Arboriculture & Urban Forestry 39(1): January 2013 significantly greater than that measured on the irrigated con- trol (Table 2). In contrast, none of the remaining treatments ex- hibited linear temperature trends with anomalies of a similar magnitude, and the linear temperature deviation measurements for the remaining treatments were not significantly different from the irrigated control. In addition, the linear temperature trend for the non-irrigated control exhibited obvious unifor- mity compared with the irrigated control. Its linear trend most closely approximated a flat line in the evening, while the ir- rigated control and other void treatments exhibited a gradient of progressively cooler temperatures at the base of the stem. DISCUSSION In both experiments, stem temperature anomalies were exclu- sively observed on stems containing 3.8 cm internal voids, and this anomaly was only apparent at 1830h in the evening. In the IR images taken at this time, obvious areas of relatively cool temper- atures were consistently observed on stems containing the largest 37 Figure 6. IR images taken in the evening revealed abnormal temperature reductions near the 3.8 cm internal void position in both experiments. Basal temperature gradients of progressively cooler temperatures were observed on all plants except one, the non-irrigated control, which presented a comparably cool, vertically homogenous temperature distribution. These observations were sup- ported by a sharp deviation in the linear temperature trend near the 3.8 cm voids and the relatively flat trend line for the non-irrigated control, respectively. In the line graph, each treatment's values were offset consistently by +1°C greater than the preceding treatment's to avoid overlapping lines in the coordinate plane. Note: The dashed horizontal reference lines show the modified treatment mean surface- air temperature differential, vertical reference line denotes the purposefully selected refer- ence point, solid zero line represents the point at which unmodified treatment surface temperatures and ambient temperatures are identical, and the error bars (± SD) illustrate the observed variability in surface temperature at regular intervals. voids, while the stem temperature distributions for the remain- ing plants were not obviously different from the irrigated control. In addition, these temperature anomalies were visibly associated with the internal void position as well as its general extent. Under the experimental conditions, these observations suggest that the infrared camera can be used to identify the existence, position, and broad extent of internal defects in the absence of external symptoms, but this diagnosis may only be possible in cases where stems contain relatively large areas of degraded tissue exceeding 76% stem cross-sectional area. It is important to note, however, that these results need to be corroborated with measurements of mature trees due to the important changes in size, shape, and anatomy during growth and development. Moreover, these results clearly show the time of day at which the technique is applied sig- nificantly affects its diagnostic accuracy. When evaluated in the morning, there was no useful basis for differentiating between any of the treatments, but the temperature distribution exhibited by the stem with the largest void was clearly distinct in the evening. In both experiments, the sta- tistics derived from longitudinal rectangular transects did not fully corroborate the image evaluation process. Within each experiment, mean temperatures exhibited by the non-irrigated control and the plant containing the 3.8 cm void at 1830h were relatively cool com- pared with all other treatments. However, none of the mean values in this experiment were signifi- cantly different from the irrigated control. In addition, mean temper- ature values representing the same treatment applied to different spe- cies were inconsistent. Notably, the average temperatures exhib- ited by the two plant species’ ir- rigated controls were not the same at either time of day. The average surface-air temperature differen- tial in the morning and evening for D. fragrans Plant 2 registered -0.23°C and -1.58°C, respective- ly, while the same measures for S. grande Plant 2 were -0.78°C and -0.32°C (Appendix). Comparable interspecific variability in statis- tics representing surface tempera- tures within rectangular transects was observed between the stems containing the largest void in both experiments. While the D. fragrans stem containing the 3.8 cm void was, on average, 0.13°C and 1.62°C below ambient tempera- tures in the morning and evening, respectively, the same treatment applied to S. grande registered 0.58°C and 0.81°C below ambient temperatures at the same times of ©2013 International Society of Arboriculture
|
Item Number:
|
|
|
Product Description:
|
|
|
|
|
Price:
|
|
|
Item Count:
|
|
January 2013
| Title Name |
Pages |
Delete |
Url |
| Empty |
AI Assistant
Ask anything about this document
AI is thinking…
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. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
