Independent Research Task Ben MacDougall 2013
Title: Does soil moisture affect the sap flow of a tree?
Abstract: The hypothesis to this experiment was that soil moisture would affect the sap flow of a certain tree. Recording of data, followed by sorting and analysing data gave opportunity to create graphs to test this hypothesis. Due to the graphs from the data collected from ICT International, it is clear that soil moisture does not affect the sap flow of a tree.
Introduction: I undertook this experiment from influential advice from MrDerrin about new technology being used to record data of the sap flow occurring in trees by ICT International. Experimenting with this new data appealed to me and I thought that it would be interesting dealing with data recorded locally, hence the reason I undertook this experiment.
Aim: The aim to this experiment is to successfully see whether soil moisture around a certain tree affects its sap flow.
Method: The method I undertook for this research task involved;
• I approached MrDerrin, telling him I was willing to undertake this experiment which led to us engaging in conversation on what the experiment was about, how I would achieve the experiment, and once done the experiment, what would possibly be the results.
• Once the data from ICT International was available to me, I downloaded the data for Sap Flow and Soil Moisture. Reading through this data gave me an idea of how to approach sorting the data and I became familiar to the data, making the whole experience much more comfortable.
• When sorting through the Sap Flow Data, I had to delete the majority of the data so that I was only left with the Date (to find where the days start and how many days. This data was not in the results), the time, and finally the Sap Flow (dependent variable) In (kg/hr).
• Now that I had only the data that I needed, I downloaded the Soil Moisture Data from the ICT International website. As the previous step, I went through and deleted a lot of the data that I did not need. This time I was only left with the date, time and Chan1 (VSW%) which was the data from a soil moisture probe measuring 30mm under ground (independent variable).
• I now had two sets of data that I wanted to compare (soil moisture & sap flow). To do this, I had to select a 5 day period from the data. In order to have the same 5 days for each
data set, I had to make sure that this five day period was recorded for the same five days to the opposite set of data. Once I’d found a 5 day period that was suitable, I needed to put the data side-by-side. There was a problem in doing this however; some data was recorded multiple times or not enough times. The data was supposed to be recorded every 15 minutes but sometimes it was recorded every 3 minutes or every 120 minutes. To overcome this issue I had to manually go through each entry of data and delete any unnecessary data entries and adding more if needed. Once the data lined up perfectly, I was finally able to compare the Soil Moisture to Sap Flow and make a conclusion on whether they have any correlation.
• To see whether there was any correlation between the sap flow of a tree with the soil moisture around the tree, I made a line graph. The graph included the time, sap flow (kg/hr) and the soil moisture all in the exact same time frame of 5 days.
• Having a complete graph, I was able to draw conclusions from the two sets of data; whether there was a correlation between them or not.
• For more accuracy, I repeated the steps of sorting through data and aligning the data with a new set of 5 days. This gives more repetition in the experiment, making my final results more reliable.
• Now that I had the data, I drew conclusions from the data, referring to my hypothesis to see whether I was correct or not.
Above: Data entered too regularly. This is an example where I had to delete unnecessary data entries.
More needed on how the sap was actually collected, what do the probes look like and how do they work? Where are the trees located?
Above: My two graphs, taken from two different lots of 5 days.
Results:Data Set #1! ! ! !
Data Set #2
These are the two sets of data collected over 5 days. This data was collected from the ICT International website and then rearranged by deleting unneeded data. These two data sets are very similar in their appearance. They both have 5 major peeks in the sap flow recording which represent a day. At approximately 18:00:00 - 18:30:00 the sap flow decreased rapidly. At approximately 07:00:00 - 07:30:00 the sap flow rapidly increased. This shows a direct relation to day time and sap flow. In day light, stomates on a tree open up, releasing oxygen into the atmosphere. This oxygen is a waste product of photosynthesis. Photosynthesis can only occur when there is sun light, so as the results show, when the sun is not shining there is no photosynthesis occurring hence not as much
sap flow compared to the sap flow amount during the sunlight (day). The difference of sap flow from light to no light is around 1.5kg/hr which is significant when looking at the graph.
The blue line on the graph represents the soil moisture probes that are in the soil around the tree that has had the sap flow monitor attached. The first set of data has recorded soil moisture from 120mm into the earth and the second set of data recorded soil moisture in the earth 30mm. Both the soil moisture probes recorded data looks similar however, data set 1 and 2 were recorded at different times. The fact that the data tells me the same thing twice at different times ensures the reliability of the data by repetition.
The data distinctly shows that there is absolutely no correlation between sap flow and soil moisture. We can see this because the soil moisture has a mostly linear line that does not react at all with the sap flow line, yet the sap flow line has a distinct pattern for each day but yet does not relate whatsoever to the soil moisture.
Getting data over a greater period of time might have provided more accurate results
[Original tabulated data located at the back of report]
Conclusions: After collecting and analysing two sets of data, I can say that with this particular tree soil moisture does not affect sap flow. This contradicts my hypothesis of soil moisture would affect sap flow.
Second-Hand Research:
Downloads of similar experiments from ICT International to get an idea of how to approach and complete the experiment and task. (Whole report)
MrDerrin’s knowledge and research that he has conducted and passed onto myself.
Example of a final report:
Tree Physiology 21, 589–598 © 2001 Heron Publishing—Victoria, Canada
Information from wikipedia including information on Stomates. (Results)
Acknowledgements:
MrDerrin for his extensive help and support towards me in carrying out this experiment and research task. ICT International and Dr Peter Cull for the access to their new technology in soil moisture probes and sap flow data loggers which gave me the data to do this research task.