Growth patterns in immature and mature western hemlock tsuga heterophylla stands infected with dwarf mistletoe arceuthobium tsugense
Thomson, A.J.; Smith, R.B.; Alfaro, R.I.
Canadian Journal of Forest Research 14(4): 518-522
ISSN/ISBN: 0045-5067 Accession: 005542653
Growth patterns of western hemlock, T. heterophylla (Raf.) Sarg. infected with dwarf mistletoe, A. tsugense (Rosendahl) G. N. Jones, were studied by stem analysis. The volume increment vs. age relationships of average trees were used to project growth and evaluate volume losses. Based on a particular assumption of growth loss ratios between infection classes, volume losses in moderately and severely infected trees by the age of 80 yr were conservatively estimated at 15 and 25%, respectively, with respect to comparable healthy trees. As these estimates were based on projection of growth curves of average trees, confidence intervals were not calculated. Healthy trees selected from a different part of the stand generally exhibited patterns of establishment and early growth which differed from the infected trees to an extent which invalidated their use as controls for infected tree growth. Moderately infected trees were more comparable to severely infected trees from the same part of the stand. The variety of growth patterns within stands is discussed in relation to the use of the stand as a sampling unit.