Author: Chris Fastie

Sound data

Part of the Vermont Center for Ecosystem Studies Vernal Pool Monitoring Project includes audio recordings to document the first calls of frogs at the pools. This year they started using AudioMoths to make the recordings. AudioMoths are open-source data loggers with a low-power sleep mode, real-time clock, microSD card slot, MEMS microphone, and circuitry to support audio capture. AudioMoths can be configured to automatically save audio recordings on a custom schedule. The AudioMoth software and hardware are well thought out and the audio quality is very good (see audio file below). The AudioMoths were deployed at about 50 Vermont vernal pools in weather-tight cases (Figure 1) and recorded for a few short sessions every night for several weeks in the spring.

Figure 1. The AudioMoth in a weather-proof case deployed at vernal pool NEW370 (near East Middlebury) between March 13 and May 8, 2021. It was configured to record for 10 minutes four times every night and save the wav files to a microSD card. The white plastic and foam is a rain hat which kept the AudioMoth drier but might have amplified the sound of big rain drops hitting it. April 11, 2021.

Unsound data

A water depth data logger has been running unattended at a vernal pool (MLS619) at Snake Mountain in Bridport since April 10. The water was a meter deep when I waded out then to change the batteries and swap the microSD card. I have not been in a hurry to do the swap again assuming that the longer I wait the less wet I will get doing it. But I didn’t know how long the batteries would power the logger. The previous record was 11+ weeks, although a similar logger has been running in my office for more than a year on the same batteries. That one only saves data when certain conditions are met but it has been waking up every 30 minutes and sensing its environment for almost 13 months. I decided 16 weeks would make a good record for field deployment at MLS619 and was pleased to find that data had been written to the microSD card once every 30 minutes during those 3.7 months.

There was a lot more water in vernal pool MLS619 on July 30 than I expected. The level was only 11 cm lower than it was on April 10 when I last serviced the logger. I was even more surprised to learn that the water temperature was only 2.5 °C warmer than it was in April. Photo by Ned.

Blueberry and hemlock

Some “then and now” sliders in the last post about Glacier Bay suggested that blueberry and hemlock were spreading in the understory at two of the older study sites we visited last month. Below I am trying out another method of displaying these pairs of old (1990 or 1995) and new (last month) photos. Some new photo pairs from York Creek and Beartrack Cove have been added as well as pairs from a third site.

  • 1995, York Creek, Plot 9, SE-NE

Camera and Crew

Last month I was on a two week camping trip in Glacier Bay National Park collecting data from thirty-year-old study plots. We measured and counted the same things (tree diameters, number of alder stems) that we did in 1988, 1989, or 1990. I brought home lots of new data to compare to the old data, and also brought home 1600 new photographs.

The photos are of four types: repeat photos of the study plots, natural history, scenery, and photos of the field crew trying to look like it’s not raining.

This is the crew and our gear being dropped on the beach in the rain at the start of our 14 day backcountry trip. This is the only time during the trip that I had my phone in my pocket and the only photo I took with it. The boat came back every few days to take us to another wet beach. June 15, 2021.

Vernal data

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.

On our first visit to the new pool (MLS619) on Snake Mountain last fall, Ned revived the HOBO logger and we installed a wooden stake for the water depth logger (left). October 23, 2020.

New Pool

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 or dolomitic quartzite, limey rocks which enrich 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.

Snake Mountain and its southern extension are mapped as Monkton quartzite which includes “well-bedded dolostone.” That is apparently the rock forming the ledges by the new pool. More massive Winooski dolostone overlays Monkton quartzite and is exposed to the east of the new pool’s ridge.

Autumnal pool

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.

Figure 1. Vernal Pool NEW370 on September 29, 2020. I swapped batteries and the SD card which had continual data from July 10. That span of 11+ weeks is so far the longest duration on batteries for this datalogger. This image is stitched from 20 photos. Click to embiggen.

Bat plus ultra

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.

Unidentified bat in pursuit of a dragonfly in my yard at 8:24 PM on August 8, 2020. Nikon D3100, Nikkor 1:2.5 105mm lens, 1/2000 second, f/2.5, ISO 12800 (Hi2).

Delta, pine, trail

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.

Figure 1. The newly cleared trail along the access corridor to the town forest. This part of the new Pitch Pine Trail traverses an area that was a sand quarry in the 1940s. August 12, 2020

A night sky to remember

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.

Comet NEOWISE. I like to think that this photo shows a hint of the separate ion tail to the left of the main dust tail, but I often think my photos are better than they really are. Nikkor 300mm 1:4.5 lens (ca. 1975) on Nikon D3100. ISO 800, f/8, 5 seconds. July 20, 2020, 11:22 PM EDT.

Dry, with a twist

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.

Data loggers near the lowest point in the vernal pool and royal fern where six to 10 inches of water are present for much of the year. July 10, 2020.