About this time last year, our vernal pool near East Middlebury had been reduced to a puddle by some warm and dry weeks in May. According to our data logger, it was completely dry on June 16. 2020. This year the pool might be dry a little earlier than last year.
In addition to the HOBO temperature logger in each vernal pool, we have a water depth data logger installed in the two pools we are watching this year. We have looked at the data from late January to early April and the loggers are continually recording new data every 30 minutes.
Ned and I have been monitoring a second vernal pool this year. The new pool is in Bridport on the southern extension of Snake Mountain. It is right in the middle of the Champlain Valley, but up on a rocky ridge. The pool is almost twice a big as our other one and a foot deeper. It is lower in elevation at 570 feet above sea level (the other one is in the foothills of the Green Mountains at 1260 feet a.s.l.).
The most important difference between the two pools might be chemical. The new pool sits between two ledges of Middle Cambrian dolostone, a limey rock which enriches the soil with calcium and magnesium. The old pool is surrounded by Cheshire quartzite and the vegetation there (red oak, beech, birch) suggests that the soils are not rich in calcium.
The vernal pool we have been monitoring has been dry since about June 17. There were a couple of rainy days in late June, but the puddles formed did not last more than a day. The pool was dry when I visited on July 10, September 29, and October 23. That is, there was no standing water, but the soil under the leaves was always damp. New data from the water depth datalogger indicate that only two rainfall events between June 30 and October 23 produced standing water in the pool.
This summer there was a bat or two flying over the yard every evening, so I started lying in wait for them with a camera. For about 15 minutes at dusk there was enough light to capture a bat silhouette if I used a good DSLR at the highest ISO. The photos were fun, but you can’t tell what kind of bats they are from the photos. Someone suggested using a bat detector — an ultrasonic microphone that listens to the otherwise silent calls of bats and even suggests which species are calling.
This year, the Salisbury Conservation Commission created a new trail in the Town Forest. This project started with a professional survey of the boundaries of the 140 acre town property which marked a little-known, half mile long, 30 foot-wide access corridor from Plains Road to the property. This now allows easy access to the western part of the town forest which few people in town had ever visited. Parts of the corridor were overgrown with invasive shrubs (honeysuckle) and a tremendous amount of labor was required to turn this corridor and the rest of the route into a hiking trail. With a small parking area on Plains Road it is now easy to visit the western end of the town forest.
Last week dozens of online photos of Comet NEOWISE enticed me to make an effort to see it for myself. At 9:00 PM on Friday I noticed that the sky was clear, threw some gear in a pack, and hiked up the hill behind the house. I sat in the grass in a big hilltop clearing as the sky darkened and first the comet, and then a million stars, and then the full sweep of the Milky Way emerged above me.
It has been three weeks since I last visited the vernal pool and installed the Version 4 (Ultrasonic) water depth data-logger. I was curious to learn whether the new logger was working and decided to collect the data and replace the batteries in both loggers — the Version 3 logger (laser rangefinder) had also been running since the last visit.
Daytime high temperatures in the first half of June in Middlebury are historically in the 70s F, but so far this year half of the days in June have been in the 80s F. Historically in June, Burlington gets 2.5 inches of rain by the 20th, but so far has gotten only 0.4 inches (last year they got 3.8 inches by now). So maybe I should not have been so surprised on Friday to find that our vernal pool was completely dry. Ned and I visited to collect data from the loggers and install a new version of the DIY water depth and water temperature logger. The new logger might not have much work to do for a while.
Six weeks ago I installed version 3 of a water depth data logger in the vernal pool we are monitoring. I liked that logger more than the earlier versions because the parts cost $35 instead of $50. After posting about it I noticed that many Arduino hobbyists measure distance with an ultrasonic rangefinder instead of the laser rangefinder I had used, so I ordered a few HC-SR04p rangefinders.
Vernal pools are enchanting places, the breeding habitat of dozens of animal species that would otherwise be absent or rare in a forest. But it is a challenge to take enchanting photos of vernal pools. If you stand far enough away to include the entire pool, lots of trees will probably block your view and the photos don’t seem to capture the essence or importance of the place.
On May 3 we made the official third visit to the vernal pool we are monitoring. During this visit we are supposed to collect the frog call recorder and do the final surveys for amphibian eggs and aquatic invertebrates. At the second visit we failed to find any fairy shrimp, so I was looking forward to adding them to my crustacean life list. I was also looking forward to collecting the microSD card from the data logger we had installed on April 17 and examining two more weeks worth of data. And at the last minute I decided to bring a 24 foot-long pole and get some “aerial” photos from above the pool. By the time we left the pool to hike back to the road, I was dismayed at my lack of success at most of these goals.
