222 Miesbauer et al.: Effects of Tree Crown Structure on Dynamic Properties number of the primary branch on which it origi- nated. Thus, the tree was “flat topped” by removing 25% of the crown height. Length was measured of each primary branch segment from branches originating in the top quartile, as well as from any branches originating lower in the crown, and trunk length in the top quartile. Total fresh mass was recorded separately for each branch (primary branch and all lateral branches) and the trunk. The remaining three quartiles were subsequently removed from the tree in descending order from the tree top, and length and mass for branches and trunk sections were measured in the same manner. The remaining trunk below the crown was cut at ground level, and length and mass were measured. Total branch length was the sum of primary branch segment lengths in each quartile and total branch mass was the cumulative mass from each quartile. Branch length and mass were catego- rized as being in the directional quadrant in which the branch originated on the trunk. Total trunk length and mass were the cumulative trunk seg- ments from the four vertical quartiles plus A four-way factorial ANOVA tested for dif- ferences in f and ζ between pulls performed on post-pruned trees in summer (in-leaf) and in winter when trees were leafless. Season, form, year, cycle, and all their interactions were main effects in the model and tree was a random effect. A two-way ANOVA tested differences in branch mass removed between excurrent and decurrent trees from each of the three annual (Summer 0, 1, 2) prun- ing events. One-way repeated measures ANOVA, with year as the within subject factor, was used to test differences in height and diameter between excur- rent and decurrent trees over the two-year period. Regression analysis was used to examine the relationship between DBH/Ht2 and f, and if that the trunk below crown. All length and mass measure- ments were made within one hour of being removed from the tree. Measuring trees in this manner allowed researchers to divide the tree canopy into 16 segments based on quartile and quadrant (four directional quadrants × four vertical quartiles). Data Analysis The experimental design was a split plot with tree form as the whole plot factor; pruning, cycle, and year were the split plot factors. Each tree was pulled from the northeast and northwest direction, giving two observations per combina- tion of treatments. Preliminary analysis showed that direction had no impact on response variables, and since direction was arbitrarily chosen it was not included in the statistical model. For tests performed in summer, a four-way fac- torial analysis of variance (ANOVA) was used to determine the effects of form, pruning, cycle, year, and all interactions on f and ζ values. In winter, a three-way factorial ANOVA tested the effects of form, cycle, year and all interactions on f and ζ values. For all ANOVAs, season, form, year, cycle and all their interactions were main effects, tree was a random effect in the models. ©2014 International Society of Arboriculture relationship was influenced by form, pruning, and year. Regression analysis examined whether f and ζ, measured on the subset of twelve dissected trees, could be predicted with the independent variables associated with the following: trunk and branch length and mass attributes; trunk taper; distribution of branch length and mass by ver- tical quartile and directional quadrant; branch base angle and total branch angle. T-tests were performed to analyze allometric and morpho- logical differences by tree form. Only Winter 2 values for f and ζ were analyzed because dissec- tions occurred immediately aſter Winter 2 tests. Statistical analyses were performed in SAS ver- sion 9.2 (SAS Institute, Cary, North Carolina, U.S.) using the PROC MIXED, GLIMMIX, GLM, REG, TTEST, and UNIVARIATE procedures. Mean separations were analyzed for main effects and interactions using Tukey’s HSD test. Differences were considered significant at a level of α = 0.05. RESULTS AND DISCUSSION The same branch mass was removed in the initial (Summer 0) excurrent and decurrent pruning treatments (Table 1). The retained lateral branches adjacent to the reduction cuts on excurrent trees reoriented upward (not measured) in the subse- quent 12 months (Summer 1), likely due to loss of apical control caused by removal of the primary terminal (Wilson 2000).Consequently, many branches on excurrent trees required more ag- gressive pruning than the decurrent trees at the second and third pruning episodes (Summers 1 and 2) to maintain the targeted excurrent crown
July 2014
| 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
