Stephen F. Austin State UniversitySFA ScholarWorksForestry Bulletins No. 1-25, 1957-1972 Journals9-1972Forestry Bulletin No. 25: Silviculture of SouthernBottomland HardwoodsLaurence C. WalkerStephen F. Austin State UniversityKenneth G. WattersonStephen F. Austin State UniversityFollow this and additional works at: http://scholarworks.sfasu.edu/forestrybulletinsPart of the Other Forestry and Forest Sciences CommonsTell us how this article helped you.This Book is brought to you for free and open access by the Journals at SFA ScholarWorks. It has been accepted for inclusion in Forestry Bulletins No.1-25, 1957-1972 by an authorized administrator of SFA ScholarWorks. For more information, please contact cdsscholarworks@sfasu.edu.Recommended CitationWalker, Laurence C. and Watterson, Kenneth G., "Forestry Bulletin No. 25: Silviculture of Southern Bottomland Hardwoods" (1972).Forestry Bulletins No. 1-25, 1957-1972. Book 22.http://scholarworks.sfasu.edu/forestrybulletins/22BULLETIN 25PRICE $2.00SEPTEMBER 1972SILVICULTURE OFSOUTHERNBOTTOMLAND HARDWOODSLaurence C. WalkerKenneth G. Wa"erston(Seventh of a Series an the Silviculture of Southern Forests)Sponsored by the Conservation FoundationSchool of ForestrySTEPHEN F. AUSTIN STATE UNIVERSITYNacogdoches, TexasDrought.. .. .. . . . . . . .. . . 41Oaks ..................................•...•...•...•......42Vigor Classes 42Site Index ...................•.......................... 42Natural Regeneration 46Artificial Regeneration ........................•...•...... 47Planting ...................•......................... 47Direct Seeding ..........................•...•... _ 47Pruning. . . . . . . . . .. . ..........•.........•...•... _ 49Injurious Agents 49Disease 49Wood Quality 53Sweetgum . . . . . . . . . . . . . . . . . . . . . . . . 54Vigor Classes ....................•...................... 54Site Index 56Injurious Agents ...............•........................ 58Disease .............................•...•............58~ roWater tupelo ............................•...•............ 61Seed viability under water 62Thinning 62American Sycamore. . . . . 64Site Index........................... . 64Regeneration 64Propagation by cutting 64Planting 65Thinning .......................•.......................66Yellow Poplar 67Fertilization . 67Flooding . . . . . . . . . . . . . 67Literature Cited. . . . . . . . . . . . . . . . . . 69Scientific names of tree species cited 75lIIIBOITOMLAND REGIONS IThe potential of southern bottomland hardwood types is clear, forthey, along with cypress, occupy about 37 million acres and comprisemore than half of the hardwood stumpage in the South (Stemitzke,1962). Although the Mississippi Delta, the broad flood plain of theMississippi and its tributaries below the mouth of the Ohio, and thebelts of hardwoods flanking the countless secondary waterwaysthroughout the South are the principal areas of growth, the type isalso found in swamps, bogs, ponds, and branch heads (Figure 1).Much of this land is inherently productive, capable of growingannually 500 board feet (Doylel of high value wood per acre. Another% cord can be produced from lopwood and small trees removed forcultural purposes.Figure 1. In addition to the flood plains of major rivers, swamps,[left] and creek and stream bottoms intersDersed amonJr pine sites[right] produce much hardwood timber. U. S. ForestService Photo.Mississippi River Delta 2Hardwood silviculture in the Mississippi River Delta is primarilysawlog silviculture aimed at producing large, defect-free timber ofhigh value for furniture, flooring, cooperage, lumber, veneer, andspecialty products. The recently expanded markp.t for pulpwood fromI MiUer 0967) is an excellent bibliography dealing with southern hardwoods.2 Putnam 0951) and Putnam, Fumival, and McKnight (19601 are excellentreferences on the subject. Much of the material that follows, not otherwise cited, isfrom these sources.Ideciduous trees in the lower part of the region is making intensivemanagement of hardwood. stands increasingly practical. Not only aregrowth rates of bottomland species excellent, reproduction isgenerally prolific and occurs naturally if sites are protected fromgrazing by wildlife and domestic stock, and from fire and disastrousflooding.In the two years, 1916 and 1925, 85 Percent of the bottoms north ofthe Red River were burned.. While wildfire has left the forest with ahigh proportion of low-grade trees, culls, and undesirable species,mere presence of recent or incipient fire injury is not sufficient reasonfor intensive salvage operations. A single fire every 10 yearsprevents restocking of good. trees and destroys the humus 50 thatsoils become puddled. and dry to rock-like hardness. Regeneration isdifficult to obtain where coarse, loose, sandy soils are at the surfaceor just below a thin veneer of fine material. In those soils, occurringbetween levees, the water table in summer is likely to be too deep toenable delivery of the moisture by capillarity through the sand.Other difficult sites are those with plastic clay, as on the low flats,and the hardpan and silty clay basins of the terraces. There, moistureand aeration are unfavorable and willow oak is generally theprincipal species present.Soils and PhysiographyBottomlands, typically hardwood. and cypress sites, have azonalsoils too immature to have well-defined horizons. Forest sites andtimber types are closely allied. to and distinguished by topographicfeatures (Table 1). First bottoms, major sites of relatively recentorigin comprising the present main flood plain, are frequentlyflooded. The soils there are chiefly waxy clay and fine sandy looms,but may be coarser. Silt is relatively less important, impervious soilshere being plastic clays. Terraces, or second bottoms, are older,higher areas which flood. only occasionally and on which acidic siltloams and silty clay loams are major textural classes. Low areas mayhave impervious silty clay.2Table 1. Southern bottomland forest types and their major characteristics [from Putnam, 1951].TypeSweetgum-water oaksWhite oaks-red oaks-other hardwoodsOccurrenceby siteIn first bottoms except deepsloughs, swamps, fronts, andpoorest flat sites. Also onon terrace flats.Best fine, sandy loam soilson first Dottom ridges andall ridges on the terraces.Type extends on first bottomridges to a few peculiar,well-drained soils other thansandy loam.General featuresMost widely distributed type.Second in quality, thoughnothing excels the best ofthis type. Produces highvalue factory lumber and ve-neer logs.Highest value type, with bestspecies and highest qualityproducts. Second only tosweetgum water oaks typein area. Produces high-qualitytight cooperage, factorylumber, veneer logs.Common vanationsin type(a) Predominately sweetgum:on well-drained first bottomridges and pervious silty clayson terrace flats. (b) Predom-inantly water oaks: on heaviersoils on first bottom ridgesand better drained flat~ unpoorly drained flats on terracesNuttall oak dominates on well-drained first bottom flats.Willow oak prevails on firstbottom ridges and poorlydrained terrace flats, i.e. pineoak flats; near the coastlaurel oak takes over.(c) Cedar elm-water oaks:on poorly drained, impervioussoils on low or indistinct firstbottom ridges. of minor im-portance on imperviousterrace soils.(a) Predominantly white oaks:on the most matured terracesoils. (b) Pine-hardwood: invery limited situations; mostcommon with loblolly onterraces, but also with sprucepine on ridges in first bottomsof small streams of theCoastal Plains east of theMississippi River.River front hardwoodsCypress-tupelo gum(Cypress-swamp blackgum)All front lands except deepsloughs and swamps.Cypress-tupelo gum in verylow, poorly drained flats, deepsloughs, and swamps in firstbottoms and terraces. Cypressswamp blackgum in swampsof the Coastal Plains andriver estuaries.pulpwood make it valuable.Usual poor quality and formmake it of little value awayfrom fronts. With cottonwood,is characteristic of fronts ofmost major streams but com-mercially important only inlower Mississippi Valley.Transition between cotton-wood or willow and thesweetgum-water oaks type.Widely distributed but res-stricted in extent. Very rapidgrowth, moderately valuableproducts for factory lumber,veneer logs, and slackcooperage stock.Widely distributed in smallareas. Extensive areas onlower reaches and estuaries ofmajor streams. Potentiallyhighest value products butgrowth is slow and repro-duction uncertain and difficultto secure.None.(a) Pure Cypress; occursscattered throughout the type.(b) Pure tupelo gum (orswamp blackgum): largelyfollows clearcutting of cypress.Ridges, flats, sloughs, and swamps are secondary sites in bothfirst and second bottoms. In second bottoms, sheet erosion haslessened their evidence. Ridges, high land 2 to 15 feet above flats, arethe banks of former stream courses. Although rarely inundated,seasonal overflows have deposited coarser materials. Surfacedrainage is better than in other topographic classes.Flats, lying between ridges, have poor surface soil drainage and,due to the high proportion of clay, internal drainage is also poor.Followmg floods or heavy seasonal rains, high flats are drained offree water within a few days after rivers or streams are again withintheir banks. Free water in low flats requires several weeks to subside.Sloughs are shallow depressions-usually filled-in streamcourses-in which water collects during wet seasons; while swamps,except during droughts. are inundated. for the greater part of everygrowing season. These alluvial swamps are distinguished fromtidewater and land-locked Coastal Plain muck swamps by a fairlyfinn clay bottom, which sometimes is permanently flooded, incontrast to organic soils c~ntinuously under water.Battures, lying between rivers and levees. usually have silty loamto sandy soils which are frequently inundated. The Mississippi Riverhas some 2,000,000 acres of forested batture containing the fastestgrowing North American hardwoods. eastern cottonwood and blackwillow (Maisenhelder and Heavrin, 1956). Brakes denote cypress-and tupelo-eovered lowlands or swamps.GrowthAverage values for diameter growth vary appreciably by species.For woods-run growing stock on all sites and without management,cottonwood is the fastest growing, exceer.ing 4 inches dbh in a10-year period. Nuttall and willow oaks rank close seconds,averaging between 3V2 and 4 inches (Bull, 1945) (Table 21.Baldcypress on those sites averages slightly less than 1 inch in aIO-year period. Under management. growth of cottonwood andcypress exceeds twice these amounts.Overmature trees. as expected, grow slowly-only 75 percent asfast as mature stems; for example. an overmature virginsweetgum-oak stand which, after a thinning removing one-half of theoriginal volume (12.5 MBM per acre)-mostly in trees over 30 inchesdbh - had an annual growth of less than 200 board feet per acre(Davis, 1935; 1935a). This is less than hali that expected fromwell-managed stands.In a one-year study in southern Louisiana, Eggler (1955) foundcottonwood the fastest growing and red. maple the slowest growingtrees on a silty soil with good drainage and no flooding during theperiod of observation. Sycamore, black willow, and hackberry6Table 2. Average 1Q-year dbh growth of the most commonbottomland hardwoods of sawlog size [after Bull, 1945].Species(Local name in parentheses)Eastern Cottonwood (cottonwood)Nuttall Oak (red oak)Willow Oak (red or pin oaklAmerican Elm (white or soft elm)Honeylocust Uocust)Red Maple (maple)Overcup Oak (white oak)Sweetgum (sweet, red, or sap gum)Green Ash (ashlSugarberry (hackberry)Cedar Elm (rock elm)Water Hickory (bitter pecan)Probable dbh average 1Inches8.!H.03.5-4.08.5-4.08.er3.53.er3.58.er8.52.5·3.02.5-3.02.5-3.02.er2.fj2.er2.fj2.0-2.5I These data apply only to well-formed dominant crop'trees in well-stocked stands.followed cottonwood. Because radial growth in summer ceased whiletemperature was high and soil moisture adequate, drought cannotalways be held responsible for growth cessation in midsummer.Continuous high summer temperatures or photoperiodism may alsobe important factors for the "march" of hardwood growth. Whilemost radial growth is over by August 1, sycamore and water tupelocontinued to grow until early November.Radial growth is subject to over-estimation for bottomland gumsin increment cores, due to failure to distinguish aU rings. Burklel1950l found over-estimation of 10 and 4 percent for blackgum andsweetgum. Maples, on the other hand, are under-estimated by 6percent because of false rings.Stand RehabilitationIn.initiating management, Putnam (1951a) shows that it is firstnecessary to determine which part of the growing stock to retain forthe future. The rest of the forest is overburden: components of thestand whose immediate removal would tend to increase total returnsfrom the stand during the next cycle, or components whose growingspace might be made available to reproduction.Most bottomland hardwood types may be managed as all-agedstands, but small areas might require even-aged stands. Individualtree quality is more important than species in choosing growingstock where quality difference is extreme. Diameter limit cuttingmust be forbidden, as it takes no account of growth rate and thevalue of individual trees.Silvicult.ural practices depend upon basal area, merchantable7volume, forest type, timber quality, markets, and results desired.Inevitably, the first treatment will be an improvement cutsupplemented with a harvest of overmature stems, except in youngstands where the supplemental treatment should be thinning frombelow. Some overburden-undesirable growing stock-should bedeadened early (Putnam and Bull, 1940).Overburden may include overmature and mature timber,undesirable immature stems, as well as culls and weeds. It. usuallycomprises about half the volume in stands not previously managed.A typical Delta stand is described as having 2.5 MBF per acre ofsawtimber in trees 12 inches dbh and over, three-fourths in treesmore than 16 to 18 inches dbh. Forty percent is probably overburdenand should be cut. One-third of the overburden might be expected toproduce No.2 logs; one-half, NO.3 logs; and the balance a fewcrossties. Only one-tenth of the overburden volume, amounting to anaverage of 2Yt trees per acre, is likely to be in cull trees. For trees lessthan 12 inches dbh, stand volumes usually amount to about 3 cordsper acre, one-half of which is overburden. If undesirable trees of thesmallest sizes are not cut, they will die. unless left in an opening,before doing any harm. Ordinarily, overburden trees more than 6inches dbh should be removed. Three-fourths of the volume in treesover 30 inches dbh is likely to be high quality, in contrast to 40percent of the volume in smaller trees.Generally, mature trees are 20 to 32 inches dbh. Occasionallystems up to 36 inches are still making sufficiently rapid growth toretain for high value products, such as face veneers.Putnam (1951) describes silvicultural objectives, priority, andresults for the first commercial improvel'T ent cuts in bottomlandhardwood stands by stand classes based on volumes and tree sizes(Table 3).Table 3. Mixed-Stand Classes: Their characteristics and nature of the first commercial improvement cut [afterPutnam, 1951].Stand class1. Heavy sawtimber (8000bd. ft. and more peracre)a. 50 percent or moreof the volume in trees 23inches dbh or larger.b. Less than 50 percentof the volume in trees23 inches dbh or larger.II. Medium sawtimber (3500·8000 bd. ft. per acre)a. 50 percent or more ofthe volume in trees 23inches dbh and larger1. Adequate supportingstand.Nature of standand productsLargest and best treesusually overmature. Productsmostly factory and veneerlogs.Skilled cutting especially de-sirable, as this class hasbest possibility of earlyformal management. Factorylogs predominate, but greatvariety in size and utility ofproducts within and betweenstands.Large trees - mostly residualold growth; overstory oftenseriously obstructing pro-mising second growth. Factorylogs of many sizes but mostlyof medium to poor quality.Cutting objectivesand priorityHarvest of mature timber,salvage of overmature anddamaged trees. High priority.Normally stand improvementand release; occasionally sal-vage; secondarily harvest.Medium priority.Harvest, salvage, stand im-provement release. Highpriority.Silvicultural results of thecutSparse residual stand, oftengood in thrifty groups.Good residual stand exceptwhere much timber is over-mature and damaged.Fair to good residual stands,scattered or in groups......oTable 3 Cont.2. Same as above, butwithout supportingstand.b. Less than 50 percentof the volume in trees 23inches dbh and larger;Supporting stand present.1III. Light sawtimber (1500-3500 bd. ft. per acre)a. 50 percent or more ofthe volume in trees 2ilinches dbh or larger.1. Adequate supportingstand.Sawtimber overstory usuallyin very poor condition fromsame causes that damageor eliminate understory. Pro-ducts largely factory logsof good size but medium topoor quality; also considerabletie-and timber-logs. Speciescomposition often poor.If undamaged, fair chanceof sustained yield after firstcut. Factory logs mediumto poor in size and qualityand often only a small major-ity of total. Tie-and 'timber-logvolume large, sometimes agood amount of bolt stockand pulpwood.Cut will usually be nearminimum operable volume.Products range widely in sizeand quality, but s lwtimberpredominately, running halffactory logs, half tie-andtimber-logs. Very desirableto integrate sawtimber withother uses.Harvest, salvage, stand im-provement. High priority.Stand improvement, release,occasionally salvage. Lowpriority.Harvest, salvage, stand im-provement, release. Highpriority.Sparse residual stand in needof regeneration.Good residual stand unlessoriginal stand had heavy earlydamage or sparse understory.Good to sparse residual stand,depending on damage anddevelopment of supportingstand.Table 3 Cont.2. Same as above, butwithout supportingstand.b. Less than 50 percentof volume in trees 23inches dbh or larger;Supporting stand present.IV. Heavy pole stand (morethan 175 trees per acre)5 to 11 inches dbhV. Light pole stand (lessthan 175 trees per acre5-11 inches dbh)a. With supporting standof saplingsb. Without supportingstand of saplingsStands mainly residual oldgrowth following heavycutting and repeated burningor grazing. Products chieflysawlogs, about half factoryand half tie-and timber-logs.Only the best such standsare operable. Sawlogs; oftenruns strongly to tie-and timber-logs, but all products usuallyoccur in substantial amounts.Integrated operation generallyimperative.Stand mainly even aged.Excellent chance of earlyformal management if notseriously damaged. Productsalmost entirely pulpwood andchemical wood, rarely pilingor low-grade local-use sawlogs.One of the most commonconditions. Products mainlylow-grade cordwood and posts,occasionally traces of low-grade, local-use sawlogs.Same as aboveHarvest and salvage; standimprovement incidental. Highpriority.Stand improvement, release,harvest, salvage. High priority.Thinning and stand improve-ment; occasional salvage.High priority.Mainly stand improvementand release; occasionalsalvage. Medium priority.Stand improvement, occa-sional salvage. Low priority.Sparse residual standneeding reproduction.Good residual stand.Excellent young residual standwith great possibilities.Sparse residual stand butestablished reproduction hasgood future.Very sparse residualstand. Reproduction badlyneeded.Table 3 Cont.VI. Saplings and seedlings(at least 250 trees peracre)VII. Non-stocked (allpotentially productive con-ditions)Low-grade cordwood, tracesof sawtimber, largely low-grade, local-use logs. Totaltoo light for commercialoperationNo produce, except perhapssome low-grade, local-usematerialRelease and stand improve-ment. Very low priority.Elimination of undesirableseed source and clearing assite preparation.Reproduction promising.Elimination of undesirable seedsource1 Rarely a medium stand of sawtimber with less than 50 perce~t of volume in trees 23 inches dbh or larger may be encountered without a supportingstand of small trees. If it occurs, treat as "medium sawtimber (Large) without supporting stand" if the stand volume is in the upper range of itsclass; treat as "light sawtimber without supporting stand" if stand volume is in lower range of its class.These early cuttings are to rehabilitate stands. Theoretically, thepermissible cut in the ideal unevenaged stand on a good site simplyserves to set the stand back to the condition in which it began thecycle (Tables 4 and 5).Table 4. Suggested optimum stocking ofan uneuen-aged bottomlandhardwood stand ona good site l [after Putnam, 1951].Midway of End of cycle: Cuttytlo M rudy forDbh. avenge stand cutting(in.'""'"Volume""'"Volume""'"VolumeNo.laere Cords2/acl'1l No.lacre Cords2/aere No.laere Corda2/acl'1l• 20.0 0.' 30.0 0.' 12.75 0.2• 13.0 •• 15.8 •• '.28 .28 '.7 .7 12.2 •• '.06 .310 7.' 1.0 '.0 1.2 2.02 ••12 '.8 1.2 7.1 1.3 .10 lS'Total 93.1 3.7 ltD. I ••• 24.20 l.lBd. Ft. Bd. ft. Bd. ft.Doyle Doyle Doyle"'.2 '22 '.0 Sl216 ••• 532 '.7 641 0.4<1 3818 '.3 no ••• 823 1.30 1'120 '.3 92' •., 1139 2.10 ...22 3.2 ,.. .., 1268 2.00 .9024 2.3 697 '.2 1248 1.60 72426 I.' 816 2.' 1170 1.20 60923 l.l 721 I., 104. .30 .2430 .30 65. 1.1 902 .65 63332 .45 ... •• SO< .53 63254 .27 329 45 647 .54 '0836 .11 165 .27 '92 .23 335,..04 54 .11 lOl .10 163.0 .02 54 .04 76 .04 76Total 31.29 7,636 36.79 10,498 11.31 5,211All"'"124.39 146.89 35.51I A cutting cycle of not less than 10 yean is aasumed_2 128 cubic feet, gross, with 75 cu. ft. assumed as the net content of wood from 4·ln.trees and 80 cu. ft. assumed from 6- to 12-inch trees. Topwood in sawtimber tnleeignored.3 Negligible.13Table 5. Hypothetical stocking and diameter distribution, with estimated development and yield per acre, forwell-managed uneven-aged Southern Hardwoods on average or better sites 1 [From Putnam, et el. 1960JDbh After cutting; beg-inning of End of cycle; ready for Cutnew cycle cuttingTrees Basal Volume 2 Trees Basal Volume 2 Trees Basal Volume 2Area Area AreaInches No. Sq. ft. Cords No. Sq. ft. Cords No. Sq. ft. Cords4············· 17.2 1.50 0.2 30.0 2.6l 0.4 12.8 1.11 0.26....·........ 10.5 2.07 .4 15.8 3.10 .6 5.3 1.03 .28..··....·.... 8.2 2.86 .6 12.2 4.27 .9 4.0 1.41 .310............· 7.0 3.82 .8 9.U 4.92 1.2 2.0 1.10 .412....·........ 6.5 5.10 1.3 6.6 5.18 1.3 .1 .08~~ Total........ 75.4 15.93 3.3 121.6 21.14 4.4 46.2 5.21 1.13Bd. ft. 3 3Bd. ft. Bd. ft.14....·..··.... 6.0 6.41 312 6.0 6.41 312 .00 016·............ 5.3 7.40 503 5.7 7.96 541 .40 .56 3818............· 4.3 7.60 632 5.6 9.90 823 1.30 2.30 1!)l20..·.......... 3.2 6.98 688 5.3 11.56 1139 2.10 4.58 45122............· 2.3 6.07 678 4.3 11.35 1268 2.00 5.28 59024............· 1.6 5.03 524 3.2 10.06 1248 1.60 5.03 72426..·.......... 1.1 4.06 561 2.3 8.48 1170 1.20 4.42 60928............·.8 3.42 524 1.6 6.84 1048 .80 3.42 52430..........·...45 2.21 369 1.1 5.40 902 .65 3.19 53332............·.27 1.51 272 .8 4.47 804 .53 2.96 53234··..........· .11 .69 139 .45 2.83 547 .34 2.14 40836............·.04 .28 57 .27 1.91 392 .23 1.63 33538............·.02 .16 28 .11 .95 191 .10 .79 16340........·.....04 .35 76 .04 .35 7642....·..·....·.02 .19 37 .02 .19 37Table 5 Cont.Total-------- 25.49All Trees-- 100.8951.8267.755,287 36.80158.4088.66109.8010,498 11.3157.5136.8442.055,2111 The cycle of development illustrated by this table will usually be completed inabout 10 years, but may reqwire 8 to 15 years, depending upon site quality.2 Saw-log volume includes all sound, reasonably straight stRms to a lO·inch minimumtop diameter, inside bark, at least 12 feet above the stump (Doyle).Cordwood volume in tops of saw-log trees, not shown, is equivalent to about one cordper thousand board feet log scale or 40 percent of the total cubic volume of such trees.3 Doyle rule.4It should be noted that there is no fixed rotation age: growth rate,condition, and product value determine that for individual trees.When a stand averaging 105 square feet per acre basal area in alltrees received an improvement cut that removed 25 square feet intrees 18 inches dbh and above, the pre-harvest volume of 3 MBF peracre in trees this large was reduced by one-half. Trees released bythis operation, which reduced the effective competition by more thanone-half, increased in diameter at a rate 26 percent above that of thelO-year period before harvest. However, removal of only one-third ofthe competition from other trees effected no change in growth rateand, in contrast, where little or no release was accomplished, growthdiminished by 17 percent (Johnson, 1950). Best. response to release insawt.imber stands is likely to be in trees less than 18 inches dbh.Thus, in initial improvement cuts, one-half of the effectivecompetition with desirable growing stock should be removed andmore than three-fourths of the competition to intermediates andcodominant.s. Low value species (overcup oak, bitter pecan,hackberry-elm-ash, and sweetgum-water oak types), on poorer sitesor abused good sites, should be converted through cutting to morefavorable species. Preharvest weeding is needed for all pure andevenaged types except cypress-tupelo. Oaks and white ash respondto release to a greater degree than green ash, hackberry, and honeylocust (Davis, 1935).Epicormic BranchingDrastic thinning encourages epicormic sprouting, an importantcause of qualit.y reduction. Branching is most frequent in stands withbasal areas below 75 square feet/acre; for the most common speciesit is inversely related to the product of tree dbh and stand basalarea (Hedlund, 1964). Thinning from below removes trees most likelyto put on epicormic branches when released, the intermediate,suppressed and injured ones. Thinning can usually wait until afterstands have adjusted to removal of undesirable stems in initial cutsof t.he overburden, when light and frequent harvests on cycles of 10years or less are suggested. Dominant and codominant trees,part.icularly yellow poplar. exhibit less epicormic branching when left.as border trees around openings than do trees of lower crown classesor other species (Smith, 1965).Coastal Plain Alluvial ValleysVirgin timber in many of the Coastal Plain bottoms of theSoutheast was cut between 1920 and 1950, taking the best stems andleaving areas ripe for weed trees and brush invasion. Stands of lessthan 5 MBF, mostly in low value species and low grade stems, aretherefore common.16Heavy initial cuts to place such stands under management amountto 3 MBF per acre and light cuts to about 2 MBF, removing about 75to 25 stems per acre to release valuable trees. Subsequent harvestson lo-year cycles are lighter. Annual growth of such stands mayrange from 200 to WOO board feet per acre, depending upon recentcutting practices. A reasonable average for some of the morefavorable bottoms, like the Tombigbee and Savannah Rivers, is SOOboard feet per acre, exceptional stems growing as much as one inch indiameter each year.Piedmont Alluvial ValleysThe forest types of the Piedmont alluvial valleys are similar tothose of the Delta Bottomland Hardwood region. Included are riverbirch, sycamore, sugarberry, and green ash in the riverfronts; blackwillow, green ash, boxelder, and the bottomland oaks throughout thewider bottoms. Yellow-poplar is encouraged in the bottoms of thePiedmont Province. There, it may be underplanted in stands ofinferior broadleaf trees on better sites, provided release is promptwhen establishment is assured (Freeze, 1951).Sweetgum and sycamore are also favored for alluvial valleys andbottoms of the Piedmont Province. These species are notdetrimentally affected by dormant season flooding. Evenagedsilvicultural techniques, perhaps by seed·tree cuttings are generallyrecommended..Site IndexSite potential is very high on alluvial soils. Where site indices areabove 90 for loblolly pine, yellow·poplar, along with sweetgum, hasgreater height growth than other hardwoods and loblolly pine.Yellow'poplar and sweetgum, therefore, are preferred on the bettersites while loblolly pine is favored on land below SI 90. Shortleaf pineat any point on the scale is inferior to yellow-poplar, sweetgum, andnorthern red oak. The oaks have lower growth rates thanyellow-poplar and sweetgum except on the poorest sites. Nodifference is reported for site indices of black, southern red, or scarletoaks (Nelson and Beaufait, 1956) (Figure 2).17,.....-'00"-'",.' ,"'00r."•••0.00•! ~••'0••• ••• •i '0f.0'0 .0 '0 to to '00 ,,. "0Figure 2. Comparison of site indit:es for several species on the sameLand in Georgia Piedmont. From Nelson and Beaufait, 1956.18-INJURIOUS AGENTS IDecayFire-caused Rot 2Virtually aU decay in bottomland hardwoods is attributed to fire;and all fire-wounded trees, regardless of species, will contain rot(Kaufert, 1933). Fires make wounds into which rots enter anddestroy desirable trees, especially in seedling and sapling stages.Undesirable species are frequently the most fire resistant and, hence,a site may be transformed by a single fire. Although injuries as smallas ODe inch in diameter will sometimes admit rot fungi whichsubsequently destroy butt logs, wounds less than 2 inches in widthare generally not important points of infection ITooie and McKnight,1956). Up to 4 years may be required for rot to reach the heartwoodbut, once there. spread is rapid-as fast as 2 feet in 10 yean. Thus,butt logs are often totally destroyed in the 15 to 20 years required forfire scars to heal. High temperature and humidity encourage spreadof decay. Gruschow and Trousdell (1959) show volume deductions byspecies in North Carolina ranging from 4 percent for yellow-poplarand white oak to 38 percent for red maple. Incidence of rot rangedfrom 16 percent for yellow-poplar to 57 percent for red maple.Ground fires are most injurious to immature trees, due to thepoorer insuiation of the cambium by the bark of younger stems.Some young trees with tight, smooth bark, such as hackberry,hickories. and red oak, are more severely scarred than those withrough. corky bark like sweetgum and white oak, but the difference isslight.Future value of a tree, in respect to rot, depends on the (1) extentof rot, (21 part of tree doty, l3) probability of breakage. and (4)degrade from stain and associated insects. Fire-damaged trees whichshould be removed in salvage cuts and subsequent harvests are thosewhere 11) bark is charred to a height of more than 6 feet above thestump or (2) char extends around more than one-half of the tree'scircumference and reaches more than 2V1 feet above the stump (Tooleand McKnight, 1956). Trees with greater external injury probablywill rot rapidly or die.Increment BoringA controversial subject is the effect of increment boring in foresttrees. Toole and Gammage (1959) report that some rot does entersuch wounds of bottomland hardwoods. preceded by stain-eausing1 Agents injuring certain species are diKussed in appropriate eections.2 See Toole U9591 for details on declly after ftre injury and Lockard, PutMm andCarpenter 09501 for illustratiotlll to aid in evaluating log defects.19....fungi. They note, however, that most stain at borer holes isphysiological in origin-reaction of chemicals in the wood to theentrance of air and contact with the steel tool. While increment borerholes callus rapidly, vertical discoloring may extend a foot in 2 years.Horizontal spread is negligible. Borer holes should be only as deep asnecessary and made as low to the ground as possible.BeaversBeaver damage in bottoms is an increasing source of butt-logdecay. As with fire damage, partial girdling by beavers results in awound subject to attack by decay-cs.using fungi. Toole and Krinard(1967) indicate that decay may be as deep as 2 inches after 6 years inash and 8 years in sweetgum. Wounds extending more thanone-quarter of the way around the circumference indicate 8 strongprobability of mortality within 10 years and such trees should beremoved in salvage cuts along with trees containing deep rots or lowvigor.InsectsTable 6 presents the important insects which damage livingbottomland trees.Tent CaterpillarThe rorest tent caterpillar defoliates tupelos. blackgum,sweetgum, willow oak, overcup oak, and river birch in southernbottomlands. Larvae spin cocoons in early May; moths are in flight 2weeks later. By June, defoliated trees may put on new leaves, butthis crop will be smaller and less abundant than normal. Fortunately,it is believed fungus, virus. or fly parasites may stop outbreaks. butnot before many trees are killed (SFES. 1960).20Table 6. Key to important insect dama.ge in lilJing soutMrnhardwood and cypress trees [after Morris, 1955~Typo .........HOLESTree lpecies Economic importanCeGrub damage. Largeholes and long tunDe1sInywhere in tn'llItrow.Grub damage. Uluallyclustered in lower b'eetn>nka.MOIl. oaks. ElpeciaDyovercup, willow, Nuttall,laurel, and water oak.Also blade oak Indwhite oak on dry sites.Cottonwood.MOlt important oe.k delectin all fOt'ellta. Worst on pool'sites and when trees are lowin vigor. Largely respons·ible for the poor reputationof overcup oak.Important. Clustered holesmay weaken young treeII10 that they break off.Holes degrade wood forlumber and pulpwood.Spotwonn. A very lmallhole filled witb dUll. andoften sU!TOUnded by 8narrow wne of brown·ltained wood.Oven:up oak, willow oak,and Nuttall oak.Of great importance in lOmeareas. Can reduce otberwiMFAS lumbel" to SoundWormy grade.Degrades veneer andlumbel".Soft maple and post oak.Flag or spot. worm.AttaclB living trees re-peatedly.Ambrosia t.etJe "wanna" Oaks, lweetgum, bitter Minor in Iiviq ~.bore into weakened and pean, ash, and Ameril:aD AtLide indicates low vigor,dam..aged tl'MI. The sman. elm dead c:ambium, 01" Lhrot treeround, open hoIeI bet:ome is dyina.lSerioul in old logsIW'l"OUnded by darir.: lap- and freah-cut lumber.)ltained areas.BARK SCARSBark 8Clrrer damage. A Overcup oak, laurel oak,patch of inner bark is willow oak, water oak,killed and the wood sur- Nuttall oak, and on poorface is stained. When sites, c:herrybark oak.overgrown, appears as a Bladegum. hickory, andstained area with ingrown yeno-poplar. Blade oakbark. Often ocxurs and white oak on high.throughout a log. dry sites.Seoond only to grub damagein most bottomland oaks,and sometimes WOl'IIe. Es-pecially bad in oven::up oe.k.Reduoee blade and t.upeklgum veneer to c.:.we ltoc:kgrade.ABNORMAL GROWTHRidges of abnormal wood Sweetgum.and ingrown bark thatdevelop from bark lesions.Cause a lumber defect aimi·lar to • ImaD catface orlarge bark 8C8I". Serious de-grade over limited arees.Ribbed swelling in the Syamoretrunk near the ground.AbnOl"llW wood growth andingrown bark cause a!umbel" degrade.GALLSGalls that girdle oaktwigs and kill the leavesand buds.Willow oak, southern redoe.k, and water oak.KiJh u- in 2 or 3 yean.I...oe8Dy important. N..rly20 million board feet of21Table 6 Cont.DEFOLIATIONDefoliltion by tenta_DefoliltionPartial to completedefoliltion.Reddening of foU.lge incypt'MS. Partial defolil·tion.Sweetgum, pecan.hackberry, and,.hk.kories.Cottonwood and willowNuttall oalr., cberrybarkoak. llOI,lthem red oak,and oven:up oak.willow oak died in ODe area. afew years ago. Seriousdamage now occurring in..............Serious, especially if defol·Uition is repeated 2 years ormot'e. Gum trees are dyingafter 3 years of defoliationon 60,000 acres north ofMobile, Ala. Also causingmortality in Caicallieu. Riverbottoms of llOI,lthwestLouisiana.Periodic defoliltion slowsgrowth and weakens tl'eeS.PeriOdic buildups serious.May injure you"8 cotton-wood in plantations andnurseries. E:lltensive planta.tion threatened at Scott,Mississippi.Weakens trees and siowlgrowth. RepMted attaekamay cause deeth. Damagenot fully evaluated.Importance not known.Growth is reduced. andweakened taft may bedamaged by otheor agencies.GrazingGraz.i.ng of domestic livestock must be excluded. from allbottomland hardwood forests. Cattle trample reproduction, browsevaluable steIns, and compact t.he soil. The soft Ooor of manybottomland forests, especially border areas of reeds and swampswhere one quickly sinks to the knees in soft, loose organic matter,discourages cattle. Perhaps too, the impalatability of swamp herbsfurther inhibits grazing, as cattle seem reluctant to graze theswamps except during the famine or extremely droughty seasons(Hall and Penfound. 1943).CompetitionAll competing vegetation except annual herbs must be eliminatedif preferred species are to grow adequately. Dominance offree.t,o.grow stems among most bottomland species is then quicklyasserted.22Fire promotes buckvine and honeysuckle sprouting, encouragingits spread. These serious pests are prevalent in sites occupied bystands which are sufficienUy sparse to permit light to penetrate thecanopy, especially on heavy, slack-water soils. As drastic thinningencourages the spread of vines, caution should be exercised inopening up stands where invasion has begun until reproduction hasan even start. Sprays such as 2,4-D and 2,4,5-T give incompletecontrol as they do not prevent germination of seed in the duff(Bruner, 1967). However, vines are seldom a serious threat wherestands are reasonably stocked.WindthrowWindthrow is important in sites with pervious soils which, in spiteof deep tap roots, afford poor support when saturated. On areas withimpervious substrata, wind removes trees with defective rootsystems and those which lean from a "root-sprung" condition.The increase in soil moisture following heavy cuttings,consequenUy raising the danger of windfall, encourages conservativeharvesting. The rise of ground water after clearcutting. convertingflats and sloughs to brushy swamps, is particularly devastatingwhere soils are too shallow for establishment of deep tap roots onpotential seed trees.Flooding EffectsAbsorption, transpiration, water movement, temperature,chemicals and organic matter in the water, microbes, algae, and thesoil physical and chemical properties all probably affect the toleranceof trees to submergence. These factors, in turn, influence the amountof free oxygen available to plants under saturated soil conditions. Itis this oxygen deficiency or carbon dioxide toxicity whichdetrimentally influences seed germination, seedling survival, andtree growth.GerminationFree oxygen is considered the limiting factor in the germination ofbottomland hardwood seeds in flooded sites. Except for siltation,'which covers seeds too deeply, flooding bottomlands for up to onemonth does not appear to reduce germinative capacity (Hosner,1957). Observations suggest that even if bottomland tree seed wereto germinate while immersed in water in actual field conditions,eventual establishment of the seedling would be most unlikely !J,nlessthe immersing waters receded before the seedling perished fromother causes (DuBarry, 1963). ConsequenUy, the normal amount offlooding is not a major cause of selective regeneration among species23until after germination, except possibly in swamps. But, inlong·inandated areas, production of great quantities of seeds areessential to offset the hazards of submergence. Red maple, silvermaple, sycamore, and elm germinate only after flooding subsides,but germination percentages for those species are probably higher asa result of short flooding. Drainage is necessary for germination oftupelo and blackgum.The amount of light reaching the forest floor also influencesgermination of bottomland hardwood seeds. Germination is morefavorable for river birch, sycamore, and American elm underconditions of full sunlight than under crown canopies. In contrast,red maple, winged elm, and alder germinate best under low lightintensity (McDermott, 1953). That may account for these lessdesirable species, with deciduous holly and dogwood, outnumberingfavorable species in some flooded bottoms where litter is deep andground vegetation dense. (New ground that is regenerated withcottonwood and subsequenUy invaded by weed trees is an exceptionto this generality.)Reproduction of desirable species is initially adequate on all sitesnot currenUy flooded, but it is best where litter is shallow or absent;the ground cover light, or absent; and the overstory sparse. In onecase, elm was the most abundant of all species where litter was deepor ground cover dense, while hickories and some oaks were moreprolific on heavier soils with high moisture--holding capacity. This,however, could be due to the greater frequency of seed·producingstems of those species on such sites (Hosner and Minckler, 1960).Survival and GrowthTrees in southern bottomlands depenri for survival upon theirability to withstand and recover from periodic and more-or·lesspermanent flooding. Species vary appreciably in their ability to doso. Up to 16 weeks of soil saturation from the time of planting doesnot significantly affect survival, date of bud·break, or initiation ofheight growth of sycamore, sweetgum, and Nuttall oak seedlings.But when soil temperatures were rapidly increasing in mid·April,saturation for more than 10 to 12 weeks Beverly reduced. height, root,and stem-diameter growth (Bonner, 1966). Willow, cottonwood, andgreen ash may survive much more than a month of inundation.Hosner and Boyce (1962) classified seedling tolerance to watersaturated soil as follows: Tolerant· green ash, pumpkin ash, watertupelo, willow; Intermediate· eastern cottonwood., boxelder, redmaple, silver maple, pin oak, sycamore; Intolerant· cherrybark oak,Shumard oak, American elm, willow oak, sweetgum, hackberry,sugarberry.Although chlorosis and reduction in height growth occur,adventitious roots permit rapid recovery after drainage (Hosner,1959,1960). Sycamore develops a brisk red chlorosis indicative of abreak down of chlorophyll in leaf cells, but color is regained uponremoval of the water. The oaks-pin, Shumard, and cherrybark,-and hackberry, red maple, sweetgum, and American elm did notrespond to drainage after long periods of inundation in southernIllinois. Height growth does not occur while seedlings are submergedbut, for some flood-tolerant species, elongation takes place if a fewleaves are above water. Lentz (1928) noted that if saplings are tallerthan high water levels, lower branches die, and growth is retarded indirect proportion to the amount of crown loss. Usually no damageoccurs to oaks, sweetgum, hickories. ash or elm if crowns are entirelyout of water; but exceptions are reported, as when trees up to 24inches dbh died, perhaps as a result of siltation, after a severe flood(Lentz. 1929). Where floods deposit silt or sand to depths as shallowas Y1 foot, all species except cottonwood and willow, regardless ofsize, will probably die (SFES, 1933). Ability to develop adventitiousroots just under the new level of the soil sourface enablescottonwoods and willows to survive.Although red maple exhibited less tolerance to flooding than didsilver maple in controlled experiments, the fonner is considered themore hydric of the two species. Silver maple did not endure even 1week of complete inundation in other tests (Hosner, 1958). There isevidence that growth of green ash in lower bottoms is favored bysevere floods. Trees in second or higher bottoms do not react toflooding in this manner (SFES, 1935). McAlpine (1961) finds greenash seedlings very tolerant of inundation, hut black walnut, whiteash, and red mulberry do not survive frequent flooding(Maisenhelder, 1957).Three-week old cottonwood, willow, sweetgum, ash, and boxelderseedlings about 3 inches tall survived under a foot of water for oneweek during the growing season. Some chlorosis of foliage occurredand leaves died, but recovery followed drainage. Ash, sweetgum, andboxelder survived over 2 weeks of this treatment (Hosner, 1958). Inthe New Orleans battures, growth of pecan and hackberry wasexcellent during floods in which water was maintained at a depth of 4to 7 feet for long periods of time (Bonck and Penfound, 1944).Neither species is considered a hydrophyte.McDermott (1954 t subjected river birch, American elm, red maple.and alder to saturated soil just after the first true leaves formed inthe spring. Soil temperature was abnormally high in contrast toexpected natural conditions. Birch and maple recovered rapidly fromsustained saturation, and elm recovered slowly (Tables 7 and 8). Thissuggests that elm is somewhat less hydric than the other speciestested, although succession in nature is usually from an alder-willowtype to a maple-elm-ash association, a transition most likelyoccurring in very wet to moderately wet habitats. Intermediate25timber types in succession may be sweetgum-yellow-poplar, purebirch, pure sycamore, or boxelder.Table 7. Mean height growth of seedUngs subjected to treatlrnmt of32 days saturation compared to mean height growth of controlseedlings 52 days later (after McDermott, 1954).Spedee No saturation SaturationRiver- birch 24.67 U.78 (.)Red maple 20.80 10.76 (.)Sycamore 14.84 12.30 (.,American elm 17.57 11.25 I·)Winged elm 16.11 6.18 (.,Alder 6.50 6.30 (ns)(.) Difference hun check significantly neptive at 5 percent probability 1ev9J, thua...."'""-Ina) No significant difference in growth re8ponlMl at 5 percent probability leveLTable 8. Relative degree of recovery after most injuriou.s treatmentcompared to recovery after most favorable treatment (afterMcDernwtt, 19541.S...... Treatment Daya Recovery RateRiver Birch Most favorable 0 Very rapid toMost injurioua 16 atunted. growth~......Red Maple Most favorable 0 Very rapid toMost injurioua S2 atunted growth"""""""Sr""""" Most favorable 1 Rapid to alightJyMoat injurious S2 atunted growth~......Amorian olm Moet favorable 0 Modente to someMoet injurious S2 atunted growth~pon~Winged elm MO!It favorable I Moderate to atuntedMoet injurioua S2 growth~......Aid" MOlIt favorable 32 Some 8llturationMost injurioua 0 growth promotingWhile flooding during dormant seasons is not injurious toyellow-poplar, growing season inun':iation of newly planted seedlingsfor even 3 or 4 days kills all trees (McAlpine, 1959b, 1961).Short-tenn floods of less than 2 days apparently are not damaging.Injured stems may appear healthy for a month or so before leaveswilt and trees die. Sudden wilting does not always foUow the26-;;.--recession of flood waters: symptoms of injury may be delayed 6weeks. When 3·year-old seedlings were continuously flooded duringthe growing season, all leaves died within 2 weeks (Kramer, 1951).Before death, they became epinastic, a state in which more vigorousgrowth of the upper surface of unfolding leaves caused downwardcurvature of leaves and twigs.In studies of tolerance of many woody plants to flooding duringthe growing season over an s.year period, it was noted t.hat chancesHEALTHY SICKLY DEAD'·;·:.;·;.:·;·;·;·:·:·:·.·.4 I.....................Bloo Cllerr,,,~.;,. Do.....~I~....-.Sonoho.Be.chY.llow - PoplarClwillfrlOi ~lI,"".....R.dctdarBlock Ald.rShoQbork Hic:k«iuLoblolly Pil\tlBlock GumWOlff OokCololpoIronwoodBirchSycamoreWin9.d ElmAmtricon ElmI'fo(kbtrrySwo"'Cl Bloc"9V'"Cow OokHone, LocVllPw,immOllWillow OakHo.S_.1911mCollonwooclOrtciclllOU' Hall,R'd hIIopl'Woler TllpeloA.,Pin OokBlillonbol IO....rcllp OakBlock WillowSwomp Ironwoodo • '0PERCENT15 20 2.5 30 35 40 45 SO 55 60OF TIME FLOODED DURING GROWING SEASONSFigure 3. Tolerance of 3-inch dbh and larger woody s~cks toflooding during the growing season. After Hall and Smith, 1955.27for survival are better if tops are above water, provided the specieshave some tolerance for high water (Hall and Smith, 1955). Thistolerance varies from 2 days for black cherry and dogwood to 42 daysfor black willow and swamp ironwood. (Figure 31. All woody plantswere killed where root crowns were periodically flooded for more thanhalf of the growing season.McAlpine 11959b) reasoned that in ponded areas exposed tosunlight after rain a temperature rise increases respiration and theactivity of micro-organisms, resulting in oxygen deficiency andcarbon dioxide toxicity. Hopkins, Specht, and Hendricks (1950)found that root growth (of a number of species) stopped when freeoxygen reached 0.5 percent in the gas around roots, but top growththen continued, accompanied by possibly toxic accumulations ofiron. Those workers further noted that while the rate of transfer ofsolutes from root to shoot is independent of aerobic mechanisms ofroots, flooding might stop downward movement of carbohydratesand aux.ins. Thus, the accumulation of plant foods and hormones atthe waLer line may account for adventitious rooting of flooded trees.Sprouting from root collars indicates that death of roots has notpreceded death of tops and, therefore, root-kill by flooding was notresponsible for tree necrosis.TransplrationParker (1950), studying the effects of flooding on transpirationand survival of various species, assumed that injury to roots causeda decrease in water absorption and, subsequently, transpiration.When oaks were flooded for one month in July, transpirationdecreased. However, upon drainage, stomatal water loss returned to60 percent of the nonnal rate within a month. Northern red, white,and swamp chestnut oaks behaved similarly, there being no evidencethat those species are superior in withstanding high water during thegrowing season. For overcup oak, under water for 4 weeks, drainagerestored transpiration to its nonnallevel (Figure 4). Overcup oaksproduced new leaves after the first few days of flooding. The suddendecrease in transpiration rate just after flooding begins suggeststhat soil moisture limits nutrient and water absorption.28" /\ /~'\ ~~ ~~'-- -......./~14040-7 -3 , 9 13 17 21 25 29 33 37 41 45TIME SINCE FLOOOING (DAYS)Figure 4. Transpiration ofouercup oak seedlings in. soil flooded in thespring for about 4 weeks. From Parker, 1950.29COT\'ONWOOD 1Cottonwood occurs on new-fonned land built up by floods, inborrow pits, and in old-fields subject to flooding. New land is fonnedas the meandering of a river cuts ita bank and deposit.s on a"point-bar" downstream the soil caved away. Succeeding floodsdeposit coarser sediments near the bank of the river, building high,welJ-drained ridges or natural levees.Cottonwood has great ability to recover from inundation. Rootsdie when soil is soaked for over 8 month, but extensive adventitiousroots quickly develop from dormant buds on the mainstem. Someheight growth is lost, but the slightly chlorotic foliage regains colorand continues growth after inundation ceases (Hosner, 19591. Evenwhen cottonwoods have been completely submerged during thegrowing season, damage is slight (Lentz, 1928), and if the flood is sosevere as to deposit as much as 3 feet of silt or sand on the bottom, 8new root system develops-in one case " feet above the originalISFES. 19331.An exception ilo the concenSU$ of opinion for the high watertolerance of cottonwood is found when newly planted stock,especially cuttings, are flooded. In the greenhouse work of Hosner(958), it was indicated that 16 days is the limit beyond which thespecies can not survive complete inundation. Earlier, Hosner (1957)found the species not only capable of withstanding a month of highwater, but seed germinated after being under water 4 days. Floodingfor a month did not reduce germinative capacity, perhaps because ofthe high water temperatures-up to 93° F.GrowthFully stocked unmanaged stands on good sites produce 10.7 MBFper acre (Doyle rule) in 25 years and 27.5 MBF in 35 years with noaccounting of salvage mortality, the latter equal to 785 board feet peracre per year (Maisenhelder, 1960). When they mature at about 45years of age, there will then be about 32 trees per acre with 30 MBF.Some stands continue rapid growth for longer periods. Naturalstands on better sites often grow % to 1 inch dbh and 4 to 5 feet inheight each year, up to age 25. Trees in plantations do better,first'year height growth from cuttings sometimes averaging 13.5feel. Well·stocked natural stands in the Mississippi Valley maycontain cottonwoods averaging 20 inches dbh and 120 feet tall at 35years, at which time growth begins to decline. Plantations at age 14have 232 trees 9 inches dbh and averaging 82 feet tall with a basalarea of about 100 square feet per acre (Wylie, 1961).ISM Applequist U959bl for A Selec:t.ed Bibliography OD Cottoawood, and Farmerand McKnight, (1967) for Popul1Ul: A Bibtiolnpb," of World Utentare, 18M·19M.31Release stimulates growth if residual trees are of good. vigor, evenwhen 30 inches dbh. Released trees on good batture sites which hadgrown 3.2 inches dbh in the 10 years preceding release increaseddiameter growth by 50 percent during the next decade(Maisenhelder, 1960).Site IndexBroadfoot (1960) has developed two techniques for estimatingcapability of mid'south soils to grow cottonwood.. The first is basedupon soil texture and internal drainage in the surface 2 feet and anocular estimate of the inherent moisture condition of the soil (Table9). ]n distinguishing texture. clays, both buckshot and gumbo, arefme; sandy soils are coarse; and the remainder are medium.Exceptionally dry and excessively drained sand ridges are notincluded in the classification, since those should not be incottonwood.. The soils are internally well-drained if no distinct grayor reddish brown mottling occurs within 2 feet of the surface.Otherwise, drainage is poor. They are inherently dry if the site is on aslope or ridge. enabling floodwaters or heavy rains to drain off. If thesites are subject to flooding, classification is moist.Table 9. Field key for estimating cottonwood site index (fromBroadfoot. 1960).Soil·site descriptionI. Fine textureA. Good inl.emal drainage1. Inherently moist2. Inherently dryB. Poor inl.emal drainage1. Inherently moist2. Inherently dryII. Medium textureA. Good int.emal drainage1. Inherently moist2. Inherently dryB. Poor internal drainagel. Inherently moist2. Inherently drySite index 130 yearslllCHI91()().10990-99..120110-1191()().10990-99Broadfoot's (1960) second method requires identification of soilseries. With either technique. the site index curves of Figure 5 areapplicable.32160140140 130"120 ~110 ~120 ,"~100 ~~ ..100.0,~• 80<>;;; 80 70•604o1---1I'--j--+---+----io0~----c,~0:---;2~0:--..,"'f;---4~0:--~!lOAGE (YEARS IFigure 5. Site index curves for eastern cottonwood in the mid-south,based upon an age of 30 years. From Broadfoot, 1960.Natural RegenerationThe life cycle of cottonwood begins in late February or early Marchwhen male and female flowers occur on separate trees as young as10 years of age. Cottonwood seeds, produced annually, mature andfall between April and July, but for some it is as late as mid-August.A freeze after flower buds begin to open will destroy the seed crop.Seeds are carried by wind and water: short floods are apparentlybeneficial for germination. The annual floods which water the landdeposit a fresh layer of silt in which the cottony seed settle out inwhite masses to germinate. Favorable soil moisture conditions mustprevail. for seeds remain viable under dry conditions only a few days.As many as ~ million seedlings per acre appear. They are delicatethe first few weeks. many being lost to hard, blowing rains and hotsun. Reproduction may occur initially on any site, but it is adequateonly on open areas of mineral soil exposed to direct sunlight for agreater part of the day, such as old fields, sand bars, and other riverdeposits subjected to frequent showers or flooding. Sites must benearly devoid of litter and ground cover for establishment ofreproduction. Once started, early dominance is asserted. so thatundersirable ::species are seldom a problem after establishment.Except on very wet areas, cottonwO;.;. < ~1t, . ..~ .t. l~.:r • •• •~"; , < • -'".;1.; '"I"·... • I ........ , r;.-- '. •. oil! , ....#. - ....~' , . 1,.,.' .~..... ?-~ ., -•. -'I.- ".,~ .-.'••"...• .,,"Figure 8. Bark of Nuttall oak. upper. willow oak, middle, and cherrybark oak, lower, showing left to right. high,medium, and poor vigorclasses. From Guttenberg and Putnam. 1951.44Table 10. Crown and bark characteristics of red and white oaks byuigor class {from Burkle and Guttenberg, 1952~High vigor Medium vigorRED OAKSCroWD: 'It or more weU- Crown: Small and poorlyformed, with abundant formed, or open thinlyfoliage, and without cloee foliated.competition. Some crownsmay be entirely free ofcompetition,but twigs~be thicker and fewer, andfoliage lUnder, than illhigh vip' crowna.BaTk: Bari&: t.h.idmess &tk: Compared withaDd color of the inner aDd high vigor, fiuuree leasouter bark, varies with the wide, inner bark dullersped•. In general, the and generally lese conspi-bark is healthy, fully cuoua. Overall, bark isnonnal in color, relatively somewhat rougher aDdthin and smooth, but .with darker.shallow fissures exposingfleshy. lighter colored innerbark that contrasts marked-ly with dark outer bark. Thebark is the most conclusiveindical.Ol'Crown: V. or more fullyformed and without. closecompetition. Full andthrifty. ProfUIle, long,upwud'rMehing youngbranchel and twigs, ligbt-oolored and lusuoua. Nodying _den or deadstubs in upper crown.Foliage abundant andlustrous.Baril.: Dark, thick, nanowlyfiuured. LJttJe or DO livetissue usx-I in flHW"ell.Crown quality and vigormonl important than lengthor volume, es:cept that a highratio of crown Jength toatem length iJ aignificant.WHITE OAKSCroWD: YI or more fully CroWD: Small and poorlyformed and without close formed or open. ThinlycompetitJon. Notably Iesa foliated.full than thoee of higb vigortrees. Branches darker, lessascending in aapect.Bark: Thick, dark.graywith distinct, long fis·sures. Ridges flat withfew crosa breaks ronningfrom fiseure to fissure.CroWD: V. or more fullyformed and without closecompetition. Full andthrift.y, branches amallsilvery, and IIlcending. Nodying leaders or deadstubs in upper crown.Bark: Thinner. Gray.Fissures ahorter and Iesadiatinct; ridges !lOme-what ICIly; crosa breaksmore common.Bull.: Thin_ Asb.gray.Fiaaunlll ahort and obacure,ridges seely, and crossbreaka abundant.45Table 11. Site index for willow oaks decreases with availability ofpotassium in river bottom soils of the Mississippi Delta (afterBeaufait. 1956).AvailablePOLIlssium·Ibs/ae100200300.00.netennined by quick-test of the surface six inches.SiteIndo.83-957&-93.....60-78Figure 9. Willow oak on good (left] and poor [right] sites.Merchantable height and log quality decrease as total height at agiven age diminishes From Beaufait, 1956 .46vary with stand density, the tabular data are adjusted to a standardbasal area of 110 square feet per acre for all trees 6 inches dbh andlarger. Broadfoot (1964) evaluates willow oak sites on the basis ofclay content in the 36- to 48·inch layer. depth to mottling, inherentmoisture condition, and presence or absence of a hard pan. Site indexincreases with decreasing clay content and increasing depth tomotUing on inherently dry sites without a ~n. Wet conditions or thepresence of a hardpan results in decreased ~wth.Table 12. Average total height of dominant willow oak at age 5()years on non-delta sites I;rom Beaufait, 1956~Available K per Topographic classacre in ().6 inch High ridge Low High LowLayer lIbe.) or front ridge flat flatF""'00 95 92 89 87200 90 87 .. 82300 82 79 76"'00 7S 7. .. ..500 .. 6' ,. ..Water oak sites are classified by the amount of sodium present in 84·foot depth. thickness of topsoil. and presence or absence of ahardpan (Broadfoot, 1963). Increased sodium content indicates highcolloidal content and reduced growth. Highest site indices areobtained on deep soils without a pan and with low colloidal content.Site index for cherrybark oak increases with increased. drainageand thickness of topsoil (Broadfoot, 1961).Natural RegenerationNatural reproduction of water oak generally occurs in densepatches in temporary shallow pools of water beneath closed canopies.Drainage is advisable as standing or moving water preventsestablishment of reproduction whenever it submerges seedlings formore than several weeks during the growing season. If submergencetakes place prior to the growing season, seedlings remain dormantlo~ger than usual in th spring and do not begin growth until afterwater recedes. Regeneration usually fails if floods during the growingseason occur too frequently for seedlings to have a chance betweenperiods of high water to grow above the average depth of flooding.Mesic oak seedlings rarely survive the low soil aerationconditions of inundation. In an extreme case, where soil wassaturated for 38 days, leaves of cherrybark and pin oak seedlings47became chlorotic and roots died. Roots were not replaced throughadventitious buds, and those formed after excess water drained wereweakly developed. Growth was not resumed following drainage(Hosner, 1959).White, cherrybark, and pin oaks do not survive and, therefore, arenot found on sites frequently flooded (Maisenhelder, 1957; Yeager,1949). Cutting for those species should be gaged to seed·years, sincerodents consume seeds stored in the duff. Gaps in seed production of6 to 8 years are not uncommon.Hosner and Minckler (19601 noted that in the upper reaches of theDelta, pin oak reproduction increases as overstories become heavieruntil basal areas reach 100 square feet per acre. Openings, therefore,will retard regeneration of that species and permit entrance of moredesirable broadleaf trees. Seedlings should be released from overheadshade, but release of water oaks which only sparsely make upadvanced regeneration may be delayed for a mirimum of 3 years. Onthe other hand, large openings seem necessary for regeneration ofcherrybark and Shumard oaks (Hook and Stubbs, 19651.Artificial RegenerationPlantingNuttal, cow, and overcup oaks do best when planted on we11-drainedsoil. Those species, however, survive in swampy or poorly drainedsites, provided (1) water recedes below tops before the growingseason begins and (2) trees grow sufficiently tall the first year toavoid being overtopped by brush in succeeding years. Nuttall andovercup delay growing until water recedesA 30·year·old mixed oak plantation on a well-drained terrace notsubject to flooding produced a basal area of 134 square feet per acreand about 0.8 cord per acre per year. The best growth on the site wasfor water oak; live and cow oaks were less productive; and the sitewas too dry for Nuttall oak (Kaszkurewicz and Bums, 1960).Creek bottom terraces recently abandoned from agriculture makeexcellent cherrybark oak sites. Seedlings survive well and averagealmost 3 feet per year height growth for the flrSt 9 years (Applequist,1959). Cherrybark oak prunes naturally but has some crook injurycasued by the hickory twig girdler which, however, is overgrown byvigorous stems.Direct SeedingDirect seeding shows promise for reproducing cherrybark andShumard. oaks under certain site conditions. Terraces are superior tobottoms as flooding damage is less severe (Table 131. and cherrybarkoak requires the better sites, regardless of flooding chances.48Acom weevils and filbert wonns destroy many bottomland oakseeds. But because unsound seeds float in water and exhibit insectentrance holes, they are readily culled by flotation and handinspection. For cow oak, and perhaps for other oaks, a single darkspot on the acom shell is sufficient indication of an opening made byan egg-laying beetle, the weevil larvae of which feed on the meat. ForShumard and cherrybark oaks, a light tan circular cup scar isindicative of sound seed. Dull brown cup scars mean defective seed(Lot.ti. 1959) (Figure 10).Table 13. Average third-year survival and height growth of directseeded oaks by site condition, Santee Experimental Forest (fromSEFES, 1959}.Species Cleared terraces Re1eaaed first bottoms 1Swvival Total Height Survival Total HeightPercent Inches Percent InchesChenybark oakShumard oak23372330 ••1328Average SO 27 6 20I ReI~ afttr one growing season.Although visual observation and hand selection make seedt.reatment with chemicals unnecessary. weevils are killed byfumigation for 4 hours in a tight container with 1 ounce of methylbromide for each 25 cubic feet of tank volume. Soaking in hot waterat 1200 F. for 30 to 45 minutes is also an effective weevilcide (Lottie.1959).Figure 10. Shumard oak acorns. Those with light colored cup scar(two on right] are sound, and those with dull coloratwn [two on left]show evidence of weeviling or rot. From SEFES Annual Report,195949PruningWillow oak pruning wounds require 2 to 3 years to heal,live-branch wounds healing faster than those caused by the removalof dead branches {Johnson, 1961). Rot and insect infestation are rarein live-branch wounds, but may occur on one-fifth of the dead-branchwounds. Most rot is confined to the cores of knots. Epicormicbranches which develop following pruning may make the practiceuneconomical.Injurious AgentsDiseaseFire wounds are the most important cause of cull in bottomlandred oaks. In order to determine the amount of decay behind old searsand to estimate rot expected from new wounds, Toole and Furnival(1957) developed graphic means applicable to a number of commonfungi: Polyporus, Corticium, Stereum, Poria, and Fornes. Inpractice. extent of rot is estimated from the length of hollow byprobing with a stick or judging the height of butt bulge (Figure Ill.Rot generally extends 2 feet above the top of the hollow or 3 Y1 feetabove the bulge. One applicable rule for deducting volume lostthrough butt rot is to reduce the merchantable length of a stem bythe length of rot, then reduce dbh by 1 inch for each 6-foot length ofrot. This calculation, however, is not applicable to decay scars morethan SO years old.Heart rot caused. by Poria spiculosa is extensive in the Delta.probably infecting more than one percent of the water and willowoaks and hickory (Toole. 1954). Small, roughly circular cankers withtraces of branch stub remaining in the usually depressed. center onboles of willow and Nuttall oaks indicate presence of the browndecay. Fruiting bodies are found only on dead wood in contract withthe ground. Well established infections exhibit brown fungus matterwhen the suspected branch tree is cut into. When P. spiculosacankers occur on the first log, that log is a total cull. The length ofthe rot, increasing about 10 inches each year, is discernable from theage of the canker, using Toole's (1954) relationship (Figure 12).Age can be readily determined by counting rings on the callustissue fonned around the infected branch trace. Early harvest in thehope of salvaging logs above the butt section is recommended.Polyporus hispidus is also a cause of cull in bottomland oaks: red.willow. Nuttall, and cherrybark. The fungus results in elongated,swollen areas surrounding dead depressions or cankers which, uponrecurrent killing of bark and cambium and renewed callus folds, givespindle-shaped swellings. Yellowish·brown to rusty·red conks 250--,•,• V./,./V.-/•i•,!'. • ••..'~-=---o----!· . "-: ,f--+-!-+/.yL---j•Ii•,1./•./V,./V·••• .,••i•iFigure 11. Extent of heart rot in red oaks is related to umgth ofhollow (0.[, age of scar Ib1 and. height of butt bulge [c~ For scar age,the relation concerns the extent of rot aboue the original scar heightfor four values ccUcualted by subtracting two from original scarwidth and dividing by stump diameter at the time of wounding.Hence. if stump diameter was 12 inches when a fire occurred and theoriginal scar width was 8 inches. then the lentlth of heart rot abouethe scar height fOT a 2Q-yeor--old scar is about 2114 feet. From Toole,195951V/',/,//V•2oo 2 4 • • 10AGE OF CANKER I YRSJFigure 12. Relation between length of heart rot and age of poriaspiculosa cankers on willow oak. The rot increases in length about 0.8foot each year. After Toole, 1954inches or more in width. spongy, hairy, and without a stalk, occur onsurfaces of well..cJeveloped cankers in fall or winter. Drying to a rigidblack mass, the conks fall to the ground by spring. Infection by thefungus entering through dead branch stubs gives rise to white orpale yellow soft rot in the wood and death of the cambium. Cankerlength, which rot len~hexceeds by about 30 inches, increases Y2 footper year (Toole, 1956) (Figure 13). Infected trees should be prompUysalvaged since they quickly become culls. Other canker-formingfungi attacking souther hardwoods are PaM laeuigata (Bottomlandred oaks and lrpex molUs (red oaks). Canker fungi enter throughstubs of dead branches, working down the heartwood and alsospreading from the point of entry to kill the cambium. Irpex cankersare irregular in shape and with a number of sunken areas. Creamywhite conks and white fungus material often occur at the base of thesunken area, the fruiting bodies varying greatly in size and havingshort, jagged teeth on the lower surface (Toole, 1959).527---HEIGHT Of ROT----___I1[I.",l OF HOL.LOW-----jHEIGHT 0,. auTT 8ULGE---!""Ml.tfT OF ORIGINAL WOUNOFigure 14. Fire-scarred Nuttal oak, wounded 16 years previously.From Toole and Furnival, 1957 .Wood QualitySouthern hardwoods in general, especiltl1y oaks. are hard andheavy because of am121e moisture and long growing seasons-acorollary of rapid growth. Low specific gravity wood. however,accompanied by slow growth, is found in overcup oaks growing inbackwater areas annually flooded for long periods (Paul and Marts.1934)_54SWEETGUMWithin the Coastal Plain, second-growth sweetgum infully-stocked, relatively pure stands on alluvial soils is frequentlyevenaged, becoming established over an 8- to IG-year period.Although many pure stands of virgin gum occur, such stands are incontrast to the species' gregarious association in primeval forests,especially on the better-drained, silty clay sites.Seed-tree cuts should be used. for regeneration of evenaged stands.Retaining too many seed trees permits enroachment of undesirableshade-tolerant species. Maintenance of approximately 70 square feetof basal area in evenaged stands seems to yield maximum cubic footgrowth (Johnson, 19681.Coppice is a common form of natural reproduction of sweetgumforests. Early growth of sprouts is considerably faster than that ofseedlings, reaching breast height in a singly year iJ:l contrast to 3 to 5years for seedlings. Sprouts 10 years old, therefore, may equal theheight of IS·year-.old saplings grown from seed.Vigor ClassesVigor classes based on bark and crowns have been derived forsweetgum by Guttenberg and Putnam (1951). High vigor treesexceed 3 inches dbh growth in 10 years, medium vigor grow between2 and 3 inches, and low vigor trees have less than a 2-inch incrementduring the period (Table 14). These vigor classes apply only to trees16 inches dbh or greater, and not to culls.Table 14. Bark and crown characteristics of sweetgum, by vigor classrfrom Guttenberg and Putnam, 1951).Higb vigorBark: Light ash.~y,corky. thick, with pro-nounced rounded ridge,.Bottoms of fissures dis·play streak of very lightinner bark.Medium vigorBark: G.-.y, thick, some-what corky (or at leastwith ridges slighl.1yrounded I, and free ofscales or plates. Bottomsof fissures narrow, onlyoccasionally displaying thinstreak of inner bark.Low vigorBark: Compared withmedium vigor, darker,thinner. flatter. No displayof inner bark. May be sally..Crown: :y., or more with- CroWQ: 'It or more well Crown: Compared wiLhout dose competition. formed and without dose medium vigor, amaller. orFull and healLhy, com- competition. Some crowns more preponderantly heavy-posed preponderantly of are small because of com· limbed and with thinnersmall ascending leaders petition, but have pre- foliage. Foliage may be paleand twigs. Foliage ponderance of small twigs Some trees msy be stag'abundand and lustrous. and abundant foliage; headed or dry-topped,Other things being others are large but areequal. high ratio of crown heavy-limbed with thinlenght to stem length foliage. Foliage all\'ays ofIndicates high vigor. good'·color.. Little sign ofdry-topping.55Simplified marking rules for intermediate and unevenaged ormixed management of sweetgum on a lO-year cutting cycle requirethat low vigor trees. regardless of diameter. be cut as soon asfinancially mature. that is. when growth rate fails to meet a specifiedinterest rate. All sweetgum 22 inches dbh and over that show nopromise of developing better than a grade No.3 butt log fall into thisclass. Where one of two trees must be selected. the one with thegrealesl polential for higher value is retained (Guttenberg andPutnam. 1951).Vigor classes. along with age. aid the marker in determining whichtrees are financially mature (Table 151. For sweetgum. low vigortrees do not grow at a 3 percent interest rate. while high vigor treesmay attain 4 percent if they are less than 26 to 29 inches dbh.Medium vigor stems are usually under 22 tQ 25 inches.Table 15. Merchantable gross board· foot uolume (Scribner) per acre,classified by site and stand-age (after Winters and Osborne, 1935).Averagebreast-highAge It diameter of Sasal area Volumebreast merchantable merchantable of men:hanllble ....height"'" ""'",- .~Years Number Inches Sq. Ft. Bd. Ft.POOR SITE - (SITE INDEX 80)40 7 14.6 7 40050 30 14.8 33 2.00060 49 15.1"4.07070 '2 15.4 75 '.28060 71 15.9 88 8.43000 77 16.5 98 10,540MEDIUM SITE· (SITE INDEX 100)40 .. 14.8 58 4,26050 54 15.4 91 8,18060 7' 16.1 115 12,40070 86 17.0 133 16,51080 93 17.8 14' 20,46000 97 18.6 156 24,120100 99 19.3 163 27,360GOOD SITE - (SITE INDEX 120130 42 14.7 47 3.43040 75 15.4 101 9.85050 89 16.3 136 16,71060 97 17.4 161 23.62070 100 18.5 179 30,12080 107 19.6 100 35,94056aSite IndexBest sites are those with the following combination ofcharacteristics; medium-texture soil, between sand and clay;moderate to good internal drainage, as is evidenced by the absence ofmottling; no hardpan within the upper 2 feet; and soil inherentlymoist. Dry slopes and ridges, a hardpan in the upper 2 feet, and poordrainage noted by the mOltJing hues of red, yellow, and blue indicatelower site indices. Hence. sweelgum sites may be evaluated by the(1) clay content of the soil and the correlated amount of exchangeablepotassium, (2) surface drainage and hardpan presence, and (3) soilseries (Broadfoot and Krinard, 1959).Table 16. Height of sweetgum at aKe 50 years, as determined fromclay and potassium contents at 36- to 48-inch soil depth (afterBroadfoot and Krinard. 1959).Clay Exchangeable potassium, in pounds per ac::rP.(Percent) • 100 200 300 ... 500F..,I. 97 100 104 loa 112"'2. 93 9. 100 104 107 III30 89 92 95 99 103 loa•• 85 88 91 95 98 10230 82 85 87 91 94 9760 78 81 84 87 90 937."77 60"86 8960 71 74 77 79 82 85Site index increases with increasing exchangeable potassium,provided the clay content remains constant (in contrast to Beaufait's(956) report for willow oak). and decreases with increasing claycontent for any given quantity of exchangeable potassium(Broadfoot and Krinard. 1959). Reduced growth with higher claycontent is probably a reflection of lower aeration and iessenedpermeability for soil moisture and root extension. Better growth withhigher exchangeable potassium is, in turn, an indication of theresponse of the species to the overall nutritional status of the soil,but. especially to this cation of unknown function in the chlorophyllof green plants.Use of surface drainage and hardpan as a method of indicatingsweetgum site potential is apparently limited to the flood plain of theMississippi River, as Broadfoot and Krinard (1959) were unable tofind this relationship in adjacent loessial and Coastal Plain alluvialsoils (Table 17). Surface soil texture alone, ranging from theextremes of buckshot and gumbo clay, is not obviously influential ingrowth responses but, as evidenced from Table 18, is necessary forusing the key which relates site index to drainaJtE! and hardpan57occurence. Although site index may be estimated by soil series, insite indices, average 104 on recent natural levee soils and 90 on slackwater soils: there is, however, a wide range within series. On Deltaand adjacent uplands, for which the table was derived, the range isfrom 71 to 121.Table 17. Site index of sweetgum by soils [after Broadfoot andKrinard, 1959).Soils Site InduSoils of recent ~turalSoils of old ~tunlISoils or a"-ek''''lIter areuBottomland soils rrom loessBottoms from mixed loess and CoastalmatarialAlluvial soils with PenniaD Red BedinfluenceSoils from Coutal Plain alluviumTence soilsSoils developed in Ioeu105-1098>-10383-8794-10596·100908>-9570-11080- 85Table 18. Site index for sweetgum for soils derived from aUuvium onthe Mississippi river flood plain1 [after Broadfoot and Krinard,1959J.Soil-site descriptionI. Fine texture lday. including buckshot and gumbo)A. Moderate to good inlftnal drainaae (DO mottling)B. Moderate to poor internal drainage (mottling)I. Without Dan in upper 2 feetII. inherently moist !subject to flooding)b. inherenlty dry (slope, ridge)2. With pan in upper two feet11. Medium texture (between clays and aandslA. Moderate to good internal dn.inage (no mottling)1. Without pan is upper two feetII. inher'ently moist (subject to flooding)b. inherently dry (slope, ridge)2. With pan in upper two feetIII. Coarse texture (aaody soilslA. Moderate to good internal drai~ge lno mottling)a. inherently moist (8ubject to flooding)b. inherently dry (slope, ridge)(not a sweetgurn site ISite indu100859570HO10575100l Key not applicabie to aoils outside the Mississippi River flood plaiD-u Ioesa andCoutU PlaiD alluvium. Sites DOt indexed are either nonexistent or are notrecommended for sweetgwn.58o to ~o 0(1 $0AGE (YEARS)0V\~0/ \~/ '/ ,y .-0 II / v .-0II /'1/ ,~--1/// /0'II /00..•""Figure 15. Site index curves for sweetgum. From Broadfoot andKrinard. 1959.Injurious AgentsDiseaseSweetgum in the bottoms is seriously affected by a blight whichmay be associated with abnormal climatic and consequentsoil-moisture conditions. No transmissible virus or infective principleis known for the malady which was first noted in 1950, a droughtyear. The first visible indicatiQD appears in late summer when leaveson some branches prematurely develop fall coloration. Crowns thenthin gradually from the top down. Some buds do not open; othersproduce small chlorotic leaves, and death to the tree comes a year ormore after symptoms first appear. Sometimes dieback is arrested,and trees appear healthy except for the dead top. As much as 90percent of the fine feeder roots in the soil surface layers are dead onblighted trees, while larger roots remain healthy in appearance(Toole, 1954, 1959a). A cut into the wood of diseased branches oftenreveals irregular tan or dark brown streaks in the white sapwood.Damage seems greatest where sweetgum is off-site, since the blightin bottomlands is more severe on slack water soils and least onnatural levees. If the malady is primarily a matter of water shortage,dense and old stands will be expected to suffer most because of theirgreat demand for moisture (Figure 16).59Figure 16. Blight damage to tree and root of sweetgum in theMississippi Delta. From Toole, 1959.At deeper levels of the soil Toole and Broadfoot (1959) found anaccumulation of sodium and potassium salts in amounts sufficient toreduce available water following years of low rainfall. They furtherobserved an inverse relation to bulk density; loose soils which drainreadily and retain less water are most susceptible to blight. Hence,the disease is twice as prevalent on upland as on bottomland sites(Toole, 1959a).No control for the blight is known. Trees with more than 10percent of the fine branches dead should be salvaged unless there isevidence that dieback has ceased. The species should not be favoredfor sawtimber on heavy, slack-water bottomland soils and on rollingupland sites except loessial bluffs. Sweetgum, however, can be grownon such soils for small products.A lesion occurring in patches of the cambium tissue is casued byan unknown fungus. Although trees are not killed, lumber isdegraded as bark is encased within the stems and bumps and ridgesof callus tissue that forms over the lesions. Damage is reported to bemost common in 10- to 20-year-old stands, principally in the lower 8feet of trunk (SFES, 1960), but small veneer timber is occasionallyseriously degraded (Figure 17).60Figure 17. Sweetgum lesions. The inactive lesion on the left has ridgeformation and overgrown patches of dead cambium. At right is ayoung lesion. From Toole, 1959.Fh-eLight ground fires seldom kill sweetgum after it is 30 to 40 yearsold, but serious basal wounds result. At that age, defects affect. 25 to40 percent of the volume. Younger trees, 10 to 15 years of age, arefrequently killed by flres of moderate intensity (Winters andOsborne, 19351.Apparently the cambium of sweetgum can be heated to the lethaltemperature of 140° F. about twice as fast as can southern pine andcypress stems of the same bark thickness ISFES, 1960). Thisaccounts for the ability of fire to kill sweetgum in hardwood controloperations and also points up the necessity for fire exclusion in themanagement of the species.61WATER TUPELOWater tupelo, or tupelo gum, and black willow behave similarly inthe forest. Both survive on swampy and poorly drained land,provided water recedes by the time the growing season begins andfirst-year height growth is above the growing season water level onthe succeeding year. Under continuous inundation from winter on,water tupelo seedlings and young saplings will maintain dormancyinto July and then proceed to grow normally.A virgin unevenaged stand averaging 200 years composedpredominantly of water tupelo stems about 16 inches in diameterabove the butt swell had a basal area of 230 square feet per acre.Basal areas in primeval water tupelo forests frequently were twicethat of old-growth timber on uplands. Because of butt swell, dbh ismeaningless; the stand mentioned above would have had a basalarea of almost toOO square feet per acre. Second-growth, too, isstongly affected by lapel', equivalent to over 150 square feet per acrebasal area.Water usually covers the swamp floor throught the winter, spring,and even until midsummer, stimulating production of swollen buttsor ·'Bottlenecks". Butt·swell increases with wetness of the site, treesize, and age. Only cypress has greater butt-swell. (Trees of thegenus Fraxinus have some swelling at their bases [SFES, 1934], andyellow-poplar seedlings, if alive after 6 weeks of submergence, will bebuttressed (Kramer, 1951).)In shallow areas, baldcypress and swamp tupelo accompany watertupelo. In deeper swamps, swamp tupelo is absent, indicating thatdepth of water is a limiting factor in the distribution of dominantarborescent species. Swamp tupelo, but not water tupelo, occurs inthe Okefenokee Swamp and in deep bogs of Louisiana and Tennessee(Mattoon, 19411. Their occurrence there reflects the secondarydistinctions within the Coastal Plain muck swamps small estuaries,and small piney woods tributary stream bottoms. In those locales,water tupelo, if present, inhabits the fresh, moving water sites alongdrainage courses and alluvial swamps, while swamp tupelo is foundin the relatively stagnant muck swamps. The two meet along themargins of live water in swamps, in some minor stream bottoms ontheir respectively preferred sites, and in the smallest estuaries.Standing water in water tupelo swamps is generally deeper, thoughof shorter duration, than that in the swamp tupelo sites.1n the Delta area, seedlings of water tupelo on the swamp floornumbered only 80 per acre, but where soil was exposed for 2 to 4inches above the water level, 1300 seedlings per acre were counted(Penfound and Hall, 1939). It seems, therefore, that slight,temporary drainage, if possible to control, may be helpful inreproducing the type, and that a seed·tree cut, anticipating evenBged62stands, would be appropriate. A two-cut modified shelterwood-theinitial harvest to provide for seed fall, seedbed preparation, andgermination-is suggested. Final harvest would await establishmentof a satisfactory stand. 1Following cutting, it is possible that in some situations high waterwill be retained for a considerably longer period. unless drained. forwater consumed in transpiration by these large trees far exceeds thatof evaporation in the openings exposed to sunlight after cutting. Onthe other hand, almost all feeder roots of swamp tupelo, but notwater tupelo, in hydric plant communities are in the organic matteron the soil surface. consisting perhaps of eight to 12 layers of leavesbelow which is decaying material to a depth of 1 foot. Drastic andsudden drainage could be catastrophic. as this zone dries out readily.Seed Viability Under WaterWater tupelo seeds retain viability for up to 14 months ofsubmergence (Applequist. 1959a). This is significant. for southernswamps supporting this species are typically flooded throughout thewinter and spring months. and occasionally remaining under waterfor an entire year. Thus, water tupelo seeds germinate but the seedsof other trees. such as baldcypress. which tolerate less than a year ofinundation, are destroyed. Sites flooded only for relatively shortperiods, therefore, are necessary for establishment of thecypress-tupelo type in swamps. Seeds have been known to germinateand survive afloat for a significant period.ThinningHypotbetical stocking and yields of pure evenaged tupelo stands,showing development from the pole class onward. are given in Table19. Expected yields from well-stocked stands can be estimated fromthe last column. provided diameter growth rates are known. Thetable, which assumes the stands are well-managed, fully stocked. andoccur on at least average sites, suggest that between one-half andone·third of the basal area of trees averaging 10 inches be removed inthinning, while among the largest trees-above 30 inches-onlyone-fourth of the basal area need be taken. Cutting cycles forthinnings or stand improvement will be between a and 15 years,depending upon (l) size of trees retained after thinning, (2) siteindex, and (3) purity of the stand. Average tree size, rather thanstand a~, determines the end of a growth period. Usually 10 yearslShelterwood is • misnomer. as shelter is noc. requin:lcl for the young seed.linga.63Table 19. Hypothetical stocking and estimated development and yields per acre, for well-managed even-aged Tupelos atend of successive growth periods on average or better sites1 [After Putnam, Fumival and McKnight, 1960]Average diameter above bottleneck Average basal area Average number of treesAll trees Leave trees Cut trees All trees leave trees Cut trees Total Leave trees Cut treesInches Inches Inches Sq. ft. Sq. ft. Sq. Ft. No. No. No.10 10.75 8.95 141.3 79.5 61.8 259 146 11314 14.80 12.45 155.8 101.6 54.2 146 95 5118 18.85 15.95 167.9 118.4 49.5 95 67 2822 22.85 19.55 176.8 131.1 45.7 67 50 1726 26.80 23.50 183.3 139.5 43.8 50 38 1230 30.70 27.35 185.5 143.2 42.3 38 29 934 34.60 31.60 183.7 142.9 40.8 29 23 638 38.50 36.30 178.7 136.2 42.5 23 17 50) 42 42.00 166.2 166.2 171701 Average sawtimber volumes SawtimberTotal Leave trees Cut trees cumulative yields 2Bd. Ft.3 Bd. Ft.3 Bd. Ft.3 Bd. Ft.33,335 3,335 3,3358,970 7,935 1,035 8,97013,800 11,615 2,185 14,83517,796 15,042 2,754 21,01621,246 17,940 3,306 27,22024,587 21,016 3,571 33,86727,945 23,794 4,151 40,79631,280 ----- 31,280 48,2821 Duration of each growth period will vary with size of residual ~owing stock (leave trees), site, species composition, and, for first cycle, on timelapse pending reproduction. End of each period is signaled by attainment of specified average size.2 Ip.cludes all sound, reasonably straight sawlong stems to a lO-inch minimum top diameter, inside bark,at least 12 feet above the stump.3 Doyle rule.AMERICAN SYCAMORESycamore is relatively easy to reproduce by vegetative cuttings onappropriate sites in Coastal Plain, Piedmont, and other bottoms.Typical cottonwood sites and some friable and loose soils too dry forcottonwood are also suitable for conversion to this species.Site ludell:Early height growth of sycamore is very rapid. tapering off atabout age 30. For that reason, the curves derived by Briscoe andFerrill (1958) are based on an age of 35 years, rather than theconventional 50-year standard (Figure 19). The stands alongLouisiana rivers used in formulating these curves were on soilsranging from loamy sand to heavy clay loam. Surface drainagevaried from poor to very good.'20120110-'"100 IOO~-....'" 90~~'- 80 ~~ 8070 ~~'"60 60 '-iO40'0~=----'-'--":'2':"0---:2':"5---:3'::0---;3,;,--7.40AGE (YRS.)Figure 18. Site Index curves for American sycamore in southeasternLouisiana.. based upon age 35. from Briscoe and Ferrill, 1958.RegenerationPropagation by CuttingsCuttings from l·year-old sprouts taken from nursery-grown stock66-initiated an adequate root system and grew well. Butt cuttings,about Yr inch in diameter at the small end. are trimmed to 20 incheswhen removed from parent seedlings and stored in moist sawdustuntil planting time.Rough, cutover land is prepared by double furrowing prior towinter planting at 9 x 9 foot spacing. Stocks are inserted in theground with 4 inches extending above the surface. Cultivationduring the latter part of the first season is essential for weed control.Late spring and midsummer cultivation is also recommended,particularly if rainfall is appreciably below normal.PlantingAutumn planting appears preferable because roots developthroughout the winter. thus providing for good height growth thefollowing spring and a hedge against drought. Planting should notprecede the earliest killing frost and the onset of dormancy, norshould it be done prior to the end of the autumn drought expected insome sections. Sixty·five percent survival and an average first'yearheight growth of 5 feet was obtained by Nelson and Martindale119571.Ferti.liz.er as a side-dressing, using 1"It ounces of 8-8·8 formulationin each of two dibble holes 1 foot deep and 4 inches from the stem onopposite sides, significantly improves growth (Huppuch, 1960).Fertilizer should not be placed in planting holes, even when a layer ofsand separates the base of the cutting from the salt. as burning oftissues results. Water standing after rain in double furrows aidssurvival and probably reduces the chance of fertiliz.er burn bydissolving and diluting the material, as fert:ilized stems not furrowedshowed poor survival.In addition to nutritional amendments, seedling growth has beenimproved by growth regulator application. Gibberellic acid, in oneinstance. stimulated height,growth (Nelson, 1957).Practically any condition of temperature and light intensity ofseedbeds under sycamore stands is expected to favor germination ofAmerican elm seed to the exclusion of sycamore establishment.Hence. to this Brunk and Hansbrough (1960) attribute thesuccessional sequence of elm in sycamore forests of the midsouth'sbottomlands, McDermott I1954a I. finding sycamore seedlings atleast as tolerant as elm. believed that the ecological tranistion to elmwas not due to light but to some other factor associated with theseedbed. Perhaps temperature of the soil. which is generally exposed,is the other factor. However, if sycamore is as tolerant as elm, itwould be but for a brief period following germination.Successful regeneration also requires subsequent removal ofundesirable hardwoods and vines. Cleanings will be needed to67remove invading boxelder, soft elm, hackberry, and sweet pecan,especially.ThinningDegrade from epicormic branching may be related. to residualdensity after thinning. In relatively dense unmanaged stands withbasal area exceeding 130 square feet per acre, most sycamores arefree of epicormic branching. Such stands may probably be safelyreduced to 80 square feet per acre, but heavier thinning results inconsiderable branch development.68poYELLOW·POPLARYellow-poplar, though generally not thought of as a Coastal Plainbottomland species, exists there. This anomalous status may beexplained by two illustrations, both emphasizing the importance ofsite identification and discrimination. For example, when poorlydrained but not flooded Coastal Plain sites were planted toyellow-poplar, survival and growth, under cultivated anduncultivated conditions, were highly inferior to either slash orloblolly pine on the same site (Jones, 1959). Survival and growthwere better, though still not satisfactory, in uncultivated sites thanin cultivated areas, possibly due to hacking of roots in plowed areas.On the other hand, yellow-poplar may grow 14 feet in 4 years inbottoms and 9 feet on lower slopes, but be unsatisfactory at higherelevations. In the Piedmont province, too, it is more appropriatelyencouraged in the bottoms thaD elsewhere (Schomader, 1957). Onloessal sites planted yellow-poplar has shown as much as twice thegrowth in young stands as other species (Johnson and Krinard,1961).The species may be underplanted in stands of infe~or broadleaftrees on better sites but, in that. case, should be promptly releasedwhen establishment is assured (Freese, 1951a). Evenagedsilvicultural techniques, perhaps by seed-tree cuttings, are generallyrecommended.FertilizationWhile coves and bottoms in the Piedmont are not deficient-in theusual sense of the word-in nutrient elements for this species,growth was stimulated by applications of up to 1000 pounds per acreof diammonium phosphate during the first spring after planting. Theoptimum rate appears, by interpolation, to be about 750 pounds peracre (McAlpine, 1959a). Beyond this, there is some increase ingrowth, but the amount diminishes. First-year height growth was 1.7feet for 750 pound rates as against 0.5 feet for unfertilized trees.Three·year growth responses were similar, but it is believed thatfuture growth will be more markedly affected. by the high-rateapplications, early vigor being influential in subsequent growth.Survival of seedlings, however, is not influenced by applications ofnitrogen and phosphorus (McAlpine, 1959a; Ike, 1962).FloodingWhile flooding during dormant seasons is not injurious toyellow-poplar, growing season inundation of seedlings for even 3 to 4days kills all tress (McAlpine, 1961). Short·term floods of less than 2days may do no damage. Injured stems appear healthy for a monthor so before leaves wilt and death follows (McAlpine, 1959). When3-year-old seedlings were continuously flooded during the growing69season, all leaves died within a week or two. Before deatb, theybecame epinastic, a state in which more vigorous growth of the uppersurface of unfolding leaves causes downward curvature of leaves andtwigs (Kramer, 1951). Saplings and small pole-size trees have alsobeen killed by growing season inundation merely above the rootcollar.McAlpine (1959) reasoned that a temperature rise in ponded areasexposed to sunlight after rain ceases, increases respiration and, atthe same time, the activity of microorganisms. An oxygen deficiencyand carbon dioxide toxicity results. Hopkins, Specht, and Hendricks(1950) found that root growth of all of a number of species testedstopped when free oxygen reached 0.5 percent in the gas aroundroots, but top growth then continued, accompanied by possibly toxicaccumulations of iron. Those workers further noted that while therate of transfer of solutes from root to shoot is independent of aerobicmechanisms of roots, flooding might stop downward movement ofcarbohydrates and auxins, and that the accumulation of plant foodsand hormones at the water line may account for adventitious rootinKof flooded trees. Some sprouting from root collars indicates thatdeath of roots does not precede death of top, and therefore, root-killby flooding was not responsible for tree necrosis.70LITERATURE CITEDAl1eIl, P. H. 1962. Black willow dominatel balcIcypr~HUpeloswamp eight yearsafter dearcuttinB. U.S. Dep. Agr. Southeutern For. Exp. Sla.., Rese8reh NoteNo. 177. 2pp.Allen, R.. M. and A. L. McComb. 1956. Rooting of cottonwood euttings. So. For. Exp.St&.., Occ. Papet' 151App1equi!lt, M. B. 1959. Growth of planwd cherryb&rk oak in aoutheutem~. 14. S"-te Univ. Sch. For. Note 26.Applequi!lt, M. B. 1959a. Longevity of aubmerged b.1pelogum and baldcypress seed.14. State Univ. Sch. For. Note 27-Applequist, M. B. 1959b. A selected bibliogt1lphy on cottonwood. La. State Univ.Sch. For. Note 24.B8I.uftlit, W. R. 1955. Soil profile obserntions relating to drought dam~e in blackwillow lltands. J. For. 53:517.Beaufait, W. R. 195&. Influenosof soilanet topogrlIpby on willow oak sites. So. For.E.p. S,,-. Occ. Paper 148.Bonck, J., and W. T. Penfound. 1944. Seuonal growth oftwip oftnlelin the Ntturelands of the New OrJe.1lII Ilnlll. Ec:oI.. 23:473-475.Bonner, F. T., 1966. Survival and flfSt-year growth of hardwoods planted in..tunted aoils. U. S. Dep. Agr., So. For. Exp. Sta., U. S. Foreet Service ResearchNote 50-32.Bri8Coe, C. B., and M. D. Ferrill. 1958. Height growth of american Iyeamore in lIOUth-8I.IlLern LoulsilIUl. La. State U. For. Note 19.BrOlldfoot, W. M. 1953. Moisture in hardwood forest floor. So. For. Exp. Sta. Note85.Broadfoot, W. M. 1960. Evaluating cottonwood sites. So. For. Exp. Ste. Occ. Paper178.Broadfoot, W. M. 1961. Guide for evaluating chenybark oa.k lites. So. For. Exp. Sta.Occ. Papet' 190.B~oot, W. M. 1963. Guide for evaluatiq: "ateroak sites. So. For. Exp. Sta., Res.Papet' 50-1.Broadfoot, W. M. 1964. Guide for enlua.ting willow oak lites. So. For. Exp. Sta.,Res. Papet' 50-13.Broadfoot, W. M. 1966. Five years of nitrogen fertiliu.tion in I lweetgum-

Texas Forestry Paper No. 23

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Texas Forestry Paper No. 23

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