Tom's Blog

Wednesday, September 8, 2010

Our wetland and the dam beavers!

The spring burn that the U.S. Fish & Wildlife Service carried out on the wetland in our area (only part of which is owned by Pleasant Valley Conservancy) had dramatic consequences. The wetland flora is fantastic this year, with greater population densities, and lots more plants of desirable species. Particularly nice this year have been swamp thistle, swamp milkweed, turtlehead, Joe pye-weed, sweet Indian plantain, Michigan (Turk's cap) lily, boneset, and lousewort. Lots more purple-stemmed aster than usual (this is an aster that grows with its "feet" in the water). Flat-top aster, a desirable "fen" species, has returned in droves after several off years.

Turtlehead (Chelone glabra) is especially abundant, probably because of the burn. (We had experienced the same result after the 2005 burn.) This very desirable plant (C value of 7) serves as food for the larval stage of the Baltimore checkerspot (Euphydras phaeton), a very desirable butterfly. After the 2005 burn, butterfly folks who visited Pleasant Valley Conservancy reported over 25 Baltimore checkerspots. This year Ann Thering reported seeing 9 on one day.

The State of Maryland designated this butterfly as its official insect in 1973. According to the Maryland State web site, this species seems to be declining in its range (much of the eastern United States). The butterfly takes its name from the black and orange checker-like pattern on its wings. These were the colors on the family coat of arms of George Calvert, the first Lord Baltimore, who helped establish the Maryland colony. The Baltimore oriole has similar colors and derives its name from the same source.

Our new boardwalk has provided nice access to parts of our wetland, making it lots easier to survey wetland plants. Our long-range plan was always to create a trail from the end of the boardwalk along the creek. We finally found time to work on this trail. Our goal was to be able to "amble" along near the edge of the creek, looking at the plants, and watching the wildlife. This great idea had lots of merit, but ran into a major snag.

Amanda and Susan spent most of a morning last week creating the first part of this new trail by cutting the tall weeds with a Stihl brushcutter. I plowed along ahead and marked the route. By staying close to the creek, I was able to trace out a trail that was dry underfoot. This time of year, however, the vegetation is very lush, and I was pushing through head-high (and higher) plants. Back in May when the vegetation was short I had walked this whole area and knew where the dry spots were (close to the creek). This worked out fairly well until we reached a remnant of an old creek bed that still had a bit of water flowing through it. I could jump across here, but we wanted people to be able to "step" across.

We had at the barn some long logs that would work fine for this purpose. So yesterday we carried these logs to the spot, in order to bridge this small gap and then get on with further trail mowing.

Imagine our surprise when we found that the trail we had so carefully mowed was now completely under water, with a stream flowing through it. Since it had not rained significantly, we knew something was radically wrong. Kathie quickly found the problem: a new beaver dam, constructed just downstream from where our trail was to run. This dam blocked Pleasant Valley Creek, causing it to overflow its bank and pool out into the wetland. Of course, the path of least resistance was the trail we had recently cut.

We have had beavers at Pleasant Valley for many years, but recently their dam was a long way from the Creek, by County Highway F, where a small creeklet joins the main creek (East Blue Mounds Creek). That dam had been active for some years, but recently someone had brought in a backhoe and pulled the whole dam out. (Easy to do, since the highway provided a firm footing for the power equipment.) Perhaps it was for that reason, or perhaps these were different beavers, but now we have a substantial beaver dam on Pleasant Valley Creek right in the middle of our wetland. No way to bridge this gap!

Someone suggested removing the beaver dam, but past experience has shown that approach to be futile. Beavers can repair any damaged dam within 24 hours. The term "busy as a beaver" is based on reality.

Obviously, we need another approach to this problem.


Blogger Emily said...

beavers are so cool! keep the beavers, Dad!!

September 8, 2010 at 7:31 PM  

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