significant component ofthe southern landscape. Some southern forests aredominated by hardwoods, such as the mesophyticforests of the Southern Appalachians and thebottomland stands that border all the major riversystems of the South. In addition, hardwoods forma significant component of many southern pinestands. Hardwoods play an important ecologicaland economic role in southern forests. Theyprovide ecological and habitat diversity, valuablelumber and veneer, and fiber for pulp and paper.

The authors first summarize the physiographic,edaphic, and climatic factors that characterize thevarious types of hardwood forests in the South.They then address the land use history andownership patterns and the role these forcesplay in determining the type of hardwood standsthat exist and their influence on objectives ofownership. Emphasis is placed on our improvedunderstanding of the role of fire in hardwoodforests and how the extent and frequency offires, both historical and current, influence thecomposition and structure of hardwood forests.A detailed description of the silviculturaltechniques for regenerating and culturing thecommercially valuable species of hardwoods isthen presented. The authors also discuss howsilvicultural practices in hardwood stands arecomplicated because many hardwood standsoccur on sites that are difficult to operateequipment and contain a diversity of speciesthat vary greatly in stumpage value. Thesefactors, along with the fact that most hardwoodstands occur on small, privately owned tracts,contribute to the fact that most hardwood standsare not actively managed and have historicallybeen exploited and high-graded.

The third chapter in this section “TheEvolution of Pine Plantation Silviculture inthe Southern United States” by Thomas R.Fox, Eric J. Jokela, and H. Lee Allen reviewsthe historical development of intensive southernpine silviculture. The acreage in pine plantationshas increased significantly over the last 50 yearsfrom < 2 million acres in 1952 to 32 million acresin 1999 (Wear and Greis 2002). More remarkableis the significant increase in per-acre productivitythat has accompanied the rapid expansion of pine

plantations. Mean annual increment of pineplantations has more than doubled, and rotationlengths have been cut by more than 50 percent.Although planted pine accounts for only 15percent of the total forest land base in the South,it accounts for 35 percent of the annual harvestvolume (Wear and Greis 2002).

The authors of this chapter highlight thechanges in pine plantation silviculture thathave occurred since 1950. The contributions toimproved plantation yields of tree improvement,improved nursery practices, site preparation,competition control, fertilization, growth-and-yieldmodeling, and land classification are presented ona decade-by-decade basis. Current state-of-the-artsilvicultural practices involving integrated, site-specific, rotation-long silvicultural manipulationsare discussed. A vision of the future presentedby the authors includes clonal deployment ofelite genotypes produced through somaticembryogenesis and managed on a site-specificbasis to optimize growth rates and financialreturns in an environmentally sustainable manner.Precision silviculture of pine plantations in the 21st

century in the South will embrace the advancescoming out of precision agriculture. The role thatcooperative research and technology transfer hadin the successful development of intensive pineplantation silviculture is emphasized throughoutthe chapter. The take-home message from theauthors is that no one single organization hadthe financial or intellectual resources requiredto develop the needed silvicultural technologyin the past. As the level of complexity of pineplantation silviculture increases in the future,concerted, cooperative research efforts willcontinue to be needed.

The fourth chapter in this section“Reproduction Cutting Methods for NaturallyRegenerated Pine Stands in the South” by JamesM. Guldin, discusses management practices innatural pine and mixed pine-hardwood stands.Although the acreage in pine plantations hasincreased significantly over the last 50 years, theauthor correctly points out that a large percentageof forest land in the South will remain in naturalstands. There are currently 62 million acres ofnatural pine or mixed pine-hardwood forests inthe South (Wear and Greis 2002). These standsmust be managed using classical silviculturalpractices that establish and maintain productive,healthy forests that provide a variety of goods andservices required by society. Natural regenerationis frequently the only option financially available

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to nonindustrial landowners. Longer rotationsrequired to produce large-diameter pine treesand other multiple-use benefits associated withthem, such as aesthetics and wildlife habitat, maynot be feasible in plantation systems. Certainlandowners and segments of the general publicmay reject the clearcut and plant approachrequired in plantation silviculture. Regulatoryrequirements, including best managementpractices in all Southern States, prohibitclearcutting in streamside management zones.Management prescriptions involving naturalregeneration that avoids high-grading andprotects water quality must be developed forthese sensitive, high-quality sites.

The author reviews silvicultural practices thatestablish and maintain naturally regenerated pineand pine-hardwood mixtures. He discusses botheven-aged and uneven-aged reproduction cuttingmethods, including seed tree and shelterwoodsystems and group and single-tree selection.He illustrates how both even-aged and uneven-aged systems can be effective in southern pinestands depending upon which species are present,the site preparation practices, and the mannerthat required intermediate treatments, such asrelease, are employed to assure adequate seedlingestablishment and rapid stand development. Theimportance of residual overstory basal area, timingof harvests to take advantage of cone crops andseed production, appropriate site preparation tocreate suitable seed beds, control of competingvegetation, and control of stand density areemphasized as key components of a successfulnatural regeneration system in southern pine.

The fifth chapter in this section “The Roleof Genetics and Tree Improvement in SouthernForest Productivity” by R.C. Schmidtling, T.L.Robison, S.E. McKeand, R.J. Rousseau, H.L.Allen, and B. Goldfarb documents the impacts thattree improvement activities have had in the Southover the last 50 years. The contributions of appliedtree improvement to the increased productivity ofsouthern pine stands are recognized throughoutthe world as one of the major success stories ofmodern forestry. Beginning with the pioneeringwork of Wakeley on seed source variation insouthern pine in the 1920s, research on treeimprovement in southern pines has progressed tothe point where loblolly pine (Pinus taeda L.) istoday probably the most domesticated and bestunderstood conifer in the world. Again, hardwoodspecies have received less attention in the Souththan have pines. However, interest in hardwoods

has recently increased because of work in thedeveloping field of forest biotechnology. Hardwoodspecies, most notably those in the genera Populusand Eucalyptus, are proving to be much easierto study and manipulate through tissue culture,genetic mapping, and genetic engineeringtechniques than conifers. Hardwoods willprobably serve as model systems wherethe gains in biotechnology are first realizedin forestry.

The authors of this chapter provide a thoroughreview of the history of forest tree improvementin the South from its infancy in the 1920s. Theyinclude a discussion of both southern pine andhardwood tree improvement programs. Theyillustrate how the observations and efforts ofpracticing foresters played an important roleduring the early phases of tree improvement.These initial efforts were superseded bywell-coordinated, sophisticated, cooperativeresearch programs involving Federal and StateGovernments, universities, and private industry.Today approximately 1 billion southern pineseedlings are planted annually, nearly all ofthem the product of tree improvement programs.The authors discuss the productivity gains madeusing first-generation slash (Pinus elliottiiEngelm.) and loblolly pine. Gains are estimatedto be 15 to 20 percent over unimproved, naturalpopulations. Additional gains will be madefrom the deployment of advanced generationmaterial from elite populations throughtechniques such as open-pollinated single-familyblock plantings, and full-sib deployment usingcontrol mass pollination. Clonal forestry loomson the horizon as an opportunity to exploit thefull genetic potential of various commercialspecies through the development of tissue culturetechniques, such as rooted cuttings and somaticembryogenesis. The science of genomics willprovide improved tools such as marker-aidedselection that will increase the efficiency of treeimprovement programs. The authors concludewith a cautionary note on the need to conservelong-term genetic diversity while managing forshort-term productivity gains.

The final chapter in this section, “ForestMensuration with Remote Sensing: ARetrospective with a Vision for the Future,”by Randolph H. Wynne, discusses the roleof remote sensing as a tool that practicingforesters can use to improve forest productivity.As management practices intensify, forestersrequire more detailed information upon which

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to base their decisions. Forestry is moving towardthe agricultural model of intensive, site-specificmanagement that can be broadly characterizedas precision forestry. Information from digitalremote sensing can be quickly integratedinto a forester’s decision process to developsophisticated, fully integrated rotation-longmanagement regimes that best meet landownerobjectives. Although forest managementat this level of intensity is often associatedwith the desire to optimize financial returns,sophisticated management scenarios are neededby any forester attempting to meet the competingdemands placed on forest resources today.For example, meeting the needs for aesthetics,recreation, wildlife habitat, water quality,endangered species, wilderness, and timberproduction is a much more complicated taskthan simply optimizing growth and associatedfinancial returns from timber management.

The chapter begins with a retrospectivediscussion of remote sensing, which reviewsthe long use of aerial photos to improve forestmanagement. A section on timber volumeestimation using aerial photos is then presented.This section explains how tree and standproperties such as stand density, tree height,crown dimensions, and crown cover can beobtained from conventional aerial photos andused to create photo volume tables. Historically,the variation in stand-volume estimates basedon aerial photos was too high (often exceeding25 percent) to be of great value for many uses.The most widespread use of remotely senseddata in forestry has been, and continues to be,to stratify and map stands, calculate land area,and simplify navigation. The value of aerial photosas a navigation tool used by foresters to increasethe efficiency of their day-to-day activities in thewoods should not be overlooked. The author then

discusses new developments in remote sensingand computer technologies, and explains how theyare being used to improve volume estimates ofstands. The developing tool of lidar (light detectingand ranging), which uses an airborne laser toaccurately estimate canopy height, crown density,and stand density is discussed. Lidar-basedmeasurements are proving to be more accurateand less biased than conventional photo-basedestimates of tree and stand parameters. Theauthor is optimistic that the high cost of cost dataacquired with these new techniques will decreaseand that the combination of decreasing cost andincreasing efficiency will improve the cost/benefitratio of this technology. The chapter concludeswith a discussion of how remote sensing utilizingthese new techniques and tools will be an integralcomponent of the new precision forestry paradigm.

LITERATURE CITEDAbt, K.L.; Winter, S.A.; Huggett, R.J., Jr. 2002. Local economic

impacts of forests. In: Wear, David N.; Greis, John G., eds.Southern forest resource assessment. Gen. Tech. Rep. SRS–53. Asheville, NC: U.S. Department of Agriculture, ForestService, Southern Research Station: 239–267.

Conner, R.C.; Hartsell, A.J. 2002. Forest area and conditions.In: Wear, David N.; Greis, John G., eds. Southern forestresource assessment. Gen. Tech. Rep. SRS–53. Asheville,NC: U.S. Department of Agriculture, Forest Service,Southern Research Station: 357–401.

Wear, David N.; Greis, John G., eds. 2002. Southern forestresource assessment. Gen. Tech. Rep. SRS–53. Asheville,NC: U.S. Department of Agriculture, Forest Service,Southern Research Station. 635 p.