34 U.S.). Total solar radiation (kWh/m2 Burcham et al.: Infrared Measurements of Mechanically Induced Voids /day) measurements for the surrounding environs were obtained from the Meteorological Services Division, National Environment Agency, Singapore. The collected data were analyzed using a concurrent, mixed methods procedure in an attempt to confirm and corroborate findings gained from both qualitative and quantitative methods (Greene et al. 1989). The two data types were analyzed concur- rently with equal priority given to each category, and the results were integrated during the interpretation and discussion phase. Qualitative Analytical Methods Individual IR images were processed using the TherMonitor® Reporter System (Thermoteknix 2001) after collection. The temperature span rendered in each image was held constant among images collected at the same time of day, and the cap- tured images were compared visually for obvious differences in stem temperature distributions. The consistent appearance of warm or cool temperature anomalies across space and time was recorded, and these areas were compared with the known internal and external features of the experimental plants. Quantitative Analytical Methods Temperature readings were extracted from the stem surfaces captured by the IR image using two separate techniques. First, temperature data were extracted from longitudinal rectangu- lar transects (10 cm × 5 cm) positioned horizontally central across the stem immediately above the top of the container in order to capture stem surface temperatures overlying the internal voids (Figure 3) similar to Burcham et al. (2011). Statistical representation of these surface temperatures was derived using measures of central tendency, the mean: and mean surface–air temperature differential: ; variability, the standard deviation: distribution symmetry, Pearson’s skewness coefficient: In these formulas, ti of data collection, at point i, tamb ; and . represents the temperature measured represents the ambient temperature at the time represents the mean temperature, and n represents the total number of points within the transect. Second, temperature data were extracted from three longitudi- nal lines positioned equidistant across the measured stem surface (Figure 3). The measurements, obtained at regular intervals of approximately 0.4 cm for D. fragrans and 0.2 cm for S. grande were averaged to combine values into a single column represent- ing the vertical temperature change along a 90 cm gradient. These temperature data extracted from each treatment were plotted against the corresponding stem height for comparison with each treatment’s values offset consistently by +1°C greater than the preceding treatment’s to avoid overlapping lines in the coordinate plane (Figure 5; Figure 6). Subsequently, the linear temperature plots were examined visually for irregularities in trending com- pared with the irrigated control (Plant 2), and individual tempera- ture measurements were compared with the mean surface temper- ature at purposefully selected reference points. These points were selected based on the position of temperature anomalies observed in the infrared images proximal to the introduced voids. Localized ©2013 International Society of Arboriculture Figure 3. Temperature data were extracted from longitudinal rect- angular transects positioned horizontally and central across the stem surface overlying the internal voids (left) and three evenly distributed lines longitudinally oriented along the stem surface (right). deviation from the mean surface temperature ( at this ref- erence point was determined for each extracted temperature line. Statistical Analysis The stem surface temperature (means, standard deviation, skewness) and localized deviation from linear trend among the treatments were compared to the irrigated control (Plant 2) using paired t-tests (α = 0.05). Assumptions of normality and homoscedasticity were checked. Statistical tests were con- ducted in SPSS Statistics 19.0 for Windows (IBM Corp. 2010). RESULTS The two experiments with D. fragrans and S. grande were con- ducted separately between June 15–18 and August 10–13, 2011, respectively. During these periods, diurnal variation in atmo- spheric conditions was typical for Singapore. Daily temperatures had a range of 26°C–34°C and the relative humidity had a range of 65%–86% (Figure 4). On average, the study site received 4.7 kWh/m2 /day of solar radiation during the same periods. Visual evaluation of infrared images captured at 0830h during the two experiments (Figure 5) did not reveal obvious variation in stem temperature among the plants. At this time of day, the tem- perature distributions observed on all treatments were spatially homogenous along the entire stem surface captured by the image. In particular, the stem temperatures above the various void treat- ments did not appear different from the irrigated control (Plant 2). In contrast, infrared images captured at 1830h during both experiments (Figure 6) showed distinct surface temperature anomalies on two treatments. First, a localized area of relatively cool surface temperatures was visible on the plant containing the 3.8 cm void. These low temperatures were strongly associ- ated with both the position and extent of the internal void in- troduced in this plant, and the temperature distributions for the others containing voids did not appear visibly different from the irrigated control. Second, the surface temperature of the non-irrigated control (Plant 1) appeared distinctively cooler and broadly homogenous along the entire stem surface captured by
|
Item Number:
|
|
|
Product Description:
|
|
|
|
|
Price:
|
|
|
Item Count:
|
|
January 2013
| Title Name |
Pages |
Delete |
Url |
| Empty |
Ai generated response may be inaccurate.
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
Enter a description for this bookmark
Your form submission was a success.
Downloading PDF
Generating your PDF, please wait...
This process might take longer please wait
