Swedish owners of poplar stands are interested in both the wood quality and the use of poplars that are soon to be harvested. An important concern is the frequency of false heartwood (FHW) in the stems. We have presented an overview of the factors causing discolored wood as well as the industrial use and quality of the end products. We have studied poplar stems growing at 22 sites in Sweden between latitudes 55° N and 60° N. The mean age of the poplar was 23 years (range 14–41), the mean stand density 1011 stems ha ？1 (range 155–3493) and the diameter at breast height (DBH) (over bark) 246 mm (range 121–447). All stands were growing on clay soils (light and medium clay and light clay tills). All of the sampled stems (42) contained false heartwood. At 0%–50% of stem height, all sampled trees were discolored and at 90% of stem height, 33% were discolored. The percentage of false heartwood area by stem area was highest at 1% and 10% of stem height (26.6% and 24.7% respectively). The “FHW” part of the stem had a radius of 47 mm (range 9–93) at 30% of stem height, which corresponds to 50% of the total stem radius. A log of six meters represents about 30% of stem height. Equations describing the correlation between DBH and the diameter of FHW at different stem heights (1%, 10%, 30%, 50%, 70% and 90%) and table describing FHW volume % by total stem volume at the first 50% of stem height were constructed. These might be helpful for estimating the percentage of fresh wood in a stem. However, most of the fast-growing poplars will be harvested as biofuel.
References
[1]
Christersson, L. Future research on hybrid aspen and hybrid poplar cultivation in Sweden. Biomass Bioenergy 1996, 11, 109–113, doi:10.1016/0961-9534(96)00014-1.
[2]
Johansson, T.; Kara？i？, A. Increment and biomass in hybrid poplar and some practical Implications. Biomass Bioenergy 2011, 35, 1925–1934, doi:10.1016/j.biombioe.2011.01.040.
[3]
Klasnja, B.; Kopiovic, S.J.; Orlovic, S. Variability of some wood properties of eastern cottonwood (Populus deltoides Bartr.) clones. Wood Sci. Technol. 2003, 37, 331–337.
[4]
Hofstra, T.S.; Stromberg, J.C.; Stutz, J.C. Factors associated with wetwood intensity of Populus fremonii (Fremont cottonwood) in Arizona. Great Basin Naturalist 1999, 59, 85–91.
[5]
Ne？esany, V. Classification of beech hearts. Drevo 1956, 11, 93–98.
[6]
Pryor, S.N. The Silviculture and Yield of Wild Cherry; Forestry Commission. Bull. No. 75; Forestry Commission: London, UK, 1988; pp. 1–23.
[7]
Drouin, M.; Beauregard, R.; Duchesne, I. Variability of wood color in paper birch in Quebec. Wood Fiber Sci. 2009, 41, 333–345.
[8]
Luostarinen, K.; Verkasalo, E. Birch as sawn timber and in mechanical further processing in Finland. A literature study. Silva Fenn. Monogr. 2000, 1, 1–40.
[9]
Benic, R. Estimation of the proportion of brown heart in the stem of Fraxinus angustifolia. Sum. List. 1954, 78, 365–379.
[10]
Jorgensen, E. Observations on the formation of protection wood. For. Chron. 1962, 38, 292–294.
[11]
Siegle, H. Microbiological and biochemical aspects of heartwood stain in Betula papyrifera Marsh. Can. J. For. Res. 1967, 7, 219–226.
[12]
Shigo, A.L. Successions of organisms in discoloration and decay of wood. In International Review of Forestry Research; Romberger, J.A., Mikola, P., Eds.; Academic Press: New York, NY, USA, 1967; Volume 2, pp. 237–299.
[13]
Shigo, A.L.; Larson, E.H. A Photo Guide to the Patterns of Discoloration and Decay in Living Northern Hardwood Trees; United States of Department of Agriculture (USDA), Forest Service, Northeastern Forest Experimental Station: Upper Darby, PA, USA, 1969; pp. 1–100.
[14]
Shigo, A.L. A New Tree Biology: Facts, Photos and Philosophies on Trees and Their Problems and Proper Care; Shigo and Trees Associates: Durham, UK, 1986; pp. 1–132.
[15]
Shigo, A.L.; Hillis, W.E. Heartwood, discolored wood and microorganisms in living trees. Ann. Rev. Phytopathol. 1973, 11, 197–222, doi:10.1146/annurev.py.11.090173.001213.
[16]
Basham, J.T. Stem Decay in Living Trees in Ontario’s Forests: A Users’ Compendium and Guide; Canadian Forest Service Great Lakes Forest Central Information Report 0-X-408; Forestry Canada, Ontario Region: Sault Ste. Marie, Canada, 1991; pp. 1–69.
[17]
Kerr, G. A review of black heart of ash (Fraxinus excelsior L.). Forestry 1998, 71, 49–56.
[18]
H？rnfeldt, R.; Droin, M.; Woxblom, L. False heartwood in beech Fagus sylvatica, birch Betula pendula, B. papyrifera and ash Fraxinus excelsior—An overview. Ecol. Bull. 2010, 53, 61–75.
[19]
Ward, J.C.; Pong, W.Y. Wetwood in Trees: A timber Resource Problem; General Technical Report PNW-112; United State Department of Agriculture (USDA), Forest Service, Pacific Northwest Forest and Range Experimental Station: Portland, OR, USA, 1980; pp. 1–57.
[20]
Hartley, C.; Davidson, R.W.; Crandell, B.S. Wetwood, Bacteria and Increased pH in Trees; United State Department of Agriculture (USDA), Forest Service, Forest Products Lab Report 2215: Madison, WI, USA, 1961.
Tiedemann, G.; Bauch, J.; Bock, E. Occurrence and significance of bacteria in living trees of Populus nigra L. Eur. J. For. Path. 1977, 7, 364–374, doi:10.1111/j.1439-0329.1977.tb00606.x.
[23]
Scott, E.S. Populations of bacteria in poplar stems. Eur. J. For. Path. 1984, 14, 103–112, doi:10.1111/j.1439-0329.1984.tb00158.x.
[24]
Bauch, J. Discoloration in the wood of living and cut trees. IAWA. Bull. N.S. 1984, 5, 92–98.
[25]
Wang, X.; Jiang, Z.; Ren, H. Distribution of wet heartwood in stems of Populus xiaohei from a spacing trial. Scand. J. For. Res. 2008, 23, 38–45, doi:10.1080/02827580701763706.
[26]
Hiratsuka, Y.; Loman, A.A. Decay of Aspen and Balsam Poplar in Alberta; Northern Forest Research Centre. Canadian Forest Service Environment: Alberta, Canada, 1984.
[27]
Sachs, I.B.; Ward, J.C.; Kinney, R.E. Scanning electron microscopy of bacterial wetwood on a normal heartwood in poplar trees. In Proceedings of the 7th Annual Scanning Electron Microscopy Symposium: Part II, Chicago, IL, USA, 10–11 April 1974; pp. 453–460.
[28]
Boone, R.S. Sorting aspen bolts and drying aspen flitches for SDR. Gen. Tech. Rep. NC-140. In Proceedings of Aspen Symposium “89”, Duluth, MN, USA, 25–27 July 1989; Adam, R.D., Ed.; United States Department of Agriculture (USDA), Forest Service North Central Forest Experimental Station: Saint Paul, MN, USA, 1990; pp. 295–299.
[29]
Mackay, J.F.G. Properties of Northern aspen discolored wood related to drying problems. Wood Fiber 1975, 6, 319–325.
[30]
Johansson, T. Biomass equations for determining fractions of pendula and pubescent birches growing on abandoned farmland and some practical implications. Biomass Bioenerg. 1999, 16, 223–238, doi:10.1016/S0961-9534(98)00075-0.
[31]
Payandeh, B. Choosing regression models for biomass prediction models. For. Chron. 1981, 57, 229–232.
[32]
SAS, Version 9.1; SAS Institute Inc.: Cary, NC, USA, 2006.
Hjelm, B. Taper and Volume Equations for Poplar Trees Growing on Farmland in Sweden; Report 29. Licentiate Thesis, Department of Energy and Technology, Swedish University of Agricultural Sciences, 2011.
[35]
Jiang, Z.-H.; Wang, X.Q.; Fei, B.-H.; Ren, H.-Q.; Lin, X.E. Effect of stand tree attributes on growth and wood quality characteristics from a spacing trial with Populus ziaohei. Ann. For. Sci. 2007, 64, 807–814, doi:10.1051/forest:2007063.
[36]
Garret, P.W.; Shigo, A.L.; Carter, J. Variation in diameter of central columns of discoloration in six hybrid poplar clones. Can. J. For. Res. 1976, 6, 475–477, doi:10.1139/x76-065.
