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BOB SIMONSON, Program Leader I&M Home << Stress Detection Summary << Test ResultsBob Monk, Project Leader |
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San Dimas Technology
& Development Center
444 E Bonita Ave
San Dimas, CA 91773
(909) 599-1267
TEST RESULTS
The results of the evaluation were tabulated and comparisons made of the results with and without the glasses. Each day was broken into five time periods to evaluate for sun angle. Data was also separated by direction of viewing (north, east, south, or west) and further segregated by the location of the sun to the observer.
Observations by time period
The data represented in Figure
1 (next page) indicates that in the first two days there were more changes
observed with the glasses than without them. This appears to reverse for the
last two days where changes observed without the glasses exceeded changes
observed with the glasses. This indicates that the glasses do aid initially
in the detection of stressed plants and are better than the naked eye. Of
the 10 time periods in the first two days the changes detected with the glasses
exceeded those without the glasses 8 out of 10 times. In the last two days
the changes detected with the glasses exceeded those without the glasses only
1 out of 9 times.
The differences in the first two days compared to the last two days can be explained by how the glasses work. The glasses make green vegetation appear gray or black but make yellows and orange brighter. This would make the vegetation with diminished chlorophyll appear bright orange. Brown or gray vegetation is not enhanced by the glasses. Therefore, over a period of time, the vegetation that initially appeared bright when it is stressed later blends in with the darker colors that the glasses turn the green vegetation.
| CHANGE OBSERVED BY TIME PERIOD | ||||
| Without glasses | With glasses | |||
7/14 to
0900 |
2 |
6 |
||
to 110 |
19 |
21 |
||
to 1400 |
41 |
55 |
||
to 1530 |
25 |
36 |
||
to 1700 |
65 |
58 |
||
7/15 to
0900 |
83 |
75 |
||
to 1100 |
90 |
103 |
||
to 1400 |
201 |
224 |
||
to 1530 |
26 |
30 |
||
to 1700 |
71 |
92 |
||
7/16 to
0900 |
170 |
170 |
||
to 1100 |
256 |
252 |
||
to 1400 |
293 |
236 |
||
to 1530 |
127 |
113 |
||
to 1700 |
65 |
80 |
||
7/17 to
0900 |
129 |
106 |
||
to 1100 |
318 |
279 |
||
to 1400 |
341 |
313 |
||
to 1530 |
245 |
223 |
||
to 1700 |
0 |
0 |
||
| Figure 1. Each day was divided into 5 periods. Due to work schedules of the participants it was not feasible to get the same number of samplings in each time period. Though the data with and without glasses is directly comparable within a time period on a given day, no comparison should be made to data between time periods. Numbers represent the total tally of assigned values (0, 1, or 2) related to observed changes in a time period. | ||||
Sun angle in relation to
observer
The data represented in Figure 2 (next page) indicates that when wearing the
glasses there is little difference between facing the sun and having the sun
at your back. However, discussion with the samplers indicates that the brightness
of the color difference is more intense when the sun is at your back.
| SUN ANGLE IN RELATION TO OBSERVER | |||||||||
| Facing the sun | Sun behind | Sun overhead ** | Sun to side (left or right)* | ||||||
| East AM | West PM | West AM | East PM | NESW Midday | So/No AM | So/No PM | |||
| 7/14/2003 | Without | 5 |
19 |
4 |
19 |
10.25 |
6 |
26 |
|
| With | 5 |
21 |
8 |
20 |
13.75 |
7 |
26.5 |
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| 7/15/2003 | Without | 36 |
25 |
46 |
19 |
50.25 |
45.5 |
26.5 |
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| With | 41 |
28 |
44 |
28 |
56 |
46.5 |
33 |
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| 7/16/2003 | Without | 99 |
46 |
109 |
48 |
73.25 |
109 |
49 |
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| With | 91 |
44 |
114 |
43 |
59 |
108.5 |
53 |
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| 7/17/2003 | Without | 109 |
60 |
112 |
63 |
85.25 |
113 |
61 |
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| With | 94 |
54 |
94 |
54 |
78.25 |
98.5 |
57.5 |
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| * Total divided by 2 because of 2 directions. | |||||||||
| ** Total divided by 4 because of 4 directions. | |||||||||
| Figure 2. The data was segregated by time periods of daylight hours with samplings up to 11 o’clock representing AM and samplings after 2 o’clock representing PM. From 11 to 2 o’clock is considered midday where the sun is overhead. Since the stress in the treated plants increased as time passed each day, the data between AM, midday, and PM are not comparable. What can be compared are the data within the same time period by direction and the data with and without glasses within the same time period and direction. | |||||||||
Because the stressed plants changed over time it is not reasonable to compare the midday readings with other data taken at different times. What this information shows is that during the initial stages of plant stress (first two days) there is a better chance of detecting stress with the glasses.
The data indicates that having the sun at the side increases the chances of observing plant stress compared to either facing the sun or having the sun at your back. This does not appear consistent with the verbal opinions of the observers. This difference is probably attributable to layout of the plants being sampled. The east/west axis of the layout was approximately twice as long as the north/south axis. This probably caused screening of some plants by others in front of them. The layout of the plant groups is indicated below.
| North |
|||||
Group
A |
Group
B |
Group
C |
Group
D |
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West |
East |
||||
Group
E |
Group
F |
Group
G |
Group
H |
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South |
|||||
Follow-up field evaluation
The SDTDC testing of stress detection glasses was on small plants.
In essence all observations were looking straight ahead or down. What differences
would there be when looking up into a tree canopy? The San Bernardino National
Forest was visited and the glasses were evaluated on trees affected by drought/bark
beetles.
Small tree at eye level
Stress detection glasses increase the color contrast of dead/dying foliage. Looking toward the sun reduces the contrast. Viewing with the sun to your back makes the color contrast of dead/dying vegetation the brightest.
Large trees looking up
Looking up into crowns at a 30 to 45 degree angle is similar to the results at eye level. However, when the sun is higher in the sky the contrast is reduced if looking at the tops of the trees. This is probably because you are again looking toward the sun.
Landscape scale viewing
On a landscape scale, dead/dying trees really stand out compared to the naked eye. When the glasses are removed the trees can still be picked out, but not as easily. The stress detection glasses could be very useful when trying to estimate mortality at long distances, such as from ridge to ridge.
General observation
The stress detection glasses
will help pick up changes to the color of the foliage. As needles or leaves
start to fade before normal cast-off they become very evident when using the
glasses. Insect damage such as needle miners becomes a lot more evident. Trees
exhibiting chlorotic foliage from mineral deficiency or disease will appear
brighter through the stress detection glasses.
Just because there is an observable effect does not necessarily mean that a tree is dying. The stress detection glasses could be useful in helping detect possible mortality during the early stages of bark beetle or other insect attack. However, they should only be used to draw your attention to the possibility of a problem. The tree should not be designated for removal based on the stress detection glasses alone. Closer inspection should be used to determine what is causing the color change.