© 2007 Heron Publishing—Victoria, Canada
Radial patterns of carbon isotopes in the xylem extractives and cellulose of Douglas-fir
Adam M. Taylor (1,2), J. Renée Brooks (3), Barbara Lachenbruch (4) and Jeffrey J. Morrell (4)
1. Department of Forestry, Wildlife and Fisheries, University of Tennessee, 2506 Jacob Drive, Knoxville, TN 37996, USA / 2. Corresponding author (adamtaylor@utk.edu) / 3. Western Ecology Division U.S. EPA/NHEERL, 200 SW 35th St., Corvallis, OR 97333, USA / 4. Department of Wood Science and Engineering, Oregon State University, 119 Richardson Hall, Corvallis, OR 97330, USA / Received May 15, 2006; accepted August 24, 2006; published online March 1, 2007
Summary
Heartwood extractives (nonstructural wood components) are believed to be formed from a combination of compounds present in
the adjacent sapwood and materials imported from the phloem. The roles of local compounds and imported material in heartwood
formation could have important implications for the wood quality of species having naturally durable wood. Stable isotope
composition (δ13C) was analyzed to assess radial variation in sapwood extractives, and to estimate the relative importance of adjacent sapwood
extractives and imported photosynthate in the formation of heartwood extractives. Cellulose and extractives from the outer
39 annual rings of six Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees were isolated and their δ13C composition determined. Although the extractives and the cellulose showed different absolute δ13C values, the patterns of change over time (as represented by the annual rings) were similar in most cases. Within an annual
ring, carbon isotope ratios of extractives were correlated with the cellulose isotope ratio (R2 = 0.33 in sapwood, R2 = 0.34 in heartwood for aqueous acetone-soluble extractives; R2 = 0.41 in sapwood for hot-water-soluble extractives). These data suggest that some sapwood extractives are formed when the
wood ring forms, and remain in place until they are converted to heartwood extractives many years later. Sapwood extractives
appear to be important sources of materials for the biosynthesis of heartwood extractives in Douglas-fir.
Keywords:
δ13C, heartwood, Pseudotsuga menziesii, sapwood, stable isotopes.
