As some of you know, Ruth Yanai, our most senior (Professor) lab member, is not the greatest at distinguishing leaves of white birch, Betula papyrifera, from yellow birch, Betula alleghaniensis. It slows things down when she has to ask a high school student to verify every leaf.
Pictured on the left are the leaves of a yellow birch tree, and on the right are the leaves of a white birch tree. Could you tell them apart? A white birch leaf is typically wider, and the petiole longer. A yellow birch leaf has a stubby petiole, and is thinner and longer. And white birch leaves have 5-9 veins, while yellow birch has 9-11 veins.
On Saturday, March 24, when Ruth was sorting with Mia, Anna, and Dan, all the birch leaves in sample HBO-4-A1 were turning out to be yellow birch. So she asked Becky, who was Lab Host that day, “Are there any white birch in this basket? This would go a lot faster if I knew there was only one kind of birch!”
Archived on the MELNHE web site, Becky found the data for HBO-4-A1 in 2010, in which there was only 1 g of white birch leaves, but 34 g of yellow birch. However, in 2015, there were 13 g of white birch leaves reported, in addition to 40 g of yellow birch leaves. It’s not surprising that the masses are not exactly the same from year to year (if they were, we wouldn’t be sorting litter every year). But this amount of difference seemed suspicious. The litter baskets are in the exact same place every year, and birch trees can’t move around or change their species.
Fortunately, the 2015 samples were still across the hall in B-6, awaiting transport to the attic of Bray Hall for Long-Term Storage. Becky found the bags from basket HBO-4-A1, and dumped out the bag labeled white birch on the table for us to sort.
The first thing Ruth noticed (remember, she’s not good at distinguishing the birches), was two beech leaves! Everyone can tell a beech from a birch, that’s easy. The rest of the team were able to verify that most of the bag was yellow birch, not white birch.
It’s alarming to find errors from past lab crews, but reassuring that we can find the samples, resort them, and reweigh them. Alex Young, a graduate student, is now making stacked bar graphs of the species in each basket over time to help us determine which samples should be rechecked. The other thing we discovered is that there is no record of who sorted (or rather failed to correctly sort) that basket from 2015. So we won’t publicly humiliate them. We do, now, record in our notes which baskets are processed each day, as well as who was present.
Thanks to Terrance and Ed for finishing with error detection and recovery of basket HBO-4-A1 from 2015 on Sunday, March 25. There were just a few leaves that were correctly classified as white birch by the crew that sorted that 2015 sample, probably some time in 2016. It turned out that they also had some birch leaves in the sugar maple bag. Ruth was proud to report that by the end of sorting the 2017 HBO-4-A1 sample, she, too, could tell a white birch from a yellow birch.
by Becky Rew and Ruth Yanai
Use this for a post about the basket labeling system: