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Western hemlock foliar nutrients and terminal growth in relation to three contrasting forest floors within a stand Inselberg, Alexander Eduard


The objective of this study is to determine whether or not foliar macro- and microelements and terminal growth are the same, within a stand for western hemlock (Tsuga heterophylla (Raf.) Sarg.) associated with three different forest floor sampling strata: 1) Orthihumimor, 2) thin forest floor, and 3) Lignohumimor. The study site is in the Wetter Maritime Coastal Western Hemlock (CWHb) biogeoclimatic subzone in the Seymour River watershed near Vancouver, British Columbia. The sample trees are natural regeneration established on sites not exposed to slash-burning, following a high-lead clearcut in 1972. Nutrient deficiency diagnosis, based on foliar analysis data, suggests a deficiency of P%, K%, and N% (in decreasing order of severity) in all three strata. Micronutrients of concern appear to be Fe and Cu in all the strata, and Zn for trees in the Lignohumimor stratum. Nitrogen fertilization might induce B deficiency on all strata. Manganese is the only micronutrient present in great excess. Terminal (leader) growth is greatest on Orthihumimors, intermediate on Lignohumimors and least on thin forest floors. A single factor ANOVA indicated differences at the 5% level for 7, and the 1% level for 6 of the 22 variables tested. Range tests were applied to determine between which of the 3 forest floor types the significant differences occurred. Backward stepwise multiple regression explained 88% of the variation in ln terminal growth on stratum 3, and 86% of the variation in terminal growth on stratum 2. Only 51% of the variation in ln terminal growth is explained by the multiple linear regression equation for stratum 1. The poor results for stratum 1 are attributed to a bimodal distribution of terminal growth. Six variables are included in the discriminant analysis of hemlock on the three forest floor strata. In the jackknifed classification procedure, 79% (or 45) of the 57 sample trees are correctly matched to their forest floor stratum. A correlation matrix of all variables versus each of the first three principal components analysis axes defines the variables, in the order of their importance, that contribute to the separation of the strata along the axes. When both nutrition and growth are considered, the statistics suggest that the Orthihumimor is the best of the 3 microsites for hemlock.

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