Summer on a Shoestring


Research part II & III: Imaging & Grinding
March 23, 2017, 5:21 pm
Filed under: Foliage, Graduate Projects, Uncategorized

So we last left off with green leaf collection efforts out in the field. Since our experimental research plots are in New Hampshire all of our leaves were frozen for transport! They arrived back in Syracuse and were taken out for our next steps! Because we’re looking at how leaves change over time we focus on dry weights and leaf area for this step.

The best way to get consistent weights on leaves is to dry them. So our frozen leaves, after being removed from the freezer, were weighed, photographed (more on this later), and then placed in our oven for drying at 60 degrees Celsius. Depending on the level of moisture in a sample 24-48 hours of drying is generally sufficient. These dried leaves were then weighed and set aside for grinding.

Did you catch that – we took pictures of leaves! One of ways to measure leaves isn’t just by mass, its by area. Specifically, specific leaf area, or SLA, which is defined as the ratio of leaf area to dry mass. The easiest way to get the area is to photograph the leaf, designate a scale for measurement and then count the pixels in regard to that scale. We used a program called ImageJ for this fancy pixel work, and it was not as hard as it sounds.

IMG_5989

Once the pictures were taken they looked like this:

IMG_1622

and then when they were analyzed for area it looked something like this:

imagej

I am focusing on Beech and Pin Cherry leaves and have less than 100 samples but it still took some time. The pictures above are pin cherry leaves that came from tree #1066 (Which I don’t remember shooting but it’s cool to think that when I go back into the plots I might remember some of the tree leaves that I got from that individual tree!)

Alas, all things come to an end, and this was the end of the road for a leaf to remain whole. After coming out of the drying ovens the bags of leaves were crunched up by hand and were then ground up into fine particles for the next step in our process.

We used a small Wiley Mill for grinding, mostly because our samples were less than 5 grams per sample. Whenever we have larger samples they get processed in a much bigger grinder. Ground samples were fed into a funnel in the machine and collected into glass vials that were labelled:

Here’s Dan looking SO excited that I was taking pictures of him.

It took approximately 5-7 minutes per sample with larger samples taking longer both because of their size but also because static electricity becomes your #1 enemy when trying to get little leaf particles off of things. Dan had this fancy tactic of vigorously hitting the wooden pestle (used for feeding leaf pieces into the mill) against the sides of the metal funnel and it made a bell sound. My experience was not as musical!

Once all of our samples had been ground we were ready for the ashing and digesting steps!

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See you next time!

Gretchen

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