70 Sanders et al.: Size Expectations for Urban Trees with Regard to Designed Space species–site cohort, those within the ninety-fifth percentile were described as the maximum size range (Table 2). This is a standard procedure for ranking populations in epidemiology and educa- tional tests, and works well for the purposes of the study (Cannell 1988; Fraenkel and Wallen 1992; Schoonjans et al. 2011). The logic is that trees no longer occurring above a certain size class were removed because of excessive size for the planting site; re- moved due to declining vigor or condition; or died before exceed- ing the observed terminal limit size. The smallest number of trees considered acceptable for inclusion within a particular site type had to be greater than seven, which was required for at least one tree for inclusion into the 95th percentile rating. For 95th DBH percentile species-specific analyses, 27,986 trees were examined. Of the 280 taxa analyzed, 31 taxa were present in large enough populations to tabulate within the size classification. Of those 31, eleven qualified for a formal species-specific analysis on whether there is a difference in site type for maximum ob- served stem diameter size In this context, the term overmature is used to draw attention to the lack of trees in a larger category, which infers loss of the species from the inventory on some level. Data were analyzed for those 11 species occurring on all three types of sites using the null hypothesis of: no difference in ter- minal size within species across the three soil types. A one-way ANOVA was used to determine if there was a statistical signifi- cance between the within-species size classes in each site type. Then DBH values within each species were then normal- ized against their associated species maximum for inclusion in the general linear model. This allowed for between spe- cies comparisons despite differences in their species-specific size distributions and expectations, allowing multiple spe- cies to be grouped together into small, medium, and large tree types. As a relative scale, the species were stacked together for a general linear model on size (small, medium, large) and site (pit, strip, non-limited), with an interaction term. There were a total of 41,771 trees examined for analysis in the general lin- ear model. This analysis proved general trends across species based on maximum plant size versus site type. A Bonferroni analysis was done on the interaction data means for DBH. All analysis was conducted in MiniTab 14.1, after the data met all assumptions for statistical analysis and alpha was set at 0.05. RESULTS The 11 species used in the species-specific analysis represented 27,986 trees, or 61.6% of the general database population (Table 1). It was found that in all 11 species that met the requirements for inclusion into the data analysis, site type made a significant difference in maximum observed size. Trees that had more avail- able soil grew larger than trees that had small amounts of soil. All 31 species included in Table 1 were large enough pop- ulations to potentially define a species overmature rating for north-central New Jersey communities. The 31 species used in the general linear model accounted for 41,771 trees or 92% of the total inventory population. Maximum DBH in small, medium, and large trees varied based on planting typologies. The general linear model showed that there was a statisti- cally significant difference (p < 0.001, SD = 18.1) between maximum DBH in small, medium, and large trees in the tree planting typologies (non-limited, planting strip, and tree pit) (Table 3). There was also a statistically significant interaction ©2013 International Society of Arboriculture Table 1. Trees observed in complete urban municipal tree census inventories from 11 communities across north-central New Jersey. A listing of the most common species occur- ring in each size class by planting zone typology, their oc- currence in the data set, and the maximum range observed DBH. Entries in bold italic were used within species-specific analysis, given their occurrence in adequate numbers across all planting typologies. Species Small Acer palmatum Cornus florida Prunus serrulata Syringa reticulata Medium Acer campestre Carpinus betulus Cladrastis kentukea Phellodendron amurense Picea pungens Prunus yedoensis Pyrus calleryana z Sophora japonica Large Acer platanoides Acer pseudoplatanus Acer rubrum Acer saccharinum Acer saccharum Aesculus hippocastanum Gleditsia triacanthos Platanus × acerifolia Prunus serotina Quercus alba Quercus bicolor Quercus coccinea Quercus palustris Quercus phellos Quercus rubra Quercus velutina Tilia cordata Ulmus americana Zelkova serrata 94 0 30 8 30 9 60 43 0 3 5 3 66 8 32 1 32 11 47 4052 14 1404 530 694 49 225 1411 13 9 69 39 1973 36 337 20 332 60 529 z Cultivar popularized and gained rapid, wide adaptation. between site type and species size (p = 0.024). Tree growth varied based on site type. Mean separation by Bonferroni on preplanned comparisons of site-type showed there was a dif- ference in growth based upon apparent available soil. Tree size was different by definition (Table 4). The general linear model exhibited an interaction of site type and tree DBH. The small, medium, and large trees have statistically larger DBH in the planting strips and non-limited soil than in the tree pit (Table 2). DISCUSSION Trees in the urban forest face many environmental stresses that are exaggerated in the developed municipal landscape when compared to their natural system counterparts. In order to dis- cuss stand management, an understanding of species senescence and mortality is needed to define a service life end point. From a budgeting perspective, it is hard to manage an urban forest if you are not aware of the end point of the varied species in the 3304 69 2408 392 1280 89 507 883 618 226 140 262 3358 172 1494 205 551 339 343 0 1 0 1 0 0 136 4 45 263 18 14 6 3 714 24 61 44 62 60 178 165 687 76 0 0 1 8 7 16 87 107 84 304 770 34 Planting zone typology Pit Strip Non-limited
March 2013
| 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
