Semester

Summer

Date of Graduation

2014

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wood Science and Technology

Committee Chair

Gregory A. Dahle

Committee Co-Chair

David DeVallance

Committee Member

Jingjing Liang

Committee Member

Mo Zhou.

Abstract

Ever increasing human populations are creating a desire, and more importantly a demand for urban forests due to a disconnection from nature as more of us become urban dwellers. Future trends predict increases in human populations which will substantially increase the amount of urban lands, especially around metropolitan areas. Urban trees are exposed to different loading regimes than similar trees growing in a traditional forest. They do not have protection from wind that is seen in the middle of a forest stand, and wind loading has been suggested as one of the more important modes of failure .;This research investigated how an urban tree withstands environmental conditions and loading during ice, wind, or snow storms. This research is important in terms of preventing cascading effects of localized tree impacts on targets. Flexure modulus of elasticity (MOE) can be defined as an object's tendency to be deformed elastically, or not permanently, when a force is applied to it This research measures flexure modulus distally along the length of the branch as well as identifies key attributes of branch elasticity during different climate periods.;Chapter 2 investigates the potential transitions of MOE of the juvenile pin oak (Quercus palustris) samples using a Dynamic Mechanical Thermal Analysis machine from tree trunk to branch tip. This chapter identifies that there is no difference in branch type (primary or secondary) within the variables of MOE, moisture content percent, slenderness ratio, end diameter, and full length. There is a significant difference between wood densities of the two branch types.;Chapter 3 helps to identify differentiating material properties of flexure MOE of seasonal periodicity between pre-dormant (leaf on) and dormant (leaf off) conditions, as well as temperature fluctuations within seasons. Within each season, half of the samples were frozen to -6.7 C while the other half were kept at ambient room temperature or 21.1 C. Two testing machines were used to measure MOE and subsequently compared to one another. In general, the data obtained from the Fakopp meter calculated MOE higher than the data from the universal test machine (UTM), but had a smaller standard error. The measurements of MOE for temperature and season between the two testing machines were compared and determined to be significantly different using one way analysis of variance of means. When using the UTM and Fakopp, significant differences were found between the cold and ambient temperature, with the cold temperature having a larger MOE. The UTM measured significantly different between seasons, with the dormant season having a higher MOE.

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