Arboriculture & Urban Forestry 42(4): July 2016 ed vines was determined by a complete absence of sprouts and lack of green coloration below the bark layer (determined by scraping the bark slightly on the stump using a pocket knife). On surviving vines, the number of sprouts and sprout length were recorded for each treated stem in 2012. It was possible that the stumps of vines were killed with treatment, but not the roots. Root suckering was evaluated by searching for suckers in a 2 m zone around each treated vine, but no suckers were observed, indicating that if the vine stump was killed, so were the roots. Only mortality was measured at the end of the sec- ond year post treatment. Of the 360 vines treated in 2011, a subset of 326 were found in 2013 because vine ID tags were lost (likely destroyed by animals). A minimum of seven vines were found in each plot in 2013, allowing for meaning- ful calculations of second year mortality levels. Data Analyses A paired t-test was used to compare oriental bit- tersweet density between field edge and interior forest quadrats. Correlation analysis was used to test the relationship between average, plot-level vine size and age. Analysis of variance using gen- eral linear models was used to test the hypothesis that efficacy as determined by percent mortality (and sprout length and number in Year 1) would vary as a function of herbicide concentration (including the untreated control—cuts with no herbicide treatment) and treatment timing for Study 1, and herbicide concentration for Study 2. While it was possible to combine each year’s mor- tality data and run a single analysis of variance using a repeated measures design to test for year (Year 1 versus Year 2) and treatment effects, sepa- rate analyses of variance were run for each year in each study, with the year effect deemed obvi- ous based on study results—Year 1 results were clearly different from Year 2. Also, since practitio- ners would most likely judge treatment efficacy after treatment effects were fully expressed, and not using the average efficacy response (which is what the main effects in a single repeated mea- sures analysis would produce), the two sepa- rate analyses of variance made practical sense. An arcsine transformation of percent mortality, which is typical for analyzing survival data to better 257 meet basic assumptions of analysis of variance (see Ahrens et al. 1990 and associated literature review), was applied to the data, but evaluation of treat- ment effects based on the transformed data did not change compared to the untransformed data. There- fore, all reported data analyses are untransformed. Treatment means were separated using Duncan’s method when P-values were ≤0.10, though P-values up to 0.15 were considered as possi- bly significant. Interaction effects were judged as statistically significant using an alpha level of 0.15 (Stehman and Meredith 1995). All statisti- cal analyses and calculations were performed with SAS® version 9.3 (SAS Institute Inc. 2011). RESULTS Oriental Bittersweet Populations Average number of small oriental bittersweet vines (<1.3 cm in diameter) across Study 1 plots was 26,334 per ha, ranging from 0 to 118,037 per ha; for Study 2, the average was 19,660 vines per ha, ranging from 0 to 42,518 per ha. Field edge quadrats averaged nearly two times higher small vine density as compared to forest interior quadrats, 32,143 versus 17,904 vines per ha, re- spectively (P < 0.001; paired t-test, n = 54 pairs). Average number of large vines (≥1.3 cm in diameter) across Study 1 plots was 2,222 per ha, ranging from 988 to 4,745 per ha; for Study 2, the average was 2,330 per ha, ranging from 946 to 4,273 per ha. These large vines were observed to be located across the plot, with only slight affinity for the field edge half (C. Nowak, per- sonal observation). It is likely that when the large vines became established, the whole plot was more open and edge-like than it is today. Average diameter of vines ≥1.3 cm across Study 1 plots was 2.8 cm, ranging from 1.5 to 6.0 cm; for Study 2, the average was 2.5 cm, ranging from 1.8 to 4.1 cm. Age of the oriental bittersweet for Study 1 averaged 18 years, ranging from 9 to 38 years, and for Study 2 the average age was 22 years, rang- ing from 10 to 36 years. The largest and oldest vine observed in the study had a stem diameter of 15.3 cm and was 48 years old. Large vine age and stem diameter were strongly, linearly corre- lated across the study sites (Studies 1 and 2 com- bined) (r = 0.77; P = <0.0001; n = 36) (Figure 1). ©2016 International Society of Arboriculture
July 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
