r *\ ~\ 59 GEORGIA FOREST RESEARCH PAPER Sept. 1985 V. yV Impact Of Competing Vegetation On Yield Of The Southern Pines By Glenn R. Glover and Dale F. Dickens p ecejv d MAY 3 1988 RESEARCH DIVISION C uGA LiSmls GEORGIA FORESTRY COMMISSION J About The Authors Glenn R. Glover is Assistant Professor of Forest Biometrics in the Alabama Agricultural Experiment Station and School of Forestry, and Associate Director of the A. U. Silvicultural Herbicide Cooperative, Auburn University, Alabama. He has a B. S. in Forest Management, and an M. S. in Quantative Methods from Auburn University; and a Ph. D. in Forest Biometrics from VPI&SU. Glover's research is presently focused on evaluating the effect of competing vegetation on southern pine growth and yield. Dale F. Dickens is Research Forester, Georgia Kraft Corporation, Coosa, Georgia, with primary responsibilities in fertilization and herbicide research. He received a B. S. in Forest Management and is completing an M. S. in Forest Biometrics at Auburn University. Dickens was a Grad- uate Research Assistant at the time this research was accomplished. ACKNOWLEDGMENTS The authors would like to thank the Georgia Forestry Commission and Dow Chemical Company for major funding support for this project, and Velsicol Chemical Company and E. I. duPont deNemours for additional funding support. The following forest industries and organizations provided time and help in locating and allowing access to comparisons and often provided aid in measurement: American Can Company (James Martin, Ron Neal); Auburn University; Chesapeake Corporation (Jim Willis, Steve Simmons); Continental Forest Industries (Ken Xydias); Georgia Kraft Corporation (John Gill, Henry Griswold); Georgia Pacific (Steve Kennerly); Tennessee River Pulp and Paper (Maurice Hamm, Rick Applegate); USDA-Forest Service (Dr. William Boyer, Dr. Charles McGee, Dr. Eugene Shoulders); and Westvaco Corporation (John Gnegy). Other companies and organizations who located installations which were not measured are also appreciated for their time and interest. 2/Georgia Forestry Commission j*~+k-~ ^7.7. ^^ INTRODUCTION One of the major problems in growing southern pines is competition from hardwood and herbaceous vegetation for moisture, nutrients and light. Uncontrolled vegetation can reduce survival as well as growth of the desired pines. Use of chemical herbicides to control unwanted vegetation has been common in forestry for three decades, but the long term effect on growth has seldom been documented. This fact became obvious during the 2,4,5-T controversy of the late 1970's (USD A 2,4,5-T Assessment Team, 1979). Within most organizations, a forester's opinion is no longer sufficient to justify the expense of chemical vegetation control. Economic criteria, such as rate of return on investment, must now be considered. To evaluate these criteria, yield information reflecting the effect of vegetation control is needed. As with most endeavors in forestry, the installation and remeasurement of studies comparing vegetation control to no control is a very long term venture. Recognition of the need for yield information relating to vegetation control has recently prompted establishment of studies, however results are several years away. In an attempt to provide interim information on pine yield response to vegetation control, the project reported on herein was initiated. The major objective of the project was to locate and measure southern pine stands where there was an existing direct comparison of chemical vegetation control to other control methods, or to no control. Impact Of Competing Vegetation On Yield Of The Southern Pines By Glenn R. Glover and Dale F. Dickens Georgia Forestry Commission/3 1 PROCEDURES Southern forest industries and organizations and chemical companies were asked to identify areas where replicated studies, paired plots, or operational comparisons of chemical vegetation control versus other methods or no control had been installed. For a comparison to be considered, an untreated or mechanically treated area had to be present within the same stand as the treated area. Stands which were treated entirely with chemicals, having no control area for comparison, were not measured. Vegetation control at any age was permissible, but at least three years had to have passed since treatment to allow for pine response. Pine stands ranging from three years to 36 A years old were located. description of each measured stand is given in Table 1. If measurement plots had been pre- viously established, they were located and remeasured. If measurement plots had not been established, a 0.1-acre circular pine measurement plot was established in the center of small treatment plots, or a series of 0.1-acre plots were systematically established throughout large treated areas. Diameter breast height (dbh) to the nearest 0.1 inch, crown class, damage and species were observed for each pine stem within a measurement plot. A representa- tive subsample of at least 10 pines per plot was measured for total height, to the nearest foot. Merchantable height, in number of 16.3-foot logs, to the nearest one-half log, was observed for each sawtimber pine. In stands less than 10 years old, each pine stem was also classified by the Virginia Division of Forestry Free-To- Grow Classification (Zutter, et al. 1985). A 0.02- to 0.1-acre hardwood measure- ment plot, depending on hardwood stem density, was established concentrically within each pine measurement plot. When there were fewer than about 1000 hardwood stems per acre, the entire pine measurement plot area was used for hardwood measurement. As hardwood stem Table 1. Location and establishment information for measured comparison Study Dubberly Escambia Fayette Floyd County Grass Creek Hobbs-Western Marston Mock Palatka Pickens Piedmont Pineville Rochelle Ross Savannah Town Sewanee Shannon Summerville-1 Summerville-2 Summerville-3 Summerville-6 Summerville-8 Summerville-9 Summerville-10 Summerville-1 Upson County Waddels Location Establishment information Long Co., GA Escambia Co., AL Fayette Co., AL Floyd Co., GA King and Queen Co., VA Hardin Co., TN Charles City Co., VA Jasper Co., SC Putnam Co., FL Pickens Co. AL King and Queen Co.,VA Rapides Parrish, LA Hardin Co. TN Hardin Co., TIM Effingham Co., GA Franklin Co., TN Floyd Co., GA Dorchester Co., SC Dorchester Co., SC Dorchester Co., SC Dorchester Co., SC Dorchester Co., SC Dorchester Co., SC Dorchester Co., SC Dorchester Co., SC Upson Co., GA New Kent Co., VA Harvested spring, 1970; entire site roller chopped and burned, summer, 1970; site prep study overlaid; machine planted with loblolly pine January, 1973 Seed tree regeneration of longleaf pine; seed trees removed, regeneration averaged approximately 10 years old at time of treatment in 1957 Conversion study; harvested 1958; mechanical and chemical treatments applied in fall, 1958 and spring, 1959; hand planted in 1959 with loblolly pine Harvested in 1970; two pass roller chopped in 1971; direct seeded in January, 1972, with loblolly pine Loblolly pine plantation, planted 1974 Sheared in 1966; ineffective burn; direct seeded January, 1967, with loblolly pine Loblolly pine plantation, planted 1973 Harvested 1965; planted stand destroyed by wildfire, 1969; harrowed and bedded in fall, 1969; machine planted February, 1970, with slash pine. Slash pine plantations (3), two planted in 1965, one planted in 1967; all sites were chopped and bedded Burned October, 1962; injected, August, 1963; hand planted January, 1963, with loblolly pine Loblolly pine plantation, planted 1974 Loblolly pine underplanted in a hardwood overstory in 1948 Disked 1976; machine planted in 1976 with loblolly pine Part bedded in 1978, part not bedded; planted in February, 1979, with loblolly pine Harvested in 1972; KG and bedded, fall, 1972; planted early, 1973, with loblolly pine Sheared and chopped, 1976; planted March, 1977, with loblolly pine at an 8'x10' spacing Site preparation study (rootraking, Velpar, check); planted March, 1978, with loblolly pine 100% KG bladed and windrowed in 1958; burned February, 1959; planted in 1959 with loblolly pine 50% KG bladed in June, 1959; burned October, 1959; planted in 1959 with loblolly pine Drained cypress/hardwood swamp; 100% KG bladed in 1957; planted in 1958 with loblolly pine Drained cypress/hardwood swamp; no mechanical preparation; burned January, 1954; planted in 1954 with loblolly pine 60-70% brush drummed in July, 1956; burned November, 1957; planted in 1957 with loblolly pine Drained cypress/hardwood swamp; 60-70% brush drummed and burned in December, 1956; planted 1957; sprayed with 2,4,5-T in 1958 100% dozer bladed and burned in January, 1961; planted in 1961 with loblolly pine 50% brush drummed and burned in February 1956; planted in 1956 with loblolly pine Site prepared with rolling brush cutter; direct seeded following 1961 growing season with loblolly pine Loblolly pine plantation, planted 1977 (Note: all establishment dates are given at the beginning of the growing season-i.e. a stand shown as being planted in 1970 was planted during the 1969-70 planting season.) 4/Georgia Forestry Commission Table 2. Description of physiography/soils and treatments by study Study name (age at treatment, measurement) Physiography/ soils 1 Treatment information Dubberly (0,11) Escambia (10,37) Fayette (0,24) Floyd (61/2 ,11) Grass Creek (5,9) Hobbs-Western (6 /1 2 ,18) Marston (5,10) Mock (0,14) North End (5,10) Palatka (12,19-WD) (12,19-PMD) (10,17-VPPD) Pickens (5,20) Piedmont (4,9) Coastal plain, Leefield-Pelham complex soil Coastal plain Upper coastal plain Ridge and valley Montevallo soil series, rocky, shallow silt-loam 5-20% slope Upper coastal plain, sandy loam sandy clay loam Split-split plot design, with 3 blocks: (a) site prep whole plots: (1) chop and burn; (2) chop, burn and bed; and (3) chop, burn, triple flat harrowed with bedding (note: chop and burn in summer, 1970; harrowing and bedding in July, 1972) (b) Herbicide subplots: (1 ) weed control (2 lb a.i./ac 2,4,5-T + 5 lb a.i./ac. dalapon + 4 lb a.i./ac. simizine)--for hardwoods and herbaceous weeds; (2) no weed control; (c) Fertilizer sub-subplots: (1) fertilized (40 Ib/ac P + 100 Ib/ac N); (2) no fertilizer Two release treatments applied by helicopter in May, 1957: (1) 1 lb. a.i./ac 2,4,5-T ester in 4% gallons of water (basically ineffective, used as a "check"); (2) 3 lb a.i./ac 2,4,5-T ester in 4% gallons of water Seven site preparation treatments: (1) bulldozed and piled; (2) check-- no treatment; (3) hardwoods girdled-- no herbicide; (4) tube injection of herbicide; (5) ax frill plus herbicide; (6) Brady chain frill plus herbicide; (7) mist blown herbicide (note: all herbicide treatments consisted of a mixture of half 2,4-D and half 2,4,5-T at a concentration of 4 lb a.e./gallon) 1 X 20 ch strips treated with helicopter on July 14, 1978, 0.5 ch buffers. Herbicides included: (1) triclopyr amine 1 lb. a.i./ac; (2) triclopyr amine, 0.5 lb a.i./ac plus 1 pint/100 gallons X77 surfactant; (3) triclopyr ester, 1 lb a.i./ac; (4) triclopyr ester, 0.5 lb a.i./ac plus 1 pint X77 surfactant; (5) glyphosate, 1 lb a.i./ac; (6) glyphosate, 2 lb a.i./ac; (7) 2,4,5-T ester, 2 lb a.i./ac; (check plots were obtained from buffer areas) 0.25 ac plots treated April, 1979 with (1) 1.0 lb a.i./ac: and (2) 1.25 lb a.i./ac hexazinone (as Velpar 2cc Gridball); (3) untreated check soil Interior low plateau Coastal plain Coastal plain Leon-Blanton soil Coastal plain Lower coastal plain Coastal plain Coastal plain 10X40 ch block operationally treated with 5/8 gal 2,4,5-T (1.25 lb a.i.) +1 gallon diesel +6 3/8 gallons water per acre in June, 1972. Untreated block in same stand adjacent to treated area used as a check 39 acres operationally sprayed in June, 1973 by helicopter with 2 lb 2,4,5-T a.i. in 1/2 gallon diesel + 4 gallons water per acre; remainder of plantation untreated Split plot design with 4 blocks: (a) fertilizer whole plots: (1 ) 40 Ib/ac P + 100 Ib/ac N; (2) no fertilizer; (b) herbicide subplots: (1) simizine, April, 1970; (2) paraquat, May, 1970; (3) no weed control 26 acres operationally sprayed in June, 1973, by helicopter with 2 lb 2,4,5-T a.i. in y2 gallon diesel + 4 gallons water per acre; remainder of plantation untreated Three sets of paired plots (approx. 0.12/ac each)-- all vegetation other than planted pines con- trolled; other plot untreated. One set of plots classified as well drained, another as somewhat poorly and moderately well drained, and the other very poorly and poorly drained. Plots were originally part of Univ. of Ga. PMRC Competing Vegetation Study Middle 40-acre portion of a 100-acre tract operationally treated with 2 lb a.i./ac 2,4,5-T in May, 1968; remaining 60 acres untreated, used as a check 48 acres operationally sprayed in June, 1973, using a helicopter with 2 lb a.i./ac 2,4,5-T in /1 2 gallon diesel+4 gallons water per acre; remainder of plantation untreated, used as a check (Table 2 Continued on Page 6) density increased above 1000 stems per acre, measurement of the entire pine measurement plot area would have taken an inordinate amount of time, so the hardwood measurement plot area was reduced to 0.05 or 0.02 acre, maintaining a minimum sample of 30 hardwood stems. All sample hardwood stems 0.5 inch dbh and larger were tallied by one-inch diameter class, 10-foot height class and species. For each comparison, information regarding date and type of stand establishment, treatments and rates applied, date treated, forest type, site index, average slope, soil type, drainage and stand history (including injury, fire history, pre- vious stand, etc.) was noted, when available. In addition, percent slope and aspect were observed at each pine measure- ment plot location. A summary of physiography/soils and treatments is given in Table 2. RESULTS AND DISCUSSION Table 3 is a summary of pine and hardwood measurements by treatment. All but five of these studies were hardwood control comparisons. The other five (Dubberly, Mock, Palatka, Ross and Savannah Town) were primarily herba- ceous or understory vegetation control studies and will be discussed separately. Examination of this table reveals a great deal of variation in pine and hardwood response to herbicide treatment. In some cases, such as Grass Creek, hardwoods were increasingly controlled (fewer, smaller hardwood stems on herbicide treated plots) and a corresponding greater pine yield was realized with increasing rates of herbicide. But in other cases, such as Pickens and Summerville-3, herbicide treatment did not seem to have an effect. All but one of the comparisons showing no response or negative response of pine yield to herbicide application were operational comparisons using 2, 4,5-T, where initial conditions, herbicide rates and application techniques were often not closely controlled. Results from 2,4,5-T are known to be highly variable, depending on species composition, weather conditions, etc., and misapplication could result in pine damage or mortality. Considering the inherent variability in operational comparisons, and the fact that several of the research comparisons were installed as tests of rates, timing, soil interactions, etc., the entire story is Georgia Forestry Commission/5 1 M Q?Jt *:&** "'.'' 2. Description of physiography/soils and treatments (continued). Study na (age at trc-atment, urement Pineville 0,1,2),36) Rochelle (2,7) Ross (0,4) Savannah Town (0,11) Sewanee (0,6) Shannon (0,5) Summerville-1 (3,25) Summerville-2 (3,25) Summerville-3 (4,26) Summerville-6 (8,30) Summerville-8 (5,27) Summerville-9 (5,27) Summerville-10 (1,23) Summerville-1 (6,28) Upson (0,6) Waddels (3,6) Physiography/ soils Coastal plain, silt and very fine sandy loam Interior low plateau 1 Treatment information Ten treatments, two replications were installed--only one replication remained intact. Plots were 0.25 acre. Treatments: (1 ) plant in openings, no release; the following 9 treatments were planted at regular intervals, selective release included control of hardwood stems greater than 3 inches dbh; complete release included control of hardwood stems greater than 0.5 inches dbh: (2) AMS selective release immediately after planting with (Ammate); (plot destroyed, no data available) (3) selective release immediately after planting by girdling; (4) selective release, AMS 1 year after planting, with (Ammate); (5) selective release, 1 year after planting, by AMS girdling; (6) selective release, 2 years after planting, with (Ammate); (7) selective release, AMS 2 years after planting, by girdling; (8) complete release, immediately after planting with (Ammate); (9) complete release, immediately after planting, by girdling; (10) no release (1) 1 lb a.i./ac hexazinone (Velpar 2 cc Gridball); (2) untreated check; 75' X 75' treatment plots Interior low Factorial with split-plot design: (a) site preparation whole plots: (1) bedded; (2) not bedded; plateau, Shutuba- (b) fertilizer subplots: (1) fertilized with DAP; (2) not fertilized; (c) herbicide sub-plots: Pickwick complex (1) hexazinone (Velpar liquid) at 1 lb a.i./ac; (2) no herbicide. (NCSFFC Regionwide Study silt-loam to fine No. 7) sandy loam soil Coastal plain, Stilson series soil Split plot design, with 4 blocks: (a) fertilizer whole plots (1) 200 Ib/ac CSP; (2) 476 Ib/ac ammonium sulfate; (b) herbicide subplots: (1) no weed control; (2) first season weed control with 2 lb a.i./ac 2,4,5-T + 2.5 lb a.i./ac dalapon + 4 lb a.i./ac simazine; (3) annual weed control using same treatment as in (2) Ridge and valley, Completely randomized design, 1-acre plots: (1) all stems 4.5 ft. or taller injected with Hartsells sandy picloram + 2,4-D (Tordon 101 R); (2) untreated loam soil Piedmont Site preparation comparison: (1) rootraking; (2) hexazinone 2 lb a.i./ac (Velpar 2cc Gridball); (3) untreated Lower coastal 3.8 acres operationally released with 2,4,5-T, 2 lb a.e./ac, June 1962; remainder of plantation plain untreated, used as a check Lower coastal 3 acres operationally released with 2,4,5-T, 2 lb a.e./ac, June, 1962; remainder of plantation plain untreated, used as a check Lower coastal 4 acres operationally released with 2,4,5-T, 2 lb a.e/ac, June 1962; remainder of plantation plain untreated, used as a check Lower coastal 4 acres operationally released with 2,4,5-T, 2 lb a.e./ac, June, 1962; remainder of plantation plain untreated, used as a check Lower coastal 4 acres operationally released with 2,4,5-T, 2 lb a.e./ac, June, 1962; remainder of plantation plain untreated, used as a check Lower coastal 5 acres operationally released with 2,4,5-T, 2 lb a.e./ac, June, 1962; remainder of plantation plain untreated, used as a check Lower coastal 4 acres operationally released with 2,4,5-T, 2 lb a.e./ac, June, 1962; remainder of plantation plain untreated, used as a check Lower coastal 5 acres operationally released with 2,4,5-T, 2 lb a.e./ac, June, 1962; remainder of plantation plain Piedmont Loamy fine sand untreated, used as a check Operational release comparison: (1) 1.5 lb a.i./ac 2,4,5-T in Vz gallon diesel + 3% gallons water per acre; (2) 2 lb a.i./ac 2,4,5-T in 1 /2 gallon diesel + 31 /a gallons water; (3) check Three replications of five treatments (replications were on ridge, northwest slope, and with sandy clay subsoil 9-24" southeast slope), 0.20 acre treatment plots: (1) 1.25 lb a.i./ac hexazinone (Velpar 2cc Gridball); (2) 1.5 lb a.i./ac hexazinone (Velpar 2cc Gridball); (3) 1.25 lb a.i./ac hexazinone (Velpar below surface granules); (4) 1.5 lb a.i./ac hexazinone (Velpar granules); (5) check i a.i. = active ingredient a.e. = acid equ ivalent Table 3. Summary of pine and hardwood information by study and treatment. Study (treatment, 2 measurement age) Treatment Number of trees per acre pine hard. Basal area per acre (sqft) pine hard. O.B. volume per acre (cu ft) pine Dubberly (0,11) CB,WC, F CB,WC, NF CB, NWC, F CB, NWC, NF CBB,WC, F CBB,WC, NF 6/Georgia Forestry Commission 552 312 79.3 474 102 47.2 542 900 62.5 624 189 66.6 629 232 116.3 561 29 96.4 3.4 1279.5 0.6 779.8 7.2 1041.1 1.0 1219.8 2.2 2234.8 0.2 1791.4 Mean dbh (in) Pi ne hard. 5.0 1.1 4.1 1.0 4.3 1.2 4.1 1.0 5.7 1.2 5.5 1.0 Mean total height (ft) pine hard. Percent hardwood basal area (%) 31 15 25 10 28 11 28 11 39 13 38 12 4.1 1.3 10.3 1.5 1.9 0.2 Table 3. Summary of pine and hardwood information (continued). Study (treatment, 2 measurement age) Treatment Number of trees per acre pine hard. Basal area per acre (sqft) pine hard. 0. B. volume per acre (cuft) pine CBB, NWC, F 620 254 77.7 CBB, NWC, NF 774 29 83.1 CBHB, WC, F 639 29 115.6 CBHB, WC,NF 620 44 104.3 CBHB, NWC, F 620 58 98.3 CBHB, NWC, NF 658 29 83.3 CB, mean 548 376 63.9 CBB, mean 646 136 93.4 CBHB, mean 634 40 100.4 WC, mean 579 125 93.2 NWC, mean 640 243 78.6 F, Mean 600 298 91.6 NF, mean 618 70 80.2 2.4 1442.1 0.2 1462.6 0.2 2186.0 0.3 1841.4 0.5 1659.8 0.0 1493.2 3.0 1080.0 1.2 1732.7 0.5 1795.1 1.2 1685.5 1.9 1386.4 2.6 1640.6 0.4 1431.4 Escambia (10,37) 1 lb 2,4,5-T 3 lb 2,4,5-T 358 454 653 471 61.2 74.4 24.6 2587.8 9.0 4933.4 Fayette (0,24) Bulldoze Hand girdled Injection+herb. Ax frill+herb. Chain frill+herb. Herbicide, mean Check 474 837 212 980 371 914 433 878 449 934 418 909 204 1045 167.2 70.5 126.1 153.3 149.2 142.9 16.9 16.3 59.4 19.9 14.8 18.5 17.7 108.7 4393.1 1763.9 3356.8 4002.9 3912.8 3757.5 359.0 Floyd County (6 1 /2,11) Grass Creek (5,9) 1 lb triclopyr amine 0.5 lb triclopyr amine + 77 1 lb triclopyr ester 0.5 lb triclopyr ester + X77 1 lb glyphosate 2 lb glyphosate 2 lb 2,4,5-T Herbicide, mean Check 1360 907 480 1160 947 907 547 901 588 1093 1107 1293 1067 1680 1427 1467 1305 1348 1.25 1b Velpar, 2cc 1 lb Velpar, 2cc Check 760 1333 783 1500 760 2183 46.4 36.5 12.1 35.7 29.9 35.5 31.1 32.5 22.8 52.7 49.6 43.6 10.6 8.9 11.2 12.1 25.8 19.8 21.1 15.6 16.0 10.6 18.7 25.5 867.5 616.7 183.0 573.9 569.6 609.4 461.7 554.5 317.2 596.1 505.0 474.3 Hobbs-Western (6%. 18) 1.25 lb 2,4,5-T Check 432 1636 227 1926 51.5 34.1 39.2 1147.4 50.6 647.9 Marston (5,10) 2 lb 2.4,5-T Check 458 1136 774 1810 22.8 22.1 13.4 23.8 252.3 313.3 Pickens (5,20) 2 lb 2,4,5-T Check 336 838 331 1032 108.6 112.3 18.3 2984.0 36.0 3150.1 Piedmont (4,9) Mock (0,14) 2 lb 2,4,5-T Check 810 264 768 1470 F,WC (simazine) 454 194 F,WC(paraquat) 427 375 F.NWC 508 230 NF,WC(simazine) 536 145 NF,WC( paraquat) 445 351 NF,NWC 490 254 F, mean 463 266 NF, mean 487 250 WC(simazine),mean 490 170 WC( paraquat), mean 436 363 WC,mean 463 266 NWC, mean 499 242 44.2 38.9 89.2 70.8 81.8 96.9 75.0 82.1 80.6 84.7 93.1 72.9 83.0 82.0 1.7 10.9 513.3 479.2 2.2 1821.6 2.2 1551.1 3.6 1643.1 1.0 1944.4 6.9 1492.3 2.0 1544.9 2.7 1671.9 3.3 1660.5 1.6 1883.0 4.6 1521.7 3.1 1702.4 2.8 1594.0 Mean dbh (in) pine hard. 4.5 1.1 4.3 1.0 5.6 1.0 5.5 1.0 5.2 1.0 4.6 0.0 4.4 1.1 5.0 1.1 5.2 1.0 5.2 1.0 4.5 1.0 5.0 1.1 4.7 1.0 5.1 2.7 4.0 1.8 7.9 1.6 7.5 2.9 7.6 1.7 7.9 1.6 7.6 1.7 7.7 1.7 3.6 3.6 2.2 1.2 2.5 1.2 2.2 1.2 2.1 1.3 2.2 1.5 2.5 1.4 2.8 1.4 2.4 1.3 2.2 1.3 3.4 1.1 3.2 1.2 3.1 1.3 4.8 1.8 5.4 1.9 2.8 1.3 2.1 1.4 7.2 1.6 7.7 2.2 2.9 1.1 2.8 1.1 5.9 1.4 5.4 1.0 5.2 1.3 5.6 1.0 5.3 1.5 5.3 1.1 5.5 1.2 5.4 1.2 5.8 1.2 5.4 1.3 5.6 1.2 5.3 1.2 Mean total height (ft) pine hard. 33 16 28 7 37 6 37 22 34 21 32 28 12 34 12 35 16 34 13 30 13 34 14 31 12 Percent hardwood basal area (%) 3.0 0.2 0.2 0.3 0.5 0.0 4.3 1.3 0.2 1.3 2.6 3.3 0.6 48 20 45 13 28.7 10.8 57 16 52 28 56 16 56 18 56 17 56 17 31 28 8.9 45.7 13.6 8.8 11.0 11.1 86.5 17 13 18.7 17 12 19.7 12 11 15 12 48.1 25.3 16 12 17 12 18 13 16 12 15 12 21 10 20 14 21 15 46.3 35.8 40.4 33.4 49.0 16.8 27.4 36.9 31 18 35 18 43.2 59.6 15 13 14 13 37.1 52.0 52 17 56 20 14.4 24.3 16 10 17 12 3.7 22.0 41 13 2.4 40 9 3.0 38 10 4.2 39 9 1.0 38 14 8.4 37 10 2.3 40 11 3.2 38 11 3.9 40 11 1.7 39 12 5.7 40 11 3.7 38 10 3.3 Georgia Forestry Commission/7 Table 3. Summary of pine and hardwood information (continued). Study (treatm 2 measurement age) Treatment Number of trees per acre pine hard. Basal area per acre (sqft) pine hard North End (5,10) 2 lb 2,4,5-T Check 1122 1138 942 2270 50.5 42.9 7.7 16.5 Palatka (12,19) (12,19) (10,17) WC-WD NWC-WD WC-PMD NWC-PMD WC-VPPD NWC-VPPD WC,mean NWC,mean 639 141.2 0.0 639 222 142.6 5.6 489 126.9 0.0 489 22 118.1 0.5 704 154.5 0.0 680 195 167.3 6.1 611 140.9 0.0 603 146 142.7 4.1 Pineville {(0,1 ,2) ,36) Open planting no release Girdle,selective immediately AMS, selective 1 year later Girdle, selective 1 year later AMS, selective 2 years later Girdle, selective 2 years later AMS, complete immediately No release Girdle, mean AMS, mean No release, mean Selective, immediately, mean Selective, 1 year later Selective, 2 years later, mean Complete, immediately, mean 280 230 210 205 330 240 230 180 226 257 230 230 208 285 230 195 125 120 140 840 370 140 260 175 367 228 125 130 605 102 122.7 125.8 137.1 126.5 93.5 155.9 116.5 "108.5 30.0 115.7 115.6 125.8 131.8 124.7 114.2 29.6 3.7 0.7 3.6 13.6 12.5 4.4 14.7 5.5 6.2 22.2 3.7 2.2 13.1 3.3 Rochelle (2,7) 1 lb Velpar Check 460 580 510 1485 26.0 19.3 4.0 17.2 Ross (0,4) B,F,WC B,F,NWC B,NF,WC B,NF,NWC NB,F,WC NB,F,NWC NB,NF,WC NB,NF,NWC B,mean NB,mean F,mean NF,mean WC,mean NWC.mean 580 70 600 60 565 103 590 47 412 212 585 158 478 258 607 225 584 70 520 213 544 125 560 158 509 161 596 122 14.7 0.4 6.1 0.3 14.8 0.6 6.2 0.3 10.4 1.2 5.8 0.9 9.4 1.5 4.8 1.3 10.5 0.4 7.6 1.2 9.3 0.7 8.8 0.9 12.3 0.9 5.7 0.7 0. B. volume per acre (cuft) pine 663.9 642.9 Mean dbh (in) pine hard. 2.5 1.1 2.7 1.1 3393.8 3325.5 3020.6 2940.9 3714.0 4210.2 3376.1 3492.2 6.2 0.0 6.3 1.9 6.7 0.0 6.6 0.5 6.2 0.0 6.6 2.0 6.4 0.0 6.5 1.5 4065.0 8.3 3.6 4608.7 9.8 2.0 4662.9 10.8 1.0 4594.8 10.1 2.1 3083.8 6.6 1.6 6102.0 10.2 2.1 4074.4 9.5 0.8 3733.0 4821.4 3940.4 3899.0 4608.7 9.7 1.8 9.8 1.8 9.0 1.1 9.0 2.7 9.8 2.0 4628.9 10.4 1.6 4592.9 8.4 1.9 4027.2 9.3 0.8 Mean total height (ft) pine hard. 16 11 17 10 51 49 10 50 52 12 50 54 12 50 52 11 63 23 79 14 74 9 73 16 50 14 79 17 73 5 63 16 76 13 66 20 63 20 79 14 74 12 64 16 73 6 283.0 258.2 134.5 54.7 139.5 54.7 90.4 50.1 78.2 42.6 95.9 65.3 82.4 78.8 110.9 50.5 3.1 1.1 2.5 1.3 2.1 1.0 1.3 1.0 2.1 1.0 1.3 1.0 2.1 1.0 1.3 1.0 1.8 1.0 1.1 1.0 1.7 1.0 1.6 1.0 1.7 1.0 1.6 1.0 2.0 1.0 1.3 1.0 17 11 16 16 12 8 9 9 12 9 9 8 12 9 9 8 11 9 9 9 10 8 10 9 10 8 10 9 12 9 9 8 Percent hardwood basal area (%) 13.2 27.8 0.0 3.8 0.0 0.4 0.0 3.5 0.0 2.6 19.4 2.8 0.5 2.8 12.7 7.4 1.8 11.9 3.7 5.6 15.7 2.8 1.7 10.1 2.7 13.3 47.1 2.8 5.1 4.0 4.0 10.3 14.1 13.7 21.0 4.0 14.8 8.1 10.7 7.7 ,,., Savannah Town F,WC(1styear) 574 508 96.0 2.8 1724.9 5.4 1.0 37 12 2.8 (0,11) F,WC(annual) 639 58 108.4 0.3 1996.2 5.5 1.0 38 10 0.3 F,NWC 537 450 80.8 2.8 1377.0 5.1 1.0 34 11 3.3 NF,WC(1styear) 566 310 99.3 1.7 1926.0 5.5 1.0 36 14 1.7 NF,WC(annual) 566 87 91.7 0.5 1550.1 5.2 1.0 34 9 0.2 NF.NWC 523 242 80.1 1.3 1384.8 5.2 1.0 34 10 1.6 WC(1st year), mean 570 409 97.7 2.3 1825.5 5.5 1.0 36 13 2.3 8/Georgia Forestry Commission ^^^MsetanBHHH Table 3. Summary of pine and hardwood information (continued). Study (treatment, 2 measurement age) Treatment Number of trees per acre pine hard. Basal area per acre (sq ft) pine hard. WC(annual),mean 602 72 100.1 0.4 WC,mean 586 241 98.9 1.3 NWC.mean 530 346 80.5 2.1 F,mean 584 339 95.1 2.0 IMF, mean 552 213 90.4 1.2 Sewanee (0,6) Tordon injected Check 523 1113 529 1693 20.8 11.6 7.4 15.4 Shannon (0,5) 2 lb Velpar Rootrake Untreated 375 950 580 295 680 770 6.3 18.8 4.2 1.6 0.4 83.1 Summerville -1 (3,25) 2 lb 2,4,5-T Check 294 215 156.4 8.3 318 516 171.1 9.4 Summerville -2 (3,25) 2 lb 2,4,5-T Check 294 265 282 552 144.0 158.2 7.8 14.7 Summerville -3 (4,26) 2 lb 2,4,5-T Check 196 666 144 764 138.1 123.7 31.9 44.9 Summerville -6 (8,30) 2 lb 2,4,5-T Check 192 452 208 656 159.1 37.5 160.0 34.5 Summerville-8 (5,27) 2 lb 2,4,5-T Check 232 200 164 524 167.8 2.8 144.4 46.4 Summerville -9 (5,27) 2 lb 2,4,5-T Check 146 220 124 618 108.3 12.5 93.7 42.9 Summerville -10 (1,23) Summerville 11 (6,28) 2 lb 2,4,5-T Check 2 lb 2,4,5-T Check 342 80 168.9 7.3 220 180 137.1 17.7 142 156 135.4 17.1 230 88 170.2 8.2 Upson (6,22) 2 lb 2,4,5-T Check 736 1711 409 1771 78.5 29.6 86.1 39.8 Waddels (3,6) 1.25 lb 2cc Velpar 1.5 lb 2cc Velpar 1.25 lb Velpar granule 1.5 lb Velpar granule Check 2cc Velpar, mean Velpar granule, mean 613 657 587 623 430 635 605 466 427 2450 970 2750 446 1710 40.2 33.0 39.1 4.3 3.3 23.8 38.8 8.0 22.5 36.6 39.0 23.2 3.8 15.9 O. B. volume per acre (cu ft) pine 1773.2 1799.3 1380.9 1699.4 1620.3 Mean dbh (in) pine hard. 5.4 1.0 5.4 1.0 5.2 1.0 5.3 1.0 5.3 1.0 228.6 175.2 2.6 1.1 1.8 1.2 99.3 44.9 6.8 1.7 1.4 1.1 1.0 0.4 3.2 5234.5 5969.9 9.8 2.4 9.9 1.6 4540.0 5418.2 9.3 1.8 10.0 1.8 4651.4 4626.1 11.1 2.8 12.1 2.8 5864.9 5803.9 12.2 3.5 12.1 2.6 6422.6 5496.2 11.2 1.1 12.5 3.7 3799.2 3359.2 11.4 2.8 11.9 3.3 5415.8 4204.2 4966.3 6465.5 9.3 3.8 10.4 4.4 13.1 4.2 11.4 4.0 1856.7 1877.5 4.1 1.5 6.1 1.7 396.0 312.7 392.0 3.3 1.1 2.9 1.1 3.3 1.1 393.8 3.2 1.2 225.3 354.4 392.9 3.0 1.1 3.1 1.1 3.2 1.2 Mean total height (ft) pine hard. 36 10 36 11 34 10 36 11 35 11 15 11 13 13 12 15 9 11 4 23 66 14 75 15 66 14 72 15 72 28 78 28 78 26 79 25 82 9 82 35 73 25 74 33 69 30 65 34 79 34 82 32 30 16 42 20 15 9 13 9 16 10 15 10 15 11 14 9 16 10 Percent hardwood basal area (%) 0.3 1.3 2.5 2.1 1.2 26.2 57.3 58.3 27.6 99.5 5.1 5.2 5.1 8.5 18.8 26.6 19.1 27.8 1.6 24.3 10.3 31.4 4.1 11.4 11.2 4.6 27.4 31.6 9.7 9.1 37.8 17.1 50.8 9.4 27.5 WC=Weed Control F=Fertilizer CB=Chop, burn B=Bedded WD=Well drained NWC=No weed control NF=Not fertilized CBB=Chop, burn, bed NB=Not bedded PMD=Poorly-moderately drained CBHB=Chop, burn, harrow, bed VPPD=Very poorly-poorly drained Georgia Forestry Commission/9 not revealed if one looks solely at treat- ment means. A more important relation- ship is pine yield versus the amount of hardwood present in the stand, regardless of herbicide treatment. One relationship which can be examined is pine yield (square feet of basal area or cubic foot yield) versus hardwood basal area. Figure I shows this relationship for the Floyd County comparison. Note the high variability and lack of a definitive trend. Figure 2 shows a transformed relationship where hardwood basal area has been ex- pressed as a percentage of the total basal area (pine plus hardwood). Variation is greatly reduced and a trend is obvious. Relative hardwood basal area appears to be a better indicator of hardwood effects and probably aids in standardizing other site and stand effects. Burkhart and Sprinz (1984) developed a yield model which incorporated this effect of hardwood basal area. Using measurements from the Fayette study at age II and age 24, they noted that percent hardwood basal area on a plot by plot basis remained constant over time. That is, if a plot had 30% hardwood basal area at age 11, it would still have 30% hardwood basal area at age 24. Although pines tend to grow faster than hardwoods, apparently pine mortality and hardwood ingrowth combine to maintain the constant proportion of hardwood basal area. This means that once hardwoods become established in a pine stand, pines do not "out-grow" and dominate the hardwoods, and that hardwoods remain as competition which adversely affects pine yield. This concept of constant proportion of hardwood basal area supports the idea that measurement of the amount of hardwood basal area in a stand several years after treatment (as was done in this ef- fort) should be an adequate indicator of initial hardwood density and/or treatment effectiveness. This assumes, of course, that hardwood stocking was equivalent across plots at time of treat- ment -- not always a good assumption, particularly in operational comparisons. The apparent lack of effectiveness of chemical treatment in some operational comparisons may be due to the violation of this assumption, as illustrated in Figure 3 for Summerville-3. The two plots with highest pine volume yield and among the lowest percent hardwood basal areas are untreated--that is, these plots apparently did not have a high proportion of hard- wood basal at time of treatment. Like- wise, the plot with the next to highest proportion of hardwood and next to lowest pine yield is a treated plot, indicating the treatment was ineffective. This points out that a comparison of treatment means alone is not sufficient. It also indicates the importance of proper plot layout during herbicide study establishment and the need to determine initial pine and hardwood stocking. Figure 4 (Summerville-6) also illustrates a strong negative effect of percent 10/Georgia Forestry Commission 70 60 50 (0 UJ 40 D