Pinus taeda L. Loblolly PinePinaceae Pine family

James B. Baker and 0. Gordon Langdon

Loblolly pine (Pinus tuedu), also called Arkansaspine, North Carolina pine, and oldfield pine, is themost commercially important forest species in thesouthern United States, where it is dominant onabout 11.7 million ha (29 million acres) and makesup over one-half of the standing pine volume. It is amedium-lived, intolerant to moderately tolerant treewith rapid juvenile growth. The species respondswell to silvicultural treatments and can be managedas either even-aged or uneven-aged natural stands,

or can be regenerated artificially and managed inplantations.

Habitat

Native Range

The native range of loblolly pine (fig. 1) extendsthrough 14 States from southern New Jersey southto central Florida and west to eastern Texas. It in-

350

Figure l-The native range of loblolly pine.

The authors are Silviculturist, Southern Forest Experiment Station,New Orleans, LA, and Silviculturist (retired), SoutheasternForest Experiment Station, Asheville, NC.

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eludes the Atlantic Plain, the Piedmont Plateau, andthe southern extremities of the Cumberland Plateau,the Highland Rim, and the Valley and Ridge Provin-ces of the Appalachian Highlands. Loblolly pine doesnot grow naturally in the Mississippi River floodplain and is scarce in the deep, coarse sands of thelower Atlantic Plain and sandhills of North andSouth Carolina; it is important only in localizedareas in southeastern Georgia and northern Florida(37,55,69).

Loblolly pine is an adaptable species that has beensuccessfully planted along the periphery of itsnatural range and has been introduced on other con-tinents with varying degrees of success.

Climate

The climate over most of the loblolly pine range ishumid, warm-temperate with long, hot summers andmild winters. Average annual rainfall varies from1020 to 1520 mm (40 to 60 in). The frost-free periodvaries from 5 months in the northern part of therange to 10 months along the southern coastalStates. Mean annual temperatures range from 13” to24” C (55” to 75” F); average July temperature is 27”C (SO’ F) and frequently exceeds 38” C (loo0 F).January temperature averages 4” to 16” C (40” to 60”F) and occasionally drops to -23” C (-10’ F) in thenorthern and western parts of the range (69).

During both winter and summer, weather withinthe range of loblolly pine differs from that immedi-ately outside the range. There are a greater numberof days with rain, a greater frequency of effectiveamounts of rain, that is, more than 13 mm (0.5 in),and higher average winter temperatures. In springand autumn, the weather within and outside therange is more nearly the same (37).

The main factor limiting northern extension of thespecies is probably low winter temperature with as-sociated damage from ice, snow, and sleet and colddamage during flowering. Lack of adequate growing-season precipitation probably limits western exten-sion of loblolly pine in Oklahoma and Texas (37).

Soils and Topography

Soils within the native range of loblolly pine arepredominantly Ultisols. Small areas of Entisols andSpodosols are found in the Southeastern States andthere are some Alfisols throughout the region. Loblol-ly pine grows on a wide variety of these soils, rangingfrom the flat, poorly drained Aquults and Aquods ofthe coastal portion of the Atlantic Plain to the rela-tively dry Psamments, Udults, and Udalfs of the in-land portion of the Atlantic Plain, Piedmont, and

upland Provinces (107). Best growth is on moderatelyacid soils with imperfect to poor surface drainage, athick medium-textured surface layer, and a fine-tex-tured subsoil. These soils are common in the uplandsof the Atlantic Plain and on the flood plains andterraces of rivers and streams. Poorest performanceis on shallow soils, eroded soils, and very wet orwaterlogged sites (37).

Some typical examples of Ultisols on which loblollypine grows include the Coxville, Bladen, Beauregard,Wahee, Dunbar, Ruston, Norfolk, Orangeburg, andSmithdale series found in the Atlantic Plain; theCecil, Davidson, and Appling series in the Piedmont;and the Hartsells and Linker series in the uplandProvinces. Ultisols have a site index measured atbase age 50 years for loblolly pine of 23 to 30 m (75to 100 ft) in the Coastal Plain, 20 to 29 m (65 to 95ft) in the Piedmont, and 18 to 24 m (60 to 80 ft) inthe upland Provinces. Typical Entisols on whichloblolly pine is found include deep sands (Chipley,Eustis, and Lakeland series) and alluvial soils (Alpinand Osier series), with a site index ranging from 20to 30 m (65 to 100 ft). Representative Spodosols in-clude the Leon and Lynn Haven series, with a siteindex of 18 to 26 m (60 to 85 ft). Within the AtlanticPlain but confined to a strip on each side of theMississippi River are loessial soils represented bythe Memphis, Grenada, Providence, Calhoun, andHenry series. These loessial soils, as well as Caddo,Wrightsville, Meggett, and Bude series, all having asite index ranging from 23 to 34 m (75 to 110 ft), aresome representative Alflsols on which loblolly pinegrows.

In the Atlantic Plain, the productivity of mineralsoils generally decreases with improvement in sur-face drainage. Productivity is sensitive to soil fer-tility, however, and if fertility is low on poorlydrained sites, productivity decreases (63). Thepresence of a spodic horizon within the rooting zone,as in the Leon series, frequently is associated withlow productivity. Deep, excessively drained sands arealso very low in site quality unless a water table ora clay lens which holds moisture lies within reach ofthe tree roots (37).

In the Piedmont Plateau, where surface drainageis well developed, physical characteristics of the soil,rather than surface drainage, determine theavailability of moisture, nutrients, and aeration.Here uneroded soils with a thick surface layer and afriable subsoil have a site index of 24 to 27 m (80 to90 ft). Common series in this category are Appling,Durham, Davidson, Georgeville, and Cecil. The leastproductive sites are eroded soils with a very plasticsubsoil such as the Orange and Iredell series. When

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the A horizon is gone, site index is less than 12 m(40 ft) (37).

In the Ridge and Valley Provinces loblolly pine siteindex of 18 to 26 m (60 to 85 R) generally increasesfrom ridge tops to bottoms. This variation is relatedto landform, slope position and aspect, and geology.Soil features that determine site quality, such as soiltemperatures, surface soil thickness, subsoil consis-tency, and soil moisture, are correlated with topog-raphy However, past land use, differences in soilparent material, and other factors also affect soilprofile development and cause variations in sitequality independent of topography (92).

Perhaps as significant as the soils on which loblollypine grows are those soils in the region where loblollypine does not grow. These are principally Mollisols ofthe Blackbelt, Entisols of calcareous river bottomsand terraces (that is, soils in the Louisa, Miller, andPrecris series characterized by high base saturationand high pH) and Alfisols of the Coastal Prairie ofLouisiana and Texas with moderately high basesaturation. These soils may also have other uniden-tified properties which exclude pine (72).

The topography throughout the loblolly pine rangevaries from flat near the coast to mountainous in theinterior highlands. The topography can best be re-lated to the physiographic regions within the loblollypine range.

The Atlantic Plain is generally flat near the coastbut becomes rolling and hilly inland with elevationsranging up to 150 m (500 ft). The Piedmont Plateauis more rolling, with highly developed drainage pat-terns and generally finer textured soils. Elevationsrange up to 305 m (1,000 ft) in Georgia. The Ridgeand Valley Province is about 64 km (40 mi) wide andextends into the loblolly pine range fromsoutheastern Tennessee into northern Georgia andAlabama. The topography is characterized by a groupof valley floors separated by long, narrow, zigzaggingridges; elevations range from about 185 m (600 ft) toabout 365 m (1,200 ft). The Cumberland Plateau,which lies just west of the Ridge and Valley Province,is underlaid by massive sandstone and its topog-raphy is characterized by winding narrow-crestedridges and narrow valleys. In some places thesandstone has given rise to local upland flats andmesa-like forms or knobs. Elevations range from 150m (500 ft) in the southern part of the region and inthe valley floors to 305 m (1,000 ft) at the northernend of the region and on ridge tops. The topographyof the Highland Rim that extends into south-centralTennessee and northern Alabama is undulating withdepressions and low domes where elevations rangefrom 150 to 245 m (500 to 800 ft).

Associated Forest Cover

Loblolly pine is found in pure stands and in mix-tures with other pines or hardwoods, and in associa-tion with a great variety of lesser vegetation. Whenloblolly pine predominates, it forms the forest covertype Loblolly Pine (Society of American ForestersType 81) (3.2). Within their natural ranges, longleaf,shortleaf, and Virginia pine (Pinus palustris, I?echinata, and P virginiana), southern red, white,post, and blackjack oak (Quercus falcata, Q. alba, Q.stellata, and Q. marilandica), sassafras (Sassafrasalbidum), and persimmon (Diospyros virginiana) arefrequent associates on well-drained sites. Pond pine(Pinus serotina), spruce pine (P glabra), blackgum(Nyssa sylvatica), red maple (Acer rubrum), andwater oak (Quercus nigra), willow oak (Q. phellos),and cherrybark oak (Q. falcata var. pagodifolia) arecommon associates on moderately to poorly drainedsites. In the southern part of its range, loblolly fre-quently is found with slash pine (Pinus elliottit) andlaurel oak (Quercus Zaurifolia).

In east Texas, southern Arkansas, Louisiana, andthe lower Piedmont, loblolly and shortleaf pine areoften found in mixed stands. In Loblolly Pine-Shortleaf Pine (Type 80), loblolly predominates ex-cept on drier sites and at higher elevations. Whenshortleaf pine predominates, the mixture formsShortleaf Pine (Type 75).

In fertile, well-drained coves and along stream bot-toms, especially in the eastern part of the range,yellow-poplar (Liriodendron tulipifera), Americanbeech (Fagus grandifolia), and white and Carolinaash (Fraxinus americana and Z? caroliniana) areoften found in the Loblolly Pine-Shortleaf Pine covertype.

Loblolly pine also grows in mixture withhardwoods throughout its range in Loblolly Pine-Hardwood (Type 82). On moist to wet sites this typeoften contains such broadleaf evergreens as sweetbay(Magnolia virginiana), southern magnolia (M. gran-diflora), and redbay (Persea borbonia), along withswamp tupelo (Nyssa aquatica), red maple, sweet-gum, water oak, cherrybark oak, swamp chestnutoak (Quercus michauxii), white ash, American elm(Ulmus americana), and water hickory (Caryaaquatica). Occasionally, slash, pond, and spruce pineare present.

In the Piedmont and in the Atlantic Plain of north-ern Virginia and Maryland, loblolly pine grows withVirginia Pine (Type 79). In northern Mississippi,Alabama, and in Tennessee it is a minor associate inthe eastern redcedar-hardwood variant of EasternRedcedar (Type 46). On moist lower Atlantic Plainsites loblolly pine is found in Longleaf Pine (Type 701,

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Longleaf Pine-Slash Pine (Type 83), and Slash Pine-Hardwood (Type 85).

In the flood plains and on terraces of major rivers(except the Mississippi River) loblolly pine is a minorassociate in Swamp Chestnut Oak-Cherrybark Oak(Type 91). On moist, lower slopes in the AtlanticPlain it is an important component in the Sweet-gum-Yellow-Poplar (Type 87). In bays, ponds,swamps, and marshes of the Atlantic Plain it is acommon associate in Pond Pine (Type 98), the cab-bage palmetto-slash pine variant of Cabbage Palmet-to (Type 74), and Sweetbay-Swamp Tupelo-Red Bay(Type 104).

There is a great variety of lesser vegetation foundin association with loblolly pine. Some common un-derstory trees and shrubs include flowering dogwood(Cornus florida), American holly (Ilex opaca), inkber-ry (I. glabra), yaupon (I. vomitoria), hawthorn(Crataegus spp.), southern bayberry (Myricacerifera), pepperbush (Clethra spp.), sumac (Rhusspp.), and a number of ericaceous shrubs. Some com-mon herbaceous species include bluestems(Andropogon spp.), panicums (Panicum spp.), sedges(Carex spp. and Cyperus spp.), and fennels(Eupatorium spp.).

Life History

Reproduction and Early Growth

Flowering and Fruiting-Loblolly pine ismonoecious; male flowers form in clusters at the tipof the preceding year’s growth and female flowersform on the new year’s growth. The pollen-bearingstaminate flowers are catkinlike in appearance; theyrange from 2.5 to 3.8 cm (1.0 to 1.5 in) in length andvary from light green to red and yellow depending onstage of development. The pistillate flowers aregenerally ovoid and range from 1.0 to 1.5 cm (0.4 to0.6 in) in length. They vary from light green throughshades of pink to red depending on stage of develop-ment.

Flowering of loblolly pine is initiated in July andAugust in a quiescent bud that is set from middleJune to early July The male strobili form in this budin late July and the female in August, but they arenot differentiated into recognizable structures untillate September or October. In October the staminatebuds develop at the base of a vegetative bud and thepistillate buds develop at the apex of a vegetativebud a few weeks later; both remain dormant untilearly February (37,41). The date of peak pollen sheddepends on the accumulation of 353” C (636” F) day-heat units above 13” C (55” F) after February 1 (16).Flowering is also related to latitude, beginning ear-

lier at lower latitudes than at higher ones, and it canoccur between February 15 and April 10. Staminateflowers on a given tree tend to mature before thepistillate flowers, which helps to reduce self-pollina-tion. Fertilization of the pistillate strobili takes placein the spring of the following year (37).

Loblolly pine does not normally flower at an earlyage, although flowering has been induced on younggrafts with scion age of only 3 years. Thephenomenon of inducing such early flowering inseedlings is dependent on reducing vegetative shootgrowth so that quiescent buds are formed in thelatter part of the growing season to allow for theinitiation and differentiation of reproductive struc-tures. The formation of quiescent buds in seedlingsand saplings does not usually occur during thatperiod because four to five growth flushes are com-mon for trees of this age. As a loblolly pine tree ages,the number of growth flushes decreases, which ac-counts in part for increased flowering of trees atolder ages. Flowering is also genetically controlledand is influenced by moisture (May-July rainfall)and nutrient stresses.

Seed Production and Dissemination-Seedproduction of loblolly pine varies according tophysiographic region, climatic factors, and tree orstand condition. In the southern coastal portions ofthe Atlantic Plain, loblolly is generally a prolific andconsistent seed producer, but in some of the inlandportions of the Atlantic Plain, the Piedmont, and inthe western extremities of its range, seed productionis often lower and more erratic. Year-to-year varia-tions in seed crops can range from failure to bumpercrops. For example, in 27 years of seedfall records inthe Atlantic Plain of South Carolina, there was oneseed-crop failure but there were three seed crops ofmore than 2.5 million sound seeds per hectare (1million/acre) with the other crops falling betweenthese extremes. At most locations where seed-croprecords have been kept, however, such wide annualvariations have not been observed.

Despite fluctuations in seed production, loblollyusually produces some seeds every year and goodseed crops normally occur at intervals of 3 to 6 years.More than 198,000 sound seeds per hectare(80,00O/acre) is considered a good seed crop; 74,000to 198,00O/ha (30,000 to 80,00O/acre) is an averagecrop, and less than 74,OOOha (3O,OOO/acre) is con-sidered marginal, depending on seedbed charac-teristics and weather conditions.

Throughout the range of loblolly pine, usuallycones mature and seeds ripen by the second Octoberafter flowering or about 26 months after the strobiliare initiated. The mature cones are light reddish

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brown and range from 7.5 to 15.0 cm (3 to 6 in) inlength. They are narrowly conical to ovoid-cylindri-cal. Each cone scale is tipped with a stout triangularspine. Mature cones have a specific gravity of 0.89 orless (they float in SAE 20 oil). Individual cones maycontain from less than 20 to more than 200 seeds,and the percentage of sound seeds may vary fromabout 15 percent to nearly 100 percent. Loblollyseeds vary in size from 27,lOOikg (12,300Ab) to58,20O/kg (26,400/1b) and average 40,10O/kg(18,20O/lb) (37,88).

Seed production of individual trees increases withtree age, size, and freedom from crown competition.By age 25, enough seeds may be produced in widelyspaced trees to regenerate a stand; however, trees at40 years generally produce three to five times more.Rotations shorter than 30 years usually do not lendthemselves to natural regeneration.

In well-stocked and overstocked stands, coneproduction of loblolly pine can be stimulatedthreefold to tenfold by releasing the seed trees fromcompetitors at least three growing seasons before theseed is needed. If seed-tree release is delayed laterthan May 1, seed-crop stimulation will be delayed 1year. In overstocked stands, if seed trees are notreleased before a harvest cutting, then seed-cropstimulation will be delayed 2 or 3 years, dependingon the season of the harvest cut (37,61,95).

Seedfall usually begins in October, and the bulk ofthe seeds are released in November and earlyDecember. Seedfall is hastened by dry, warm, windyweather and retarded by cool, wet weather. Seeddispersal in or adjacent to a stand varies with heightand stocking level of the seed-source trees, mag-nitude of the seed crop, terrain, and weather condi-tions at the time of seedfall. The effective seedingdistance ranges from 61 to 91 m (200 to 300 ft) in adownwind direction from the seed source and 23 to30 m (75 to 100 ft) in other directions. Viability ofseeds varies with seed-crop size and the month thatthe seed is dispersed. Seed viability is often lower inyears of poor seed crops and in seeds dispersed latein the season (37).

Loblolly pine seeds generally go through a stage ofdormancy after seedfall, which lasts longer than thatof any other southern pine. Seed dormancy is relatedto the impermeable properties of the seedcoat thatconstrain water imbibition and oxygen uptake;chemical germination inhibitors do not play a sig-nificant role (11,73). Dormancy is broken naturallyas the seeds overwinter on the forest floor. Germina-tion is epigeal(88). Natural seed germination usuallybegins in March when daytime temperatures rangebetween 18” and 27” C (65” and 80” F). Few seedsremain viable (not more than 0.1 percent) on the

forest floor for germination in the second year afterseedfall (70). Secondary seed dormancy can be in-duced during seed handling procedures. Cold, moiststratification of the seed for 30 to 90 days attemperatures 3” to 5” C (37” to 41” F) are generallyrecommended to artificially break dormancy fordirect seeding or for nursery sowing (74).

Seedling Development-Moisture is a criticalfactor in seed germination and seedling estab-lishment; the amount of rainfall in the spring is re-lated directly to seedling catches. Scarifying theseedbed exposes mineral soil and increases contact ofthe seeds with moist soil surfaces. Failure of the rootradicle to penetrate compacted or puddled soil sur-faces reduces seedling establishment, especially onmajor skid trails and log decks. Soil compaction andpuddling also reduce root growth, seedling survival,and shoot growth (36,37,40,61).

Seedbed preparation by scarification or burninggreatly increases seed germination and seedling sur-vival, which reduces the number of seeds required toproduce one seedling. For example, undisturbedseedbeds with a litter depth of 8 to 10 cm (3 to 4 in)require 5 to 6 times more seeds to produce the num-ber of seedlings produced in disturbed seedbeds.

Seed germination decreases with age of seedbedand increases with clay content of the soil. Two-year-old seedbeds require 3 to 4 times more seed for suc-cessful establishment than do l-year-old seedbeds,and 3-year-old seedbeds require 9 to 14 times moreseed than is needed in the first year. Thus, favorableseedbeds usually exist for only 1 year after distur-bance, after which they rapidly deteriorate. Heaviertextured soils provide better seedbeds which resultsin higher seedling survival than do lighter texturedsoils (37,104).

Drought is a major cause of mortality for plantedloblolly pine seedlings, especially in areas with lowrainfall during the growing season. Improper care,handling, and planting of nursery stock and inade-quate site preparation for control of competingvegetation also contribute to poor survival by in-directly increasing moisture strees (34,57).

Height growth of loblolly pine seedlings occurs an-nually in a series of two to five growth flushes andis dependent on variables such as temperature, daylength, soil moisture, nutrients, competition, andgenetics. Temperature has a dominant influence onthe initiation of height growth in the spring. Highday temperatures increase height growth, but highnight temperatures decrease it. When day and nighttemperatures differ by 12” to 13” C (54” to 55” F),the best height growth occurs (15,43).

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Soil moisture influences growth of loblolly pine byits effect on internal water relations and vitalphysiological processes. Growth is reduced with in-creasing water deficits. For example, at a soil mois-ture tension of 1520 mm of mercury (2 atm), heightgrowth of loblolly pine seedlings is greatly reducedand at 2660 mm of mercury (3.5 atm), height growthceases. Height and diameter growth are significantlyreduced by a late spring and summer drought, whichalso reduces early height growth the following year(37,98,116).

Growth of loblolly pine seedlings in a natural standis inversely related to overstory stocking of pine andhardwoods. As the proportion of hardwoods increasesfor a given pine stocking, loblolly pine seedlinggrowth decreases. Size and shape of openings affectseedling growth up to 9 m (30 ft) from edges ofopenings. Seedlings growing beneath overstoryhardwoods are not likely to survive more than a fewyears and if they do survive their growth will be slow.Growth and survival of loblolly pine seedlings duringthe first 7 years after a stand is regenerated may bereduced by 80 percent because of the faster growthof competing hardwood sprouts and shrubs. Pineseedlings not overtopped by hardwoods at age 3 orolder have an excellent chance to outgrow thehardwood competition (37).

Photosynthesis in loblolly pine seedlings is relatedto light and soil moisture conditions, which in turnare affected by competing hardwoods. Photosyntheticrates of many hardwoods are inherently higher thanthose of loblolly pine at relatively low light inten-sities and with low soil moisture (37).

Fertilization often increases seedling growth inwaterlogged soils. In some instances where specificnutrients are limiting growth, fertilization results ingrowth equal to or greater than that with drainage.Loblolly pine grows well on wet, fertile sites becauseof the effects of moisture on nutrient availability(63,101).

Vegetative Reproduction-Young loblolly pineseedlings up to 3 years of age may sprout from budsin axils of primary needles if tops are clipped off, butolder trees will not produce basal sprouts at rootcollars if stems are cut or top-killed by fire, nor dothey produce root sprouts. Rooting is related to treeage and is more successful with cuttings fromyounger trees. Techniques and materials used to rootcuttings are of critical importance. For example, afine mist over the rooting bench is better than aheavy mist, and Hare’s powder is a better compoundto use than indolebutyric acid when rooting loblollypine cuttings. Although needle bundles and buds ofloblolly pine have been rooted, the success rate has

been low. Air layering, a modification of rooting cut-tings, has been the more successful method of thetwo. Success rates have been high for young trees butolder trees are more difficult to air layer(29,42,48,110).

Grafting is the most common method of vegetativepropagation used to produce genetically uniformtrees, especially in seed orchards. Grafting success isusually high but varies with scion material becauseproblems may develop from incompatibility of scionand root stock (29,37,66).

Producing genetically uniform plantlets from tis-sue cultures is a promising technique, and researchis underway to develop procedures for the commer-cial production of loblolly pine clones (19,94).

Sapling and Pole Stages to Maturity

Growth and Yield-Growth of loblolly pinestands is inherently good when compared to mosthardwood competitors and on many sites doubles ortriples the production of common associates (108).Growth is influenced by the physical and chemicalproperties of soils (texture, compaction, aeration,moisture, pH, nutrients), light, temperature,photoperiod, allelopathy, precipitation and itsseasonal pattern, and intra- and inter-species com-petition for space and essential elements. Becausemany of these factors interact, it is difficult to specifythe most limiting one. Consequently, these biotic andenvironmental effects are commonly expressed as theaverage height of dominant trees at age 50 years,that is, site index.

Yield estimates for natural, even-aged loblolly pine(fig. 2) in fully stocked stands were first made morethan 50 years ago (3,106). Additional estimates havebeen made in more recent years for stands of variousstocking levels (18,81,90,99).

Normal yields of natural, even-aged loblolly pinestands on average sites, such as those with a siteindex of 27 m (90 ft), have ranged from 133.0 m3/ha(1,900 ft3/acre) in trees 9 cm (3.6 in) and larger ind.b.h. including 29.4 m3/ha (2,100 fbmacre) in trees24 cm (9.6 in> and larger d.b.h. at age 20 to 427.7m3/ha (6,110 ft3 or 40,000 fbmacre) at age 60 (allboard-foot volumes reported in Internationalquarter-inch rule). Mean annual cubic volumegrowth generally culminates at about age 40 on thesesites with approximately 8.0 m3ka (115 ft3/acre). Asa result of larger sawtimber merchantability limits,mean annual board-foot growth culminates at aboutage 50 at a rate of 9.5m3/ha (680 ibmacre).

Growth of loblolly pine may be affected adverselyby drought, excess moisture (flooding), and nutrientdeficiencies. Growth of this species is highly corre-

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Figure a-Old-field stand of natural, even-aged loblolly pine.

lated with departure from the normal rainfall ofApril through October. Extreme negative and posi-tive departures (-117 vs. 229 mm or -4.6 vs. 9.0 in)in seasonal rainfall over 21 years resulted in dif-ferences of nearly 2.1 m3 (74 ft3) of annual growth(l&39,65). Drainage (including bedding) and fer-tilization have been shown to increase dominantheight and basal-area growth, resulting in dramaticincreases in volume growth (45,63,76,101).

Growth of planted loblolly pine is affected by thesame factors affecting natural stands. Sites areusually prepared before planting on cutover lands,and some are fertilized to correct nutrient deficien-cies. Such practices are applied to control competi-tion and to supply nutrients at optimum levels toestablish vigorous, uniform stands at spacings thatwill fully utilize site potentials (fig. 3).

Yields of planted loblolly pine vary with plantationage, site quality, number of trees planted, and inter-actions of these variables. Yields generally increasewith increasing age and site quality. Yields also in-crease with higher planting density or closer spacing;

however, on some sites, moderately wide spacing of2.4 by 2.4 m (8 by 8 ft) or 3.0 by 3.0 m (10 by 10 R)outproduce both wider and closer spacing. Mean an-nual increment culminates at younger ages on bettersites than on poorer ones. Better sites can carry morestocking than poor sites; consequently, initial spacingcan be closer (9,77,93).

Closer spacing tends to produce higher total cubicvolumes at younger ages than does wider spacing;however, average tree sizes are larger on wider spac-ings than on closer ones, If sawtimber is a primarymanagement objective, then wider spacing or lowerdensity would be advantageous. Although thinningseldom increases cubic volume yield of loblolly pine,light thinnings that salvage suppressed andmoribund trees have increased net yields by as muchas 20 percent in 50 years, Thinnings usually resultin increased diameter growth of residual trees andallow the growth to be put on the better trees in thestand. Another benefit is that thinnings provide in-termediate returns on investment (2,17).

Average total solid-wood yields of unthinned loblol-ly pine planted at 1,730 seedlings per hectare(7OO/acre) on non-old-field sites at various locationswithin its range were predicted to increase from ap-

Figure 3-The A. J. Mitchell loblolly pine plantation, WadmalawIsland, SC, at age 12.

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proximately 155 m3/ha (2,200 ft3/acrel at age 15 to300 m3/ha (4,200 ft3/acre) at age 30. Mean annualincrement at age 30 was about 10 m3/ha (145 R3/acre)(1,4,27,33,67). Estimates are also available for avariety of site and stand conditions and geographicareas (8,21,22,23,25,44,68,71).

Growth and yield in natural uneven-aged loblollypine stands is dependent on stand structure, stock-ing, and site quality. To optimize average annualgrowth on average sites with a site index of 27 m (90ft), stand structure should be manipulated so thatapproximately 70 percent of the merchantable cubicvolume is in the saw-log portion of the stand, that is,trees 25 cm (10 in) in d.b.h. and larger. On averagesites, stands with approximately 17 m2/ha (75ft2/acre) of basal area, or 140 m3/ha (2,000 ft3/acre)total merchantable volume, or 10,000 fbm saw-logvolume at the end of the cutting cycle would be con-sidered well stocked (5,84,86).

On good sites in southern Arkansas, with a siteindex of 27 m (90 ft) managed uneven-aged loblollypine stands that are well stocked have averaged 0.7m2/ha (3 ft2/acre) of basal-area growth, 5.6 m3/ha (80ft3/acre) of merchantable volume growth, or 432fbm/acre of saw-log volume growth per year for a29-year period. On somewhat poorer sites in theGeorgia Piedmont with a site index of 23 m (75 ft),annual growth has averaged 5.3 m3/ha (76 ft3/acre>or 319 fbm/acre over a 21-year period (5,17,82,85,86).

In sapling stands, differences in growth rate ofindividual loblolly pines are evident at early ageswhen competition between trees begins. The growthdifferentiation process begins at earlier ages on bet-ter sites or at higher levels of stocking; it begins lateron poor sites or at low levels of stocking (51). Theresult is separation of trees into crown classes.Growth in height is a critical factor in the occupationof available space. Loblolly pine is a species in whichindividual trees tend to express dominance at anearly age, and the most vigorous individuals that arebest adapted to the microsite environment becomedominants as the stand ages.

Faster growing trees develop larger live-crownratios than do slower growing trees. Diametergrowth of individual trees generally increases ascrown surface area and crown ratio increase, withoptimal diameter growth occurring when trees haveat least a 40 percent live-crown ratio. Diameter in-crement does not occur uniformly on portions of thebole. Annual diameter growth is greatest within thecrown and decreases with increased distance belowthe crown. This phenomenon causes the bole ofloblolly pine trees to become cylindrical with increas-ing age (fig. 4). Height growth is not as sensitive asdiameter growth to differences in crown size. Height

Figure 4-A 61-cm (2&n) loblolly pine with three clear logs, onCrossett Experimental Forest, AR.

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growth of codominants is significantly less, however,in dense stands of trees with small crowns than inlow-density stands of trees with larger crowns(37,38,51).

Loblolly pine is a medium-lived tree. Maximumrecorded age of one tree in a small stand of 20 treesin North Carolina was 245 years, with the groupaveraging 240 years. The largest tree in this standwas 135 cm (53 in) in d.b.h. and 45.7 m (150 ft) tall.Currently, the champion for the species in the “Na-tional Register of Big Trees” is located near Urania,LA, and is 143 cm (56.3 in) in d.b.h. and 49.7 m (163ft) tall (52).

Rooting Habit-The rooting habit of loblolly pineis strongly influenced by tree age, soil, and the soilenvironment. A young tree develops a short taprootbut in most cases it ceases growth in favor of anextensive lateral-root system. A taproot 1.5 to 2.0 m(5.0 to 6.5 ft) long is often produced on deep, sandyor loamy soils. On heavy clay soils, the taproot tendsto be stout and short. Taproots of loblolly pines aremuch smaller and shorter than those of shortleaf andlongleaf pines. On excessively wet sites or when awater table or an impenetrable hardpan confines theroots to surface layers of soil, lateral roots areprominent in a superficial system (3,50,108).

In a 6-year-old loblolly pine plantation in southeastLouisiana, 83 percent of total root weight was in theupper 46 cm (18 in) of soil. In a 31-year-old naturalstand in North Carolina, the majority of the feederroots less than 2.5 mm (0.1 in) in diameter wereconcentrated in the 15-cm (6-in) deep A horizon; prac-tically no lateral roots were found below the 15- to53-cm (6- to 21-in) depth of the B horizon (14,59).

Roots of loblolly generally spread laterally fartherthan their crowns. As a result, root grafting is acommon occurrence both in natural stands and close-ly spaced plantations. Roots grow at all times of theyear, but most root growth occurs in April and May,and in late summer and early fall (37,80,89,108).

Reaction to Competition-Loblolly pine ismoderately tolerant when young but becomes in-tolerant of shade with age. Its shade tolerance issimilar to that of shortleaf and Virginia pines, lessthan that of most hardwoods, and more than that ofslash and longleaf pines (31,37,108). Loblolly pine ismost accurately classed as intolerant of shade.

Succession in loblolly pine stands that originate inold fields and cutover lands exhibit a rather predict-able pattern. The more tolerant hardwoods (includ-ing various species of oaks and hickories, sweetgum,blackgum, beech, magnolia, holly, and dogwood) in-vade the understory of loblolly pine stands and, with

time, gradually increase in numbers and in basalarea. The hardwoods finally share dominance witheach other and with loblolly pine (37,83,.200).

The climax forest for the loblolly pine type hasbeen described as oak-hickory, beech-maple, mag-nolia-beech, and oak-hickory-pine in various parts ofits range (28,37). Others view the climax forest asseveral possible combinations of hardwood speciesand loblolly pine. There is evidence that within therange of loblolly pine several different tree speciescould potentially occupy a given area for an in-definite period of time and that disturbance is anaturally occurring phenomenon. If this is so, thenthe climax for this southern forest might best betermed the southern mixed hardwood-pine forest(83).

Competition affects the growth of loblolly pine invarying degrees depending on the site, the amountand size of competing vegetation, and age of theloblolly pine stand. Across the southern region,average loss of volume production resulting fromhardwood competition has been estimated at 25 per-cent in natural stands and 14 percent in plantations(35). In a North Carolina study, residual hardwoodsafter logging reduced cubic-volume growth of a newstand of loblolly pine by 50 percent at 20 years, andwhere additional small hardwoods of sprout andseedling origin were present, growth was reduced byanother 20 percent by age 20 (10,64). Similar growthresponses in young seedling and sapling stands havebeen observed in Arkansas, Louisiana, and Texas(24,26,39). Although several short-term studies (5years or less) of the effects of understory hardwoodson growth of older loblolly pine did not showmeasurable effects (58), a long-term study (11 to 14years) showed growth increases of 20 to 43 percentin cubic volume and 21 to 54 percent in board-footvolume after removal of understory vegetation (39).Control of both residual overstory and understoryhardwoods is a financially attractive silviculturaltreatment for loblolly pine management (10).

Silvicultural practices such as prescribed burns,the use of herbicides, and mechanical treatments ar-rest natural succession in loblolly pine stands byretarding the growth and development of hardwoodunderstories. Prescribed fire is effective formanipulating understory vegetation, reducing exces-sive fuel (hazard reduction), disposing of loggingslash, preparing planting sites and seedbeds, andimproving wildlife habitat. Responses of the under-story to prescribed fire varies with frequency andseason of burning. Periodic winter burns keephardwood understories in check, while a series ofannual summer burns usually reduces vigor and in-creases mortality of hardwood rootstocks (62). In the

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Atlantic Coastal Plain, a series of prescribed burns,such as a winter burn followed by three annual sum-mer burns before a harvest cut, has been more effec-tive than disking for control of competing hardwoodvegetation and improvement of pine seedling growthafter establishment of natural regeneration(103,104).

Loblolly pine expresses dominance early, andvarious crown classes develop rapidly under competi-tion on good sites; but in dense stands on poor sites,expression of dominance and crown differentiationare slower (37).

Dense natural stands of loblolly pine usuallyrespond well to precommercial thinning. To ensurethe best volume gains, stocking should be reduced to1,235 to 1,730 stems per hectare (500 to 700/acre) byage 5. When managing for sawtimber, thinnings in-crease diameter growth of residual trees and allowgrowth to be put on the better trees in the stand,thus maximizing saw-log volume growth andp r o f i t a b i l i t y (56,78).

Loblolly pines that have developed in a suppressedcondition respond in varying degrees to release. In-creases in diameter growth after release are relatedto live-crown ratio and crown growing space, buttrees of large diameter generally respond less thantrees of small diameter. Trees with well-developedcrowns usually respond best to release. Trees longsuppressed may also grow much faster in both heightand diameter after release but may never attain thegrowth rate of trees that were never suppressed(37,751.

Loblolly pine can be regenerated and managedwith any of the four recognized reproduction cuttingmethods and silvicultural systems. Even-agedmanagement is most commonly used on largeacreages; however, uneven-aged management withselection cutting has proved to be a successful alter-native.

Damaging Agents-Agents that cause periodicdamage to individual trees or stands of loblolly pineinclude wind, lightning, temperature extremes, ice,drought, flooding, insects, and diseases. Voluminousliterature about the effects of these agents in loblollypine stands on a range of sites, soils, and standconditions is available; a brief summary follows.

Large dominant trees usually are more vulnerableto high winds than smaller trees, and trees withlarge cankers caused by rust disease break morereadily than sound trees. In general, damage result-ing from severe winds associated with hurricanes orthunderstorms is caused primarily by windthrow orblowdown. Windthrow is most common on shallowsoils with coarse-textured profiles. Wind damage is

also more likely to occur in recently thinned stands(37,105).

Direct losses to lightning are small, averaging onlyabout 5 trees per 100 hectares (2/100 acres> per year.Large, dominant, open-grown trees are generally themost vulnerable to lightning strikes. Probably moreimportant than the direct damage caused by light-ning is the possibility that a lightning-struck treewill become a center for insect infestation (37).

Damage or seedling mortality caused by low orfreezing temperatures occurs primarily in the north-ern extremities of the loblolly pine range. Older,vigorous trees can usually withstand occasional lowtemperatures (37,79). Greater damage frequently oc-curs from ice or glaze storms. This damage is nor-mally associated with branch and stem breakage,severe bending and, in some cases, uprooting. Icedamage is usually more severe in recently thinned(particularly row thinned) plantations and in heavilystocked stands made up of slender, small-crownedtrees (37,91). Extremely high summer temperaturesand drought often cause mortality of seedlings and,in some cases, of larger trees. Heat and drought moreoften cause stress and a resultant loss of vigor andgrowth in larger trees, which can lead to moreserious problems with insect infestations.

Loblolly pine seedlings or saplings cannotwithstand prolonged flooding. Complete inundationfor more than 2 weeks during the growing seasonoften results in significant mortality. Larger trees areclassed as moderately tolerant of flooding; typicallythey can survive one season but usually succumbduring the second growing season if continuously in0.3 m (1 ft) or more of water (37,113).

A comprehensive review of insects associated withloblolly pine is provided by Baker (7). Loblolly pineserves as host to a multitude of insect pests; however,insect outbreaks vary greatly in frequency, area, andduration. The majority of outbreaks are small andshort-lived and usually consist of only one or a fewspots in a stand, but some may expand until theyencompass hundreds of hectares and last for severalyears before subsiding. With only a few exceptions,the majority of the insects that attack loblolly pineare insignificant in terms of damage or mortality.

The most serious insect pests to loblolly pine arebark beetles, particularly the southern pine beetle(Dendroctonus frontalis), whose attack may result inextensive mortality, and pine engraver beetles (Ipsspp.), that can cause death of isolated or smallgroups of trees; pine tip moths (Bhyacionia spp.),that often infest young trees; seedling debarkingweevils (Hylobius spp. and Pachylobius spp.), thatsometimes result in girdling and death of youngseedlings up to 13 mm (0.5 in> in d.b.h.; and cone and

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seed feeders (Dioryctria spp. and Leptoglossus spp.),that can seriously reduce seed crops. Loblolly pine isgenerally the preferred host of the southern pinebeetle, which is the most destructive insect for thisspecies (102). Most infestations originate in standsthat are under stress because of poor site, adverseweather, overstocking, or overmaturity. Once a build-up of southern pine beetle occurs, adjacent well-managed stands may also be attacked. Preventivemeasures include avoidance of planting offsite andmaintenance of vigorous stands through silviculturalpractices such as controlling density through thin-ning and harvesting trees at or before maturity(6,102).

A general account of diseases associated withloblolly pine is provided by Hepting (54). The mostcommon disease problems in loblolly pine are relatedto seedling susceptibility to black root rot (Fusariumspp., Macrophomina spp., and possibly others) andfusiform rust (Cronartium quercuum f. sp.fusiforme); sapling susceptibility to fusiform rust;root rot by Heterobasidion annosum in thinnedstands; and heart rot in old stands with Phellinuspini in the bole and Phaeolus schweinitzii primarilyin the butt.

Nursery seedlings are subject to root rot in soilswith pH above 6.0 under moist conditions; however,root rot becomes severe only if soil temperaturesremain above 32” C (90” F) for long periods. Fusiformrust is also a major nursery disease in many partsof the South, requiring rigid spray programs to keepinfections low.

The most serious stem disease is fusiform rust,which kills and disfigures young trees from Virginiato Texas. Saplings and older trees, especially ifplanted, are subject to attacks by Heterobasidion an-nosum in stands where some cutting has taken place.It is considered a disease problem in plantationmanagement second only to fusiform rust. Losses innatural stands or in the absence of some cutting aregenerally negligible.

Phaeolus schweinitzii causes a root and butt rot,usually after basal or root injuries, and in the DeepSouth it has caused more loss in some areas thanHeterobasidion annosum. Red heart (Phellinus pinil,entering almost entirely through dead branch stubs,is rarely a factor under the age of 60 years. However,when large branches that have heartwood begin todie, red heart can set in and destroy much of a tree.

Special Uses

Natural loblolly pine stands as well as intensivelymanaged plantations provide habitat for a variety ofgame and nongame wildlife species. The primary

game species that inhabit pine and pine-hardwoodforests include white-tailed deer, gray and fox squir-rel, bobwhite quail, wild turkey, mourning doves, andrabbits (94). Some of these species utilize the habitatthrough all stages of stand development, while othersare attracted for only a short time during a par-ticular stage of development. For example, a loblollypine plantation can provide forage for deer only fromthe time of planting to crown closure. Withoutmodifying management practices, this usually occursin 8 to 10 years (13). Bobwhite tend to use the plan-tation until a decline in favored food species occurs(20). As the habitat deteriorates, deer and quailusually move to mature pine or pine-hardwoodforests (47) or to other newly established plantations.Management modifications such as wider plantingspacing and early and frequent thinnings will delaycrown closure, and periodic prescribed burns willstimulate wildlife food production.

Wild turkeys inhabit upland pine and pine-hardwood forests and do particularly well on largetracts of mature timber with frequent openings andwhere prescribed burning is conducted (96,97).

Pine lands are the chief habitat for some birdssuch as the pine warbler, brown-headed nuthatch,and Bachman’s warbler. Old-growth stands are veryimportant to the existence of the red-cockaded wood-pecker. Large loblolly pine trees are favorite roostingplaces for many birds and provide an important nest-ing site for ospreys and the bald eagle (46).

In urban forestry, loblolly pines often are used asshade trees and for wind and noise barriersthroughout the South. They also have been used ex-tensively for soil stabilization and control of areassubject to severe surface erosion and gullying. Loblol-ly pine provides rapid growth and site occupancy andgood litter production for these purposes (114,115).

Biomass for energy is currently being obtainedfrom precommercial thinnings and from loggingresidue in loblolly pine stands. Utilization of theseenergy sources will undoubtedly increase, and loblol-ly pine energy plantations may become a reality.

Genetics

Population Differences

Many studies of racial and geographical variationin loblolly pine have been carried out since researchwith loblolly pine began in the early part of thiscentury. Provenance studies have shown differencesin survival, growth, disease resistance, drought har-diness, and cold hardiness attributable to source ofthe seed. The many findings of geographical differen-ces (some of which show continuous, others discon-

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tinuous variation with geographic location) have ledgeneticists to consider some differences to be racial.Although distinct races of loblolly pine have not beennamed and described, recommended zones for collect-ing seed for planting of seedlings in a givengeographic area have been established. Seed or-chards for producing seed for specific areas havebeen established (29,30,111).

Resistance of certain families of loblolly pine tofusiform rust and the geographic variation in suscep-tibility of loblolly pine to the rust are important re-search findings now in use. Special rust-resistantseed orchards have been established with the mostrust-resistant clones producing seed for specificgeographic areas. Rust resistance of seedlings is lowfrom seed sources in some areas such as east Texasand high for those in other areas such as Georgiaand South Carolina. Rust resistance seems to beclinal and is strongly related to longitude of the seedsource-the westerly sources are more resistant thanthe easterly ones (30,109, II 7).

Loblolly pine from the Lost Pines area of eastTexas is more drought resistant than those withmore easterly seed sources. The use of drought-hardystrains of loblolly pine for planting in drought-proneareas is most important. Cold hardiness is also animportant characteristic to be considered, especiallyif loblolly is to be planted north or inland of itsnatural range. As expected, the more northerly sour-ces of loblolly pine are more cold resistant (29,37).

Seed source affects yields of loblolly pine. Theseyield differences are usually attributable to the com-bined effects of seed source on survival, height anddiameter growth, and susceptibility to fusiform-rustinfection. Clinal effects in growth also are evident inthe data, with trees from coastal areas growingfaster than those from inland sources, except in nor-therly plantings. Loblolly pine trees within a seedsource also vary in growth. Progeny tests of half-sibfamilies (most of which are less than 10 years old)have shown significant differences in height growthwith differences between races and families beingadditive. Nursery-bed selections of plus-seedlingshave been effective in producing height growth gainsfor loblolly pine of 45 percent at age 10, and volumeof the average plus-tree was 3.4 times that of thecontrol. Although gains in other traits are not consis-tent, nursery-bed selection appears to be an effectivefirst step in choosing fast-growing seedlings(30,53,109,112).

Wood characteristics of loblolly pine have been ex-tensively investigated. Specific gravity generallydecreases from southeast to northeast and from thecoastal areas to the Piedmont. Wide tree-to-treevariation also has been found for specific gravity,

tracheid length, fiber angle, and cellulose type. Amost important research result for geneticists hasbeen that wood quality characteristics and growthrate at older ages are not highly correlated and, moreimportant, not negatively correlated, which allowsbreeding for several traits (30).

Hybrids

The best-known southern pine hybrid is Sondereg-ger pine (Pinus x sondereggeri H. H. Chapm.), across between longleaf and loblolly pine. This naturalhybrid occurs quite frequently in Louisiana and eastTexas. It is conspicuous in nursery beds and plant-ings of longleaf pine because the hybrid gains heightgrowth in the first year in contrast to longleaf seed-lings, which do not. Natural hybrids of pond andloblolly pine have been observed in North Carolina,and those of pond, loblolly, and pitch pine have beenrecognized and studied in New Jersey, Delaware, andMaryland (37,87). Natural hybrids of loblolly andshortleaf are known to occur in Oklahoma and eastTexas (29,37,49), and based on observations of treecharacteristics intermediate between loblolly andshortleaf, they probably also occur in Louisiana andArkansas in areas where the two species commonlyoccur together. Hybridization between these twospecies is thought to contribute to the fusiform-rustresistance of loblolly pine from those sources (29).

Artificial hybrids of loblolly pine and the othersouthern yellow pines have been produced. ‘Iwo cros-ses-loblolly x shortleaf pine and loblolly x pitchpine-show considerable promise for use on a com-mercial scale. The loblolly x shortleaf cross will beused in areas with high fusiform-rust incidence forbreeding a strain of loblolly pine resistant to thedisease (60). The loblolly x pitch cross has growthcharacteristics of loblolly pine and cold resistance ofpitch pine, making the hybrid more suitable forplantings in the north (30).

Literature Cited

1. Amateis, Ralph L., Harold E. Burkhart, Bruce R. Knoebel,and Peter T. Sprinz. 1984. Yields and size classdistributions for unthinned loblolly pine plantations oncutover site-prepared lands. School of Forestry and WildlifeResources Publication No. FWS-2-84. Virginia PolytechnicInstitute and State University, Blacksburg, VA. 69 p.

2. Andrulot, A. E., L. P. Blackwell, and P. Y. Burns. 1972.Effects of thinning on yield of loblolly pine in centralLouisiana. Louisiana Tech. University, Bulletin 6. Ruston.145 p.

3. Ashe, W. W. 1915. Loblolly or North Carolina pine. NorthCarolina Geological and Economic Survey, Bulletin 24.Raleigh. 176 p.

Pinus taeda

4. Bailey, Robert L., Galen E. Grider, John W. Rheney, andLeon V. Pienaar. 1985. Stand structure and yields for site-prepared loblolly pine plantations in the Piedmont andupper coastal plain of Alabama, Georgia, and SouthCarolina. The University of Georgia College of AgricultureExperiment Stations Research Bulletin 328. The Universityof Georgia, Athens. 118 p.

5. Baker, James B. 1986. The Crossett farm forestry fortiesafter 41 years of selection management. Southern Journalof Applied Forestry 10(4):233-237.

6. Baker, James B., and William E. Balmer. 1983. Silvicultural systems for the major forest types of theUnited States. Russell M. Burns, tech. camp. p. 148-152.USDA Forest Service, Agriculture Handbook 445.Washington,DC.

7. Baker, Whiteford L. 1972. Eastern forest insects. U.S.Department of Agriculture, Miscellaneous Publication 1175.Washington, DC. 642 p.

8. Baldwin, V. C., Jr., and D. P. Feduccia. 1987. Loblolly pinegrowth and yield prediction for managed West Gulfplantations. USDA Forest Service, Research Paper SO-236.Southern Forest Experiment Station, New Orleans, LA.27 p.

9. Balmer, W. E., E. G. Owens, and J. R. Jorgenson. 1975.Effects of spacings on loblolly pine growth 15 years afterplanting. USDA Forest Service, Research Note SE-211.Southeastern Forest Experiment Station, Asheville, NC.7 P.

10. Balmer, W. E., K. A. Utz, and 0. G. Langdon. 1978.Financial return from cultural work in natural loblolly pinestands. Southern Journal of Applied Forestry 2(4):111-117.

11. Barnett, J. P. 1970. Germination inhibitors unimportant indormancy of southern pine seeds. USDA Forest Service,Research Note SO-112. Southern Forest ExperimentStation, New Orleans, LA. 4 p.

12. Bassett, J. R. 1964. Tree growth as affected by soil moistureavailability. Soil Science Society of America Proceedings28~436-438.

13. Blair, R. M., and H. G. Enghardt. 1976. Deer forage andoverstory dynamics in a loblolly pine plantation. Journal ofRange Management 29(2):104-108.

14. Box, B. H. 1967. A study of root extension and biomass in asix-year-old pine plantation in southeast Louisiana. Thesis(Ph.D.). Duke University, School of Forest Resources,Durham, NC. 178 p.

15. Boyer, William D. 1970. Shoot growth patterns of youngloblolly pine. Forest Science 16(4):472-482.

16. Boyer, William D. 1978. Heat accumulation: an easy way toanticipate the flowering of southern pines. Journal ofForestry 76(1):20-23.

17. Brender, E. V. 1973. Silviculture of loblolly pine in theGeorgia Piedmont, Georgia Forest Research Council, Report33. Macon. 74 p.

18. Brender, E. V., and J. L. Clutter. 1970. Yield of even-agednatural stands of loblolly pine. Georgia Forest ResearchCouncil, Report 23. Macon. 7 p.

19. Brown, Claud L. 1976. Forests as energy sources in the year2000: what man can imagine, man can do. Journal ofForestry 74(1):7-12.

20. Brunswig, N. L., and A. S. Johnson. 1972. Bobwhite quailfoods and populations in the Georgia Piedmont during thefirst seven years following site preparation. ProceedingsSoutheastern Association of Game and Fish Commissioners26:96-107.

21. Burkhart, Harold E., and Peter T. Sprinz. 1984. A model forassessing hardwood competition effects on yields of loblollypine plantations. School of Forestry and Wildlife ResourcesPublication No. FWS-3-84. Virginia Polytechnic Instituteand State University, Blacksburg, VA. 55 p.

22. Burkhart, Harold E., Quang V. Cao, and Kenneth D. Ware.1981. A comparison of growth and yield prediction modelsfor loblolly pine. School of Forestry and Wildlife ResourcesPublication No. FSW-2-81. Virginia Polytechnic Instituteand State University, Blacksburg, VA. 59 p.

23. Burkhart, Harold E., Kenneth D. Farrar, Ralph L. Amateis,and Richard F. Daniels. 1987. Simulation of individual treegrowth and stand development in loblolly pine plantationson cutover, site-prepared areas. School of Forestry andWildlife Resources Publication No. FWS-1-87. VirginiaPolytechnic Institute and State University, Blacksburg, VA.47 p.

24. Cain, M. D., and W. F. Mann, Jr. 1980. Annual brushcontrol increases early growth of loblolly pine (Pinus tuedu).Southern Journal of Applied Forestry 4(2):67-70.

25. Cao, Quang V., Harold E. Burkhart, and Ronald C. Lemin,Jr. 1982. Diameter distributions and yields of thinnedloblolly pine plantations. School of Forestry and WildlifeResources Publication No. FWS-1-82. Virginia PolytechnicInstitute and State University, Blacksburg, VA. 62 p.

26. Clason, T. R. 1978. Removal of hardwood vegetationincreases growth and yield of a young loblolly stand.Southern Journal of Applied Forestry 2(3):96-97.

27. Clutter, Jerome L., William R. Harms, Graham H. Brister,and John W. Rheney. 1984. Stand structure and yields ofsite-prepared loblolly pine plantations in the lower coastalplain of the Carolinas, Georgia, and north Florida. USDAForest Service, General Technical Report SE-27.Southeastern Forest Experiment Station, Asheville, NC.173 p.

28. Delcourt, H. R., and P. A. Delcourt. 1977. Presettlementmagnolia-beech climax of the Gulf coastal plain:quantitative evidence from the Apalachicola river bluffs,north-central Florida. Ecology 55:1085-1093.

29. Dorman, Keith W. 1976. The genetics and breeding ofsouthern pines. U. S. Department of Agriculture,Agriculture Handbook 471. Washington, DC. 407 p.

30. Dorman, Keith W., and B. J. Zobel. 1973. Genetics ofloblolly pine. USDA Forest Service, Research Paper WO-19.Washington, DC. 21 p.

31. Eyre, F. H., ed. 1980. Forest cover types of the UnitedStates and Canada. Society of American Foresters,Washington, DC. 148 p.

32. Farrar, Robert M., Jr., Paul A. Murphy, and R. LarryWillett. 1984. Tables for estimating growth and yield ofuneven-aged stands of loblolly-shortleaf pine on averagesites in the West Gulf area. Arkansas AgriculturalExperiment Station Bulletin 874. University of Arkansas,Fayetteville, AR. 21 p.

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3 3 . Feduccia, D. P., T. R. Dell, W. F. Mann, Jr., T. E. Campbell,and B. H. Polmer. 1979. Yields of unthinned loblolly pineplantations on cutover sites in the West Gulf region. USDAForest Service, Research Paper SO-148. Southern ForestExperiment Station, New Orleans, LA. 88 p.

34. Ferguson, E. R. 1956. Causes of first-year mortality ofplanted loblolly pines in east Texas. In Proceedings, AnnualMeeting, Society of American Foresters, 1956. p. 89-92.

35. Fitzgerald, Charles H., Fred A. Peevy, and Darwin E.Fender. 1973. Rehabilitation of forest land: the SouthernRegion. Journal of Forestry 71(3):148-162.

36. Foil, R. R., and C. W. Ralston. 1967. The establishment andgrowth of loblolly pine seedlings on compacted soils. SoilScience Society of America Proceedings 31(4):565-568.

37. Fowells, H. A., camp. 1965. Silvics of forest trees of theUnited States. U.S. Department of Agriculture, AgricultureHandbook 271. Washington, DC. 762 p.

3 8 . Grano, Charles X. 1969. Precommercial thinning of loblollypine. Journal of Forestry 67(11):825-827.

39. Grano, C. X. 1970. Small hardwoods reduce growth of pineoverstory. USDA Forest Service, Research Paper SO-55.Southern Forest Experiment Station, New Orleans, LA. 9 p.

40. Grano, C. X. 1971. Conditioning loessial soils for naturalloblolly and shortleaf pine seeding. USDA Forest Service,Research Note SO-116. Southern Forest ExperimentStation, New Orleans, LA. 4 p.

4 1 . Greenwood, M. S. 1978. Flowering induced on young loblollypine grafts by out-of-phase dormancy. Science201(4354):443-444,

42. Greenwood, M. S., T. M. Marino, R. D. Meier, and K. W.Shahan. 1980. The role of mist and chemical treatments inrooting loblolly and shortleaf pine cuttings. Forest Science26(4):651-655.

43. Griffing, Charles G., and William W. Elam. 1971. Heightgrowth patterns of loblolly pine saplings. Forest Science17:52-54.

4 4 . Hafley, W. L., W. D. Smith, and M. A. Buford. 1982. A newyield prediction model for unthinned loblolly pineplantations. Southern Forest Research Center, School ofForest Resources Technical Report No. 1. North CarolinaState University, Raleigh. 65 p,

45. Haines, L. W., T. E. Maki, S. G. Sanderford, and others.1975. The effect of mechanical site preparation treatmentson soil productivity and tree (Pinus taeda & P. elliottii)growth. In Forest soils and forestland management,Proceedings, Fourth North American Forest SoilsConference. p. 379-386. Lava1 University Press, Quebec,PQ.

4 6 . Halls, Lowell K., ed. 1977. Southern fruit-producing woodyplants used by wildlife. USDA Forest Service, GeneralTechnical Report SO-16. Southern Forest ExperimentStation, New Orleans, LA. 235 p.

47. Halls, L. K., and J. J. Stransky. 1971. Atlas of southernforest game. USDA Forest Service, Southern ForestExperiment Station, New Orleans, LA, 24 p.

48. Hare, R. C. 1965. Breaking and rooting of fascicle buds insouthern pines. Journal of Forestry 63:544-546.

49. Hare, R. C., and G. L. Switzer. 1969. Introgression withshortleaf pine may explain rust resistance in westernloblolly pine. USDA Forest Service, Research Note SO-88.Southern Forest Experiment Station, New Orleans, LA. 7 p.

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50. Harlow, W. M., E. S. Harrar, and F. M. White. 1978.Textbook of Dendrology. 6th ed. McGraw-Hill, New York.510 p.

51. Harms, William R., and 0. Gordon Langdon. 1976.Development of loblolly pine in dense stands. Forest Science22(3):331-337.

52. Hartman, Kay. 1982. National register of big trees.American Forests 88(4):17-31,34-48.

53. Hatchell, Glyndon E., Keith W. Dorman, and 0. GordonLangdon. 1972. Performance of loblolly and slash pinenursery selection. Forest Science 18(4):308-313.

54. Hepting, George H. 1971. Diseases of forest and shade treesof the United States. U.S. Department of Agriculture,Agriculture Handbook 386. Washington, DC. 658 p.

55. Hunt, C. B. 1967. Physiography of the United States. W. H.Freemont Company, San Francisco, CA. 480 p.

56. Jones, E. P. 1974. Precommercial thinning for slash andloblolly pines. In Proceedings, Symposium on Managementof Young Pines. p. 229-233. USDA Forest Service,Southeastern Area State and Private Forestry, Atlanta, GA.

57. Jones, Leroy, and Sam Thacker. 1965. Survival. In A guideto loblolly and slash pine plantation management insoutheastern USA. p. 68-73. Georgia Forest ResearchCouncil, Report 14. Macon.

58. Klawitter, R. A. 1966. Diameter growth of mature loblollyunaffected by understory control. Southern Lumberman213(2656):154-155.

59. Korstian, C. F., and T. S. Coile. 1938. Plant competition inforest stands. Duke University School of Forest Resources,Bulletin 3. Durham, NC. 125 p.

60. Kraus, J. F., and T. LaFarge. 1977. The use of Pinusechinata x taeda hybrids for the development of P. taedaresistant to Cronartium fusifofme. In Intraspecifichybridization in plant breeding. p. 377-381. Proceedings of8th EUCARPIA Congress. (Madrid, Spain)

61. Langdon, 0. Gordon. 1979. Natural regeneration of loblollypine. In Proceedings, National Silviculture Workshop. p.191-116. USDA Forest Service, Washington, DC.

62. Langdon, 0. G. 1981. Some effects of prescribed fire onunderstory vegetation in loblolly pine stands. In PrescribedFires and Wildlife in Southern Forests: Proceedings of aSymposium; April 6-8, Myrtle Beach, SC. Gene W. Wood,ed. p. 143-154. Belle Baruch Forest Institute, Georgetown,SC.

63. Langdon, 0. G., and W. H. McKee, Jr. 1981. Canfertilization of loblolly pine on wet sites reduce the need fordrainage? In Proceedings, First Biennial SouthernSilvicultural Research Conference. p. 212-218. USDAForest Service, General Technical Report SO-34. SouthernForest Experiment Station, New Orleans, LA.

64. Langdon, 0. G., and K. B. Trousdell. 1974. Increasinggrowth and yield of natural loblolly pine by young standmanagement. In Proceedings, Symposium on Managementof Young Pines. p. 288-296. USDA Forest Service,Southeastern Area State and Private Forestry, Atlanta, GA.

65. Langdon, 0. G., and K. B. Trousdell. 1978. Standmanipulation: effects on soil moisture and tree growth insouthern pine and pine-hardwood stands. In Proceedings,Symposium on Soil Moisture-Site Productivity, MyrtleBeach, SC. p. 221-236. USDA Forest Service, SoutheasternArea State and Private Forestry, Atlanta, GA.

6 6 . Lantz, C. W. 1973. Survey of graft incompatibility in loblollypine. In Proceedings, Twelfth Southern Forest TreeImprovement Conference. p. 79-85.

67. Ledbetter, Julia R., Alfred D. Sullivan, and Thomas G.Matney. 1986. Yield tables for cutover site-prepared loblollypine plantations in the Gulf coastal plain. MississippiAgricultural and Forestry Experiment Station TechnicalBulletin 135. Mississippi State University, MississippiState. 31 p.

68. Lenhart, David J. 1988. Diameter-distribution yield-prediction system for unthinned loblolly and slash pineplantations on non-old-fields in East Texas. SouthernJournal of Applied Forestry 12(41:239-242.

69. Little, Elbert L., Jr. 1971. Atlas of United States trees.vol. 1. Conifers and important hardwoods. U.S. Departmentof Agriculture, Miscellaneous Publication 1146.Washington, DC. 9 p., 313 maps.

70. Little, S., and H. A. Somes. 1959. Viability of loblolly pineseed stored in the forest floor. Journal of Forestry57(11):848-849.

71. Matney, T. G., A. D. Sullivan, and J. R. Ledbetter. 1986.Diameter distributions and merchantable volumes forplanted loblolly pine in cutover site-prepared land in theWest Gulf coastal plain. Mississippi Agricultural andForestry Experiment Station Technical Bulletin 132.Mississippi State University, Mississippi State. 12 p.

72. McKee, W. F., Jr. 1981. Personal communication. USDAForest Service, Southeastern Forest Experiment Station,Asheville, NC.

73. McLemore, B. F. 1964. Light during stratification hastensdark-germination of loblolly pine seed. Forest Science10(3):348-349.

74. McLemore, B. F. 1966. Temperature effects on dormancyand germination of loblolly pine seed. Forest Science12(3):284-289.

75. McLemore, B. F. 1987. Development of intermediate andsuppressed loblolly pines following release. In Proceedings,Fourth Biennial Southern Silvicultural ResearchConference. p. 439-444. USDA Forest Service, GeneralTechnical Report SE-42. Southeastern Forest ExperimentStation, Asheville, NC.

76. Maki, T. E. 1971. Drainage: effect on productivity. InProceedings, Annual Meeting, Society of AmericanForesters, Applied Section. p. 16-23.

77. Mann, W. F., Jr., and T. R. Dell. 1971. Yields of l7-year-oldloblolly pine planted on cutover site at various spacings.USDA Forest Service, Research Paper SO-70. SouthernForest Experiment Station, New Orleans, LA. 9 p.

78. Mann, W. F., Jr., and R. E. Lohrey. 1974. Precommercialthinning of southern pine. Journal of Forestry42(9):557-560.

79. Mignery, A. L. 1967. Winter injury to loblolly pine inTennessee related to seed origin. Southern Lumberman215(2680):146.

80. Miller, L., and F. W. Woods. 1965. Root-grafting in loblollypine. Botanical Gazette 126:252-255.

81. Murphy, Paul A. 1983. Merchantable and sawtimbervolumes for natural even-aged stands of loblolly pine in theWest Gulf region. USDA Forest Service, Research PaperSO-194. Southern Forest Experiment Station, NewOrleans, LA. 38 p.

Pinus taeda

82. Murphy, P. A., and R. M. Farrar. 1982. Interim models forbasal area and volume projection of uneven-aged loblolly-shortleaf pine stands. Southern Journal of Applied Forestry6(2):115-119.

83. Quarterman, E., and C. Keever. 1962. Southern mixedhardwood forest: climax in the southeastern coastal plainUnited States of America. Ecological Monographs32(2):167-185.

84. Reynolds, R. R. 1959. Eighteen years of selection timbermanagement on the Crossett Experimental Forest. U.S.Department of Agriculture, Technical Bulletin 1206.Washington, DC. 68 p.

85. Reynolds, R. R. 1969. Twenty-nine years of selection timbermanagement on the Crossett Experimental Forest. USDAForest Service, Research Paper SO-40. Southern ForestExperiment Station, New Orleans, LA. 19 p.

86. Reynolds, R. R., James B. Baker, and Timothy T. Ku. 1984.Four decades of selection management on the Crossett farmforestry forties. Arkansas Agricultural Experiment StationBulletin 872. University of Arkansas, Fayettevile, AR. 43 p.

87. Saylor, L. C., and K. W. Kang. 1973. A study of sympatricpopulations of Pinus taeda L. and Pinus serotina Michx. inNorth Carolina. Journal of the Elisha Mitchell ScientificSociety 89:101-110.

88. Schopmeyer, C. S., tech. coord. 1974. Seeds of woody plantsin the United States. U.S. Department of Agriculture,Agriculture Handbook 450. Washington, DC. 883 p.

89. Schultz, Robert P., and Frank W. Woods. 1967. Thefrequency and implications of intraspecific root-grafting inloblolly pine. Forest Science 13:226-239.

90. Schumacher, F. X., and T. S. Coile. 1960. Growth and yieldof natural stands of the southern pines. T. S. Coile, Inc.Durham, NC. 115 p.

91. Shepard, R. K., Jr. 1974. Ice storm damage to thinnedloblolly pine plantations in northern Louisiana. SouthernJournal of Applied Forestry 2(3):83-85.

92. Smalley, G. W. 1979. Classification and evaluation of forestsites on the southern Cumberland Plateau. USDA ForestService, General Technical Report SO-23. Southern ForestExperiment Station, New Orleans, LA. 59 p.

93. Smalley, G. W., and R. L. Bailey. 1974. Yield tables andstand structure for loblolly pine plantations in Tennessee,Alabama, and Georgia highlands. USDA Forest Service,Research Paper SO-96. Southern Forest ExperimentStation, New Orleans, LA. 81 p.

94. Smeltzer, R. H., R. L. Mott, and A. Mehra-Polta. 1977.Influence of parental tree genotype in the potential for invitro cloning progenation from loblolly pine embryos. InForest biology wood chemical conference, 1977. p. 5-8.Tappi Press, Atlanta, GA.

95. Stewart, J. T. 1965. Regenerating loblolly pine with fourseed trees. Virginia Forests 20(2):14-B% 26,28.

96. Stoddard, H. L. 1963. Maintenance and increase of theeastern wild turkey on private lands of the Coastal Plain ofthe Deep Southeast. Tall Timbers Research Station,Bulletin 3. Tallahassee, FL. 49 p.

97. Stransky, J. J., and L. K. Halls. 1967. Timber and gamefood relations in pine-hardwood forests of the southernUnited States. In Proceedings, Fourteenth InternationalUnion of Forestry Research Organizations Congress. p.208-217.

511

Pinus taeda

9 8 .

9 9 .

100.

101.

102.

103.

104.

105.

106.

Stransky, J. J., and D. R. Wilson. 1964. Terminal elongationof loblolly and shortleaf pine seedlings under soil moisturestress. Soil Science Society of America Proceedings28:439-440.Sullivan, Alfred D., and Jerome L. Clutter. 1972. Asimultaneous growth and yield model for loblolly pine.Forest Science 18(1):76-86.Switzer, G. L., M. G. Shelton, and L. E. Nelson. 1979.Successional development of the forest floor and soil surfaceon upland sites of the East Gulf Coastal Plain. Ecology60(6):1162- 1171.Terry, T. A., and J. H. Hughes. 1975. The effects ofintensive management on planted loblolly pine (Pinus toedaL.) growth on poorly drained soils of the Atlantic CoastalPlain. In Forest soils and forest land management.Proceedings, Fourth North American Forest SoilsConference. p. 351-377. Lava1 University Press, Quebec,PQ.Thatcher, R. C., J. L. Searcy, J. E. Coster, and others, eds.1980. The southern pine beetle. U.S. Department ofAgriculture, Technical Bulletin 1631. Washington, DC.267 p.Trousdell, K. B. 1970. Disking and prescribed burning: sixthyear residual effects on loblolly pine and competingvegetation. USDA Forest Service, Research Note SE-133.Southeastern Forest Experiment Station, Asheville, NC.6 P.Trousdell, Kenneth B., and 0. Gordon Langdon. 1967.Disking and prescribed burning for loblolly pineregeneration. Journal of Forestry 65(5):548-551.Trousdell, Kenneth B., Wilfred C. Williams, and Thomas C.Nelson. 1965. Damage to recently thinned loblolly pinestands by Hurricane Donna. Journal of Forestry63(2):96-100.U.S. Department of Agriculture, Forest Service. 1929.Volume, yield, and stand tables for second-growth southernstands. U.S. Department of Agriculture, MiscellaneousPublication 50. Washington, DC. 202 p.

107.

108.

109.

110.

111.

112.

113.

114.

115.

116.

117.

U.S. Department of Agriculture, Soil Conservation Service.1975. Soil taxonomy: a basic system of soil classification formaking and interpreting soil surveys. Soil Survey Staff,coords. U.S. Department of Agriculture, AgricultureHandbook 436. Washington, DC. 754 p.Wahlenberg, W. G. 1960. Loblolly pine: its use, ecology,regeneration, protection, growth, and management. DukeUniversity, School of Forestry, Durham, NC. 603 p.Wakeley, Philip C., and T. E. Bercaw. 1965. Loblolly pineprovenance test at age 35. Journal of Forestry 63:168-174.Wells, D. W., and M. Reines. 1965. Vegetative propagationof needle bundles of pines. Georgia Forest Research Council,Report 26. Macon. 8 p.Wells, 0. 0. 1969. Results of the southwide pine seed sourcestudy through 1968-69. In Proceedings, Tenth SouthernForest Tree Improvement Conference. p. 117-129.Wells, 0. O., and P. C. Wakeley. 1966. Geographic variationin survival, growth, and fusiform-rust infection of plantedloblolly pine. U.S. Department of Agriculture, Monograph11. Washington, DC. 40 p.Williston, H. L. 1962. Loblolly seedlings survive twelvedays’ submergence. Journal of Forestry 60:412.Williston, H. L. 1971. Guidelines for planting andmaintaining loblolly pine and other cover for road bankstabilization. Tree Planters’ Notes 22(2):14-17.Williston, H. L., and S. J. Ursic. 1979. Planting loblolly pinefor erosion control: a review. Tree Planters’ Notes30(2):15-18.Zahner, R. 1968. Water deficits and the growth of trees. InWater deficits and plant growth, vol. 2. Plant waterconsumption and response. p. 191-254. Academic Press,New York.Zobel, Bruce J., Roger Blair, and Marvin Zoerb. 1971. Usingresearch data: disease resistance. Journal of Forestry69:486-489.

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