In 1994 eighty four permanent research plots were established in two twelve year-old loblolly pine (Pinus taeda) plantations in East Texas. Plots differed in relation to: soil-site type, density of trees per acre, fertilization treatments, and competing vegetation control. Three levels of thinning treatments reduced the basal areas to 36,60, and 84 square feet of basal area (approximately 100,200, and 300 stems, respectively) per acre. All residual trees were pruned to a height of 25 feet. Plots were re-measured in 1995, 1996, and 1998. Significant differences in diameter and height growth rates were detected in 1996 and 1998. Average diameter growth rates from 1995 to 1998 ranged from 0.64 to 0.31 inches per year depending on density class and treatment type

Dale, Leslie A.

Holley, A. Gordon

Kronrad, Gary D.

SFA ScholarWorks

Stephen F. Austin State UniversitySFA ScholarWorksFaculty Publications Forestry1999Four-year Growth Results from 16 Year OldIntensively Managed Low Density Loblolly PinePlantationsA. Gordon HolleyArthur Temple College of Forestry and Agriculture, Stephen F. Austin State UniversityLeslie A. DaleArthur Temple College of Forestry and Agriculture, Stephen F. Austin State UniversityGary D. KronradArthur Temple College of Forestry and Agriculture, Stephen F. Austin State UniversityFollow this and additional works at: http://scholarworks.sfasu.edu/forestryPart of the Forest Management CommonsTell us how this article helped you.This Conference Proceeding is brought to you for free and open access by the Forestry at SFA ScholarWorks. It has been accepted for inclusion inFaculty Publications by an authorized administrator of SFA ScholarWorks. For more information, please contact cdsscholarworks@sfasu.edu.Recommended CitationHolley, A. Gordon; Dale, Leslie A.; and Kronrad, Gary D., "Four-year Growth Results from 16 Year Old Intensively Managed LowDensity Loblolly Pine Plantations" (1999). Faculty Publications. Paper 231.http://scholarworks.sfasu.edu/forestry/231FOUR-YEAR GROWTH RESULTS FROM 16-YEAR-OLD  INTENSIVELYMANAGED LOW DENSITY LOBLOLLY PINE PLANTATIONS’A. Gordon Halley, Leslie A. Dale, and Gary Di Kronrad’Abstract-In 1994 eighty four permanent research plots were established in two twelve year-old loblolly pine (Pinus taeda)plantations in East Texas. Plots differed in relation to: soil-site type, density of trees per acre, fertilization treatments, andcompeting vegetation control. Three levels of thinning treatments reduced the basal areas to 36,60,  and 84 square feet ofbasal area (approximately 100,200, and 300 stems, respectively) per acre. All residual trees were pruned to a height of 25feet. Plots were re-measured in 1995, 1996, and 1998. Significant differences in diameter and height growth rates weredetected in 1996 and 1998. Average diameter growth rates from 1995 to 1998 ranged from 0.64 to 0.31 inches per yeardepending on density class and treatment type.INTRODUCTIONIn 1994, Stephen F. Austin State University in cooperationwith Temple-Inland Forest Products Corp., established 84monumented experimental plots in two typical loblolly (Pinustaecfa)  pine plantations in East Texas. This study wasdesigned to evaluate the effects of heavy thinning, pruning,fertilization, and competition control, the goal being toproduce large clear sawtimber on short rotations. Thisproject was based on studies reported by Burton (1982) andWiley and Zeida (1992). The style of management on thesestudies are sometimes referred to as “Sudden Sawlog”. Bothstudies used very intensive management practices such asmultiple thinnings, bush-hoggings, and prunings, the laterstudy also included three prescribed burnings. While thesestudies utilized silvicultural practices to maximize sawtimberproduction, there was no consideration given to the costsassociated with this management. The main goal of ourstudy is to grow the largest amount of high quality, knot free,wood while being able to recapture the management costsand still be a profitable investment. The objectives of thisstudy were to report on the growth results four years afterthinning treatments were applied.STUDY SITESThe two study sites differ in relation to soil drainage type.Site one is located in the southern comer of AngelinaCounty and is considered a moderately drained site with aMoswell complex (Dolezel 1988). Site two is located insouth-eastern Anderson County and is considered a welldrained site with a Fuquay series (Coffee 1975). Both studyareas were on non-old-field sites that were previouslyforested with loblolly pine. Both stands were planted in 1982with a local variety seed source. Site one was more denselyplanted with approximately 800 stems per acre while site twowas planted with approximately 800 trees per acre. Theunderstory in site one was almost non-existent, while sitetwo contained a heavy mix of woody shrubs and hardwoodsaplings.METHODSThe study was implemented during the summer of 1994,while the stands were in their twelfth growing season. Threetreatments were installed in a completely randomized with-out replacement factorial design with three replications foreach treatment. Treatments included in the study were threelevels of residual densities (35, 60 and 84 square feet ofbasal area per acre), two levels of fertilization (fertilized andnon-fertilized), and two levels of competition control(herbicide and non-herbicide). For each level of thinning,one plot would receive no fertilization and no competitioncontrol; one plot would receive fertilization only; one plotwould receive competition control only and one plot wouldreceive both fertilization and competition control. Six controlplots per site were also established which would receive astandard row thin and no other silvicultural treatment. Plotswere positioned within the two stands in a strip-wise patternas closely together as possible while maintaining uniformityand avoidance of windrows, skid roads, drainages, trails andother anomalies. Each plot consisted of a square one-quarter-acre inner plot surrounded by a 33 foot wide buffer.Plot buffers would receive the same treatment as the plotthey surrounded, but would not be used in data collection.Each tree in a plot was measured for diameter in inches at4.5 feet above ground level (dbh), total height in feet, heightto first live branch, and crown width. Presence of fusiformrust (Cronafium  quercuum  f. sp. fusifome),  crooks, forks orother defects were also tallied.After plot boundaries were established and tree data wererecorded, each plot was revisited for residual crop treesselection. Residual trees were selected in the following fivecriteria, in order of decreasing importance: (1) Larger dbh,(2) stem form, (3) taller trees, (4) spatial distribution, and (5)crown quality. Residual densities were achieved using amodified form of Reineke’s stand density index (SDI) (Zeide1985). Selected densities can then be calculated using thefollowing equation:/ nl1.7SLY=  ”Y I10Where:N = Number of stems per acreD = Quadratic mean diameter(1)’  Paper presented at the Tenth Biennial Southern Silvicultural Research Conference, Shreveport, LA, February 16-18, 1999.‘Visiting Scientist, Forest Resources Institute, Arthur Temple College of Forestry, Stephen F. Austin State University, Nacogdoches, TX 75964;and Research Associate and Professor, Arthur Temple College of Forestry, Stephen F. Austin State University, Nacogdoches, TX 75964,respectively.426Table 1 shows residual density relationships. Thinningtreatments were conducted in the fall of 1994 and allharvested trees were hauled to area mills. All residual treesin treatment plots were subsequently pruned during thewinter of 1994-l 995 to a height of 25 feet. The followingsummer (1995) each tree was numbered and remeasured.That fall, plots to receive competition control were treated byhand spraying of herbicides. Herbicide application consistedof approximately 16 ounces of Arsenol AC, 24 ounces ofGarlon 4, and 32 ounces of Red River 90 per acre. Mixturetotaled approximately 30 gallons per acre for application.Hardwood trees and shrubs greater than two inches indiameter were also “hacked and squirted”. In the spring of1996, fertilization plots were treated with a combination ofUrea and Diamonium Phosphate (DAP) giving a blendedanalysis of 29.21-16.79-O. Fertilizer was applied withshoulder mount hand crank spreaders at a rate of 563pounds per acre. Plots were remeasured again during thesummers of 1996 and 1996.RESULTSStand attributes before thinning are given in Table 2.Dominant heights at site one were in the mid to upper sixtiesand in the mid to upper fifties on site two. For both sites thisis out of the range of most site quality curves. Maximumdiameters for both sites were in the 11 inch class. Standattributes after thinning are shown in Table 3. For both sitesthe average diameter increased with decreasing density.Table l-Density attributes after thinning for the twostudy sitesStandDensity Density density Basa StemsS i t e class level index area/acre per acreFf1 Low 1 70 35.6 103.71 Med 2 120 60.1 196.31 High 3 170 63.7 300.02 Low 1 70 35.6 105.32 Med 2 120 60.6 190.32 High 3 170 64.2 290.0This is due to the selection method in which the biggest andbest trees were selected for the lowest density plots. Whilethe higher density plots contained the same kind of trees astheir lower density counterparts they also contained “lessthan the best” trees as well. The same relationship holdstrue for the average total tree heights.Diameter GrowthTree tagging accomplished in 1995 allowed tracking ofindividual tree growth through 1996. If treatments besidesthinning are disregarded, significant differences in diametergrowth (alpha = 0.05) were detected between each of thethinning levels. At both sites, diameter growth was greatestfor the lowest density level and decreased with increasingdensity. Growth rates ranged from 0.27 inches per year fordensity class three on site one to 0.64 inches per year fordensity class one on site two (table 4).When all treatments were added back into the model, nointeractions were detected between the three factors. Foreach density level with the exception of density class one onsite two, diameter growth was significantly greater withfertilization treatments. Even at the exception, plots with thefertilization treatment had a greater, although not statisticallysignificant growth rate. There were no significant differencesdetected due to the competition control treatments (table 5).Height GrowthWhen looking only at thinning treatments no significantdifferences in height growth where detected for site one. Sitetwo however showed density one had significantly slowerheight growth than the group of density class two and three.As shown in Table 6, height growth ranged from one foot peryear for site one density two to 2.3 feet per year for densitylevel three on site two. Additionally, although the trees wheretaller on site one, site two had significantly greater heightgrowth. Site two had an overall average yearly height growthof 2.0 feet, while site one’s growth was 1 .I feet per year.No interactions were found between fertilization andcompetition control treatments. Significant differencesbetween fertilization treatments were found on density levelsone and two for site one. For those two treatment levelsfertilization increased height growth. For the competitioncontrol treatment, density level one and two on site oneshowed significantly different height growth. No competitioncontrol for density level one on site one yielded greaterheight growth, while on density level two on site one growthwas higher for the competition control treatment. For theremaining density and site levels no recognizable trendswere present (table 7).Table P-Initial stand attributes (before thinning) for the twostudy areasSiteBasal Average AverageStems area Average total volumeper acre per acre diameter height per acre: 7 1 0 . 5  5 5 0 . 9Ft2166.6 132.4Inches6.3 6.4Feet4 6 . 1  4 3 . 6Ft33,699.5  2,767.0427Table 3-After thinning stand attributes for the two Table 4-Average diameters and diameter growthstudy areas by site and density level between 1995 and 1998Average AverageDensity Average total volumeSite level diameter height per acreInches Ft fp31 : 7.81 52.8 889.21 7.33 51.9 1,438.41 3 8.98 51.3 1,988.02 : 7.83 45.1 885.12 7.54 44.8 1,468.l2 3 7.20 44.5 1,951.7Average diameterSite levelDensity1995 1998Growthper year1 1 8.07 9.75 0.56 A1 2 7.55 8.77 .40 B1 3 7.28 8.03 .27 C2 1 8.12 10.04 .64A2 2 7.78 9.08 .43 B2 3 7.40 8.33 .31  ca  Like letters within the same site show no significant differenceusing Duncan’s multiple range test at the alpha =  0.05 level.Table !&Average  yearly diameter growth between 1995 and 1998 by site,density level, fertilization, and competltlon control treatmentsTreatmentsDensityS i t e level Fertilization No fertilization Competition No competition1 1 0.60 A 0.53 B 0.57 A 0.56 A1 2 .45A .36 B .42A .38A1 3 .29 A .25 B .28A .26A; 2 1 .68A  .49 A .61 39 A B .67A  45 .62A  42 3 .33A .29 B .32A .3OALike letters within the same site, density, and treatment type show no significantdifference using Duncan’s multiple range test at the alpha = .05  level.DISCUSSIONDiameter GrowthWhen thinning treatments are looked at independent of theother treatments, heavier thinning or less residual densitiesresulted in greater diameter growth. This could beattributable to two causes. First, the objective of thinning isto re-distribute growth to the fewer residual trees. Therefore,the lower the residual density the more growth can beallocated to each remaining tree. Second, increased growthcould be due to the residual selection method, where on thelowest density plots the absolute best trees were selected asthe crop trees. The medium density class would then containthe best trees as well as the next to the best trees.Finally, the highest density plots would contain the best ofthe best, the next to the best, and then other less desirablestems to maintain spacing and density requirements.When looking at diameter growth in relation to density andthe fertilization treatment, higher growth rates resulted fromtrees being fertilized. Although one exception was noted,probably due to some unknown variation, the trend was thesame.Competition control treatments made no significantdifference in relation to diameter growth. There was,however, a trend favoring competition control. Although428Table 9-Average  heights and height growthbetweeh1995and1998Average heightS i t e levelDensity Growth1995 1998 per year_ _ _ _ _ _ _ _ _ _ Fe& ________1 1 56.6 59.5 l.OA1 2 55.7 59.2 1.2 A1 3 55.1 58.5 1.1 A2 1 48.8 53.6 1 . 6 B2 2 48.2 54.5 2.1 A2 3 47.9 54.8 2.3 Aa  L i k e  l e t t e r s  w i t h i n  t h e  s a m e  s i t e  s h o w  n o  s i g n i f i c a n t  d i f f e r e n c eu s i n g  D u n c a n ’ s  m u l t i p l e  r a n g e  t e s t  a t  t h e  a l p h a  =  0 . 0 5  l e v e l .Table 7-Average yearly height growth between 1995 and 1998 by site,density level, fertilization, and competition control treatmentsTreatmentsDensitySite level Fertilizationa No fertilization Competition No competition1 1 1.7A1 2 1.5A1 3 1.3 A0.7 B 0.5 A 1 . 4 B.a B 1.5A .a 61 . 0 A 1.1 A 1.1 A2 1 1 . 4 A 1.8 A 1 . 6 A 1 . 6 A2 2 2.1 A 2.1 A 2.0 A 2.2 A2 3 2.4 A 2.2 A 2.3 A 2.3 A’ L i k e  l e t t e r s  w i t h i n  t h e  s a m e  s i t e ,  d e n s i t y ,  a n d  t r e a t m e n t  t y p e  s h o w  n o  s i g n i f i c a n t  d i f f e r e n c eu s i n g  D u n c a n ’ s  m u l t i p l e  r a n g e  t e s t  a t  t h e  a l p h a  =  0 . 0 5  l e v e l .the average difference only amounted to 0.026 inches peryear, the trend was consistent.Height GrowthNo significant differences in height growth were detected insite one and only density class one was significantly lowerthan either class two and three on site two. The trend inlower height growth on lower densities that occurred in sitetwo would seem logical in that on lower density conditionsthere would be less competition for light. However, site onedid not display the same relationship.When looking at the effects of fertilization and competitioncontrol combined with density levels, a small percentage ofstatistically significant differences were detected. However, itwould seem there was no logical pattern that arose andtherefore it was concluded there was no practicalsignificance and differences may be attributed tohappenstance and/or measurement anomalies.In summary, a surprising preliminary result was that site twostarted out with virtually the same average diameter as siteone: Site one had trees averaging over seven feet taller:429and site two has out performed site one both in diameterand height growth. Although site one was considered to bemuch better than site two at the beginning of the study,growth rates could be better at site two for three reasons.First, site two initially had much more competing vegetationthan site one. Therefore, by reducing the non-plantedvegetation as well as the competing pines, by means ofthinning, the residual crop trees could be responding at agreater rate. Second, it is possible that site two could havereceived more rain during the two severe droughts that EastTexas had experienced since the study plots wereestablished. The third possibility may also be that lands oflower site quality respond more favorably to intensive lowdensity management.REFERENCESBurton, J.D. 1982. Sawtimber by prescription - the sudden sawlogstory through age 33. Res. Pap. SO 179. New Orleans: U.S.Department of Agriculture, Forest Service, Southern ForestE x p e r i m e n t  S t a t i o n .  9  p .Coffee, D.R. 1975. Soil survey of Anderson County, Texas. U.S.D e p a r t m e n t  o f  A g r i c u l t u r e ,  S o i l  C o n s e r v a t i o n  S e r v i c e ,  T e x a sA g r i c u l t u r a l  E x p e r i m e n t  S t a t i o n .Dolezel,  R .  1 9 8 8 .  S o i l  s u r v e y  o f  A n g e l i n a  C o u n t y ,  T e x a s .  U . S .D e p a r t m e n t  o f  A g r i c u l t u r e ,  S o i l  C o n s e r v a t i o n  S e r v i c e ,  T e x a sA g r i c u l t u r a l  E x p e r i m e n t  S t a t i o n .W i l e y ,  S . ;  Z e i d e ,  B .  1 9 9 2 .  D e v e l o p m e n t  o f  a  l o b l o l l y  p i n e  p l a n t a t i o nthinned to different density levels in southern Arkansas. Rep. Ser.3 2 2 .  A r k a n s a s  A g r i c u l t u r e  E x p e r i m e n t  S t a t i o n .  4 4  p .Zeide, B. 1985. Tolerance and self-tolerance of trees. ForestE c o l o g y  a n d  M a n a g e m e n t .  1 3 :  1 4 9 - 1 8 8 .430

Four-year Growth Results from 16 Year Old Intensively Managed Low Density Loblolly Pine Plantations

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Four-year Growth Results from 16 Year Old Intensively Managed Low Density Loblolly Pine Plantations

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