Changes In A Few Miles

This year saw me change assignments at work. The actual location was about 16 miles of road distance from where I’d been, but the “as the crow flies” distance was only around 6 miles. What was interesting to observe was the changes in the mix of species I saw. You see, I crossed a divide.

Here’s where I used to work:
Sargent Ridge
Pretty, right? The water you see in the foreground flows into the Hudson River. On the other side of that ridge? It all flows into the St Lawrence River. This is on the way to the St Lawrence:
river below dam
In the macro sense, there isn’t a lot of difference. You see the same animals, the same tree mix, the lakes have mostly the same kinds of fish, and the same kinds of biting insects. So even though you’re on the other side of a divide, and there really isn’t a big distance, there wouldn’t be any other changes. Which turned out to be not quite true.

On the Hudson side, the most common undergrowth brush was this plant:
Hobblebush
It’s locally known as “hobblebush.” It’s scientific name is Viburnum lantanoides. The reason it’s known as “hobblebush” is it’s habit of putting new roots out of its stem, and forming a rather impenetrable tangle. On the St. Lawrence side? This plant:
Gray Dogwood
It’s Gray Dogwood, or Cornus racemosa. Like the hobblebush, it also roots out of stems, and forms impenetrable tangles. Both are found on either side of the divide, but they switch places. You can find a small patch of rather scraggly looking plants of one, while the other is all over the place.

Another difference I saw was the dragonflies. On the Hudson side, the predominate dragonflies were skimmers (chalk-fronted corporals) or darners. On the St. Lawrence side? The skimmers weren’t very common, an occasional darner, but a lot of clubtails and baskettails.

Why the difference? I don’t know. That’s the fun part. There doesn’t seem that there should be a difference, except where the water ends up. They’re much the same geology, same soil types, same trees, and the same verterbrates. There’s not a lot of distance between them, and the ridge isn’t all that high. Yet, for some reason, there are changes. I may never know why, but it just goes to show that you can always be surprised.

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10 Comments

Filed under Parks, Science

10 responses to “Changes In A Few Miles

  1. Looks like Darwin’s natural selection theory at work. Even in areas so close to each other the slight change in vegetation can effect the mutations of dragon flies species. How neat that you captured this.

    • Not quite. :lol: These are actually rather common dragonflies, just of different families. What makes it interesting is that there’s not a huge barrier to any of them migrating over to the other watershed, in fact a couple of hundred yards puts you on one side or the other. I’m something of a dragonfly maven (my nickname at work is “the bug guy”) and I’d never seen a clubtail in my previous work locations. So suddenly seeing them made me sit up and take notice.

  2. see above

    Is it possible it could be related to what the glaciers left behind, how deep or shallow or the composition of the soil. I know from gardening that even on my plot of land the soil varies greatly from one site to another. I loved seeing the wild varieties of plants I grow here in MN on my litlle plot that I try to keep as natural as possible

  3. aquagranny911

    Cool diary! You do live & work in a very beautiful environment. We find the same type of things here in the desert where certain species of cactus will only grow in certain places not separated by much but a few feet of elevation or a bare inch of rainfall.

    I loved your talk of the dragon flies. We only started to have them here after we put in our small fish pond. Last summer one actually landed on my hand for just a brief moment. So beautiful, so delicate. I will have to go look up the ones that you mentioned.

    I’m so glad you have more time for diaries now.

    • Just click on the links, and you’ll see pictures of them. ;-) Unfortunately, my current camera isn’t up to taking pictures of them, unless they’re staying still for longer than a few seconds. Since my wanting to take a picture usually means “out of here!” I don’t have any. That’s when I remember to carry it in the first place. :roll:

      • aquagranny911

        I do ♥ you Norbrook for inspiring me to do some research on dragon flies. Here is a link which I don’t know if it will post because I’ve never tried to post a link here but I will try:

        http://www.azdragonfly.net/species/western-pondhawk

        This is our local species which seems smaller & more delicate than the more robust ones from your area. They seem to be tough little survivors finding water where ever they can but now I do know their name “Western Pondhawk” which is very cool.

        • aquagranny911

          I forgot to add that after this research I now know that the dragonfly who landed on my hand so briefly was a female pondhawk. Gracias!

        • They come in many sizes, we have some that are pretty small. The darners are the largest of the group. The damselflies (mainly bluets) are even more delicate. They’re one of the older orders of insects. The nymphs have a really neat (gruesome, but neat) jaw structure to capture prey.

  4. Vic78

    My guess is that life is good where they decided to settle. There could have been a truce. I’ll stay on my side and you’ll stay on your side. There could’ve been a conflict over territory in the past then decided there’s enough of this river for everyone to eat. I don’t have any theories to explain the plants.