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Trust Me, I’m an Engineer… in the Forest.


Wednesday, July 12, 2017, by Valentin Degtyarev
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When you think of someone who is in the field of Computer Engineering, you picture someone who sits indoors in their little cubicle, working with a computer all day. Even when you Google search a computer engineer, you are only shown pictures of geeks like me working indoors, sticking their hands in the complicated wiring of a computer system. That’s more or less what I expected to be doing with the rest of my life when I made the decision to take this career path. Next thing I know, I get hired to do research for Harvard Forest where I will be applying my skills on some sort of project outdoors.

[Tram tower. Photo by Valentin Degtyarev] “So what do you even do here?” is a frequently asked question by other fellow researchers at Harvard Forest. So far this summer, I have been guided by my two mentors Paul Siqueira, a professor at UMass Amherst, and Xingjian Chen, a Ph.D. student also at UMass Amherst. I have also been working alongside with Corey Carter, an undergraduate student from the University of Minnesota. My project focuses on tracking the process of plants absorbing water through their roots and then giving off water vapor through their leaves, otherwise known as transpiration. Over the past couple of years, some of the researchers at Harvard Forest have engineered a tram system which would automatically monitor the water content of the local forest. This tram is a large plastic box that moves back and forth along fifty meters of metal cable held up by two tall towers. The towers are tall enough to make sure the cables which the tram travels on are hanging over the tree canopy. The inside of the tram box has been loaded up with a series of sensors which collect data and send it back to the central base station computer, located at the bottom of one of the towers.

 [Val holding five Sap Flow Sensors. Photo by Jolene Saldivar]One of the new sensors being implemented inside of the tram is called the Ground-Based Synthetic Radar. The goal of this radar system is to measure the water content of the trees within its proximity. In order to verify the accuracy of the data being collected by this radar, we would have to find a different way of measuring the water content of the trees. This method of verification is what I have been assigned to work with during the summer. Because water will at one point travel through the trunk of the tree, the flow of sap within the trunk would have a direct correlation with the amount of water being passed through it. By using simple, custom-built hardware called the Sap Flow Sensor System, we could take measurements of the sap flow within a tree and obtain an image of what the water content looks like. A Sap Flow Sensor is a small circuit board that takes temperature readings from the tree it’s stuck to and converts them into a digital signal so that the computer is able to read the data. The temperature is taken by two different probes, or little needles that get stuck in the tree. One probe reads the standard temperature of the tree, and the other one has a thin, metal wire coiled around the needle so that it gets heated up inside the tree as current flows through it. Then by plugging in the two collected values of the temperature into a formula, you can obtain the sap flux density, a value used to determine the flow of sap through trees.

     The Sap Flow Sensor System for this project has been in development for the past few years by previous generations of undergraduate students working at Harvard Forest. They have developed a couple of different models which all successfully measure the sap flow in a single tree. However, there are several improvements which could be made to the most recent model. My partner Corey and I took some of these issues into consideration and decided to split the project into two essential roles. Corey decided that he would work on major improvements to the old software to make data collection more automated, while I decided that I would fix and improve the hardware and circuitry of the system.

     The main issue with the old hardware which I hoped to fix first was the method of supplying power to the entire system. We all know that batteries lose their charge over time. The battery which was used before did not have a way of being charged, which resulted in the whole system losing power every couple of days. This required the team to drive out fifteen minutes into the forest, charge the battery over a couple hours, and reset everything. To fix this issue, I decided to use a continuous source of power from the battery bank at the bottom of the tower which gets recharged by the solar panels on top of the tower. We know the tower will not run out of power, so the data would consistently be collected for a very long time. [Photo of one Sap Flow Sensor with two temperature probes. Photo by Valentin Degtyarev]Another advancement to the Sap Flow Sensor System would be the use of multiple Sap Flow Sensors. I have built additional sensors which could be placed in a waterproof box, mounted to a tree, and then deployed in the forest. We hope to put nine sensors in a 3x3 grid formation in the forest, with twenty meters of cable in between each sensor. Each one of these sensors will collect data from the tree it is attached to and report back to the central computer. By measuring nine different trees instead of just one, we would produce data with higher accuracy.

     These improvements are still being worked on, but they are coming along very nicely. Along the way, we have hit a couple difficult roadblocks which prevented us from moving on for a few days at a time. One of these roadblocks was when we first started placing our circuitry outside, components would break as soon as we hooked everything up. This kept us stuck in the same place for two whole weeks. With plenty of troubleshooting and redesigning, we managed to overcome these issues and continue our task of improving the system. With these new improvements to the Sap Flow Sensor System, Corey and I hope to produce a consistent and accurate method of collecting data. This data will help verify the results obtained by the Ground-Based Synthetic Radar which will be an easier method of measuring the water content of the forest around it. By the end of this summer program, we hope that what we have worked on can be used by other researchers in the field of ecology.

     In the middle of the forest, where there is no phone signal, no Wi-Fi, and ticks crawling up your entire body does not sound like the ideal place to be working. However, this summer has been an amazing experience where I could just relax on top of my tower under the sun with a nice cool breeze and enjoy the sounds of birds chirping all around as I do my work. Regardless where I go in the future, Harvard Forest has shown me that there is more to computer engineering than just circuits and programming. It showed me that you never know where your career path will take you. Maybe my next workplace will be under water not far from a tropical island? Or maybe off the side of the steepest cliff in the world?

 

Valentin Degtyarev currently attends the University of Massachusetts, Amherst and is studying Computer Systems Engineering.

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