Temperature

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Methods / Materials:

            The temperature was measured with sensors called “ibuttons.”  Seventeen ibuttons were buried at the beginning of the study.  About halfway through the study an additional seven ibuttons were buried, making a total of 24.  In order to make retrieval easier, the ibuttons were placed in a wire cage and tied to a nail.  Seven were buried along each fence, five were buried along “wood road,” and five were buried along “metal road.”  They were buried approximately 0.2 meters from the fence or road and 1.2 meters apart.  These are similar locations of the natural turtle nests.  The ibuttons recorded a temperature reading every hour for the entire time they were in the ground (July 7, 2006 – July 26, 2006).  After their retrieval, the ibuttons were read using the program “ibutton – TMEX.”

 

Results:

            Of the total 24 ibuttons buried 16 successfully took the temperature of the soil for the duration of the study.  One ibutton failed and the seven ibuttons buried halfway through the study were incorrectly formatted:

Location	Successful	Incorrectly Formatted	Failed	Total
Wood Fence	5	2	0	7
Wood Road	3	1	1	5
Metal Fence	5	2	0	7
Metal Road	3	2	0	5

Figure 1

The data from each ibutton was averaged to find the mean temperature for each of the four test sites:

Location	1st ibutton	2nd ibutton	3rd ibutton	4th ibutton	5th ibutton	Mean Temperature
Wood Fence	22.4° C	22.7° C	24.4° C	23.9° C	24.2° C	23.4° C
Wood Road	25.7° C	25.2° C	25.3° C	----	----	25.4° C
Metal Fence	21.4° C	22.5° C	22.2° C	23.0° C	22.9° C	22.6° C
Metal Road	25.4° C	25.1° C	24.8° C	----	----	25.1° C

Figure 2

The data from the ibuttons was then graphed to show how the temperature changes over the course of one week.  To show this the week of July 9, 2006 to July 15, 2006 was chosen as a sample week.  This week was chosen because of the variation in the weather patters.  The 9th, 13th, and 14th, were sunny or partly cloudy and the rest of the week was rainy (www.weatherunderground.com 2006).  The highs in air temperature ranged from 30 to 22° C (www.weatherunderground.com 2006).  The mean temperature was found for every twenty four hours of data for the sample week, along with the mean air temperature for each day of the week:

 

 

 

 

Date	Air Temp   (° C)	Wood Road ibuttons (° C)	Wood Fence ibuttons (° C)	Metal Road ibuttons (° C)	Metal Fence ibuttons (° C)
9-Jul	21.0	25.5	24.0	26.4	22.5
10-Jul	22.0	25.9	24.2	26.6	22.5
11-Jul	21.0	24.6	22.7	24.0	21.8
12-Jul	20.0	22.2	20.8	22.3	20.4
13-Jul	23.0	23.9	22.9	23.7	22.0
14-Jul	25.0	25.5	24.3	25.2	23.3
15-Jul	22.0	25.3	23.5	24.8	22.9

Figure 3
This information was then graphed to show the temperature change throughout the week:

Graph 1

To determine how the surface structure affects the daily fluctuation of temperature a temperature graph was made showing the average temperature of each hour in a sample day.  The day chosen as the sample day was July 9th, 2006.  It was chosen because it there was no precipitation and there was a high degree of change between the maximum and minimum air temperatures.  The maximum was 27° C and the minimum was 12° C.  The mean air temperature was 21° C.  The hourly air temperature change was compared to the hourly soil temperature change at each of the four areas used in this study:

Air Temp (° C)	Wood Road ibuttons (° C)	Wood Fence ibuttons (° C)	Metal Road ibuttons (° C)	Metal Fence ibuttons (° C)
16.7	21.7	24.2	23.8	20.2
15.6	21.2	23.8	23.5	19.7
15.0	20.7	23.2	23.2	19.7
13.9	20.3	22.7	19.8	19.1
13.9	19.8	22.4	19.2	18.9
16.7	20.2	22.0	19.5	19.3
19.4	20.8	21.5	20.3	19.7
21.7	22.2	21.3	22.3	20.6
23.3	24.5	21.3	24.8	21.3
25.0	26.3	21.3	27.3	22.6
26.1	27.8	21.6	29.8	24.4
26.7	29.7	22.4	31.5	25.5
27.2	30.3	23.3	33.5	26.4
27.8	32.3	24.5	34.3	26.2
26.7	32.8	25.5	34.3	26.2
27.2	32.7	26.1	33.7	26.4
25.6	30.8	26.8	31.8	25.2
25.6	28.7	27.0	29.7	24.4
23.9	28.2	27.0	29.0	24.2
21.1	26.7	26.8	26.8	23.2
20.6	25.0	26.4	25.0	22.3
18.9	24.3	25.9	24.0	21.8
18.9	23.5	25.3	23.2	21.6

Figure 4

 

 

 

This data was then graphed to show the daily variation in temperature:

Graph 2

Discussion / Conclusion:

            Figure 2 indicates how each area affects the average soil temperature.  This chart shows how the highway causes the soil to become hotter.  It can be seen that the mean temperature along the road is greater than 25° C and the mean temperature along each fence ranges from 22.5 to 23.5° C.   This two degree difference can dramatically change the sex ratio of the turtles.  Snapping turtles have reported to have a dramatic difference in the sex ratio when the temperature of the nest was changed from 25.8° C to 23.9° C (Kolbe 2002).  Painted turtles’ sex ratio shifts when the temperature changes from 26.6° C to 24.5° C (Kolbe 2002).  This means that snapping turtle nest located along the road are likely to have a large percentage of female hatchlings, and conversely, the nests built near the fences are likely more male hatchlings.  The painted turtle nests near the road are predicted to be biased toward the female sex, while nests near the fences may produce a large number of all-male nests.
            The change in temperature from day to day, as shown in figure 3 and chart 1, displays how each area reacts to the weather patterns.  The two roadways consistently have higher temperatures then the two fences.  This difference between the air and soil temperature at the two sections of road ranges from 0.5° C to greater then 4.0° C.  As the air temperature increased between July 13, 2006 and July 14, 2006 from 23.0° C to 25.0° C the soil temperature also increased at a similar rate.  However, from July 14, 2006 to July 15, 2006 the air temperature dropped back to 22.0° C.  This drop was not mimicked by the soil at either of the roads.  The failure of the soil to cool is a result of the surface material.  The pavement acts to heat the soil during hot days and may also prevent the soil from losing that heat during cooler days.  This is the reason why the soil around the road is warmer than in other places.  The fences, however, do appear to mimic the air temperature but do not show such dramatic shifts in temperature.  This is because of the delay between the shift in air temperature and the time it takes for the ground to adjust.  It can also be seen that the wooden fence is slightly warmer then the metal fence.  This in contrary to what was expected.  It is believed that this happened because of the location of the ibuttons relative to the fence.  The ibuttons were buried on the eastern side of the fence.  Because the sun rises in the east, they received sun all morning and through the hotter parts of the day.  The shadow that was expected to cool the ibuttons and cause the temperature to be lower was not present until the sun was setting.  This means the effects of the shadow worked synergistically with the cooling of the air and therefore did not act have as large affect on the soil temperature as was predicted.  The weekly data indicates that nests on the road for both painted and snapping turtles have a larger probability of producing female hatchlings and the nests closer the fences may have more male hatchlings.  If, however, the turtles construct their nest on the eastern side of the wooden fence, as is expected, it is possible for them to have more female hatchlings then they would by the metal fence.

            The hourly change in temperature, shown in figure 4 and graph 2, displays the fluctuation of soil temperature through a single day.  It can be seen that as the air temperature rises, the soil temperature by the two roads rises at a faster rate.  This is because the pavement on the road absorbs a large amount of the sun’s energy and transfers it to the soil.  The dark color of the pavement causes the soil to heat faster and to higher temperatures than it would in other places.  Because the fences do not have a surface material similar to the pavement, they do not retain such a large amount of heat.  The metal fence has a smaller delay time between the shift in air temperature and the shift is soil temperature than the wooden fence.  One explanation for this may be because the metal is conducting heat into the soil during the hotter parts of the day and is conduction heat out of the soil during the cooler parts of the day.  The daily change in temperature shows once again that the roads tend to have warmer temperatures then the fences.  It also shows that the roads fluctuate more.  This constant change in microclimate may cause the hatchlings to be unhealthy.  The fences have the smoothest transition from one extreme to the other.  This means that there is not sudden rise or drop in temperature and therefore the microclimate will be more stable.  The hatchling from these more stable environments will be healthier and have a high chance of survival.