Summer on a Shoestring

Going with the flow
July 27, 2018, 1:13 pm
Filed under: Uncategorized

Hi there!! My name is Ari Libenson and this is my blog post about my summer research project measuring sap flow and some of the tribulations that I have faced.

When my crew-mates and I aren’t off adventuring in the White Mountains or playing hide-and-seek with our house pet/Beanie Baby, named Scorpie (see below: “Diary of an Introverted Scorpion”), we are nose-deep in our research projects. By using the phrase “nose-deep,” I mean this literally as well as figuratively as some of our projects (i.e. digging soil pits) require us to get down and dirty. My project, however, is a relatively clean one considering the fact that I am basically studying the movement of water. More specifically, I am measuring the movement of xylem sap within trees in order to determine whether nutrient additions (nitrogen, phosphorus, or calcium) impact this process.

To measure sap flow, I use the Granier Method to quantify the flux of sap through a tree. This method works by measuring the temperature difference between two probes (together they make a sensor) inserted into the tree one above the other. The bottom probe is the reference and above it is the heated probe, which receives a constant amount of heat. As sap flows through the xylem, it cools the heated probe. The temperature difference between the heated and reference probe can then be converted into sap flux using a computer software called BaseLiner.


Granier method set-up (Lu et al., 2004).


One of the sensors installed into a tree!

While my project may not be quite as dirty as digging massive holes in the ground, it has not all been smooth sailing. One of my greatest struggles coming into this project was learning how to build the sap flow sensors, which also required learning how to wire. In order to make the sensors, I first had to build the probes.


The probes connected together to make a sensor.

This process entailed cutting off the pointy end of a hypodermic needle and inserting a pair of wires, called a thermocouple, all the way through the needle shaft. Having had no previous wiring experience of any kind, the only thing I could compare this to was sewing. If you’ve ever sewed before, you likely know the frustration of trying to thread a needle. Now imagine that on steroids. That’s what it was like trying to gently force those feebly thin strands of wire through the needles. And I thought I was out of the woods once I finally achieved that feat. How naïve I was. I quickly came to realize that even though I may have successfully threaded the needle, that wasn’t a guarantee that the probes would actually function. After all that effort, I had to throw away several probes that either had a faulty connection or a lack of connection between the wires. Such is the world of science: it is tedious and at times, quite monotonous, but occasionally it comes together in the end. Currently, my sensors are all up and running in the field after two full days of instrumenting trees at one of our Hubbard Brook stands.


All of the interns about to carry 50 lb. batteries into the field!


Alex Rice hard at work connecting sensors to the data-loggers.


I even roped my brother, Jonathan, into helping install sensors.

Looking back at all of the work that was put into this project, including all of the invaluable help from my fellow crew-mates and crew-leaders, I am so happy with how far it has come. I finally have sap flow data to analyze!!!



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