350 Harper and Weston: Alternative Tsuga spp. as Landscape Replacements for T. canadensis ence or absence of HWA and EHS was noted aſter inspecting several branches from each tree using a simple binary (presence/absence) classification. Propagation of T. chinensis Hardwood cuttings of the most recent year’s growth were taken from T. chinensis growing in the research plots on 20 January 2014, and aver- aged 12.5–15 cm in length. Cuttings were kept in closed plastic bags, transported to the UMass College of Natural Sciences greenhouse, and pot- ted on 22 January 2014 (Figure 1). The cut ends were dipped in a liquid rooting concentrate (Dip’N Grow, Inc., Clackamas, Oregon, U.S.) at a concen- tration of 5,000 ppm IBA and 2,500 ppm NAA before potting in sand:perlite (1:1) in standard 50- plug, 25.4 cm × 50.8 cm grow trays. Two growing conditions were compared: 1) under a polyethyl- ene (poly) moisture tent with bottom heat (21°C), and 2) on a mist bench with no bottom heat (air temperature 24°C). Four flats of 50 cuttings each (200 cuttings total) were reared in the poly tent and six flats (300 cuttings total) were reared on the mist bench. Rooting could not be verified until cuttings remained for a “3–4 month” period un- der the aforementioned conditions (J. Alexander, Arnold Arboretum at Harvard University, pers. comm.). Establishment and vigor were assessed at various times over the following ten months. Vigor was assessed visually on a whole-tray basis using a 0–5 visual rating system, where 0 = 100% mortality of grow tray specimens and 5 = 100% viability and lush, green needles, similar to the vigor rating used to assess tree health in the field. Data Analysis Tree height was analyzed using randomized complete block analysis of variance (ANOVA) and vigor was analyzed with Kruskal-Wallis one-way non-parametric ANOVA because the data did not meet the assumptions of random- ized complete block ANOVA. Because of the low number of trees surviving for many of the test species, these analyses were performed only for T. canadensis and T. chinensis. Survivorship was analyzed for all species, using χ2 for the total number of each of the test species surviving, regardless of plot (replicate), and propagation results were analyzed with a two-sample t-test. Analyses were performed with Statistix 9 (Ana- lytical Software, Tallahassee, Florida, U.S.). RESULTS AND DISCUSSION Figure 1. Early-stage Tsuga chinensis cuttings under poly tent in greenhouse. ©2016 International Society of Arboriculture Soil Analysis Texture-by-feel evaluation revealed a loam soil comprising the growing media in all three of the experimental plots in which the Tsuga spp. trees were growing. Bulk density readings were 0.96 g/ cc (Front Gate), 0.98 g/cc (Magnolia Garden), and 0.81 g/cc (Hemlock Hedge). Bulk density may be one significant factor useful in identifying com- pacted soils; these values indicate that from a structural standpoint, the soil in the research plots was well below levels considered restrictive to root growth (i.e., 1.40–1.65 g/cc) (Alberty et al. 1984). This was further corroborated by data from the penetrometer readings, which revealed root pen- etration to a depth of 18–23 cm throughout the three plots: 19.2 cm (Front Gate), 17.9 cm (Magno- lia Garden), and 21.3 cm (Hemlock Hedge). A sig- nificant layer of organic matter had accumulated on the three plots, which is likely responsible for the soil organic matter (SOM) reading of 10.4% in the Front Gate Plot, although SOM readings for the other two plots were more within normal levels of nearly 5% (4.7% Magnolia Garden; 3.8% Hemlock Hedge) (Harris et al. 2004). The pH read- ings from the soil test report indicated the fol- lowing values: Front Gate, 5.4; Magnolia Garden, 5.4; and Hemlock Hedge, 5.2. Since T. canadensis is found growing on soils that range from “very acidic” to “nearly neutral” (Godman and Lancaster 1990), these values should not be limiting factors.
September 2016
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