Arboriculture & Urban Forestry 42(5): September 2016 The pattern of tree growth observed between 2004 and 2008 (Weston and Harper 2009) largely continued between 2008 and 2012. Specimens of T. canadensis continued to measure the tallest of the seven species, but T. heterophylla was now similar in height to T. canadensis (Figure 2). Speci- mens of T. chinensis were nearly as tall as the tallest two species, but were significantly shorter than T. canadensis (P < 0.01), although the actual differ- ence was relatively small. Specimens of T. diver- sifolia were numerically less than half as tall as the tallest trees, and the remaining species were minuscule in comparison (these differences were not statistically testable). Obtaining an accurate estimate of the height of the smallest was com- promised because very few specimens of each of these species survived through 2012 (Table 2). 351 values of 72.2% and 94.4%, respectively. The big- gest change from 2008 was T. heterophylla, which dropped from 75% to 36% survivorship, apparently suffering substantial winter mortality as evidenced by the consistent brown-chlorotic appearance of the foliage aſter each winter season. Specific infor- mation pertaining to the provenance of these Tsuga spp. was unavailable, and it is important to note that the particular area of origin of a species (and speci- men) may influence factors like plant hardiness. Another measure of performance of the test trees was the vigor rating. Vigor ratings for T. canadensis and T. chinensis were identical in 2008 at 4.2 + 0.4 (mean + standard deviation), but dropped to 3.7 + 0.8 for T. canadensis by 2012. On the other hand, the vigor rating of T. chinensis increased to 5.0 + 0.0 in 2012. This difference in vigor rating was statis- tically significant (F = 60.0, df = 1, 42, P < 0.001). Figure 2. Height of Tsuga spp. in the research plots at Las- don Park. Bars for 2012 accompanied by the same letter are not significantly different as determined by ANOVA followed by mean comparisons using LSD at P = 0.05 (only T. canadensis and T. chinensis could be tested; see text for details). Species abbreviations are as follows: can = T. canadensis, car = T. caroliniana, het = T. heterophylla, mer = T. mertensiana, chi = T. chinensis, div = T. diversifolia, sie = T. sieboldii. Substantial differences existed in the ability of the seven species to survive the conditions in the research plots in the northeastern U.S. The differ- ences in survivorship among the species observed in 2008 (Weston and Harper 2009) were accentu- ated in 2012; the four species with the lowest sur- vivorship in 2008 (T. caroliniana, T. mertensiana, T. diversifolia, and T. sieboldii) displayed even lower survivorship in 2012 (Table 2), ranging between 5% and 17%. Tsuga canadensis and T. chinensis continued to display the highest survivorship, with Pest Presence In 2008, populations of EHS were found on 73 and 35% of the specimens of T. canadensis and T. chinen- sis, respectively (Weston and Harper 2009). Data col- lection during July 2012 revealed HWA to be present on none of the 17 surviving specimens of T. chinen- sis, while EHS was present on all of the T. chinen- sis specimens (though no negative effects appeared to be associated with the presence of this insect on these trees). HWA was found to be present on 27 of the 28 surviving T. canadensis specimens (96.43%), while EHS was found to be present on all T. canaden- sis trees in the study plots. In fact, all of the remain- ing specimens of Tsuga spp. were positively infested with EHS, regardless of species. These results would indicate that further study concerning this insect and its effect on various Tsuga spp. would be in order. Vegetative Propagation The T. chinensis cuttings that were potted as part of the exploratory propagation proof-of-concept were evaluated approximately six weeks aſter pot- ting (28 February) and appeared to have started well; all of the 200 cuttings that were potted and placed under the poly tent with bottom heat had maintained their needles and were lush/green with buds flushing new growth. The cuttings un- der the mist heads also appeared to be getting a good start, with 296 of the 300 having maintained needles, a lush/green appearance, and new growth ©2016 International Society of Arboriculture
September 2016
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
