- ?l A GEORGIA FOREST RESEARCH PAPER 42 March, 1983 TOTAL TREE AND PRODUCT WEIGHT OF BEETLE-KILLED LOBLOLLY PINES IN NORTHEAST GEORGIA BY Received W. HENRY Mc NAB DOCUMENTS J RESEARCH DIVISION GEORGIA FORESTRY COMMISSION COVER These loblolly pines were recently killed by southern pine beetles and are still merchantable for a variety of products, including saw logs, pulpwood, and total tree fuel- wood chips. Note particularly the low-value understory hardwoods, which have been released from competition and may soon dominate this pine site. WILLIAM H. McNAB is a Research Forester with the Southeastern Forest Experiment Station at Athens, Geor- gia. He has a BS degree in Forest Man- agement and MS in Silviculture, both from the University of Florida. He is a member of the Utilization of Southern Timber Research Work Unit, where he works mainly on problems related to the effects of silvicultural practices on biomass yields and utilization of forest residues. ACKNOWLEDGMENT Received OCT 4683 DOCUMENTS UGA LIBRARIES The author gratefully acknowledges the financial support and assistance given by the Georgia Forestry Commission for making this research possible. Special thanks are given to B. F. Young, Superintendent, Hard Labor Creek State Park, and Roswell P. Goolsby, Assistant Ranger, Oconee National Forest, for assistance in locating the trees sampled in this study. TOTAL TREE AND PRODUCT WEIGHT OF BEETLE-KILLED LOBLOLLY PINES IN NORTHEAST GEORGIA BY W. HENRY Mc NAB INTRODUCTION Utilization of beetle-killed trees not only helps control the spread of southern pine beetles, but is a good management practice to increase profits. Recently killed trees are usually merchantable with little loss of quality and lower stumpage value. However, during severe outbreaks of southern pine beetles, immediate utili- zation of dead trees may not be possible because of oversupply at the mill. Standing dead trees will deteriorate rapidly in the warm, humid climate of the South. Barron (1971) found that within several months of their death, beetle-killed trees lose little wood sub- stance but over half of their moisture content. Since half of the total weight of live loblolly pines consists of water (Taras and Clark 1975), this loss of water results in a major reduction of tree weight, especially if beetle-killed trees are marketed on a weight basis. The yield of harvested southern pine timber is commonly measured on a weight basis for convenience and, with proper factors, is converted to conventional volume units by the buyer. Conversion factors are available for live pine sawlog and pulpwood timber (Saucier and others 1981) but they should not be applied to beetle-killed trees because of the lower moisture content of dead trees. Reported here are the results of a study to develop prediction equations and tables for estimating the weight of trees killed by southern pine beetles. PROCEDURE Loblolly pine trees killed by southern pine beetles during 1980 and 1981 were selected from natural upland stands at four locations in northeast Georgia (Figure 1). Sixty trees, ranging from 5 to 18 inches d.b.h., were sampled and grouped in two classes according to crown ap- pearance (Table 1). Trees in class A were estimated to have been dead from 5 to 7 months, and still had fine twigs attached to the larger branches (Figure 2). Those in class B had lost some of their small branches and had been dead from 10 to more than 18 months (Figure 3). The amount of bark remaining on the trees varied widely, particularly between classes. Levi (1981) found that the pres- ence or absence of bark is not a reliable indicator of wood quality. Generally, all stem bark was still attached on trees in class A and was present on the lower half of trees in class B. All trees sampled had bark present at 4.5 feet. The 13 sawtim- A ber-size trees sampled in class averaged 12.9 inches d.b.h. and contained an average of 2.5 to 3.0 saw logs 16.3 feet in length. Trees were felled with a chain saw, limbed, and the main stem was bucked into major products of saw logs and pulpwood, depending on tree class and size. In class A, saw logs to a 7-inch d.o.b. or merchantable top were cut from trees greater than 9 inches d.b.h. Pulpwood was cut to a 4-inch d.o.b. top from the stem above the saw-log top, and from smaller trees. No saw logs were cut from trees in class B because of probable low grade and loss of strength resulting from blue stain, decay, or insect damage ( Levi 1 981 ). The crown, consisting of stem wood above the 4-inch top and all branches, was weighed separately to the nearest pound. Broken branches and topwood were included in the weighing when they could be found and identified according to the proper tree. Samples of stem and branch wood were collected and returned to the laboratory for determination of moisture content. Figure 3. -Class B beetle-killed loblolly pines have broken branches and lack fine branch twigs. SAMPLING LOCATIONS Figure 1. -Sampling locations of beetle-killed loblolly pines in northeast Georgia. A Figure 2. -Class beetle-killed loblolly pines still have fine twigs attached to the main branches. >\_ \ A * **4l^ vj>^* V *"m jfjp /^3 ^_J_i A J .,.,,_ *^y y\ I j j/F k^*<*js&j$ ^^^N f$kl *m&~ 4i-- RESULTS AND DISCUSSION Preliminary analysis of the weight data showed no practical difference in total tree or product weight between the two tree classes. Wood moisture content was also similar between the two classes of trees: Tree Class A B Main Stem Branches Percent- - 62 24 45 26 Except for the saw-log weights, total tree and pulpwood weight data from both classes were combined into a single group for further analysis. Total Tree Weight The relationship of average total tree green weight by d.b.h. class is shown in Figure 4. Results are presented for tree wood content only, and do not include bark. Even though bark was present on most of the bole on trees in class A, it was loosely attached and would probably be lost during felling and skidding opera- tions. 8 10 12 14 D.B.H. CLASS (INCHES) Figure 4. --Relationship of total-tree green weight to d.b.h. class of beetle-killed loblolly pines in northeast Georgia. I00r- CROWN PULPWOOD mi SAW LOGS 80 A considerable amount of crown ma- terial was often broken from trees in class B during felling. On the average, about 15 percent of the total tree weight in branches and top wood was broken and probably would not be recovered for utilization. Larger trees appeared to lose a higher proportion of crown wood than small trees. Product Weight 60 Q: 40 20 8 10 12 14 16 D.B.H. CLASS (INCHES) The distribution of pulpwood and sawlog product weight as a percentage of A total tree weight is shown in Figure 5. large proporation of total tree weight consists of pulpwood in the bole to a 4inch d.o.b. top, indicating that recover- A able crown weight is relatively small. similar trend occurs between the bole weight to a 4-inch top and saw-log weight. The proportion of weight in saw logs increased until tree d.b.h. reached 14 inches, where it leveled off at about 83 percent. Figure 5. -Proportion of total-tree green weight in crown, pulpwood, and saw logs for beetle-killed loblolly pines. Predicition Equations Prediction equations were developed from common cruise variables to estimate A total tree and product weight. predic- tion equation for pulpwood weight was developed by using d.b.h. and height to a 4-inch d.o.b. top. Total tree weight was estimated by developing a prediction equation for the crown separately, and adding it to the predicted weight of pulpwood. An equation using d.b.h. and merchantable height was developed to allow estimation of saw-log weight. All equations were sufficiently accurate to ac- count for over 95 percent of the variation associated with total tree or product weight. Weight Scale Factors Factors for converting weight to units of volume were calculated from field weights and published volume tables (Knight and McClure 1974 Mesavage and Girard 1956). An average of 2,996 pounds of wood from 8-inch d.b.h., beetle-killed trees was required for a stacked cord containing 68 cubic feet of wood. For sawtimber in our study, the average weight per thousand board feet (Scribner log rule, form class 78) was about 10,600 pounds. Saw-log conversion factors were also calculated from d.b.h. class and estimated weights (Table 2). Weight Tables Prediction equations were used to construct Tables 3, 4, and 5 for estimating saw-log, pulpwood, and total tree green weight. Other components may also be estimated by using values from these tables. For example, pulpwood above the saw-log merchantable top can be determined by subtracting saw-log weight from weight to a 4-inch top. Likewise, crown weight can be estimated by subtracting pulpwood weight from total tree weight. As with any table of this type, predicted weights are most accurate near the center of the "blocked-in" area and, where possible, predicted weights should be verified for accuracy. branch wood moisture content of live loblolly pines is slightly over 100 percent (Taras and Clark 1974), almost double the amount measured in beetle-killed trees. Tables for estimating the weight of the total tree and products, and weight-scaling factors were developed for beetle-killed loblolly pines. If markets are not available or if excessive deterioration lowers qood quality for conventional products, beetle-killed trees can be harvested for fuelwood chips. -- Table 1. Means and ranges in dimensions of beetle-killed loblolly pines sampled in northeast Georgia Tree Trees class sampled Number A 26 B 34 All 60 D.b.h. Height to 4-inch top Mean Range Mean Range - - -Inches- - - -Feet 9.8 11.6 5.1-15.3 46 5.2-18.8 56 14-72 14-82 10.8 5.1-18.8 52 14-82 -- Table 2. Estimated green weight of pulpwood and saw logs per unit volume for beetle-killed loblolly pines in northeast Georgia D.b.h. class (inches) Pulpwood 1/ Saw 2/ log Merchantable height Weight Lb /cord Feet Lh/MBF 2,745 3,064 10 3,290 12 3,452 14 3,573 16 3,672 18 3,748 1.5 12,700 2.0 11,200 2.5 10,300 3.0 9,600 3/ 9,100 SUMMARY AND CONCLUSIONS Pines killed by beetles are merchantable for various products if harvested soon after attack. In the South, however, significant weight loss occurs quickly, especially during the summer months, and will affect accurate conversion of weight to volumes if factors for live trees are used. For example, the main stem and -- Cubic feet of wood per cord from Knight and McClure 19 74. Average field weight of wood and bark per cubic foot of wood was about 45 pounds for the main stem. 2/ Scribner log rule; form class 78. 3/ No trees measured in this d.b.h. class weight extrapolated. -- Table 3. Predicted green weight of wood to a saw-log merchantable height for beetle-killed loblolly pines in northeast Georgia D.b.h. class (inches) 1.0 9 288 10 359 11 437 12 523 13 617 14 719 15 16 17 18 19 20 Merchantable saw-log top (16-foot L/ logs) J 1.5 2.0 2.5 3.0 3.5 - - -Pounds-- - - - 379 472 5 74 688 811 946 1091 1247 461 573 698 836 987 1150 1326 1516 1718 1934 537 668 813 973 1149 1339 1544 1765 2000 2252 2518 2800 608 756 921 1102 1301 1516 1749 1999 2266 2550 2852 3171 1023 1225 1446 1685 1943 2221 2518 2833 3169 3523 1/ Blocked-in area indicates range of data, y y= o^ocdV-^V) - 68894 . where: Y = saw-log weight in pounds, D = d.b.h. in inches, Mh = saw-log merchantable height in 16-foot logs : 3 2106 DMSSM 5M75 Table 4.- -Predicted green weight of wood to a 4 -inch d .o.b. top for beetle--killed loblolly pines in northeast Geo rgia D.b.h. Heigh t to 4-inch top (feet)-7 class (inches) 10 20 30 40 50 60 70 80 - - Pounds-- - - 5 37 70 103 134 166 197 6 52 99 144 189 233 277 7 69 132 193 253 311 369 427 8 88 169 248 324 400 475 548 9 110 211 309 405 499 592 684 755 10 134 257 377 49 3 608 721 833 944 11 308 450 590 727 862 996 1129 12 362 530 694 856 1015 1173 1329 13 616 806 994 1180 1363 1545 14 708 927 1142 1355 1566 1775 15 1055 1300 1543 1782 2020 16 1190 1467 1741 2012 2280 17 1644 1951 2254 2555 18 1830 2171 2509 2844 19 2403 2777 3147 20 2646 305 7 3465 1/ Blocked-in area indicates range of data. y2 93763 Y - 0.20679(D H4)- . where Y = stem weight to 4-inch d.o.b. top, D = d.b.h. in inches, H4 = height to 4-inch top. : ' -- Table 5. Predicted green weight of total tree wood for beetle-killed loblolly pines in northeast Georgia D.b.h. Hei ght to 4 -inch top 1/ (feet) class (inches) 10 20 30 40 50 60 70 80 - - Pounds2--/- - 5 56 97 135 172 208 242 6 74 131 184 234 283 331 7 95 169 238 305 370 433 495 8 119 212 299 384 466 547 626 9 144 259 367 471 573 673 771 869 10 172 310 441 567 690 811 930 1048 11 366 521 671 817 961 1103 1243 12 425 607 782 954 1123 1289 1453 13 699 902 1101 1296 1488 1678 14 797 1029 1257 1480 1701 1919 15 1164 1422 1676 1926 2174 16 1307 1598 1883 2165 2444 17 1782 2102 2417 2728 18 1976 2331 2681 3027 19 2571 2958 3341 20 2822 3248 3668 1/ Blocked-in area indicates range of data. -' Y = 2 0.20679(D H4) ' 93763 2 4866 + 1. 30503(D H4) where Y = total tree weight in pounds, D = d.b.h. in inches, H4 = height to 4-inch top. 10 LITERATURE CITED Barron, Edwin H. 1971 . Deterioration of southern pine beetle-killed trees. For. Prod. J. 21(3): 57-59. Knight, H. A.; McClure, J. P. 1974. Georgia's timber, 1972. Resour. Bull. SE-27. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station; 19 p. Levi, Michael P. 1981. A guide for using beetle-killed southern pine based on tree appearance. Agric. Handb. 572. Wash- ington, DC: U.S. Department of Agriculture; 19 p. Mesavage, Clement; Girard, J. W. 1956. Tables for estimating board-foot volume of timber. Washington, DC: U. S. De- partment of Agriculture, Forest Service; 94 p. Saucier, J. R.; Phillips, D. R.; Williams, J. G. 1981. Green weight, volume, board-foot, and cord tables for the major southern pine species. Ga. For. Res. Pap. 19. Macon, GA: Georgia Forestry Commission; 63 p. Taras, M. A.; Clark, A. 1975. Aboveground biomass of loblolly pine in a natural uneven-aged sawtimber stand in central Alabama. Tappi 58(2): 103-105. GEORGIA FORESTRY, \er> #*\%*J John W. Mixon, Director J. Fred Allen, Chief of Forest Research