Hemlocks, Woolly Adelgid, and Fish - Oh My

Hi Everyone,

I was XC Skiing up at our farm in Chester, MA yesterday.  It's pretty high up in the mountains and is much colder than down by Westfield State University.  Ten or twelve years ago, we had an extreme cold snap.  Here at my house in Huntington, the temperatures dropped down around to -11 - -13 degrees F.  As it happened, Dr. Parshall (from the ENVS Department at WSU) had a temperature logger deployed up in the forest, and it recorded (if I remember correctly) -23 degrees F.  

He had the logger deployed as part of an ongoing study of the spread of Hemlock Woolly Adelgid, a deadly insect that kills Hemlock trees.  So far, there is no known control of the insect, and basically, if / when you get it in your forest, the Hemlock trees will be dead within a few years.  So, loggers and foresters are doing preemptive harvests in MA to remove the trees while the timber is still valuable. Dr. Parshall was wondering if extreme cold in the winter can limit the spread of adelgids.  Luckily, so far our hemlock stand does not have the insect...so maybe it does work.  More likely, our stand is just isolated and hasn't been infested yet.

On our property, the hemlocks take up about 3-5 acres.  In this picture, you can see the distinct border between the mixed deciduous forest on the left and the hemlock stand on the right.  Those are White Pines off in the distance on the left, not Hemlocks.  Hemlocks tend to form dense stands and you rarely see solitary trees.  

Here, you can see how dense the hemlocks are in the stand.  It turns out that this is very important to aquatic ecosystems.  These thick, shade-giving trees keep the headwaters of streams cool in the spring time, conditions that most aquatic organisms in our cold-water streams need to thrive.  In fact, there's a nice sized stream in the middle of that Hemlock Stand.

This past fall, one of our graduating seniors, Casey Duggan, did a research project to determine the difference between temperatures in the hemlock stand, the deciduous forest, and an open field.  The goal was to determine how effective the Hemlock stand was at cooling the ecosystem.  Things were about like you'd expect during the day - the hemlocks shaded the area and temperatures were cooler.  Late at night and in the early morning, however, the hemlocks actually held heat in, and that area of the forest was a little bit warmer than surrounding areas and the field, which radiated heat to the atmosphere and cooled off more rapidly.  

That sort of result fascinates me - when things don't match my expectations and pre-conceived notions - and I learn something new.

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